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Positive Feedback ISSUE 49
may/june 2010


audio horizons

TP 2.2 preamplifier

as reviewed by Ryan Coleman







WIlson Watt Puppies 6

Einstein the Tube mk2 linestage. McIntosh MC501 monoblocks.

EMM Labs CDSA (w/ latest transport). Kenwood KT8300 tuner (with beaucoup self-designed mods; btw, I'm known as a heavy tweaker/modder) w/9ft Yagi directional antenna. Slimdevices Squeezebox 3 (with mods to analog output stage and custom power supply, all my own design).

ICs (balanced) by TG Audio, Speaker by Isoclean (Focus), AC by TG Audio & my own design.

Four dedicated lines; three Oyaide R1 outlets; Acoustic Revive RTP-4 AC conditioner for front end; DIY designed passive AC conditioners for amps (using Isoclean AC outlets). Ultrasonic Maple Racks, w/inner tube isolation platform under CD player. 10 tube traps, eight bass panels (all DIY products.


Well, the world didn't end.

Oh sure, back in October 2008 we were told that the global economy was on the verge of a global collapse and, frankly, it was. Libor was spiking, mark-to-market values were rendering banks insolvent, and the commercial paper market was slammed shut; without the dramatic, prompt, and overwhelming response of the federal authorities, I've no doubt we'd be in a depression at the present time. Anyone who says "Abolish the Fed!" clearly does not understand what we went through.

Not that times are good; U6 unemployment (which is a more comprehensive measure than the 9.6% unemployment rate bantered about) still stands north of 16%, equity prices are still down more than 30% from their peaks, and around 25% of homeowners owe more on their homes than the property is worth! Ouch! So, not to be a Negative Nellie, but I'm not expecting any sort of return to the happy-go-lucky credit-fueled living-beyond-my-means spending by the consumer of last resort, Joe Q Public, residence Anywheresville, USA.

So, what does this have to do with audio? Plenty, dear reader, plenty. Audio equipment, much like jewelry and Harleys, is a purely discretionary purchase; if the consumer is feeling poorer, he's far more inclined to cut his budget for cables or electronics than he is to skimp at the grocery store or for his kid's school supplies. Everyone has to prioritize what they spend their money on.

Same thing is true for manufacturers. Sure, there are some 'cost-no-object' products out there which target the Gates' and the Buffetts' of the world, but for those of us who have bills and worries, cost is an object. Manufacturers designing to meet a price point must allocate their cost of materials as best they can to add value to their customers.

All of this bloviating brings me to the subject of this review, the Audio Horizons preamplifier. I've not come across a product that challenges my notion of what one is paying for, and what one is paying extra for. And let me cut to the chase: this may be the best value in all of high-end audio.


Audio Horizons is the baby of Joseph Chow, the design brawn of the operation. The Audio Horizons website goes into extensive detail of Joseph's design philosophy and provides a nice background of the preamplifier, so I'd direct the reader there for further info rather than try to summarize. Audio Horizons also offers other components (a DAC, a phono preamp, cabling, and equipment modification services), but this review will be limited to the TP 2.2.

Let me throw some stones that must be thrown. For those who demand their gear is 'audio jewelry', do not pursue this unit. It is housed in a remarkably thin chassis which vibrates while music is playing (but responds to mass loading very well), has a sad little plastic remote (10 buttons, but only 2 are operational: volume up and down), and is, in my opinion, rather homely. The digital display is fixed, showing the name of the company, just in case you'd forget. The chassis is about as thick as found on a $400 Sony receiver. In a targeting-a-price-point product like this, clearly the manufacturer saved a bundle by going this route. But make no mistake, vainglorious pride of ownership is low; this unit will draw no attention from your friends (while it's off), nor will you lust to press buttons or turn knobs—its appearance just doesn't inspire that kind of behavior.

And let me throw this out there, dear reader: audio is, to some degree, tactile. The designs of products we use, the intricacy of manipulating software (especially analog), the tubes and the finishes on speakers, all this stuff is designed to inspire its use. If you are drawn to equipment of immaculate fit and finish, you can end up paying more, as a bullet-proof anodized chassis costs more. While build quality is functional in high end audio (as vibrations smear and obscure details), it's also a psychological tool designed to generate tactile desire, which leads to two behaviors: purchase, and use. When you plunk down your money, you are always buying more than just a box of wires—it just takes some time to realize what else you're paying for.

