The Early Beginnings

Theta was a research project long before it became a manufacturing company.

When it began to become clear that compact discs were going to become the dominant music recording format, a small group of music lovers started to seek out ways to deal with the harsh, lifeless, irritating sound they were getting from what had been introduced as a "perfect" medium. The very best of the CD players on the market was horribly below the standards of these audiophiles. They examined flaws in design and execution, and just plain shoddy standards-everything from misunderstandings about what human hearing perceives to how cheap a part can be used and still make sound. Over a two year period of working on weekends and spare evenings, this little group experimented, listening to the results every step of the way, to see where improvements could be made, and what kind of changes had beneficial effects on the sound.

The very first units from this design team, in early 1986, were modifications to early Philips CD players. Modifications included new analog "brick wall" filters utilizing Mills resistors, Teflon and polystyrene capacitors and digital signal re-clocking. These improvements led to a whole new analog section with new DACs, op-amps and power supplies on a Teflon circuit board. The improvements that these modifications made clearly showed that digital had potential.

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Frankenstein

Next came "Frankenstein." This was a three-box set connecting a CD player used as a transport, a power supply, and a digital / analog unit. All of the analog section from the CD player was removed and only the necessary circuitry needed to play a CD and get a digital signal from it were left intact. The digital signal from the transport was then fed to the processing section, which reclocked the signal, oversampled the data by 8x, and calculated accurate interpolated data points.

This was the first step in the implementation of DSP (digital signal processing) in a consumer digital to analog converter. It used Texas Instruments 16 bit microprocessors running at 10 MIPS (10 millions of instructions per second). The signal was then routed to the analog section. A Teflon circuit board contained circuitry similar to those early modified Phillips CD players, with additional improvements like more advanced 16 bit DACs (Burr-Brown PCM 56) and optical isolators which kept digital high frequency signals from corrupting the analog section.

This was also the first implementation of the Buf 03 output buffer. The digital to analog converters themselves were hand trimmed on a $10,000 Hewlett-Packard dynamic signal analyzer. This was not being done by any other manufacturers, despite the clear necessity of doing so to assure acceptable low level linearity, and a reliably standardized level of performance. The early Frankensteins were not pretty to look at (OK, they were ugly) and were cumbersome (three units connected together) but were a huge leap in digital sound.

The Frankensteins were not intended to be in production and were never sold to the general public. They were only sold to friends and their friends who wanted better sound from digital. The demand became so great for these units that a more affordable, better-looking, less cumbersome "Theta" unit became the thrust of the design team's efforts.

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DS Pre

The result of those efforts was the original Theta Digital DS Pre, released in 1988. This was the first DSP-based outboard digital to analog converter. This unit was an instant success due to its dramatic superiority over the then state-of-the-art solid state and vacuum tube CD players. The wealth of reveled musical information previously unknown to digital sound reproduction was the most obvious and remarkable aspect to the Theta.

The unit had several unique design aspects worth noting. It contained totally isolated power supplies, digital board and analog board within a single chassis using Faraday cages. This was a direct result of research and development invested in the Frankenstein, which confirmed that this isolation was critical for a truly breathtaking listening experience. The power supply featured four totally isolated transformers, which separately powered the digital, DAC and analog sections. An advanced phase locked loop was implemented to cope with the large amount of jitter being generated by early CD players.

The digital section was designed to accept plug-in ROM (read only memory) chips so that as research into better sounding algorithms progressed, Theta owners could keep their units current.

The DS Pre was radical in many ways; most of them technical, but perhaps the least appreciated advantage was its function as a preamplifier. By including some basic switching and a superb analogue volume control - using discrete resistor networks to turn the high-voltage output signal down - the DS Pre offered to eliminate an entire component; a series of gain stages and all the signal degradation that went with them. It had an analog input, balance control and a muting circuit so that the unit could be used in a system sans customary preamplifier. However, we did not supply a phono stage for playback of vinyl records. Many audiophiles, still devoted to LPs, were happy with the phono stages in existing high-end preamplifiers and had no desire to go to an outboard phono stage.

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DS Pro

We recognized the need for what became known as the DS Pro: essentially the same as the DS Pre, minus all preamplifier functions. The DS Pro was embraced by audiophiles who already had high quality preamplifiers. The disadvantage of the DS Pro / preamplifier configuration was the routing of CD music signals through an extra set of wires and gain stages. A great secret of the late 1980's was that most all-digital systems could have been dramatically improved by omitting a component most people thought of as indispensable.

Research into all aspects of the Theta continued. Specifically, more processing power was needed to run a newly developed algorithm that could more accurately interpolate oversampling points. New DACs with higher resolution were becoming available from Analog Devices. Microprocessors from Motorola were released which had higher accuracy and speed. The use of tantalum electrolytic capacitors was found to decrease noise in the digital section, due to the higher frequency capability of these components.

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DS Pre Generation II and DS Pro Generation II

The result of that research was the DS Pre Generation II and DS Pro Generation II, released in 1990. These products incorporated all-new digital and analog boards. The digital board utilized two 24 bit Motorola 56001 microprocessors running at 24 MHz which was a two-fold increase in computing power over the DS Pre. The analog board was upgraded to 18 bit Analog Devices AD 1860 DACs.

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DS Pro Basic and DS Pre Basic

Shortly thereafter, a new product line was released. The DS Pro Basic and DS Pre Basic, lower priced versions of the Generation II predecessors, allowed many more music lovers to obtain satisfying digital sound. A Basic unit had a thin-line chassis containing a single circuit board, which had all three of the required sections (power supply, digital, and analog), on it. The digital and analog sections were similar to the DS Pro Generation II, so the Basic had a very similar sound, but didn't have as much resolution as its larger sibling.

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Fully Balanced Differential Layout

At this time Theta's engineers started investigating the benefits of balanced operation. Balancing a Generation II produced a profound decrease in digital harshness and glare, and was immediately made available as an upgrade or as an option on new units. Theta was the first digital manufacturer to "balance the hard way." This means that the whole analog section is duplicated including DACs, the only way to truly realize the improvements of balanced operation.

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DS Pro Prime

One-bit technology was headline news around this time. It was touted by major hi-fi manufacturers as being the next revolution in digital sound. They said multi-bit technology was dead. Theta's design team tried this new technology in high-performance designs and found it smooth sounding but lacking in aliveness, dynamics and bass. They envisioned one-bit technology as a palliative for less expensive products. Most inexpensive CD players and outboard D to A converters sounded shrill and harsh. The smoothness of the one-bit D to A could be implemented to reduce "glare" and other irritating characteristics, to bring new musicality to otherwise unacceptable components. It meant Theta had something to offer in a price realm previously thought hopelessly compromised. The DS Pro Prime was introduced in May of 1991.

The Prime was similar to the Basic in construction, different in circuit design. It had a single circuit board which contained the power supply, digital and analog sections. The digital section employed a single Motorola 56001 microprocessor running at 30 MHz. It was a 4x-oversampling unit and thus didn't have the huge amount of information presented in the Basic or the Generation III. Compared to other D to A converters in its price class, however, it was nothing short of a miraculous improvement. Where previously there was only harsh, strident sound, lacking in detail, there was now musicality and enjoyment.

