December 2004

Antique Sound Lab's Remarkable $1,095 AQ1003 DT Engine
The AQ1003 DT Integrated Amplifier
Review By A. Colin Flood

  I am a big fan of the Internet amplifiers offered by ASL (Antique Sound Labs). Have been since I was blown away by the $99 ASL Wave 8 tube mono-amplifiers in March 2002 (These matured to $249 Wave AV-20 DTs). The 45-pound, sweet sounding 30-watt "Class A" ASL AQ1003 DT integrated tube amplifier retails for only $1,095 and doesn't change my favorable impression one bit. This is how amplifiers should be built: beefy, powerful, yet sweet and delicate; with fun-to-use bias and remote controls; and relatively low-cost. A very good value for sound and quality.

On the Aperion 522 Powered Towers ($1,000/pr.), the initial impression was of immediacy and texture. Flutes seemed smooth. There was delectable quickness to the notes, with powerful mid-bass. Music was involving. With the 150-watt sub-woofers in the Aperions, the mid and upper bass was solid and moving. Almost everything you want it to be. The treble was better than the massive harmon kardon AV630 receiver (75W/5-ch.), but still a little sharp. Yet, the snap of the drums and the blat of the horns returned. Compared to the HK AV630 receiver, it takes a hemi of a tube amp to provide the same bass hauling capacity of a modern solid-state receiver.

It made the reluctant Aperion powered towers sound like they were playing music again. What a good combination it is to mix tube amplification of the mid and high range with solid-state support of the lower and upper bass!

Comparisons
Compared to the ASL Wave 8s, my Bottlehead 2A3 Paramours, Cayin TA30, and refurbished Scott 299C integrated amplifiers -- all of which I've heard at least briefly on big ole horns -- the AQ1003 DT is a heavier, slightly expensive unit with unique and easy-to-use modern features. With its pre-amplifier, the AQ is smoother, more accurate, more powerful and more fulfilling than the bargain basement Wave 8 monoblock amps.

For a few hundred, plus requisite refurbishing, the ancient Scott integrated tube amplifiers are a wonderful value in the refurbished world, but I think their bass is smoked by the heft of the AQ. My low powered Paramours are still the sweetest (see my Reviewer's Bio for the context of all my reviews), but they are unsuitable for all but the most ultra-sensitive loudspeakers.

The AQ is a better value for most audiophiles, more solid and powerful, with stronger bass, and more practical, and yet without the Nth degree of delicacy and mid-range smoothness of the Paramours' 2A3 tubes. The lesser-known, copper-colored Cayin TA30 is also a four EL34 tube unit, imported from China for $200 less and a few pounds heavier. Therefore, I would have to hear the Cayins back-to-back with the AQ to be able to honestly say which one I like better.

Though I am reluctant to think that certain tube amplifiers might go as well on cone loudspeakers as they do on horns, I am forced to admit that this amplifier and loudspeaker was one winning combination. Movies and music are a joy with ASL's hefty city of lights. The AQ presence infects the house with music listening sessions as quickly as a winter cold. Everyone breaks out this or that CD. Whenever the movie and music reproduction system was in one stage of undress or another, I would get a call: "Colin, do you mind if we put the new amplifier back in?"

On my big ole horns, the soundstage was wide, brassy, and gloriously dynamic with a quick leading edge and rapid twinkling of the high end – you could hear cymbals like scrub-brush steel. The AQ provided a good, solid foundation, a little better than the Paramours did, creating an instant indoor concert.

What You Get
ASL is the business vehicle of Tasha Goka. How did you get into this? "Way back when I was a student in the UK," Goka said, "I was asked to join a group of other art students to assist a teacher of mine to produce some music he collected in the East. It was in a large studio complex with a lot of nice people around who also cared about the sound and musicality. It stuck with me until I found an opportunity to make it my business. It has been my interest for over thirty and my business for 24 years.

