NEW TD 3.1 & TD 3.0
Digital Analog Converter
"I am going to keep this awesome [TD 3.0] DAC. . . . I traded in a $6000 CD Player, have better sound, and have money left for a lot of CD's."
TD 3.0 Digital Analog Converter

NEW Audio Horizons 32/192 Upsampling TD 3.1 DAC
Many people believe that the newer, more expensive CD Players possess Digital Analog Converters so good it makes no sense to buy a separate DAC. Some audiophiles fail to realize that CDP’s with integrated DAC’s tend to skimp on the digital output section of their CDP since it is rarely used. Not aware of this fact, and not realizing that the inferior digital output transformer on their CDP is compromising the signal out to the external DAC and thus robbing the DAC of its ability to perform to its full potential, they end up disappointed in the sonic benefits derived from trying out an external DAC with their CDP.

To maximize the benefit of an external DAC, and to gain the many more analog-sounding benefits that a really first rate DAC can provide, one needs to upgrade the digital output transformers on the CDP. So important is this upgrade in maximizing a DAC’s potential performance that Joseph Chow offers this $200 upgrade free to all Audio Horizons DAC purchasers.

This problem of inferior digital output transformers exists less frequently with expensive, first rate transports, though even there we have found that many transports can benefit from this upgrade. Concern, therefore, with the quality of the transport’s digital output section becomes critical when auditioning a really superb DAC such as the new Audio Horizons TD 3.1 Tube DAC. This DAC is a striking improvement over Audio Horizons’ previous superb DAC, the justly praised TD 3.0. The TD 3.1 not only sounds far, far better and much closer to smooth analog sound than the TD 3.0, its specifications are far better.

Let’s briefly compare the specs of this new TD 3.1 priced at $3050 and the old top of the line TD 3.0n priced at $2650.

TD 3.0n DAC TD 3.1 DAC
Freq Response: 4-20kHz +/-1 dB 4-48kHz +/- 1 dB
THD: 0.01 % @ 1kHz -20dbFs 0.004% @ 1kHz 0dBFs
Dynamic Range: 100 dB 105 dB or better
Signal to Noise Ratio: 105 dB weighted 108 dB weighted
Channel Separation: 105 dB 120 dB
Output Impedance: 280 ohms 280 ohms
Resolution: 24 bits 32 bits
Max fs: 96 kHz
192 kHz
Power consumption: 30 Watts 35 Watts

Not only transports can benefit from a superb DAC, so can various other music reproduction systems, like the Squeezebox and Sonus.

Of course, specs are not the whole story. By virtue of its higher bit resolution, lower distortion and superior dynamic range, the TD 3.1 comes far closer to defeating the digital edge and unduly crisp attacks that define digital sound, and achieves reproduction with smooth, soft edges and clear but soft musical attacks that characterize analog reproduction. And it does all this without rolling off the top end or lowering overall transparency. You have to hear the improvement to believe it.

In addition to the new DAC chip and improved specs, the cosmetics of the TD 3.0 have been totally redesigned, giving it a new, handsome slim line look.

Though the TD 3.0 can’t hold a candle sonically to the TD 3.1, below are some words of praise for the TD. 3.0 as a reference. You will just have to take my word for it that the TD 3.1 is far, far superior in its performance to the TD 3.0.

And for those who want the ultimate in Digital Analog Conversion, we offer two upgrade versions of the TD 3.1—the TD 3.1cv, which upgrades the caps to Clarity MR caps, upgrades resistors in the signal path to Vishay premium resistors, and performs a harmonic alignment on the TD 3.1. It is priced at $3695. Our top of the line DAC is the TD 3.1cvt. It adds a bank of chokes for improved micro-detail retrieval, better imagining and a more realistic soundstage. It costs $3995.

Words of Praise for Audio Horizons Tube DAC

Jaymark begins:

"I got a chance to do some listening while I was off for the holidays. I absolutely love what I hear. The Audio Horizons TP 2.0 and Audio Horizons TD 3.0 are very musical. . . . The Audio Horizons tube DAC, fed by a decent transport, gives a refined, spacious, liquid presentation of recorded digital music. Your ears get the collection of tonal and spatial cues that leaves you within striking distance of a live performance. The Audio Horizons tube DAC is a giant killer!