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Transports

Transports were the next frontier for Theta. Transports made a real, audible difference to the absolute quality level Theta's signal processing could attain. Theta's people searched long and hard to find a CD player that would function as a truly high-quality transport to support Theta's digital signal processors. It seemed a bit of an absurd compromise to urge audiophiles to buy cheap CD players to extract digital signals, but that was the state of affairs for several years. People used whichever CD players had reasonably reliable transport sections and offered a way to pass a signal out of the digital stage. Experiments with numerous CD players showed them to be inadequate for the basic function of providing a clean jitter-free digital signal.

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Data

The solution to this perplexing problem was another Theta first: the Data Universal Transport, a laserdisc player used as a transport. This, of course, was not just a laserdisc player with the Theta name on it. The digital signal was extensively improved by re-clocking it with high-speed CMOS logic devices and pulse transformers. Data's heavy-duty steel chassis and isolation spike helped suppress and neutralize vibration. The Data was a revelatory experience for audiophiles and an instant success. Other digital audio companies quickly followed with laserdisc transports of their own.

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Data II

Following the original Data was the Data II. The Data II was different from the original Data mostly in its power supply. A whole new power supply circuit board was added which isolated the delicate re-clocking board from the rest of the unit. As originally conceived, the Data was only intended as a CD transport. People asked, naturally, why Theta was ignoring the opportunity to tune up the video aspects of the Data. Improvements to the video quality in Data II were much appreciated by videophiles, who quickly discovered that the Data was the best laserdisc player around for video quality.

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Basic II

The research that was invested into the Prime and DS Pro Generation II Balanced paid dividends in other products as well. The Basic II was released in late 1991, offering sound quality many thought comparable to the Pro II. Balancing was available as an option, which was by this time becoming a standard for many digital based systems. It was, of course, balanced "the hard way" as previously described. It also featured a new DAC from Burr-Brown, the PCM 67. This was an 18-bit combination DAC that operated as a multi-bit DAC for the upper portion of its range and as a one bit DAC for the lower portion. This DAC is still used today in the Prime II, Progeny and Cobalt. New op-amps, the Analog Devices AD829 and AD707 were also utilized.

The design team continued to delve into sources of dissatisfaction with digital sound. Again they found that increased processing power and digital filter accuracy was essential for further resolution enhancements. New op-amps that had faster slew rates and settling times were investigated. Improvements to the digital section's power supply were found to decrease harshness and interference between different parts of the digital circuit.

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DS Pro Generation III

The Generation III emerged in 1993 as the beneficiary of that research. The digital section was upgraded to include three Motorola 56001s running at 30 MHz instead of just two. This increased the computing horsepower by a factor of two again over the Generation II. Many of the high-speed logic ICs used on the Generation II board were replaced with two field-programmable-gate-arrays. The PLL (phase lock loop) circuitry was improved by separating the standard 32 KHz-48 KHz PLL into 3 different PLLs. On the analog side, new Burr-Brown 20 bit DACs (PCM 63) were employed in addition to new op-amps (Analog Devices AD 841) and improvements were made to the servo. More power supply capability was added.

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Cobalt

In late 1992 Theta's first non-DSP digital-to-analogue converter was released. The Cobalt, based on an off-the-shelf Sony digital filter chip, in comparison with alternatives in its modest price range provided a smoother, less strained, more dynamic sound. While certainly no match for any of the DSP based Thetas, it provided welcome musicality for audiophiles on a budget, and die-hard analog fans. The Cobalt uses the same construction techniques and parts quality as the most expensive Thetas, including the Burr-Brown PCM 67 DAC; Analog Devices AD 841 op-amp; and Crystal CS 8412 input receiving IC.

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Data Basic

During all of this developmental work in digital-to-analog converters, transport development continued on its own design track. The Data Basic transport, available in early 1993, quickly established itself as the standard against which all other CD-only transports would be measured. It is not a remanufactured product, as most U.S. CD transports are, but instead a wholly in-house manufactured product built to the highest standards of quality. Separately isolated power supply, mechanism and digital / re-clocking circuit boards, along with improved re-clocking circuitry, combined to produce what some reviewers refer to as its "lively, upbeat" sound quality.

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Prime II

Despite the promised benefits of one-bit technology, it had all but disappeared from mass-market CD players. The Prime was reevaluated using the Burr-Brown PCM 67 DAC. The smoothness in the old Prime was still present, but a new range of dynamic contrast and detail became evident. It was clear that huge leaps had been made since the original Prime was designed, both in the technology available and in our knowledge of how to produce the best digital sound. The Prime II implemented a similar digital section to the original Prime but included a brand new analog section. It was balanced using two Burr-Brown PCM 67 DACs, Analog Devices AD 841 op-amps and National Semiconductor LM6321 buffers. Special circuitry was designed to take advantage of balanced operation through the single-ended outputs. The Prime II also had extensive PLL technology to reduce the effects of jitter to a minimum.

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Timebase Linque Conditioner

Originally, there was only one method available to connect a CD player / transport to an outboard D to A converter, that being coaxial. The mass-market manufacturers then produced players with the inferior TosLink plastic fiber optic output. AT&T glass fiber optics also became available as a means to interconnect digital equipment. All of these termination methods posed a problem for people trying to buy components that would interface with each other. The Timebase Linque Conditioner was designed to solve these problems. It accepted TosLink and coaxial inputs and output coaxial and optionally AT&T or Theta's Laserlinque. It also contained extensive re-clocking circuitry to combat the deleterious effects of jitter. Poor quality transports still pervaded the market, reducing the effective quality level Theta's D to As could offer. The Timebase Linque Conditioner ameliorated some of the problems. It was even found to improve the sound of our then best combination, the Data III / Generation V.

All of the digital-to-analog converters up until that time used integrated circuits (ICs) called op-amps, for the critical current-to-voltage conversion that occurs following the DAC, and for the output buffers. At that time, integrated circuit chips generally were used as cost-efficient compromises, which lowered the quality of components that depended on them, in comparison with equivalent circuits made up of discrete elements on a circuit board. After about a year of research, a new analog section was developed for the Generation III, based entirely on discrete class-A bipolar transistor. This circuitry offered greater processing speed, which produced more detail and a smoother sound.

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DS Pro Generation V & Progeny

Previously, a balanced Generation III required two separate analog boards for balanced operation; in the new design only one board was needed for fully balanced operation. The single ended left and right analog outputs take advantage of the balanced signal, just as in the Prime II. Improvements to the power supply came with the new analog section, including regulation on the analog board itself. The vast improvements wrought by these changes deemed a new product name: the DS Pro Generation V. It was previewed at the Las Vegas CES in January of 1994. The Progeny, essentially a single ended version of the Prime II was introduced in November of 1994.

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Basic III

The Pro Basic III was also released about the same time. The Prime II showed that the benefits of fully balanced operation and the summing circuitry utilized for the single ended outputs were worthy of introduction into the basic line. Prototyping confirmed this and soon the basic III presented itself as a true contender for the best sound attainable from a CD. New 20 bit Burr-Brown PCM 1702 DACs, which are very similar to the PCM 63 used in the Generation V, were found to bring the basic III to a new price / performance level. The digital section was also redesigned from the ground up, taking advantage of many of the techniques learned from the development of the DS Pro Generation III. Field-programmable-gate-arrays replaced huge quantities of individual CMOS ICs and the inherent difficulties of designing circuit boards with them.