While I couldn't have been less impressed with the outside, I couldn't have been more pleased with the inside. The unit has an overbuilt solid-state power supply, and I couldn't have been more shocked to see 3 discrete bridge rectifiers (responsible for turning wall AC into DC to power the circuitry in the unit) made with fast low noise, soft recovery diodes. Bob Crump (RIP, big guy), famous for his work with John Curl in CTC Builders and for Parasound's awesome Halo line, was a pioneer in parts optimization in audio equipment, and he would always say that the most important part to get right was the bridge rectifier (another part bugaboo: filtered IECs). I've seen gear costing $20k that uses $8 crappy off-the-shelf rectifiers which exhibit the typical sonic faults of such a crappy part: glare in the upper midrange. In my years in audio, I must have upgraded bridge rectifiers with my own soldering iron a dozen times, and whenever I've upgraded a bridge rectifier to a fast, soft recovery rectifier, I've reduced glare and improved transparency in the upper midrange. Well, Audio Horizons was smart enough to spend the $$ on the inside rather than the outside. And they spent it in the right areas: the power supply!

Digging through the inside further, it's a bit of a puzzle. The KISS principle of Keep It Simple Stupid is clearly in effect at times; I count about 12 parts per channel of the gain stage, and 2 of those are the 6922 tubes. For the purists out there, the less parts the better---well, this are only 12, and two of them are tubes that you can select to your liking. This sample unit has the upgraded capacitor option, which means the unit is fitted with Clarity Cap MR coupling caps in the gain stage—one coupling cap per channel, and it's a premium quality part. Another surprise was the inclusion of HiFi Tuning Fuses and a Furtech Gold IEC; I've routinely used these parts to help improve the tonal balance of gear I put them in (they sound a bit warmer and have better harmonic depth), but these things are not cheap when compared to run-of-the-mill 95-cent IECs and fuses, so to see them in such a modestly priced unit was a surprise. Moving on, one thing that caught my attention was that I counted a total of four transformers in the signal path if you're going balanced in and out (but zero if you're using RCA inputs and outputs). They're very high quality Jensen transformers (see a trend here? Fewer, but very high quality parts inside). Output transformers are a great way to change a single ended signal to balanced while reducing noise and overcoming any difficulties associated with long cable runs or impedance mismatches with the partnering amplifier.

However, there's no free lunch: output transformers also can reduce transparency and screw up phase relationships; the more junctions and parts a signal has to travel through, the more likely you'll get anomalies in transparency and temporal relationships (manifest as confused staging and sonic fuzziness). In my auditioning, I did hear slight but consistent differences between going single ended and balanced in the TP 2.2: the balanced in and out configuration rendered a sweeter top end, greater extension at the extremes, and a blacker background (likely from the higher Signal / Noise ratio generated via the Jensen transformers), but these benefits seemed to cost the unit some dynamic expression. Was it a big difference? Nah, I've heard a much bigger difference changing the plating on IEC connectors; you likely won't be disappointed running the unit either way. (BTW, adding the balanced input and output transformers is not included in the stock unit; you have to pay for their inclusion, which adds a good chunk of $$ to the overall cost.)

Also, unless you have a phase switch on your source, or your amp reverses phase, you'll need to reverse the leads on your speakers with this preamplifier. The Audio Horizons TP 2.2 reverses phase, so do make arrangements to reverse it again at some point in the signal path.

Listening Impressions

One of the first things I do when I get a preamp in for evaluation is the old tweeter test. Put a CD in and press 'play' and then 'pause' and slowly ride the volume up while your ear is at the tweeter; good equipment has a low noise floor, while lesser equipment has a lot of noise that comes in the higher the volume goes. Well, the Audio Horizons is a standard-setter when it comes to this test. I can literally go all the way to maximum on the volume control and not pick up any noise at my listening seat, with 90db speakers in a small room. Why is this relevant? Well, low level detail in a recording can only be heard above the noise floor of the system; lots of folks pooh-pooh measurements, but when it comes to preamplifiers, one to pay careful attention to is Signal to Noise. As we lower the noise floor, we get more detail, more dynamics, more transparency—more audio goodness. And like I said, the Audio Horizons is in rare territory for a tube preamplifier, with a S/N ratio of > 120dB when run in balanced configuration.