“Why don't you actually put up one of the 3.0 DACs and 2.0 pre-amps for sale, with pictures, Audiogon? This equipment is very high quality and sounds better than a lot of the highly regarded stuff for sale - and in this price range, it is going to be awfully hard to beat.”

Cedar writes:

“I just returned from Las Vegas where I attended the 2006 CES and T.H.E. Show. This visit only confirmed my opinion about the excellence of the Audio Horizons TD 3.0 tube DAC and the TP 2.0 tube preamplifier. The performance/price ratio is the best I have heard anywhere. I hope Joseph will bring these products to the Rocky Mountain Audio Fest next year so that more audiophiles can hear them.

“I first became acquainted with the tube preamplifier in its production prototype form. Even as a prototype, it left my VTL 5.5 preamp in the dust. Soundstage, resolution, dynamics and musicality of the TP 2.0 prototype were much better than the VTL 5.5, which I sold subsequently. The production model is even better. Joseph continued to improve parts and layout. Just to give you a sense of the performance - the production unit [TP 2.0nB] I've used measures better than -115 dBv signal to noise in both channels.

“My conclusion about the TP 3.0 tube DAC is the same - an unbeatable combination of performance and price. Initially, I switched to the Audio Horizons solid state DAC, after using various solid state DACs from other manufacturers. At $1295, the Audio Horizons DAC 2a was more musical, dynamic and quieter than other DACs in its class. The TD 3.0, however, is in a class of its own. Dead quiet, musically involving. I strongly recommend using the upgraded components and tubes that Joseph offers. At less than $2500, my TP 3.0 competes with any DAC.”

Gamecock has ordered special mods on his TD 3.0 so he has not yet received it, but listen to what he says about the companion TP 2.0 preamplifier. He was so impressed with the TP 2.0 he sold his $16,500 First Sound Paramount SE:

"Two things were immediately apparent. The 2.0 is much, much quieter than the First Sound, and it also has more apparent gain, which is a good thing in my system. I should also mention the 2.0's superior channel separation. The 2.0 is quite impressive 'right out of the box'.

"Another characteristic of Joseph's preamp became evident. That is, there is a startling clarity of the musical presentation. I found myself paying less and less attention to ascertaining the 'sonic characteristics' of the 2.0, as I was totally immersed in the simple joy of listening. Perhaps this is the highest praise I can give at this point.

"Two quick words, and then I simply must return to listening: soundstage and dynamics. Both are stunning! The 2.0 is clearly superior to the First Sound Paramount SE (and the SE currently retails for $16,500, no kidding). In my opinion, this is a monumental achievement for Joseph. We have got to spread the word about his craftsmanship."

We use Audiogon names of the owners to establish that these are actual quotes from actual owners.

Free Home Audition

We are so persuaded of the superb performance and superior value of the NEW Audio Horizons TD 3.1 that we want you to listen to it in your own home over your own sound system. We therefore offer everyone who qualifies a free home audition. We’ll even pay the freight to you. If you are not persuaded that this is a stunning preamplifier and one you want to keep, return it within ten days. That’s it. Or if you’d like more time to evaluate it, buy it under our money back guarantee program and take 30 days to make up your mind.

To qualify for a free audition, you must:

      1. Have an Audiogon Positive score of 30 or better and no Negatives

      2. You must have a transport of sufficient quality to audition the TD 3.1 properly.

To learn more about what makes the TD 3.1 such a superb performing DAC, read on.

Tubes versus Solid State
One of the oldest debates in high end audio is between the proponents of tube equipment and those committed to solid state designs.  There are arguments to support each position.

Solid state equipment is hassle-free—there's no need to replace tubes at periodic intervals; warm up time until reasonable performance is briefer than it is for tubes; and the component can be left on for long periods of time (and oddly, this will improve performance) without exhausting the finite life expectancy of tubes.  More significant in terms of performance, solid state equipment has better S/N figures than can usually be achieved by tube equipment, in part because of the inherent residual noise level of tubes.  Solid state equipment produces crisper edges, and thus sharper transients, because solid state IC's and transistors have a faster decay time than tubes.  Finally, far lower Harmonic Distortion figures can be reached with solid state equipment than can be reached by tube equipment, again in part because of the residual higher distortion levels of tubes.  There are other areas, such as Dynamic Range   where solid state equipment again usually excels over tube equipment, but the first three produce the greatest challenge for tube designers.