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Data III

The Data III Universal Transport was introduced at the 1995 Winter CES in Las Vegas. The Data III incorporated the knowledge gained from the original Data, the Data II and the Data basic. Much of the massive unit (all of one side) was reserved for power supplies. Research into voltage-controlled oscillators provided even better jitter immunity and stable signal transfer. Each unit was hand calibrated with a high-precision time-interval counter to conform to the CD standard for digital data transmission. It came with coaxial, BNC, AES / EBU and optional optics outputs for easily integration into any system. When playing a laserdisc, the Data III has the ability to play both sides without user intervention and a special CD-only drawer, which greatly reduced access time.

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Pearl

Released in February of 1997, Pearl CD Transport was Theta's lowest cost transport ever, yet offered a lot of the proprietary technology found in earlier, more expensive units. Based on the Pioneer Stable Table, which was an extremely stable transport mechanism, it incorporated jitter reduction circuitry, and multiple high quality power supplies.

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Miles

Miles was Theta Digital's first Compact Disc Player. First released in June of 1997, Miles was based on the Pearl's ultra-stable transport, with the all-important additions of D to A conversion using Theta's proprietary algorithms on a high powered computer, and an analog volume control similar to Casablanca's. The DAC was a hybrid combining the advantages of one-bit with those of 18 bit technology. Miles had excellent power supplies (four of them); Theta's jitter reduction technology, and was offered with a choice of either single ended or fully differential balanced output.

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Jade

The Jade CD Transport, introduced in November of 1997, was the first Theta product to take advantage of the intensive digital signal buffering Theta calls Jitter Jail technology, since incorporated into succeeding processors and transports.

Taking advantage of the technology used in the Pearl CD transport, Jade had a massive power supply comprised of multiple high-current, low-flux transformers. Individual, highly regulated voltages were fed to all critical circuits. This separation of supplies kept each circuit noise-free and isolated from spurious signals. While not surprising to see in high-priced components, this kind of quality was not at all common in a component as reasonably priced as Jade, nor was its bi-laminate steel chassis and RFI shielding.

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DaViD and Voyager

DaViD DVD / CD Transport was released in April 1998. Voyager Universal Transport, which played DVD, CD, and LD discs, was introduced two months later, in June 1998. They are very much alike, except for the greater versatility of the Voyager.

DVD, as a medium, presented new challenges. The audio sampling frequencies are higher than CD's 44.1 kHz: 48 kHz and 96 kHz, and the video is presented in a purely digital form, unlike laser discs, which are recorded and played back in analog format.

DVD's disparate clock speeds (16 MHz audio and 18 MHz video) multiply digital noise, as they tend to interact. This noise can degrade both sound and picture, creating less than satisfying audio performance and video that is unclear, noisy and lacking three dimensionality. Theta's proprietary Jitter Jail technology and other digital noise reduction strategies were called upon to deal with the most pervasive problems in digital signal processing.

In the audio section, high-speed CMOS logic gates used in reclocking and extensive use of ground planes prevented digital noise and hash from corrupting pure clock signal. Theta-designed low-flux transformers and high isolation power supplies fed each key area of the audio board, isolating clocks and DSP sections. The signal was output through extremely high frequency pulse transformers to the various output terminals.

The video sections were handled as meticulously as the audio: multiple transformers and high isolation power supplies separately fed critical areas of the video section, including the clocks, output circuits and main DVD decoder circuits. The motor controller and display were isolated from the rest of the circuits. Each DaViD had six transformers and fourteen highly regulated power supplies. The Voyager had seven transformers and twenty-one highly regulated power supplies.

The point of all this careful separation of audio, video, display and motor power supplies was to keep circuits from interacting, contaminating one another. Each circuit was kept as free from both digital and electromechanical noise as possible. The DVD decoder power section was then filtered again at key points to further minimize residual noise.

After the digital video signals were converted to analog signals, they were sent to individual Theta-designed video filters and extremely high-speed output buffers.

The Voyager used two separate laser head pickups. The laser used for the playback of DVD source material has a wavelength of 650nm. The second laser, for playback of CD's and Laser Discs, has a wavelength of 780nm. This provided optimum performance for each type of source material.

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Carmen

Carmen DVD transport, released in January 2000, was an evolutionary step forward for DVD transports. Theta's newly designed audio and video circuits met the challenges of developments in DVD technology. Carmen was another of Theta's ongoing efforts to bring superb performance and sound quality to lower priced components.

Carmen accommodated sampling frequencies of 44.1 kHz, 48 kHz and 96 kHz and bit rates of 16, 20 and 24.

Audio and video were processed in circuits completely separate from each other. This separation kept video noise out of the audio circuits and audio noise out of the video circuits. Carmen used discrete low-jitter crystal oscillators for video and audio frequencies: Data was then buffered; re-clocked, corrected for errors in timing and realigned before output, eliminating 'artifacts' from both audio and video. DVD and CD sound both Benefited from this scrupulousness.

Digital video signals were converted to analog, filtered and sent to extremely high-speed output buffers, for a DVD picture quality that is clear, color balanced and three-dimensional.

Carmen's multiple transformers fed fourteen highly filtered and regulated power supplies, for extreme isolation between circuits, each supply and circuit with its own integral RF suppression filter to further reduce interaction between the stages of each independent circuit, and between the audio and video sections.

Carmen's drive mechanism used twin laser diodes, 650nm for DVD and 780nm for CD, CD-R, CD-RW and VCD, minimizing errors. Low-jitter digital servo circuits controlled motor speed, laser tracking and focus.

The most noteworthy of Carmen's optional features were 4:2:2 Serial Digital Video Out and Ultrasync™ Progressive Scan (480p).

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DaViD II

DaViD II DVD / CD Transport, released in May 2000, might best be described as an audiophile quality CD transport and a separate videophile DVD transport that happened to share one chassis. The audio and video circuits of the unit were completely independent, and thus did not compromise one another.

DaViD II took advantage of all of the technological advances that went into Carmen, and added features of its own. DaViD II used multiple analog power supplies comprised of six low-flux, Theta designed transformers – giving extreme isolation between circuits – and sixteen highly filtered and regulated supplies.

Like Carmen, DaViD II had an advanced drive mechanism with twin laser diodes, 650nm for DVD and 780nm for CD, CD-R, CD-RW and VCD. DaViD's options included 4:2:2 Serial Digital Video Out and / or Ultrasync ™ Progressive Scan (480p).

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Carmen II

For the Carmen II DVD / CD Transport, Theta redesigned and enhanced virtually every internal component of the original Carmen, equipping Carmen II with a new DVD board and drive, new audio and video circuits, a new power supply, and a new front-panel display.

Carmen II was designed to appeal to both movie lovers and music lovers, incorporating important features and technologies, all while attempting to keep it at an affordable price. Carmen II handled digital audio at 44.1, 48, and 96 kHz with resolutions of 16, 20, and 24 bits. An advanced drive mechanism with twin laser diodes-650 nm for DVD and 780 nm for all CD formats made it compatible with just about any disc or format.

