If the Audiopax Stereo 88 looks familiar enough to produce a case of déjà vu, it should. Srajan's introduction of the Audiopax Mono 88s spanned 3 websites and culminated in his March 2003 review in these pages. It's a worthy read for anybody considering even the Stereo version under evaluation today. In his review, our Editor went into great detail (much more than I will here) describing Audiopax designer Eduardo de Lima's 'Timbre Lock' system. Very briefly, Timbre Lock is an ingenious method of electrically tailoring the interface between these fine amps and your speaker system in order to optimize harmonic distortion characteristics. The biggest fundamental difference between the Mono version and the Stereo version (obvious differences aside) is that the mono version houses essentially two distinct amplifiers per chassis, each "half" with its own output transformer. The Timbre Lock system plays each transformer against the other to actually tailor THD characteristics such that they cancel out-of-phase distortion generated by the speaker at the listening seat. Additionally, the listener is invited to experiment with reversing absolute polarity at the amplifier (by reversing speaker leads) in order to hear which wiring scheme nets the greatest out-of-phase cancellation. The stereo version is essentially a single Mono 88 amplifier with those two channels kept separate, each side of the amplifier now offering half of the Mono 88's 30 watts - or 15 watts per channel. For that reason, the Stereo 88's Timbre Lock, while still extremely effective, works differently.

According to de Lima, "The output transformers of the Stereo 88 have been slightly modified over the Model 88s'. This compensates for the lack of the 'sliding axis' offset feature that's intrinsic to the monos' Timbre Lock but absent in the stereo amp. After all, both channels must be set identically. The left/right, counter-clockwise/clockwise adjustability of the Stereo's bias controls affects the harmonic distortion interaction between amp and speakers. It alters a number of values along an axis optimized by our proprietary transformers." I was also told to consider the left pole colder and more analytical (lower bias current) and the right pole warmer and more saturated (higher bias current).

If all of this sounds like cause for gnashing teeth, relax. In operation, the procedure is simple [see Timbre Lock dials and rings of display LEDs above]. The differences involved in adjustments are immediately evident and not subtle. But more on this later.


I've been looking at the pictures of Srajan's Audiopax Mono 88s since publication and now realize that they make the amplifiers look deceptively small. At 13½" x 9" x 14½" (H x W x D) and 42lbs, the Stereo 88 is a good chunk of 15-watt per channel amplifier. It also has a strikingly refined appearance, as it should for the handsome price of $5,970 US. The chrome-finished brass fascia shows a modicum of orange peeling but everything else about it indicates first-class craftsmanship. Like its mono sibling, the Stereo 88 utilizes dual KT88 tubes in a dual mono configuration, as well as dual 12AT7 driver tubes. Around back, the Stereo 88 sports a very high quality pair of Cardas rhodium-plated 5-way binding posts and RCA inputs, an IEC power input and a circuit breaker switch.

Audiopax specs this zero global negative-feedback amplifier at 14Hz to 90kHz (-3dB) and - 0.0dB down at 20KHz. The 15-watt maximum output is measured at 1kHz into 8 ohms. Also specified is a signal-to-noise ratio in excess of 95 dB, an output impedance of 3.5 ohms as well as an input impedance of greater than 82 kOhms.

What remains unspecified is the Stereo 88's input sensitivity. I can tell you that it's fairly low. It demands a good amount of voltage from the preamplifier before achieving the amp's rated output. When one considers that the Audiopax is likely to also be used with super-efficient loudspeakers, this makes sense. It allows fuller use of a preamplifier's volume control.

Otherwise, the volume control would seldom see use outside of the 6 to 8 o'clock positions, with fine variations almost impossible. As it was, the volume control on my Herron VTSP-1a frequently saw the 1 o'clock position, making fine adjustments a breeze. I had no problem driving the Stereo 88.

Blind date: Getting to know you

As it happens, a pair of Magnepan MG 1.6QRs had been residing in my listening room powered by a pair of very large and expensive amplifiers that I won't name. In preparation for the Stereo 88's arrival I had, only a couple of days prior, swapped out the Maggies in favor of the more efficient and very tube-friendly Silverline Sonata IIs. One morning I put on the old warhorse "Famous Blue Raincoat" by Jennifer Warnes [Private Music 01005-82092-2] and was taken aback. True, I hadn't listened to the album in a while, but I sure remembered her vocals sounding a lot more detailed, uncolored and transparent. Was my memory playing tricks? As compared to the ultra-transparent Maggies, had my Silverlines suddenly gone more opaque, become more colored? I spent the next couple days swapping out speaker wires and cables figuring that something had to be wrong - my memory isn't that bad.

