DATE: May 07, 1999 Review by Jim Kain

The Zen amp is made by Steve Deckert of Illinois, using a triode circuit with one 6N1P input tube, and a 5Y3WGTA rectifier, and two SV83 power tubes, putting out about 5 watts per channel. The design does seem to be inspired by the Zen principles of simplicity, directness, and integrity. It uses a minimum number of quality parts and the shortest point-to-point layout, in a simple, no-frills symmetrical box design. The footprint is small (6" x 10"), the box is finished in a plain grey enamel finish. It has one set of gold plated phono inputs and a gain control in the back, so it can be used without a preamp. Speaker outputs are 3-way banana jacks on the top rear on either side of the transformer. There is a bias switch (toggle) for the input tube on the front of the top panel; I don't know precisely what it does, but it offers two different and distinct sound signatures.

I've had the amp a couple months now and I am just getting a handle on a way to describe it. It took a little playing around for it to find a home. I've tried it directly from CDP/DAC, with a preamp, with Vandersteen 2Cs, and with Sonus Faber Concertos (with and without a sub). Neither of these speakers have exceptionally high sensitivity recommended for low power amps, so that is a problem. The Vandies, at 86db, proved to be too demanding of the amp; too much clipping too often told me there wasn't a good match here (although when they weren't clipping, the speakers were sounding better than I have heard with my other amps). So I switched to the Concertos, listed at 87db. These were more steady, no clipping; but straight in from the CDP/DAC/ZEN the gain had to be maxed to get a full range sound. At that, most small scale instrumental acoustic music played out very well, but it did not reach satisfying levels with music of greater dynamic range or scale, like orchestral or progressive rock, or recordings with very low gain. So that's when I introduced the preamp: Conrad Johnson PV10A. This pre adds enough gain to make a significant difference, and of course it provides the extra inputs, tape loop, and particularly useful--the phono pre. Though the preamp colors the sound of the amp the slightest bit (it seemed to take on a hint of gold) it didn't seem to interfere in any other way. So now with the CDP/DAC/Preamp/Zen/SF Concertos I had the system I wanted to run.

For comparisons sake, the only other tube amps I've heard for any kind of extended listening were the Conrad Johnson MV55, Cary KT88, and the Jolida 302A (which I also own). In my experience, the Jolida and the CJ have similar sonic characteristics, which could be expected from the use of the EL34s in both. They offer a lot of what is often described as the typical tube sound: warm, bloomy low-mid range, rounded liquid tones, sweet rolled off highs, a lush sound that complements acoustic and vocal music especially well. I found the CJ to be bolder, more robust, more agile, and at the same time a little more refined than the Jolida (I bought the Jolida because I could afford it). My experience with the Cary KT88 left me perplexed. I heard it in a poor listening room with Paradigm Monitor 7s that did not seem to do the amp any justice, so I'm not sure I heard what it really can do. But what I did hear was not like the others; the sounds were glassy and clear, almost brittle, cold and revealing, thin at times. There was some realistic 3-D presence but it felt like sleet--very different from the honey tones of the EL34s. Anyway, I say this to give a point of reference.

The trouble I've had with the Zen amp is figuring out how to describe the sound, but now I can say it doesn't sound like any of those I've described, nor like any typical SS amp. It is not warm and lush unless the music is warm and lush. It's not liquid or glassy, though I might call it pearly as it's not edgy or grainy either. It's not thin sounding, but will reveal thinly recorded music. It has no extraneous mid or low range bloom, but it offers more bass that is tighter, better defined and deeper than all the others. It portrays a wide dynamic range with consistency and refinement, without any obvious or characteristic sonic signature of its own (I guess this too fits well with the principle of zen).

The switch on the front offers two settings with distinctly different sounds. In the front setting, there is lower output, but the images are more distinct and the primary tonal and timbrel characteristics are full and true. There seems to be a lot of resolution in this setting and more space between the tones. It works particularly well with solo instruments and small acoustic ensembles. It portrays an involving intimate and rich musical experience. Switching to the back position adds secondary, harmonic material, more detail around the notes and a more contiguous soundstage. The images blend together more and there seems to be altogether more sound. I can compare the difference to focusing a lens on a camera. The front setting has a deep field, but a short range of focus, so only the primary subjects are highlighted from a muted background (thus enhancing the depth and quality of the subjects). The back setting expands the range of focus, bringing more elements up front and a clearer relation between the main images and the background. I haven't decided which setting I prefer; I like both of them for different reasons, and I like having both of them--like having two amps for the price of one! I'm finding though that the front setting works best with audiophile quality recordings and seems to place more attention on the musician's performance, while the rear setting brings out more of the total sound of the performance. This difference is most apparent with vocals which come forward, apart from the instrumentation with the amp switch in the forward setting. So this is definitely the setting for those vocalists like Diana Krall, Holly Cole, and Loreena McKennitt. Enya on the other hand with her multiple layers of voices and choral groups seem to be best served with the rear setting.