Carmen II's drive mechanism, like DaViD II's, had low-jitter digital servo circuits to control motor speed, laser tracking and focus. It automatically selected the proper laser for the type of disc being played, enhancing read-out precision and keeping errors to a minimum. Errors introduced by fingerprints, dust and warping were corrected by parametric statistical analysis circuits. Carmen II had a massive, shielded, 65-watt main DC power supply. It was highly filtered at both the input and output stages to keep unwanted noise from degrading the power used by the signal processing circuits. CD and DVD sections were addressed separately, with interaction between the circuits kept to a minimum. Separate, extremely low-jitter clocks for both the CD and DVD playback dramatically reduced digital noise that can degrade sound and picture. The audio and video circuits were also isolated from each other. Multiple regulated subordinate power supplies were dedicated to each section. Each power supply and circuit had integral RF suppression filters to prevent interaction between the stages of each independent circuit, and between the audio and video sections. Theta's Digital Direct Ultra-Sync II Progressive Scan System de-interlaced the video signal in the digital domain before it was converted to analog. Theta-designed discrete video filters and high-speed video amplifiers, with 108 MHz, 12-bit video digital / analog controllers, were coupled with Faroudja Laboratories' acclaimed DCDi™ deinterlacing technology, assuring an accurately rendered 480p picture, free from the motion artifacts inherent in the performance of players using off-the-shelf progressive scan solutions. All this was standard on Carmen II, while the Ultra-Sync System was a costly option on the earlier unit. Theta's proprietary ultra-low jitter video re-clocking circuits and video correction software completed the picture. A 4:2:2 Serial Digital Interface (SDI) for Video, to keep the signal in the digital domain, was available as an option. Keeping the signal in the digital domain, rather than subjecting it to further conversions to analog and back again, avoided major sources of degradation, which were particularly noticeable in high definition video systems. The picture quality on flat-panel plasma screens and digital video projectors was particularly revealing of the performance advantages of SDI's purer digital signal. 4:2:2 was an option on all DaViDs, Carmens, and Voyager transports.

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Compli

The Compli came as close to serving as a universal format source component as A / V technology allowed when it came out. The Compli's combination of sophistication and exceptional versatility provided extraordinarily high quality playback for a multiplicity of listening and viewing formats.

The Compli's unique blend of uncompromised performance, flexibility and advanced technology made it ideal for any high-end home theater or home entertainment application. It had six-channel analog audio outputs, and digital outputs for PCM, DTS and Dolby Digital. It came equipped for RS-232 control, and with composite, S-video, component and 480p video outputs. It let you play nearly any audio, video, and image format of the time: DVD-Audio, DVD-Video, DVD-R, DVD-RW, SACD, Audio CD, Video CD, CD-R, CD-RW. The Compli also had limited ability to work with CD-R / RW, DVD-R / RW and mp3 formatted material.

Options for Compli included a Serial Digital Interface (SDI) and Theta's Ultra Sync II 480p output board using Faroudja Labs' Directional Correlational Deinterlacing® (DCDi®) technology. SDI kept the signal in the digital domain, rather than subjecting it to further conversions to analog and back again. This avoided major sources of degradation, which was noticeable in high-definition video systems. SDI's purer digital signal was especially effective in enhancing picture quality on flat-panel plasma screens and from digital video projectors. (SDI, a professional standard, was not distance restrictive like consumer digital video transmission methods.) The Ultra Sync II option eliminated the staircasing or jagged edge artifacts often visible along the diagonal edges in video generated by conventional upconverters. It did so by adjusting each pixel in each moving edge in a scene to align with the movement, instead of crossing it. The result was a smoother, more film-like, more engaging image.

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Compli Blu

Theta Digital's Compli Blu, the latest and most powerful in a long line of transports, is designed to bring the maximum levels of sound quality and video performance from the company whose expertise in this field spans over two decades.


Read A Review!


"Using versatility and performance as yardsticks, this new model from Theta Digital potentially, at least, comes near the top of the list and, perhaps, at the absolute pinnacle."

Alvin Gold, Hi-Fi Choice

Read the Full Hi-Fi Choice Compli Blu Review Here

The Compli Blu, like all the other transports before it, is based on a manufacturing kit obtained from a third party, then optimized by Theta Digital's experts to bring it up to our high standards. In the past, we've partnered with Sony, Phillips and Pioneer. This time, we're pleased to partner with Oppo, whose recent transports have garnered quite a following. Both Oppo and Theta Digital are delighted to bring this top performing product to you, and to build upon the already desirable performance of the BPD-83 and establish yet another benchmark of performance by Theta Digital in the transport product category.

As it becomes available during its product life-cycle, updated firmware for the Compli Blu will be posted in the Downloads area of Theta Digital's website here

Here is the core of what Theta Digital has done this time around to "turbo charge" an existing transport:

  1. Heavy 16 gauge steel chassis for rigidity.
  2. Positions of transport mechanism and display have been swapped. Lowering the mechanism allows for elimination of an intermediary mounting bracket and long standoffs, resulting in greater rigidity.
  3. Completely rigid mounted mechanism replaces the original spring mounted system.
  4. Special 3M adhesive damping material used on drawer assembly, further reducing vibration energy.
  5. RS-232 control is included as a standard.
  6. Custom designed front panel PCB.
  7. Custom designed analog power supply, which includes the following:
    1. An 80 Watt ultra-quiet toroidal transformer.
    2. Additional, independent 10 Watt transformer for Standby circuit.
    3. A total of 7 Amps of power available to supply the unit.
    4. Four independently rectified and regulated power supplies.
    5. Over 40,000 uF filter capacitance, in small, low ESR multiples.
    6. 2 oz. gold plated copper used throughout.
  8. Proprietary Theta Digital customized software for superior performance, and that can be easily updated through USB port on the rear panel, or via Ethernet connection to Theta Digital's website.
  9. Standard thick, brushed aluminum alloy cover provides better sonics and aesthetics as it reduces vibration energy further.
  10. 1/2" thick Tower and Faceplate matches other Theta Digital products.
  11. Music and Cinema Controllers

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    Casablanca I

    Most innovations in consumer electronics are refinements on pre-existing ways of doing things. Casablanca began as a more abstract concept, a departure from previous assumptions about how to process music and sound.

    In 1995, it was becoming evident that high-end consumer electronics was changing in fundamental ways. What had been the realm of "audiophiles", who delighted in the faithful reproduction of musical performances, was becoming "home entertainment", increasingly the province of home theater. Theta hadn't addressed the reproduction of movie sound tracks apart from their nature as audio signals, but clearly would need to do so or become obsolete. Devoted to two-channel, Theta's challenge was to embrace multi-channel as well.

    This was a time when new standards were proliferating at an increasingly accelerated rate, creating tremendous confusion. Theta, positioned on the leading edge of "state of the art" was expected to guess (correctly) which of the new standards and technologies would turn out to be important; even to anticipate the advent of new technologies and standards announced in the press. HDCD, for example, was a "hot" technology in 1995.

    Theta had a fundamental policy of non-obsolescence and upgradeability to uphold. The founders of Theta were dedicated to offering "no waste" components that people could cherish, maintain, and upgrade. How to reconcile the latest in cutting edge technology with non-obsolescence became a very serious question, as Theta's customers expected both.

    All of these factors provoked a radical shift in thinking about the nature of audio components. In 1995, Theta's answer to all of these challenges was the Casablanca Music and Cinema Controller.

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    Open Architecture

    The November 1995 press release announced:

    "Theta has invented a new kind of product for high end audio and audio / video systems.

    The Theta Casablanca is a:

    • High performance D to A converter
    • A high performance analog preamp
    • Surround sound processor with Dolby Pro Logic®
    • Surround sound processor with Dolby 5.1®
    • Surround sound processor with DTS®
    • High performance digital preamp
    • High fidelity video switcher
    • And it's open to anything the future is likely to throw at us!