I never did get to the bottom of this mystery - until I inserted the Audiopax Stereo 88. Talk about blessed relief! As it turns out, the problem wasn't with cables, it wasn't my memory and it wasn't the Silverlines (whew!). It was with the large amplifiers which I won't name since as of this writing, I haven't ruled out that they might not be malfunctioning. Because I had purchased them specifically for the Maggies and never used them with anything else, I had no clue how they would sound with the Silverlines. By contrast, the Audiopax Stereo 88 was a welcome ray of cleansing sunshine. It came to the rescue of the music's purity, not to mention my sanity.

Practically speaking, this amp's a dream. It doesn't produce much heat, it's mechanically silent and it's uniquely handsome. The only issue one may take is with the fact that one must reach around back to power it up. There are no power or stand-by switches at the front panel. Why? Because it doesn't use power switches anywhere. In the interest of signal purity, the Stereo 88 eschews the use of protection fuses and favors a switched circuit breaker. It is this rear-mounted breaker that powers the amplifier on and off. Inconvenient? A little. Worth the inconvenience? Particularly in light of the fact that its use instigates a soft power-up sequence, I'd say so.

Dinner conversation

Starting in the bottom octaves, the Stereo 88 combines excellent linearity with a surprising amount of control. I'd liken this aspect of performance to a cut of fine aged Filet Mignon -a choice piece of beef both tender and juicy but without the fat, body and saturated flavor of a slab of Prime Rib. While the 88 doesn't accentuate the bass as some monster amps may, it is completely composed and relatively unshakable. Some feat for a 15-watt tube amp. Acoustic basses and even a guitar's bass strings take on a more musical and natural presence than with most amps I've used. You hear the transient pluck of the string followed by a strong and clear resonance of the fundamental. It is all reproduced with such control as to allow the subsequent harmonics a most pleasing sustain.

Upper bass and lower mids are absolutely superb and the reason that most listeners will never miss the explosive low bass that some more powerful solid-state amplifiers may (but not always) provide. While never sounding over-ripe and never intruding on the splendor of the midrange, the Stereo 88 produces a very meaty authority that superbly bridges bass and midrange. Where some tubes and tube amps may sound a little hollow, threadbare or harmonically thin, the Stereo 88 is warm, lush, and harmonically full - but never too much so.

Like a good Crème Brule, the Stereo 88 produces a treble that has just the right amount of sweetness on the pallet complimented with the occasional bite of reality -never in excess and always in proper balance. If the Stereo 88 deviates from absolute neutrality anywhere in the spectrum, I'd guess it does so in the treble where it sounds ever so perceptibility shelved down. By no means does it achieve its silky smoothness by being dark or recessed - but neither does it have the ultimate flat-line of the Audio Research VS55, for instance, which sounds absolutely ruler flat for better or worse.

No, I'd liken the Stereo 88's treble performance more on par with the Conrad-Johnson MV60, which struck me as having a near perfect balance of honesty and listenability. Like the excellent MV60, the Stereo 88 manages to sound both extended and honest while being neither brutally frank nor hopelessly romantic; inviting and musical, never excitable or insipid.

Well, if the early octaves produced by the Stereo 88 are aged Filet Mignon, then the midrange that follows would best be described as a Maitre d'Hotel butter: Rich and flavorful but with not so much as a hint of personality to be anything but the perfect extension of theme. It has one of the cleanest, most transparent and musically accurate midranges I've ever used. It strikes me as absolutely neutral. But don't confuse neutral with bland. No, the Stereo 88 produces a full spectrum of flavors with little or no editorializing, certainly not lackluster, but neither what some would call emotionally charged. Actually, as compared to certain other amplifiers, I'd categorize the Stereo 88 as somewhat intellectual. It has no overriding personality that superimposes itself on the music. Rather, it's like a good reporter - just the facts. If an emotionally charged listening session is what you're after, don't look to the Audiopax - look to the music. If it's in the music, you will get it at the listening chair. I promise.

For the Stereo 88's success, linearity is equally as important as transparency. When you combine such neutrality with a high degree of transparency, the result is an amp that's almost not there. And as any seasoned audiophile knows, when it comes to audio, less is always more.