The AQ 1003 was first manufactured many years ago. ASL is the transformer manufacturer, in ASL's own factory.  They design and manufacture all transformers and chassis parts used in ASL amplifiers. ASL also supplies transformers to many other manufacturers. Amplifiers are built in China, about 50 kilometers from Hong Kong. The DT on all ASL products sold in North America stands for Divergent Technologies.  DT products have additional design features for enhancing performance (higher quality parts) and user convenience (calibrated external bias adjustment, etc.). The DT version is a classic amp with a few charming modern touches.

The AQ1003 model has been around for a long time. "It never," Goka says, "was discontinued." The AQ price was bumped up a hundred bucks recently to provide for added features, including the tube cage, wood remote and a new fused internal protection circuit.

Doubled-boxed in Styrofoam, the amplifier is the size of a small dog cage. It is constructed of heavy gauge extruded aluminum with 12 mm side panels. Aluminum powder coats the transformer covers. The white tube sockets and bias adjustment screws on the AQ's heavy-duty silver plating are clearly labeled.  First impression is of masterful quality and value.

A square, stainless-steel wire cage (not shown) around the top half of the hefty amp is a near perfect solution as an inexpensive tube cover: it lets the tubes breathe air from all sides, protects them from curious cats and kids, and allows audiophiles to bask in the tube's musical glow. It is easy to leave the AQ cage unscrewed, or partially screwed. The cage rests on top; even one screw holds it in place, requiring only a gentle push to nudge it aside.

Unusual Remote
Wood has qualities beyond that of merely sonic value. We know that wood makes beautiful sounding and looking cabinets. Yet wood has a warm tactile feel to it too. We touch wood. We stroke it. Steering wheels, handrails and doorknobs are made of wood. More touchable things should be. Though there is nothing antique about this modern tube amplifier, the AQ has a small, light tan, wood remote control -- not the chunk in the picture. The body of the slim piece of wood is simple; quite the contrast to the row of sleek black Hershey bars parked on the coffee table. The back door of the remote slides into place like a child's jewelry box. The remote is wood, Goka says, because "we did not like the cheap plastic. This is nicer don't you think?"

The remote buttons are equally simple: four soft pencil-eraser size black nibs, along with two up/down volume ones.  Yet the uncomplicated little remote was a pleasure to see and feel. The remote even included batteries (another nice consumer friendly touch). There is a small, dull red input eye on the front of the silver AQ panel for the remote, which looks like Hal 9000 when he is turned off. You "kinda hafta" be in front of the dull Hal eye when using the remote, otherwise the AQ may not respond.

The AQ itself is a robust amp. Be careful picking this thing up - all the weight is in the rear. Three 5" high black transformers -- a central power and two output ones -- tower over the smaller tubes, like ominous dark skyscrapers over glass silos. I believe the size of output transformers on tube amplifiers should be as big as possible. They should at least exceed the size of output tubes. To me, vaulted transformer height indicates admirable, toe-tapping bass control; the kind that tweaking audiophiles drool over with hyper-expensive, concrete-block super-amplifiers, like the $6K Pass Laboratories X250 (500-watts into 4-ohms, peak power of 1800-watts)!

Though I do not warehouse every amplifier I seriously audition, for side-by-side comparisons, I sense that the AQ's chunky black transformers will give even superlative quality solid-state amplifiers a photo-finish in the mid and upper range vocal stakes, while providing a touchingly tactile challenge in the bass department.

The brushed silver front panel has only two medium size silver knobs, a small black rocker switch and a sparkling blue sapphire jewel, indicating power (the tiny dot next to the rocker in the picture). In vivid contrast to the dull orange glow of the tubes, the sparkling sapphire signifies music creation by this glowing factory. This is one amp that looks and sounds as good in the dark as it does in the daylight.

There are no tone or balance controls, which can make balancing less than perfect rooms difficult. The rear panel is simple and straightforward. On the rear, the gold binding posts are indented, as if a wrench should be used to screw them down tight. There are both four and 8-ohm taps, with space around the posts for my heavy Coincident CST 1 rattlesnake cables.