    You select which features you want from the available options. You can start with a simple set-up, like a preamp / D to A converter, and then add to your array of capabilities. You can even select, and change, the quality level of your digital to analog conversion.

    Coming soon to a Theta dealer near you..."

    In reality, it took until 1997 for the first Casablanca to reach a Theta dealer, though it was officially introduced at the 1996 January Consumer Electronics Show. From the press release for the 1996 January CES:

    "Casablanca is a multi-purpose component, flexible beyond any previous audio or video equipment. It can be configured to meet current needs for individual audio and video systems, and then be reconfigured as systems grow, to meet changing standards and keep current with the state of the art in audio and audio / video.

    A further development in Theta Digital's history of inventing whole new types of components as the needs and technological capabilities arise, Casablanca will bridge a gap between audiophile level sound reproduction and the need for a quality interface with video.

    Casablanca accepts both analog and digital input signals, and can be configured as a preamplifier / digital to analog converter. It can also be configured to perform digital domain surround sound processing. There is also a high end video switching option.

    Casablanca can be operated by remote control or by buttons on its faceplate. Communication is done via its active LCD display, or via a video display on a TV monitor.

    Casablanca is easy to use. Both the LCD front panel and the on-screen video display offer information and choices of various functions and selections of surround modes.

    Signals coming in through any of Casablanca's six analog inputs can be converted to digital, for DSP controlled surround sound processing, or directed through normal "stereo" as pure, unprocessed analog. For Dolby 5.1 surround sound, AC-3 inputs are available as an option.

    The tremendous flexibility of the Casablanca is designed in, using a "mother board" and "daughter boards" in an open architecture topology. The mother board provides signal routing and the daughter boards contain the actual circuitry. Casablanca can be expanded, changed and upgraded by changing daughter cards, which is very easy to do.

    The separate daughter cards are: Main digital in, Video in / out, Analog in, Analog out, Main / Dolby Pro Logic processing, Dolby 5.1 processing, and DTS coherent Acoustics processing.

    There are two levels of digital to analog conversion: consumers can choose one using high quality stock parts such as you might find in other companies' D to A converters, or opt for more powerful digital signal processing computers running Theta's proprietary digital signal processing algorithm..."

    The heart of a Casablanca was basically a cluster of computer boards. Casablanca comprised a relatively simple, unintelligent motherboard for "command central" and a flock of specialized daughter boards, each devoted to designated subordinate functions, including the actual signal processing circuits.

    Writing the software for these systems turned out to be very tricky, difficult and time consuming. In beta testing, numerous "bugs" turned up in the fresh software; some glitches arose from "standard" protocols which were not as specified, and some surprises came from the sheer complexity of all the interactions called for in Casablanca's manifold functions. There were things that needed to be smoothed out before Casablanca was ready to go out in the world. Casablanca turned into a major programming project with complications unforeseen in the optimistic design phases.

    The mathematician who wrote Theta's original processing algorithms and who was writing Casablanca's software, responding to a family obligation, left the team, putting the whole project into a deep setback. The engineer who took over software development continued to be optimistic, though. As a result, Theta placed Casablanca advertisements for about a year before any were finally made available.

    Over the course of time it took to refine the software, Theta's engineers developed new innovations which had to be incorporated. By the time Casablanca came to market in 1997, it had acquired more options and capabilities. Notably, it offered a phase-perfect electronic crossover, of great value in fine-tuning overall sonic balance to the peculiarities of room acoustics, and fully balanced circuit options became available.

    Parts quality was uniformly exceptional. The analog volume control was a tour-de-force in high-quality discrete resistors. Extensive shielding of signal paths, power supplies and digital RF (noise) sources from each other, and multiple, high-grade power supplies made the Casablanca quite a hefty piece. While an average audio / video component weighed 8 to 12 lbs., a fully loaded Casablanca weighs nearly 50 lbs.

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    Casa Nova

    Casa Nova was developed as a less expensive version of Casablanca. Theta's habit was to design an all-out assault on a given problem, and to follow that up with refinements and improvements; then "plan B" is to see how much they could cut costs with a minimal impact on performance. Casa Nova was the inheritor of a great deal of knowledge acquired from Casablanca's design, but with cost savings in mind.

    Casa Nova was introduced in November of 1998. Benefiting from Theta's R&D advances since Casablanca's introduction, it actually offered some improvements over the original Casablanca.

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    Casablanca II

    Casablanca II was the recipient of a great many improvements on the original Casablanca, and all of the updates necessary to keep pace with current technology and standards for sound processing. Perhaps the most significant improvement was that the Casablanca II simply sounded better than the original.

    Some innovations in the II version were new and different enough to call for particular attention.

    Theta had originated several unique features and modes that no other company could offer.

    Center Power Redistribution (CPR) corrected for theater sound mixes, which bunched up much of the sound in the center channel - great for a vast theater, but terrible in a home environment where the center channel was often the weakest. CPR enhanced the quality and dynamic range of sound while making much better use of the best speakers.

    "Center Circle Surround" (Theta's proprietary application of Circle Surround) offered superior channel separation to THX EX on Center Rear Channel. A Party Mode generated a sum of all channels, which was added to the signal going to each speaker. This provided a low level of "fill-in" sound in the vicinity of each speaker, though each individual channel remained predominant for each speaker.

    Casablanca II base model included Dolby Digital, Pro Logic, and DTS processing.

    Circle Surround was an option that made it possible to produce a convincing multichannel sound field from any stereo (two-channel) source.

    Ideally, there should have been a Casablanca II available sometime in the years between the first and second versions. As new ideas took shape and demanded the time to fully implement (and debug them), new technology from outside Theta also had to be accommodated; this also demanded time to incorporate into Theta's circuitry.

    The original Casablanca was complex enough that it was important for the dealer to be deeply involved in the initial setup of a new Casablanca owner's system. Theta began offering factory training on how to optimize the performance of entire audio / video systems using Casablanca's many control features. By the time Casablanca II was ready, it was clearly not something the average consumer could be expected to know how to set up for optimal performance. Theta announced to dealers and distributors worldwide that each dealer and distributor would be required by Theta to have their key technical staff members attend training seminars offered at the factory, at trade shows, or in classes Theta held in Europe for those not traveling to the US. Despite a flurry of exasperated calls from both domestic dealers and overseas distributors, Theta flatly refused to ship a Casablanca II to any location not thoroughly factory-trained.

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    Volume Control

    Casablanca I's volume control was performed 100% in the analog domain! Digital volume control is simple to implement, but at a cost. It works by throwing away information; "bits" of resolution, which shape the sound. Losing this information means that the quality of sound deteriorates; as you lower the volume level, the quality of sound becomes worse and worse. Casablanca I kept all the resolution there was, even when one turned the sound down to a whisper.

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    Circle Surround

    Circle Surround provided realistic surround environments from two-channel music recordings. Accurate surround sound signals based on the stereo information in the recording provided a musical experience with sonic integrity, which allowed you to believe in what you were hearing. Circle Surround also created a believable front soundstage, apportioning the stereo signal more comfortably across your three front channel speakers. This made your Home cinema system music-friendly in a way that it otherwise would not have been. Circle Surround was clearly the preferred mode for music listening.

    Casablanca I was able to offer the fullest realization of Circle Surround's potential. Most other implementations of Circle Surround were done in the analog domain. Casablanca's implementation was fully digital, and was incorporated into the digital signal processing, which kept errors and noise from creeping in.