At first glance, this is an impressive list of advantages, whose sonic effects would weigh in favor of solid state designs.  But there are certain advantages that tube designs have over solid state designs that make the choice more complex.   

Tubes produce a rounder, fuller sound than do solid state components.  For many this adds a pleasing warmth and body to the music not easily achievable with solid state equipment.  In addition, tubes are better able to capture those higher order harmonics that distinguish the reedy quality of an oboe from that of a clarinet, the resinous quality of a string bass from that of a drum bass, and the sound of a soprano's breathy vocal chords better than solid state equipment.  For tube aficionados, this too is a big plus.  Finally, tubes, because of their inherently slower decay times, are better able to capture the musical rise and fall and ebb and flow of live music, which does not turn on and off the way solid state component parts do but instead flows imperceptibly from one rising or falling phrase into another. For many listeners, this slower decay time of tubes enhances the listener's experience of the music—that is, the music sounds more musical and involving when played over tube equipment.

Must one choose between these two opposing excellences?  The answer is no.  If the designer is insightful and creative enough, he can minimize the shortcomings of tube equipment while still preserving their excellences.  In effect, he can narrow and almost eliminate the advantages unique to solid state equipment. 

Since Signal-to-Noise is among the two or three most critical parameters of sonic excellence—one can't hear any micro-detail below the noise floor--a tube designer must first attempt to bridge the gap between solid state designs and tube designs in this critical area.  Many tube designers achieve this narrowing by elaborate feedback circuits.  While the use of feedback does lower the noise floor, the elaborate circuits required to do so complicate the signal path and thus introduce signal compression.  Thus while they gain in reducing S/N, they lose in sonic openness and transparency.  Joseph Chow avoids feedback entirely. But by virtue of his deep insight into materials and circuits he is able with his tube designs to achieve S/N levels that would do many solid state designers proud.  For example the S/N for the Audio Horizons TD 3.1 is an incredible -108dBv.

These are superb for a tube DAC when one realizes that a well known tube DAC with separate power supply costing over $12,000 boast the same -108 dBv S/N figure. Frequently, the S/N levels are reported using higher than 1 volt output ratings (usually signaled by the abbreviation dBv), say 2 volts or 3 volts, but the S/N at 3 volts, for example, will be about -10 dB better than at 1 volt. Thus by using 3 volts output, the manufacturer is able to use a -10 dB lower S/N figure than he would if he used the generally agreed upon 1 volt standard. Some manufacturers call this marketing. In addition, sometimes the S/N figures on tube equipment are so poor they are not indicated in the website spec sheet.

By virtue of avoiding feedback and using a philosophy of classic design, Joseph is able to achieve the clear edges and fine transients characteristic of solid state designs.  And by designing balanced geometry interconnects with carefully designed capacitance, whether using RCA or XLR jacks, Joseph  is able to create tube designs that have clean but soft edges, that in a word, preserve all the excellences of tube design while achieving those common to solid state designs.

Finally, while Joseph can not overcome the residual higher distortion common to tubes, at 0.01% THD @ -20dBFs he has achieved superb specs, where only the most rarified ear can hear the difference.  The same is true for his specs for Dynamic Range (better than 100 dB) and crosstalk or channel separation (95 dB @ 20-20kHz).  These are outstanding specs for a tube component and approach or exceed the specs of excellent high end solid state designs.

In essence, Joseph has created a tube DAC that weds the virtues of solid state design to those of tube design to create a  superbly trans parent sounding DAC.     

TD 3.1 Design Features

The TD 3.1 includes the following design features in its power supply:
  • A premium low noise power supply transformer. 
  • An adequate power supply that uses a 10 times larger VA than needed in order to insure a stable soundstage.  
  • R core transformers, for digital and EI core for tube buffer section, one for the filament and the other for high voltage analog power supplies.
  • Three stages of regulation in the digital supply interface to reduce interference between the digital and analog sections and crosstalk, and achieve quieter digital noise levels by lowering the impedance and providing better isolation.