Now more on the music: The harps in the Harpestry album seem to be sitting in my living room well away from the speakers, and the strings are clearly spaced across the soundstage. The overtones hang in the air and meld together like liquid. Electronic music with syncopated percussive sounds (Suzanne Ciani's Hotel Luna) take on a 3-D presence throughout the room in ways I've never heard here before. There is a cleaner and clearer presentation of densely textured instrumental music, both electronic and acoustic, though it reveals more of the sound editing and processing than I was used to hearing. I'm also hearing more distinct differences among the strings in chamber music. Paganini's Dream, a duet with piano and violin, features rich and resonant tones that seem to breathe on their own. And cello and bass music (David Darling's Eight String Religion and Michael Manring's Unusual Weather LP) is handled with strength, deep sonority, and sensitivity. This is some of my favorite music, so I was even more impressed and pleased when about five weeks into listening I replaced the MITerminator 4 speaker cable with TARA RSC Generation 2. There was an immediate difference: first, the upper mids and highs took on a more lustrous sheen where there should be sheen (cymbals, percussion); but the biggest difference was in the bass. Suddenly there was tight well delineated bass in multiple registers. It was punchy, solid and had real tonality, not just pressure and sound. And it was vinyl that brought this to my attention. Both Manring's LP and the Beatles Eleanor Rigbyprojected some bass and cello sounds that startled me for their depth, color and presence. This made me go out and purchase a record cleaning machine and sent me to the local used record store, as I am rediscovering the value of Lps: this is the best sound of vinyl I've ever had.

So with extended use I was learning that I haven't heard the best of the amp yet, and I get the sense that I am not getting the most out of this system. The amp seems to be sensitive to everything up and down the line, so it reveals the limits of my sources, cables and speakers. While the Concertos are steady and beautifully performing speakers, they seem to want more power to sound their best. They aren't the best match for this amp unless they are used in a smallish room with mostly acoustic music. So I've tested the amp with a few other speakers that I auditioned at a showroom, or happened to have available through a friend. I was able to bring some Paradigm Monitor 9s home. At sensitivity around 92db, they were much less of a load for the amp. There was more ease of presentation of detail and the music seemed to project from the plane of the speaker into the listening room more; I was getting a sense of what can happen with more sensitive speakers, but tonally, the Paradigms couldn't match the Concertos and they colored the sound with a veil that seemed to level out all the dynamic differences in the music.

Likewise, when I auditioned some Tannoy S8s (92db) in a showroom, they projected a lot of sound with a lot of punch, but they muted everything, especially in the mid range. Now this room was about the size of my listening room, but much better set up for sound. And I was using a much better CDPlayer (Wadia--I don't remember what model), so it was a different kind of test for the amp. The guys at this place were very accommodating as I spent a good 2 to 3 hours with the room to myself as they lugged speakers in and out. The best performers were JMLabs Cobalt 820 (91db). Tonally they were a lot like the Concertos, but as towers, they had a deeper more coherent bass making for an apparently broader dynamic range. Their increased sensitivity allowed them to fill the room with a big sound; the amp gain control set at about 10 o'clock. I had some compilation CDs of favorite tests cuts I made myself, so I put them through a good workout of pieces I knew very well. I was impressed, and so were some of the people at the shop who poked their heads into the room occasionally to see what was playing. There in the middle of this room was this little amp the size of a lunch box putting out some respectable sounds. Overall the sound was better than what I was getting at home, but partly because of the Wadia which was smoother and warmer than my Marantz/Music Fidelity DAC.

This only confirmed my suspicion that the Zen amp could perform better with better speakers. So I can't wait to try it with something more appropriate for low power tubes, to see what it really can do. In conclusion, I'm very pleased with the performance of this amp; it's making me listen in a new way to music that I thought I was very familiar with. It is an easy amp to listen to for a long time as it only seems to get sweeter as it warms up. It also is making me look more closely at the rest of my system in order to get the most out of it. As much as I love the SF Concertos (and the sound is really good with them right now), I know that this amp can sound better with more sensitive speakers, so I will be searching for the right match. My limited experience with other tube amps (300B, 2A3, etc) prevents me from making any useful comparisons. I don't know how the Zen compares with other low power SETs, but compared to push-pulls using EL34s and SS amps, it provides a simply different kind of experience--clear refined sound that draws attention to the music more than to itself. While my Jolida 302A seems warm enough to mask the flaws in the rest of my equipment and make anything sound pleasurable, the Zen pushes the rest of my equipment to its limits, revealing the strengths and flaws at once, yet still making for a musical experience.

Jim Kain Glen Riddle, Pennsylvania May 7, 1999

------------------------------------------------------------------------------- Product Weakness: low output demands a speaker with high sensitivity and steady load. Not at home with poorly recorded rock and pop music. Plain jane looks (it looks like a kit), though the simplicity and symmetry of the design is unpretentious and appealing in its own way. Product Strengths: neutral presentation; wide, well delineated dynamic range; strong taut bass with real tonality, if not a lot of boom and slam; pearly mids and highs crisp as mountain air; price.

-------------------------------------------------------------------------------- Associated Equipment for this Review:

Amplifier: Decware Zen amp SV84B
Preamplifier (or None if Integrated): Conrad-Johnson PV10A preamp w/ phono
Sources (CDP/Turntable): Marantz CC67 CD player > Music Fidelity X-ACT DAC
Speakers: Sonus Faber Concerto
Cables/Interconnects: Kimber Kable Hero Interconnects
Music Used (Genre/Selections): Phil Keaggy: Acoustic Sketches (guitar)
Room Size (LxWxH): 25 x 11 x 8.5
Room Comments/Treatments: no special treatments
Time Period/Length of Audition: 4 months
Type of Audition/Review: Product Owner