In yet another nice modern convenience, there are RCA subwoofer outputs! This means that the lush and liquid mid-range sound, that tubes are renown for, can be coupled with the robust solid-state thump of subwoofers of low bass impedances, to create a magical combination of thunk and golden vibes.

The Manual
Like the amp design, the manual is a few simple and straightforward pages. It says to use thick speaker cables. The "Quickstart" section however, should say to seat the tubes gently, but firmly. The manual also says the inputs are Tuner and Auxiliary, while the amp says SACD and DVD. For tweaking audiophiles, there is a circuit diagram for one channel.

Tweaking audiophiles know that solid-state receivers quit suddenly. When a part, however small fails, the entire unit dies. But the dirty little secret tube-ophiles neglect to mention is that tube amplifiers degrade slowly. The amplifiers go on happily making sound, while their parts deteriorate or wear out. Without quarterly or annual check-ups, the sound of a tube amp gets slowly worse. So slowly does it degrade that even golden audiophile ears might not notice.

Enter the calibrated bias meter for convenient tube check-up and maintenance. Though implementation of built-in meters may be too expensive for some manufacturers, the AQ has a handy bias meter, and it is a dream to use.

On the silver top, between the glass tubes are four bias adjustment screws, a small knob and a tiny analog meter (in a shallow depression at the center of the top plate, between the knob and the logo). The directions are simple. With speakers hooked up and power warmed up, turn the knob to select the tube. If necessary, turn the bias screw until the needle is dead center -- between the two marks indicated. Check each tube, turn off the meter, enjoy the music, and recheck in... oh, maybe three or four months.  My unit came with perfectly adjusted tubes and took only a few minutes to warm-up.

This is an amp made for the tube-wary. Neophytes should not fear this amp. The two-click-step of the bias meter removes all fear for tube neophytes. Without the meter, checking tubes is problematic. The meter clearly shows when bias screws need tweaking or tubes need replacing. Except for the capacitors and tubes, there is little other circuitry to degrade on a "Class A" amplifier.

Although there are sub-woofer outputs, there are no pre-amplifier inputs on the AQ (darn!). Everything else about the AQ made me feel as if I was getting a quality product with the money spent on production, not marketing hype or distribution channel.

Its considerable heft makes the AQ feel as if it could master most stubborn impedances. This powerful sounding amplifier can drive a 2-ohm dip in loudspeaker loads, but should not be paired continuously with such a load. The noise floor is 80dB (1.2 milivolt) and frequency response at 1 Watt with less than 1% distortion from 18Hz to 25kHz.

Tubes
The small driver tubes in front are classic 12AU7s, from JJ Electronics. The tubes arrive double-bagged in bubble-wrap, coddled as carefully as a light bulb in a catcher's mitt. There also spare tubes are included. (Nice touch!) The tube boxes are labeled for their individual sockets - any tube will work in any socket - as long as the bias is adjusted again. The tubes are tested and biased on the bench prior to packing.

The EL34 tube is a classic, well-established and stable design. Tubes used in the AQ are currently manufactured by several factories. Other US and European amplifier manufacturers similar designs to the AQ, but not near this price.

The AQ output tubes are classic EL34s by well-known Sovtek. Some audiophiles rate Sovtek tubes as good or better values. The EL 34 is the only tube used in this amplifier but the next model up, the AQ1001 DT (50-watts, $1,495), accepts several octal tubes including the KT88, EL34, 6L6, KT90, 6550 etc.  A variety of possible tubes allows tweaking audiophiles to experiment with rolling new sounds through their home movie and music reproduction systems.

The EL34 is the workhorse tube of the forties: a low cost, mid-size tube combining both mid & upper range delicacy with moderate power. Compared to the classic EL 34 tubes, Goka says, "the 2A3 and 300B tubes are both power triodes and normally used in purist single ended triode (SET) designs."