Many high end DAC’s, often priced far higher than the TD 3.1 lack more than one of these power supply features, with all the attendant sonic shortcomings that follow from an inferior power supply section.

Amplification and Analog Sections: It is here that creative engineering design plays its greatest role and contributes greatly to whether a DAC fully realizes the potential inherent in a superb DAC chip.  By examining the long list of design features in the TD 3.1 one can understand better the ingenious means Joseph Chow has used to exploit the already excellent qualities of the DAC chip used:
  • Burr-Brown Op Amps, specifically the highly acclaimed OPA 627.
  • Direct coupling used to bridge the digital and analog section.
  • Blackgate coupling capacitors are used to bridge the digital and analog section.
  • The use of a low ESR capacitor bank, with an extremely high 8,800 uf of storage in the analog section, to provide extra reserves when sudden sonic demands are made on the DAC.
  • In addition, the use of a push-pull analog section increases the system's dynamic range and responsiveness, thereby producing a punchier sound.
  • The absence of a built-in clock circuit reduces digital jitter and lowers the noise floor to produce a very quiet DAC even by DAC standards with extremely high signal-to-noise.
  • The circuit design reduces jitter to a minimum by using the shortest digital signal path possible.
  • The low output impedance design permits the use of long interconnects with minimal sonic degradation.
  • All inner wiring uses Teflon silver coated wiring to provide optimum performance for many years, and to protect those who live in environments with high humidity. 
  • The tube buffer stage and push-pull topology employed create designs that better capture upper level harmonics.
  • Uses four 6922/6DJ8/ECC88 tubes, which are the most common triode design and therefore easy to upgrade to premium low noise gold pin tubes.
  • A capacitor bank comprising 12,000uf on the DC filament.
  • Independent channels each with a pure DC filament supply to reduce crosstalk between channels.
  • Thirteen stages of regulation on high voltage provide better ripple regulation, which results in quieter noise levels.
  • The use of a low ESR capacitor bank, with an extremely high 2,860 uf of storage in the HV section, to provide extra reserves when sudden sonic demands are made.
  • 30 second delay after power is turned on to insure low start up noise and pop.
  • RF shielded balance/XLR connectors eliminate contact impedance, insuring the lowest possible noise floor.
  • All gold plated Teflon RCA jacks insure low connector loss and insure high signal transfer.

The Audio Horizons TD 3.1 Digital Analog Converter is a high end tube DAC boasting specifications found only in DAC’s costing many times more. We invite you to compare these confirmed specifications with those published by other manufacturers of high end tube DAC’s. Then we invite you to audition the TD 3.1.

While the extensive list of design features described above indicates some of the features that contribute to the TD 3.1’s superb performance, they do not fully explain it. Too truly understand how Joseph Chow has managed to achieve spectacular performance at a relatively modest cost, we have to spend a moment explaining how Joseph Chow’s classic design philosophy differs from typical audio design philosophy.

Audio Horizons Design
Most of us are aware of the well-known division among audiophile designers between those who prefer solid state designs and those who prefer tube designs, but few are aware of other deep divisions.  The most important of these is between two audio electronic design philosophies--between those who seek to prune away as severely as possible the materials and circuitry used (who, for example, when designing a preamplifier have as their ideal, “a straight line with gain”).

Opposed to these minimalist designers are those who seek to overcome the inherent limitations of the materials used by elaborating circuits and feedback.  These designers seem wed to complex circuitries.  For purposes of this discussion, we will call designs of severe simplicity, the school of simple design.  The second group, which attempts to perfect designs via circuit complexity, we will call the school of exotic design.  Most designers fall somewhere in between, but within the parameters of one or the other of these ruling philosophies.

Joseph Chow has chosen a third way of design, one neither simple nor exotic, but one which seeks instead to look deeply into the circuit function, the materials used in it, and the sonic goals to be achieved.  By analyzing these, especially the inherent sonic characteristics of the materials and components at every stage, Joseph Chow seeks neither to eliminate components, as those in the simple design school do, nor to compensate for them, as those in the exotic design school do.  Instead, we seek to harmonize the inherent characteristics of materials with the circuit design itself.  This search for harmony between the materials used and their function within the overall architecture is what defines and distinguishes Audio Horizon design.  The focus is always on the sound characteristics inherent in the materials themselves and, given their characteristics, to achieve at an affordable price the highest quality sound possible.   