(Note, the aforementioned was using the balanced connections, and the accompanying input / output transformers with their inherent S/N advantages; when running single-ended, the S/N ratio drops 10dB. When testing single-ended, the amount of noise I picked up at my listening seat was just a bit at maximum gain, a level that would never be touched in regular listening. It was so slight that I had to shut my window and turn off the fan to hear it at all. Incredible.)

With such a remarkable lack of noise per unit of signal, it was no surprise to find the TP 2.2 delivered a remarkable amount of micro-detail, allowing musical cues that are frequently lost to come through. Frankly this was the first thing I noticed when I plugged the unit in, as one isn't expecting world-class detail retrieval at this price point, but there it was. On the track "The Soldiering Life" by The Decemberists, I could hear the singer moving slightly back and forth towards the microphone—I've never heard that before the TP 2.2 was in my system. It's all revealed with the TP 2.2 in the system. None of this detail was of the artificially-hyped spotlight sort, which, while initially impressive, grows tiresome—which I suppose speaks to the unit's well balanced treble; nothing sticks out in the top end. Detail is useless if it's inconsistent with the broader musical message, but the TP 2.2 delivers terrific detail retrieval without a false etch.

Another area that caught my ear and kept my attention throughout was the TP 2.2's dynamics. While micro-dynamics are a function of detail retrieval, its macro-dynamics, the big musical swings, that float my musical boat (thus the Wilson loudspeakers). I've said it in almost every review I've written about amplifying devices: you are listening to your power supply. Well, the TP 2.2 has an overbuilt power supply, which no doubt enables it to deliver the current that will swing voltages up and down as quickly as the music demands. The trombone at the end of Tom Waits' "Burma Shave" is like a gunshot in the room with the TP 2.2. Further, demanding transients are rendered with excellent attack. I never felt the unit compress or harden during dynamic passages, in either balanced or single ended configuration (though, when pressed, I'd say the single ended connections were more dynamic). Most stereos fail in reproducing dynamics properly, but the TP 2.2 is a world class performer in this parameter.

Insofar as tone goes, let me reveal my biases first: I've always liked at least one tube in the signal path, somewhere. Tubes do something that transistors do not; they provide a bit more warmth, sweeter and generally more extended decays, and a bit more harmonic development in the midrange. I've heard solid state sources, preamps and amps that I've liked and enjoyed, but I've always felt that a tube should be in the signal path somewhere (again, my bias) in order to get those aforementioned benefits. However, tubes have their detractors, and understandably so; in addition to more maintenance, tubes generally do not have the frequency extension or the silence that solid state components have. Well, the TP 2.2 has a nice dose of the typical tube-goodness when it comes to tone (extended decays and full harmonic development in the midrange).

As mentioned earlier, the TP 2.2 is exceedingly quiet, and tube rush or hiss will not be an issue intruding on the signal. Frequency extension is excellent, with bass articulation that reaches to house rumbling frequencies, though perhaps shortened a tad. Let me reiterate: I was very surprised by the degree of bass articulation that the TP 2.2 could deliver, as frequently lower priced products can deliver bass articulation, or extension, but not both. The TP 2.2 delivers both in a manner I've not come to expect from a product at this price point. That's what a good power supply will do for you folks; it gets you good bass.

At its price point, I'm loathe to find fault, as it's so good for the money that nit-picking just makes me feel like a testosterone-fueled teenage boy judging the swimsuit segment of a Miss Universe contest. But I've a responsibility to point out areas that I find could be better. So, when compared to some significantly more expensive preamps (i.e. north of $10k), the TP 2.2 has more grain on the signal. It reminds me of when I compared interconnects for a cable manufacturer, where the only change between the cables was in the purity of the wire; the less pure wire had a bit more grunge, and more artifacts riding on the signal, making it seem like fine harmonic details were being lost in an electronic fuzz. I noted the same sensation with the TP 2.2, but this will likely only be noted in highly transparent and ambitious systems.