    There were three Circle Surround modes in Casablanca: Encoded, Non-Encoded, and Cinema. Encoded was for use with material encoded with the Circle Surround 5.2.5 process.

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    Center Power Redistribution

    Think about how movies are mixed, with all the dialogue and most of the important stuff steered toward the center speakers. Sure, that makes lots of sense in a theater, because most people are sitting well off center axis. It is usually it doesn't make a qualitative difference in the sound because theater PA systems are designed for exactly this kind of mix.

    Now visualize the home theater system with some rinky-dink center channel, perhaps hidden away behind the screen or lurking in some credenza. That's the dialogue speaker. It is delivering all this dialogue, intermingled with anything else that the movie's sound-mixer thought should image front and center. The poorest sounding speaker in a home system is given the most critical tasks! What CPR did was get the stereo speakers involved. This made all kinds of sense from the perspective of power distribution (think of the power handling capability of those poor little center channels), so it opened up the dynamic range, and greatly enhanced the overall sound quality.

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    Computer Assisted Setup - Theta Logic Enabled (CASTLE)

    Introduced in 2000, this tool greatly assisted set-up of Casa Nova. CASTLE was a Windows '98 based setup program for the Casa Nova. CRYSTAL was the new program for Casablanca II, which was related to CASTLE, but offered comprehensive programming to assist in all aspects of Casablanca II's more extensive setup.

    This user-friendly software came on a CD ROM (or on floppy discs), which you used on your PC. Casa Nova's optional RS-232 port connected to your computer; you used the software to choose your system setup, and it relayed instructions to your Casa Nova.

    You then saved personalized "default" settings in your computer, as a backup. With your programming instructions safely stored away, you didn't have to worry about experimenting with new settings. You could save and then reinstall any number of complete setups.

    CASTLE made it fast and simple for you to experiment with different setups, to make your Casa Nova easier for you and your whole family to use. You could also experiment with different crossover settings to improve the sound of your whole system. You could do all this knowing that it was easy to get back to your original settings whenever you wanted to.

    Your dealer may have offered to store your default system setup in his computer. This could have been valuable if the need arose to diagnose your system's behavior, or to restore your original (installation) settings. This could have turned a potential house-call into a phone call!

    CASTLE software was very easy to use. All changes were in real time, so you could monitor the programming as it took place. For instance, there was a layout of all speaker crossover choices, which made the choosing process intuitively logical.

    You could enter audio and video jack names and input select button names for both LCD and On Screen Display by simply typing them in.

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    Casablanca II Capabilities

    One key "feature" of the Casablanca II was BETTER SOUND. Sonic excellence resulted from a myriad of interrelated factors; improvements in sound resulted from overall improvements of many different kinds:

    1. Digital Input Cards: 6 coax RCA, 3 TosLink, 1 AES / EBU, 1 coax BNC; 2 digital coax RCA digital tape outputs.
    2. Analog input board (6 stereo analog inputs, 2 stereo analog tape outputs).2 RF inputs for Dolby Digital laser disc.
    3. 96 kHz/ 24 bit capability in all twelve channels (depending upon DAC choices). Circle Surround, Dolby Pro Logic, Matrix, Special Matrix, Stereo, Mono modes all capable of 96 kHz/ 24bit.
    4. RS-232 control
    5. Ability to download new software: DSP software and control system software was downloaded as a file from the Theta Digital web site to a PC (not available for Macintosh computers), then sent to the Casablanca II.
    6. Twelve channel capability (1. Front Left / 2. Front Center / 3. Front Right / 4. Surround Left / 5. Surround Right / 6. Side Left / 7. Side Right / 8. Front Left Sub / 9. Front Right Sub / 10. Surround Left Sub / 11. Surround Right Sub / 12. Front Center Sub or Surround Center)
    7. Surround Center capable.
    8. Full speaker configuration for each input (helped optimize the system for two-channel playback on one input, home theater on another).
    9. 3 different types of crossovers selectable for each speaker set (speaker set = left / right, center, surround, Theta Center Surround™ Types of crossovers = phase perfect, Butterworth, Linkwitz-Riley.
    10. 6 crossover frequencies and four slope options were available for each speaker set.
    11. Capable of 5 subwoofers (left / right / center / left surround / right surround).
    12. Two options for a two-subwoofer setup: left / right or front / rear.
    13. Hi frequency equalization in all channels.
    14. Jitter Jail, digitally stored audio samples in a buffer, and then clocked them to the DACs using a high-quality crystal oscillator section. (You could have spent nearly $2,000 for a similar circuit in a standalone box!)
    15. Side channels, with separately adjustable levels and delays.
    16. Could optimize level and delay settings for Dolby Digital; DTS; and Circle Surround - each process had separate controls for speaker levels and delays.
    17. Dolby Digital®
    18. DTS®
    19. Ability to apply matrix, special matrix, Circle Surround (optional) to stereo (two channel) Dolby Digital sources.
    20. Discrete IR command brought Casablanca II in and out of standby.
    21. Serial number was programmed into the unit at the factory, accessible when the unit booted up via the LCD.
    22. Maximum Level Limiter: governor was set and released by owner to protect system from being overdriven by zealous or experimenting friends and loved ones.
    23. Casablanca II owners could password-protect the unit's settings.
    24. Highly readable blue vacuum fluorescent display.
    25. Inputs could be given any name you chose.
    26. Customizable Un-mute trigger. You selected the response of the Un-mute function: Did pressing the volume Un-mute the unit if muted? Or only by pressing mute again?
    27. Stand-by Release offered customizable level. You selected the volume level at which the Casablanca came out of standby. You chose either a pre-defined level, which you programmed in, or set it to resume at the same volume level at which it was put into standby.
    28. Overall delay (applied to all channels), by input, to match video delay through a video processor (up to 110mSec.).
    29. Party mode (sent sum of all channels to all speakers, with dominance of speaker's main source).
    30. Stereo front / rear mode
    31. Complete cabling / setup freedom - any jack could be routed to any and every input select button
    32. Four 12v trigger jacks with variable timing; pulse or DC, variable pulse length.

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    Casablanca II Options

    1. The Casablanca II could have from 2 to 12 channels: you chose among these three 3 types of DAC's for your configuration – (a) 3 channel superior DAC (balanced and single ended), could handle 96 KHz source. (b) 3 channel standard DAC (balanced and single ended), muted on 96 KHz source. (c) 6 channel standard DAC (single ended only); muted on 96 KHz source.
    2. Broadcast quality video switching: 6 composite, 4 s-video inputs, 1 composite tape out, 1 composite main out, 1 s-video tape out, 1 s-video main out.
    3. Broadcast quality video switching: 8 s-video inputs, 2 s-video tape out, 2 s-video main out.
    4. Rack mount.
    5. Anodized aluminum cover (vibration resistant, heat dissipating, and an aesthetic match for the brushed aluminum front panel).
    6. Tape DAC, for recording or sending to a second zone one digital source while listening to another.
    7. PC control software, for saving the full CBII setup to your PC and for fully controlling / setting up the unit from a PC (This option was not available for use with Macintosh computers)
    8. 6 or 12 channel digital output card, 96 KHz capable, with or without center channel Superior DAC (also 96 KHz capable). (Yes, you could hook up 6 Generation V 96 KHz and have all twelve channels be 96 KHz compatible.)