The Audio Horizons designer looks as deeply as possible into the circuit path, and into the sound characteristics of the materials and components used, and he does this at the smallest level possible.  His search for distortion and noise at the minutest circuit and material level begins, first, with a desire to eliminate all spurious noise and, second, with a respect for the importance of Q [defined as the “quality factor of an inductor or capacitor.  It is the ratio of a component's reactance ... to its effective series resistance” Dictionary of Electronics].”  

We seek to lower noise because only by lowering noise are the sonic characteristics of individual components revealed.   No designer, no matter how fine his ear, can improve a design below the noise level, for at that level he cannot hear the difference between one component make or value and another, one circuit modification and another.  Low noise permits the designer to hear more clearly the very fine sonic differences small component changes and slight circuit modifications make.

Typical of Audio Horizon's attention to the smallest detail, the designer has specified that the input jacks be Teflon insulated because the Teflon reduces signal loss, and because it has a high Q.

In addition to a focus on high Q, Audio Horizons' classic design leads it to eliminate all spurious, little used features, ones that may add glamorous complexity and the appearance of quality to the product, but yield no sonic improvement and in fact present design problems of their own.  This is in keeping with Audio Horizons' desire to keep distortion, the noise level, and costs as low as possible at every stage.  Thus, as part of his desire for a classic line, at every stage the Audio Horizons designer seeks to keep the signal as clean as possible with the minimum number of parts.  If three parts, however, will yield a cleaner signal than one part, without altering or degrading the signal, then three parts is both theoretically and sonically the minimum number of parts required. 

Concern with a clean signal begins as soon as the power enters the circuit system, which is why the TD 3.1 has a filter in the line immediately after the AC power input, and has separate power supplies for digital and analog functions.  Throughout the circuit, noise and distortion are reduced by providing clean, high Q signal paths that make the signal timing more accurate and lifelike.

But that's enough about design theory and about why the TD 3.1 specifications and performance are so outstanding.  The proof of the pudding, as they say, is in the tasting.  Listen to the TD 3.1.   When you listen, the first thing that strikes you is how the sound emerges from out of the very blackest silence. Then you are struck by the harmonics, by how well you can hear the reedy overtones of a clarinet and the resinous string quality of a cello.  Soon you realize there are no hard edges, that the spurious warm edges lent to music by distortion are gone.  Little by little, you begin to realize how wide the soundstage is, how sharp the imaging, how airy the high end is and how rich and tight the bass is.  And on and on your appreciation for this marvelous instrument and this brilliant designer grows. But don't take our word for it.  Listen to it with your own ears.  Better yet, listen to it over your own system. You will clearly recognize its superior performance. 

The TD 3.1 comes in three configurations: The TD 3.1, the TD 3.1cv which boasts added noise suppression, upgraded Clarity MR capacitors and premium Vishay resistors for an even sweeter and smoother response, and the TD 3.1cvt, which raises the performance to even greater heights by adding a bank of four coils before the outputs.

Frequency Response: 10 Hz to 48kHz    +/-1 dB
Total Harmonic Distortion (THD):  0.004 % @ 0dBFs
Dynamic Range: 105 dB
Signal to Noise Ratio: 108 dB
Channel Separation: 120 dB
Output Impedance: 280 ohms
Resolution: 32 bits
Max fs: 192 kHz
Output Voltage: 1.75 Volts (single-ended)
 Approximately 2.5 Volts (balanced)

AC Voltage:

1.75 Volts (single-ended)
 Approximately 2.5 Volts (balanced)

AC Frequency:  50/60 Hz.
AC Power cord: None supplied (20% discount on Audio Horizons AC Power Cord)
Power Consumption: 25 Watts
Input Complement: 1 RCA-type female connector
1 XLR-type  female connector
Output Complement: 1 pair RCA-type female connectors
1 pair XLR-type male connectors
Tube Complement: Four 6922 type Tesla E88CC tubes
Outside Dimensions: 17” wide x 15” deep x 4.25” high
Shipping weight:  10 kg. (22 lbs.)