Another area I'd have preferred to see otherwise was in staging; images are well focused on a compact stage, but everything is shrunk down a bit. Myself, I prefer a more prototypical tube soundstage, which is room melting soundstage and holographic imaging, but the TP 2.2 is more concise. Some will prefer staging as the TP 2.2 delivers; c'est la vie. Moving on, bass was deep and extended and articulate, but it was not full or lingering, it was like the foundation ran out of steam after the initial attack, leaving the overall presentation a bit thinned out. But if you're willing to do a bit of tube swapping, most of these bass and thinness gripes can be removed; tube rollers will salivate over what they can do with the myriad 6922 flavors that they can swap in. In terms of configuration, while the unit was consistent through either configuration, I found myself preferring the single ended inputs and outputs in order to maximize dynamics, while the balanced cables were better for a more sweet yet orderly presentation.


I've always felt that loudspeakers had the toughest job in a stereo system; they have to convert an electrical impulse into a mechanical one that vibrates air in a manner that represents what is on the recording. But I never really thought about what piece in a stereo had the easiest job.

Now? Though subject to constant change, I have formed an opinion of what has the easiest job: it's the preamp. A preamp's job is simple: straight wire with adjustable gain and ability to switch sources. Seemingly simple, no? Well, in my 15 years of experience in this hobby, I can say unequivocally that preamps, all preamps, fail in this regard. They color the sound, commit tonal manipulations, have poor extension at the frequency extremes, or obscure detail—these things are problems in all preamps. It was an unfortunate fact that the preamps which made the fewest errors were also the most expensive. And to a large extent, that's still the case.

However, the Audio Horizons TP 2.2, like all preamps, is not perfect, but the degree of errors it commits is not high, certainly not high enough to preclude its use in very high end systems, and some of those errors can even be corrected with tube rolling. What you get in the TP 2.2 is reference caliber detail and dynamics, along with a smidge of tube sweetness (and the ability to tube roll with great results), at a price that doesn't keep Junior out of college. Would it sound better if it used a 1" thick chassis, or if it were hard wired throughout? Sure it would, those things matter—in the pursuit of the live music experience at home, everything matters! But the designer made the decision: keep the cost of materials down where it most inflates final cost and matters least to sonic performance. Well, it's safe this time around to say: Mission Accomplished.

And while it delivers terrific performance straight up, the TP 2.2 rewards owners who spend some time optimizing it. Give it good power, good tubes, and vibration damping, and it gets into high oxygen country without the "I fly first class on my vacation" cost. Oh, and you have to find yourself a good power cord—I find amusing that Audio Horizons thinks so little of the stock vortex power cords (and believes that audiophiles think the same thing) that they don't even include one in the box; the user will find something better, and should (I did not have the Audio Horizons power cord to audition.). I find the absence of a power cord is just another example of Audio Horizons not adding one unnecessary cent to the cost of the product.

I recall reading a review where the author said that regardless of the uber-performance of stereo equipment that costs as much as a Corvette, it was easier to be enthusiastic about less expensive products that deliver a whole deep-in-the-heart-of-Texas heaping serving of the high-end experience, as they do so with a price that can be afforded by most readers—think Benchmark DAC-1, a product that took the audiophile world by storm, not because of its absolute performance, but because of how good it was for a grand. The MBA's of the world would assign that concept one word: value. It is 'value' when you get more than your money's worth. The consumer and the manufacturer both win in a transaction that offers 'value'.

In this case, audiophiles win. While I've come across better performance, I've not come across a better value in high end audio than the Audio Horizons TP 2.2. And while I did not buy the sample, let me end the suspense: I bought one configured to my tastes (as yours would be). This is a must audition product if you're in the market for a preamp.

(PS: As an owner and an audio DIYer who's pretty slick with a soldering iron, I will be modifying this preamplifier in my user system on, so check into the Rhyno's Den from time to time.) Ryan Coleman

TP 2.2 Linestage
Retail: $2750 for base model, $4825 fully loaded RcvB

Audio Horizons
web address:
TEL: 916. 739. 6788