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Equipment Review

July 2003

Wyetech Labs 572B Stereo Amplifier

by Marc Mickelson

Click to view measurements of this product

Review Summary
Sound "Ravishing way with voice, male or female," a conglomeration of a few things: midrange transparency, image specificity, smoothness and fullness"; treble is "a paradox of sorts"-- "slightly soft" yet "also captures the highest of high frequencies with rare acuity"; "bass is full, round and weighty, but…more atmospheric than pounding."
Features "A single-ended design that uses the Svetlana 572-10 direct-heated triode output…to produce a claimed 23Wpc in what Wyetech calls class-A1 operation"; "auto-bias circuit, standby mode, and turn-on relays to extend tube life; 20-year warranty.
Use "SET amps have always been a niche-within-a-niche product for those tube audiophiles who love horns or who don't ever listen to their music at realistic levels," but "the Topaz 572B is one of very few SET amps that seemingly has power to spare."
Value "In the case of the Topaz 572B, its music-loving owner gets a lot in return: a hand-crafted amplifier that sounds wonderful and competes with other amps, like the Lamm ML2, that cost much more."

Wyetech Labs electronics are not unknown to SoundStage! readers. We have reviewed two of the company's amps and one preamp, and the verdict on these all-tube products has been very positive. Therefore, I was certainly interested in hearing the Topaz 572B stereo amp, even though Doug Schneider had reviewed the similar Topaz 211 in early 2000. I knew a change of output tube alone could make a huge sonic difference, and I'm a nosy audiophile at heart and one who admires tubes at that. So I didn't need much convincing to hear another tube amp, especially this one.

What's so intriguing about the Topaz 572B? First, it's a single-ended design that uses the Svetlana 572-10 direct-heated triode output tube, which looks like a cross between a 300B and 211. It's an impressively big tube and puts out quite a bit of light and heat -- byproducts of the amp's 375-watt power draw. The Topaz 572B uses two of these along with single 6SN7WGTA and 6BX7GT tubes to produce a claimed 23Wpc in what Wyetech calls class-A1 operation. The amp uses no negative feedback. The parts list is extensive: large-value Solen polypropylene coupling capacitors; Audio Note output transformers; and separate power transformers and filters for the two high-voltage power supplies, which also employ a total of six heavy chokes and seven large polypropylene capacitors.

The Topaz 572B's 16"W x 22"L x 10"H chassis is made of 12-gauge steel and has a baked-enamel finish that looks like a cross between violet and gray in color. It's a nice change from the binary color palettes of most high-end gear -- black or silver. A pair of handles are perfectly placed to balance the amp's weight and make moving the 102-pound Topaz 572B a little easier.

Single-ended inputs and speaker outputs are located on the front of the amp, I assume as a way to shorten the signal path, along with LEDs that signal the amp is working through its 60-second power-on cycle or ready to make music. Three time-delay relays are said to extend tube life. On the top plate are switches to match the amp to the output impedance of the speaker -- 4 and 8 ohms -- along with probe inputs marked "bias." The Topaz 572B has an auto-bias circuit, so I suspect these are for diagnostics if the amp should need servicing. The rear panel has only the operate/off/standby switch, IEC power-cord receptacle, and a fuse holder.

All in all, the Topaz 572B impresses as an intelligently designed and thoughtfully manufactured amplifier, and its 20-year warranty shows that Wyetech Labs has great confidence in its work. As an added nicety, each amp comes with a gold-plated brass nameplate engraved with the unit's serial number. The stereo Topaz 572B costs $9250 USD, but Wyetech also makes a mono version of the amp that doubles the power output and sells for exactly double that of the stereo version: $18,500 per pair.

Review system and issues

I used the Topaz 572B with a large complement of electronics, including Lamm L2, Audio Research Reference Two Mk II and Wyetech Labs Pearl preamps, the latter of which is brand new to the company's lineup. Speakers were Wilson Audio WATT/Puppy 7s. Sources were either an Esoteric DV-50 universal A/V player or the wonderful combination of a Zanden Model 5000 Mk III DAC and Mark Levinson No.37 transport, with the i2digital X-60 BNC-terminated digital cable in between. Interconnects and speaker cables were from Shunyata Research (Aries and Andromeda), MIT (Oracle v2.1), Acoustic Zen (Silver Reference II and Hologram II), and Nordost (Valkyrja), while all power cords were from Shunyata Research (Anaconda Vx, Python, and Taipan). Power was provided by a Shunyata Research Hydra or Sound Applications XE-12S with 20-amp Elrod power cord. Preamps and amps sat on Silent Running isoBase 3.0 equipment platforms, while the transport rested on a pair of sand-filled Bright Star Audio Big Rock bases and a Townsend Seismic Sink. A pair of Target equipment racks provided additional support for electronics. For comparison, my Lamm ML2 amps made yet another appearance.