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    HDCD

    The Pacific Microsonics HDCD chip could be used to convert regular CDs as well as HDCD encoded discs. In comparison with most other ready-made, preprogrammed digital filter chips it was a definite improvement. This was because most of the other available off-the-shelf digital conversion programs were simply inadequate, by audiophile standards, to do anything but a rudimentary, unsatisfactory job.

    The HDCD chip actually encompassed two filters, one for HDCD and a normal conversion filter for all non-HDCD discs.

    When comparing most CD converters' and players' digital filters head-to-head with the normal filter in the HDCD chip, the Pacific Microsonics chip sounded better, as a lot of care went into its programming.

    With that perspective in mind, we conducted extensive listening tests to find out how the HDCD chip compared with Theta's digital conversion section. Our listening staff included Theta employees and a number of "educated listeners" we had come to trust for insightful, accurate feedback on sound quality.

    On HDCD encoded discs, nearly all listeners preferred the sound of the HDCD conversion chip. However, there was a general consensus among listeners that Theta's digital filter was much better on all other discs.

    Theta's engineers put years into the development of a very complex digital decoding algorithm, which required the powerful computing section supplied in Theta's processors, to do much more complete, detailed, correct digital decoding than ordinary CD processors could. Perfect in phase, frequency and time, Theta offered performance literally an order of magnitude beyond the power of all but a tiny handful of extremely expensive processors.

    The advantages Theta offered were in all areas of sound that affect music reproduction: subtleties of tone, temporal nuances that translated into superb depth and solidity of image, fine detail resolution, exciting, full bodied bass, clarity, "air", all the cues that added up to a sense of verisimilitude. Theta's powerful digital decoding left no trace of the harshness induced by inadequate converters. Listeners sensed a graceful, inviting effortlessness. Most CD reproduction seemed stressful. Theta listeners found themselves drawn into the music.

    Theta made Generation V and Basic III units available with HDCD as an option. Also, we offered HDCD modules as a retrofit for those models, as well as the Generation III, for those who already had them. The HDCD module were available as an option for those upgrading from a Basic II to Basic III. Non-HDCD encoded discs were played through Theta's digital section.

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    Power Amplifiers

    Theta had always concentrated on doing digital signal processing, pressing the boundaries to derive the finest analog music signals possible, and left it to others to amplify them. Having great respect for the engineers who created some truly wonderful two-channel amplifiers, Theta's engineers concentrated on areas that needed their expertise. It seemed reasonable to assume that those same great designers at those audiophile-oriented companies would take up the challenges of multi-channel sound, and provide what was needed.

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    Not so great expectations

    What actually happened instead seems to have been a lot of compromises and lowered standards. Two kinds of multi-channel amplifiers came into being, both presuming that standards for home theater amplification are not very demanding.

    Many multi-channel amplifiers were available from companies that did not make music-oriented amplifiers. For music, these amplifiers were highly uninspiring, but they were considered acceptable for home theater.

    Some "high-end" companies offered multi-channel amplifiers better than those from companies whose main orientation was home theater. Yet in comparison with their own high-end stereo amplifiers these sounded lackluster and pallid. This could have been a result of cynicism and a desire to capitalize on a market geared to people presumed to be sonically na�ve, or a disdain for home theater as a less exalted form of entertainment than music listening alone. The reasons were mysterious.

    Granted, multi-channel amplifiers were designed to take price into account. It was tempting to reason that there was a natural enmity between quality and quantity. Aware of economies made possible by combining channels on one chassis, Theta's engineers felt there should be BETTER quality per channel in a given price range, in a well-designed multi-channel amplifier.

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    Dreadnaught

    Where was a multi-channel amplifier that took musical performance seriously? Baffled that no one else was meeting this need, Theta set to work in new terrain. A number of radical ideas went into development, notably a foray into the elimination of global negative feedback. This work evolved into the Dreadnaught power amplifier, which began shipping in early 1999. The Dreadnaught was not a compromise. It was not a downgrade of any pre-existing two-channel design. Dreadnaught was conceived and created from the ground up to deliver flexibility and performance; and met needs that simply had not been met before.

    Casablanca's modular, custom configurations were inspirational; Dreadnaught was designed for total flexibility. Dreadnaught owners weren't forced to get everything all at once. They didn't pay extra to start with a stereo amplifier and add channels later. The quality of a Dreadnaught amplifier didn't go down when you added more channels.

    Home Theater amplifiers were generally right at the borderline of offering sufficient power. Speakers starved for power couldn't perform up to their capabilities, and an amplifier that was strained to its limit produces fatiguing distortion. Each Dreadnaught channel was rated at 200 watts into 8 Ohms, 400 into 4, and even more into 2 Ohms. Dreadnaught could be a two-channel amplifier, or loaded with up to five channels, each with enough power to properly do home theater. The Two-Channel Module made it possible for the Dreadnaught to generate up to 10 channels of fully balanced power amplification.

    In September of 2000, Theta introduced a new module that could fit into any of Dreadnaught's five slots, producing two channels, each rated at 100 watts into 8 Ohms. These modules could be combined with single-channel modules, extending the flexibility of the Dreadnaught still further.

    With multichannel formats exceeding the conventional 5.1 channels, a typical configuration in a Home Theater environment might have consisted of three single-channel and two two-channel modules. The single channels drove the front left, right, and center channels and the two-channel modules powered the left / right surrounds and left / right side channels, resulting in a seven-channel setup, not counting subwoofers.

    The stereo module extended the application opportunities of the Dreadnaught for multi-room use, providing audiophile-grade audio for whole house sound systems. Where it might have been cost or installation prohibitive to have a Dreadnaught power a separate whole house system, the new two-channel module could effectively drive a whole house system and a 5.1 Home Theater without draining or compromising the Dreadnaught capabilities.

    Each Dreadnaught module had single-ended and balanced inputs for each channel, along with buss selection for stereo or surround modes. Dreadnaught modules produced a fully balanced output with either a balanced (XLR type) input or a single-ended (RCA type) input.

    Dreadnaught's power supply acted as a power reservoir. Its massive 2.2 KVA power transformer was common to all channels. Any single channel confronted with a full-level signal had the entire current capability of the transformer at its disposal.

    In fact, in single-channel power tests, the power transformer did not limit the output power. Unless all modules were driven to full power, which never occurred in real-world situations, the channels not being driven hard effectively lent their portion of the transformer's power to the active channels. This was true for all Dreadnaught modules.

    One of Dreadnaught's features was a button that selected channels that had been assigned to stereo or surround busses via a switch on each module.

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    Dual Differential True Balanced Design

    Signals coming in are balanced at the input to the very first gain stage. What did that mean? In essence, each amplifier module was really two mirror imaged signal paths for each channel. The signal was cloned, and the phase-inverted duplicate sent through a path identical and proximate to its twin. Then, at the amp's output, the two signals were reconciled. Anything not a perfectly "mirror imaged" between the two signals was discarded (called "common mode rejection"). Those discontinuities were noise picked up in the course of amplification. Eliminating noise* this way preserved the integrity of the amplified signal nearly perfectly.

    This no-compromise technique was rarely used, however, because it required almost twice as many devices as conventional, single-track amplification. Most companies just didn't do this rigorous a job. We wouldn't have invested this much in high quality components either, if we could have figured out any easier way of getting such pristine results. Other means of dealing with noise were crude in comparison, "dirty" in that they left artifacts in the signal; phase anomalies (which impacted spatial cues) and intermodulation distortion (which made timbres sound wrong, and otherwise cluttered the sound). (And no, these parameters were NOT quantified in measurements on the "spec sheets" you typically see.)