Compared to SETs
My survey of four dozen loudspeaker reviews shows average audiophile loudspeakers are 84-86dB per watt per meter (dB/W/m) sensitive. Yet with above-average sensitive loudspeakers and easy impedance loads, Goka said, "SET amplifiers sound more coherent and life-like. Less efficient loudspeakers, with more complex impedance loads, benefit from the higher power and control of the push-pull designs," like the AQ.

He says, "although SETs are less efficient designs, delivering low power, the signal is processed in more straight forward fashion and the sound is more fluid and coherent. Tetrode KT88 and pentode EL34 tubes are usually used in more efficient push-pull designs," he says, "delivering higher power with good control and drive capabilities." This cohesive smoothness was certainly true with the "Classic Audio Reproductions' Cinema Ensemble Loudspeakers" and the winners of my Wife Acceptance Award, the "Omega TS1 Single Driver Loudspeakers." Break-in period for the ASL's 30-watt EL34 integrated tube amplifier is about 30 to 50 hours initially, after the break-in period, the AQ will only take a few minutes to sound good.

Some amplifier designs overdrive their tubes. Overdriven tubes provide more power, but then burn up quicker. In the long term, this is a major expense for some exotic amplifiers. The AQ1003 tubes are conservatively rated at 30 watts, "even though it is possible to get over 40 watts. This way tubes are not stressed and the unit sounds better." Although Goka says it is hard to rate their longevity, the tubes should "should last a long time as they are not operating at their maximum power rating."

There upgrades or modifications hobbyists can make to the AQ. Apart from rolling from one different tube to another, some critical part changes make significant improvements. Though the AQ is a good design with excellent transformers; signal path can always be better with more expensive and better parts. Good power cords and A/C line filters will also help. ASL sells tube-damping rings that make an easy and meaningful improvement.

The closest major city to ASL is Toronto, Canada, about sixty miles. ASL has a lab where they evaluate their loudspeakers and amplifiers. A few retail stores do sell ASL products. Goka does not sell direct retail in areas where ASL products are presented. On a side note, Goka plans on a new all tube phono stage and a new high resolution pre-amplifier soon.

Sumptuous In Silver
Though I normally grade on a miserly scale, I lavish four Blue Notes on many of the Enjoy The Music.com's categories -- with no perceived weakness in any of the others! At $1,095, there is very little to buy in the way of excellent tube pre or power amplifiers with good looks, hefty build, decent sound quality and modern features. Yet, this integrated EL34 unit is a winner at a point where separate components only begin to sound really good. Bravo!

Watch out for this company. The ASL's robust and practical construction, design and price guarantee that their Internet offerings are vicious contenders in any heavyweight tube contest. This is one hard-to-beat modern version of a classic amplifier. With above-average sensitive or powered loudspeakers, any tweaking audiophile would be proud to own, listen and enjoy these remarkably musical amps for a very long time.

Specifications
Type: Integrated stereo amplifier using tube output stage

Tube Complement: four EL34 output, four 12AU7 driver

Frequency Response: 24Hz to 40KHz

THD: 1% @ 1 watt

S/N Ratio / Noise level: mV 80 dB /1.5mV

Input Impedance: 100K

Output Impedance: 4, 8, 16 Ohm

Input sensitive: 165mV

Power Cord: Detachable /Fixed Detachable

Input Sockets: RCA Gold Plated

Output Terminal: Heavy duty, Gold Plate 5 ways loudspeaker post

Chassis Finish: Polished Steel 

Front Panel: Finish Silver anodized, brushed aluminum

Dimension: 15 x 12 x 9 WxDxH in inches)

Net Weight: 45 lbs

Company Information
Divergent Technologies
342 Frederick Street
Kitchener, Ontario
Canada N2H 2N9

Voice: (519) 749-1565
Fax: (519) 749-2863
Website: www.divertech.com