I did have one persistent problem with the Topaz 572B: a faint hum that came from the amp itself as well as through the speakers. I told Roger Hebert of Wyetech Labs about this early on, and he first sent new tubes (the problem remained), then suggested lifting the ground of the amp's power cord (no luck), and finally advised using shorting plugs on the amp's inputs (the hum was gone, but so was the signal). I also tried the amp in another room and system -- same results. Roger eventually sent along his Pearl line stage to use with the amp; it was slightly quieter than either of the preamps I had on hand -- producing less background hiss from the speakers -- but it didn't solve the hum issue.

Given the nature of the hum, coming both from amp and speakers, one conclusion is that the amp was somehow damaged in shipping but was still fully functional; another was that there was some sort of interaction between the amp and the wiring of my house -- results with the shorting plugs suggest that the hum is not coming from the amp itself. Roger Hebert was adamant: "The Topaz doesn't hum, period." However, it's only fair to point out that no other amp has exhibited this same problem when used in my system.

One more operational note. In the past, I've listened to my Wilson Audio WATT/Puppy 7 speakers via 4-ohm and 8-ohm amplifier outputs and heard little or no difference. If anything, I've preferred the 8-ohm taps on various amplifiers over the 4-ohm. I also listened to the Topaz 572B with its top-mounted impedance-matching switches set at both 4 and 8 ohms, and to my ears, the sound was a touch more incisive via the 4-ohm setting. The WATT/Puppy 7s are a 4-ohm load, but even so, experimenting is easy and won't hurt amp or speaker (unless you drive the amp into clipping), so why not give it a try?

Like a rock?

If you're a fan of vocal music, you will likely fall hard for the Topaz 572B. Its ravishing way with voice, male or female, had me pulling out favorites as well as discs I hadn't listened to in a long time just to experience them with this amp. This performance was a conglomeration of a few things: midrange transparency, image specificity, smoothness and fullness. I'm confident that Ross Mantle of Ultra Audio would sum it up as voluptuousness. Whatever the case may be, the Topaz 572B portrayed vocal performances with presence that is unmatched by any amplifier I've heard.

Bascom's take

In measuring power amplifiers for SoundStage!, I normally don't comment on their sonic attributes, but I was asked to do so with this amplifier. A number of years ago, I heard an earlier version of this amp that used the physically larger 211 output tube. I did a "Playback" (brief review) of it in Audio. As I recall, I thought that amp sounded very good at the time. It was accompanied by a wonderful Wyetech preamp, which was also very good-sounding.

Fast-forwarding to the present; this new Topaz looks like the prior one with the exception of the output tubes, which are now the newer Svetlana directly heated triodes. Although smaller, these tubes are similar to the original 211s in electrical characteristics but with 25% greater plate dissipation. Wyetech has utilized this property to attain a higher power output than the earlier design.

My present listening arrangement consists of a pair of B&W 801 Series 3 speakers up on Sound Anchor stands; a Quicksilver line-stage preamp; and various CD, LP record, tuner, and tape sources. I normally use an Arnoux 7 switching power amp driven from the tape output of the system preamp and control volume with the Arnoux 7. In this configuration, the preamp is not powered on. I also use a pair of Quicksilver Silver 60 tube power amps driven off the main outputs of the preamp when the preamp is on. When listening to other power amps like the Wyetech, I use the main output of the preamp. The B&W speakers are not an ideal match for a SET amp, with sensitivity on the order of 86dB. However, I have listened to quite a few SET amps offering 8-25Wpc of power with these speakers, and for my listening preferences and levels, results are generally OK and musically satisfying.

My initial impression of this new Topaz was that it was pretty good but not great -- this right out of the box. After I measured it and got some lab time on it, I reinstalled it in my system. This time, after a good warm up, its true strengths became apparent. I first noticed, being a guitar enthusiast, an unusually vivid definition of guitar extraneous sounds like finger squeaks and the like. While I listened to other material, it quickly became evident that the quality and tunefulness of bass reproduction was quite good along with a very musical and well-defined midrange and treble.

Overall sound was of quite high definition; it didn't smooth out and gloss over program material that normally tended to be edgy. When the program material was good, the sound was very good with the Topaz 572B. For those with the wherewithal and inclination to consider SET amps for their systems, the Topaz 572B should surely be seriously considered.

...Bascom King

Linda Thompson's Fashionably Late [Rounder 1161-3182-2] has garnered a great deal of critical acclaim, and it's all deserved. It's an album that sounds both old and new at the same time, and it was a great treat over the Topaz 572B. On "Evona Darling," a duet between Thompson and son Teddy on which Van Dyke Parks plays accordion and Hammond B-3, the voices are lifelike in size and intermingle to wonderful effect. The Topaz 572B sorts it all out and reproduces the earnest vocals with aching beauty. "It was just me and singers in the room" is an overused reviewing line, but I jotted it into my listening notes just the same. Audio reviewing is work, and one of the things that makes it so is that you have to dissect small sonic traits while listening to music you presumably enjoy and that can easily carry you away. This is made all the harder by amplifiers like the Wyetech Topaz 572B. I needed all of my power of concentration while reviewing it.