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    Zero Feedback Design

    Dreadnaught used no global negative feedback. What is feedback? Like a snake biting its tail, a negative feedback loop sends some of its output signal back to its input. To cancel out the errors that have crept in during the amplification process, a compensation signal was applied at the input. Obviously, this correction could not actually take place instantaneously.

    Small amounts of feedback, within a single gain stage (called "local"), helped ensure circuit stability and kept the circuit's processes on track. Delay was miniscule in local feedback. Nearly all analog circuits relied on this kind of benign feedback.

    However, when applied to an entire amplification chain, often comprising several gain stages, time delay became a significant problem. The "envelope" was too big, resulting in serious phase shift and intermodulation of the signal with its own error products. This fantastic complex of distortions went unmeasured (in all the usual specifications), and was not correctable. Dreadnaught used none of this kind of "global" feedback!

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    Intrepid

    Intrepid Power Amplifier, a five-channel, 100 Watt per Channel Amp, was introduced in October 2000. Delivering a powerful 100-watts / channel into an 8-ohm load, each of the Intrepid's channels had single-ended and balanced inputs. Building on the foundations of the knowledge gained in producing the Dreadnaught, Theta engineers produced a less powerful amplifier of similarly high quality. The Intrepid Power Amplifier was a solid state, fully balanced power amplifier with five built-in channels. The nominal power rating into 8 Ohms with one or all five channels driven was 100 Watts per channel, and 200 Watts into 4 Ohms. Each channel had single-ended and balanced inputs, and a high-current, dual binding post output connector. Like the Dreadnaught I, Intrepid produced a fully balanced output with either a balanced (XLR type) input or a single-ended (RCA type) input. Like the Dreadnaught, the Intrepid used no global negative feedback. Though it was less powerful than Dreadnaught, its actual performance was superior to what its power rating would suggest, because of its tremendous dynamic headroom. Similarly rated home theater amplifiers were grossly underpowered for serious music and home theater performance. Intrepid's muscular power supply was fully capable of delivering 100 watts into 8 Ohms, 200 watts into 4 Ohms and even more into 2 Ohms. The dynamic headroom of the Intrepid allowed it to deliver even greater power than these steady state ratings. The power transformer and output stage bridge rectifier were common to all channels in the Intrepid. This was the same "Power Reservoir" topology used by Dreadnaught. There was considerable debate on the subject of power transformers in multi-channel amplifiers. Some manufacturers provided a transformer for each channel; others divided the amplifier into one two-channel section with its own transformer and another three-channel section with its own transformer. Intrepid used a single massive 1100 VA power transformer and a 35 Amp bridge rectifier for all five channels. The inherent benefit of this approach was that any single channel confronted with a full-level signal would have the entire current capability of the transformer at its disposal.

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    Citadel

    The Citadel was a monaural power amplifier. It was as great an amplifier as Theta's engineers, building on the knowledge gained in the design and refinement of the Dreadnaught, knew how to make. Citadel embodied a level of performance Theta could produce when the design team was not much constrained by concerns of cost, although it was also true that nothing spent on the Citadel was frivolous. Citadel was built to stand up to the most demanding systems. More than an iron fist, Citadel was made for delivering exquisitely revealing two-channel music reproduction. And Citadel was the best choice for powering home theater systems, as it packed the massive power to recreate even the most spectacular, floor-shaking, chandelier-rattling soundtracks. The heart of the Citadel was fully-balanced differential, zero-feedback circuitry. Component parts in every stage were selected for optimum performance, and for performance of the amplifier as a whole. Custom-made capacitors, Vishay precision resistors, copper buss bars, Litz / Teflon wires, and a custom-made output connector contributed to the performance. Citadel's power supply was an exercise in brute power and complete control. The output stage had a high-current Kilowatt power transformer, which fed a unique dual-choke and capacitive filtering system. This technique was rarely applied because of the huge choke size necessary to avoid impeding high current demands. Citadel's filtering system employed two massive chokes almost as large as the power transformer. These were fed from an ultra-fast / soft-recovery 35 Amp full bridge rectifier, which was then filtered by two capacitive banks totaling 80,000uF. The synergistic effect of this filtering system resulted in high-current power supply lines that were more than 8000% cleaner than conventional supplies. The sonic result of these super clean supply lines to the output transistors had not previously been achieved at high power levels. The mechanical housing for Citadel was no less specialized than its internal components. More than an aesthetic statement, its seamless housing, free of traditional fasteners on top, front, and sides, provided a strong and stable environment for the operation of the amplifier. The power supply resided in its base, isolated from the amplifier module above. Nominal power rating for the Citadel was 400 Watts into 8 Ohms.

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    Notes

    Although many highly regarded amplifiers provide XLR input connectors to receive balanced signals, the mere presence of "balanced inputs" is no guarantee that any balanced circuitry is present in the amplifier itself.

    Full balanced differential circuits are rarely used in amplification. This no-compromise technique requires almost twice as many devices as conventional, single-track amplification. Most companies just don't do this rigorous a job. We wouldn't invest this much in high quality components either, if we could figure out any easier way of getting such pristine results.

    Theta's goal is to create very sonically accurate components. Measurements typically published as "specifications" do not reflect some of the most important aspects of sonic performance. It is quite possible to design circuits that measure well but sound bad. In fact, it's done all the time.

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    Jitter

    From the very beginning of the research project that led to Theta being created, the engineering team was aware that Jitter is one of the major factors in the degradation of digital signals.

    As data streams make their way through circuits, connections and components, they have a tendency to become temporally misaligned. This is an inherent vulnerability. The errors tend to be cumulative, and as the misalignment worsens, it can become impossible to correct.

    These timing errors, which we call jitter, translate into harmonic distortions to the music. Once incorporated into a musical signal, these errors are inextricably part of what you hear, and since they are mathematical artifacts unrelated to music, the sound can be quite stressful to endure. Even when jitter is reasonably low, rather than providing you with a headache, these residual errors can cloud the music and dirty up the sound.

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    Maintaining Signal Integrity

    Theta used many methods to minimize jitter at points where the signal was particularly vulnerable. All digital signals were reclocked as they came in to any of Theta's D to A converters. Theta dealt in other ways with jitter problems originating in transports. Maintaining signal integrity all along the digital chain was the goal.

    "Jitter Jail" technology, introduced in 1998, was a revolutionary new tool developed as an even more effective technology than reclocking the signal "on the fly." A custom-manufactured low-jitter crystal oscillator at its heart, Jitter Jail acted as a buffer, actually storing the digital signal long enough to reclock it much more perfectly than we could do as it was streaming by.

    First incorporated in Theta's Jade CD transport, the circuit's master clock realigned data, correcting raw data as it came from the disc.

    This high-precision buffer became your source, rather than the CD, which had jitter problems of its own. CDs were not physically perfect and the recording and editing leading up to the CD had its own accumulated jitter. The pits were unevenly aligned, there were deformities in the material of the substrate, and the clear plastic was not perfectly clear. By reclocking the data from your CDs you could actually recreate a truer representation of the music, as it was created, than the raw data coming direct from the CD.

    The Jade transport was the first Theta product to take advantage of this kind of digital buffering, but succeeding processors and transports all made use of this technology.

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