In the high frequencies, the Topaz 572B is a paradox of sorts. It will never irritate -- its treble is slightly soft, more a persistent glow than a sharp-edged flash of energy -- but the amp also captures the highest of high frequencies with rare acuity, reproducing the leading edge of cymbal strikes and recorded ambience as well as any amp I've heard. "Scherzo in G" from the Gosford Park Soundtrack [Decca 289 470 387-2] is a short lively string piece that I put on my CES demo CD-R because I wanted to hear how various systems would handle it. The strings can sound overly strident, just about right but leaning toward stridency (this is what I hear on my system), or lacking the edginess that's part of their recording. With the Wyetech amp, the strings are slightly subdued but still able to portray their bite -- a different portrayal but one that's as equally valid as that of my reference amps.

There are some impressive low-end moments on the Jacques Loussier Trio's Baroque Favorites [Telarc CD-83516], and while the Wyetech amp conveys their thunder, it doesn't have the sheer power and slam of a solid-state amp and even some tube amps that do bass with uncommon authority. The Wyetech amp's bass is full, round and weighty, but also a bit indistinct, more atmospheric than pounding. Undoubtedly, the Wilson Audio WATCH Dog subwoofer would help out here -- and how -- but I don't want to make too much of this. I found the Topaz 572B's bass to be wholly acceptable, and you won't buy a tube amp if you are an admirer of low frequencies above all other parts of the sonic spectrum anyway.

Finally, the Topaz 572B is one of very few SET amps that seemingly has power to spare. This is not to say that you can't clip this amp (although I never did), but the thought of doing so won't be primary in your mind and turn you into a volume-control jockey. This SET amp does dynamics (within reason, that is), and guitar-heavy rock like Lou Reed's New York [Sire 9 25829-2] is handled very well. Of course, the sensitivity of your speakers will have a role in this, but once you hear "Dirty Blvd." through this amp at party-approved levels, you'll be surprised that the Topaz 572B is rated at only 23Wpc.

SET comparison

Once again, Lamm's ML2 monoblocks put in another showing, and this time the comparison is an obvious one to make. The Lamms are also SET amps, albeit monoblocks, and their 18W power output is close to that of the Topaz 572B. Where the two converge most radically is in terms of cost, the Lamms coming in at a shade under $30,000 per pair, three times the cost of the Wyetech Labs amp.

In broad ways, these two amps are cut from the same sonic cloth: wonderfully refined up top and gorgeously communicative in the midrange. They are both pleasing to the extreme, especially if you have a speaker like the Wilson Audio WATT/Puppy 7, which from my experience works in great harmony with SET amps. Wilson Audio speakers are often demonstrated at shows with high-power solid-state or tube amps, but they are also a SET admirer's speaker.

There are differences between the Lamm and Wyetech Labs amps as well. In the treble, the Wyetech's softness is replaced by the Lamm's greater solidity and incisiveness. The Lamms' bass is also more punchy and powerful -- the very best I've heard from a SET amp. In the midrange, the Lamm amps can't quite hang with the Topaz 572B, which offers a bit more body and richness, although both are at the very apex of the curve for midrange loveliness. The amps' power output seems about equal, with perhaps the Wyetech amp playing more loudly before it lets you know that it has reached its limit. Both amps get to the point where turning up the volume doesn't produce higher SPLs but does make you realize that one more click may cause clipping.

Bottom line: I prefer the Lamm amps to the Wyetech 572B, but not by as great a margin as the difference in price would suggest. If you have your ears set on a pair of Lamm ML2s, I strongly suggest you also hear the Topaz 572B, and perhaps the mono version of the amp as well. In either iteration, the Wyetech amp is a worthy end of the audio road.


While discussing the Topaz 572B with Doug Schneider before writing this review, I called the amp "a poor man's Lamm ML2," to which Doug immediately replied "poor man's?" We both realize that $9250 is a steep price for anything but a low-mileage full-sized SUV, but in the case of the Topaz 572B, its music-loving owner gets a lot in return: a hand-crafted amplifier that sounds wonderful and competes with other amps, like the Lamm ML2, that cost much more. I can still hear the way this amp does vocals (partly because it's playing in the background right now!), but perhaps even more significant is that the Topaz 572B is a SET amp with some real-world power on tap. It's not just for string quartets and jazz trios. With reasonably sensitive speakers, you can play your Metallica or Mahler as well.

SET amps have always been a niche-within-a-niche product for those tube audiophiles who love horns or who never listen to their music at realistic levels. Wyetech Labs' Topaz 572B doesn't necessarily fit into this mold, but its sound will certainly make SET lovers very happy.

...Marc Mickelson

Wyetech Labs Topaz 572B Stereo Amplifier
$9250 USD.
Warranty: Three years parts and labor on amplifier (20-year optional warranty); one year on

Wyetech Labs
1662 St. Bernard Street
Gloucester, ON Canada K1T 3P7
Phone: (613) 526-5390
Fax: (613) 526-5797

E-mail: wyetech@istar.ca
Website: www.wyetechlabs.com

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