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Positive Feedback ISSUE 2
august/september 2002



Zen SE84B triode amplifier

as reviewed by Mark Katz, Victor Chavira, and Dave Clark


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Soundlab A-1s or Tannoy Saturn 8s.

Melos 402 Gold Triode monoblocks with MAT 1000 circuit boards. Kora Triode preamplifier.

CEC TL-1, Marigo Reference 3 Digital Inteconnect, and Museatex Bidat DAC. CAL Icon II CD player and Audio Alchemy DAC. Day Sequerra FM Reference tuner.

Goertz AG2 or FMS Black speaker cables. Goertz Triode Quartz and Clarity Custom Connections interconnects.


one.jpg (6551 bytes)  The Decware SE84B stereo amp is a small, shiny, gray box with four tubes, modest but functional binding posts, and a black Hammond power transformer. The box resembles a military surplus piece from the ‘50s. You can hold it in one hand without too much strain, which I find is a pleasant contrast to amps that are better carried with a hoist and crane!  The glossy fact sheet proudly points out that the amp is hand built, with point to point wiring and only a capacitor and two resistors in the signal path, is self biasing, and can be used without a preamp due to the variable input sensitivity. It can easily be externally wired to be used as a monoblock, if the owner decides that two amps are better than one. It generates an optimistically rated 5 watts, about 9 watts if used as a monoblock. It is available prebuilt for $549, or discounted as a kit, directly from Steve Deckert in Peoria, Illinois.

There’s a input tube bias switch in the front which changes the sound of the amp, and emits a loud pop if you are brave enough to use it with the amp turned on. The power switch is on the back, along with a volume pot shaft (no knob). The tubes are currently available and quite inexpensive—a Svetlana 6N1P serves as the input tube, a 5Y3GT as the rectifier tube, and two Svetlana SV83s wired in triode as the output tubes. The manufacturer estimates a total retube would run about $30, but only the output tubes are likely to require frequent replacement. At first I thought these slightly unusual tubes might be hard to replace if Svetlana stopped making them, but I found out that one may substitute a common 6DJ8 for the input tube and EL84s for the outputs.

I first hooked up the SE84B to the Tannoy Saturn S8s in my living room video system, with a Kora Triode preamp and a Pioneer 701 Laser Disc player. The treble was excellent and the speakers could play fairly loudly, but unfortunately the lower mids on down sounded muddy.

While the speakers are relatively efficient at 91dB, they are rated at 6ohm nominal impedance, and the pairing wasn’t ideal. The Music Reference RM10 works much better with these speakers, though the Decware might work well as a treble amp in a biamped system. Next up was my homebrew Tannoy Monitor Gold 12 dual concentric in Lockwood Studio cabinets, also about 92dB efficiency but an easier 8 ohm load. This made a more appropriate pairing. The rest of the system included a CAL Icon II HDCD player as transport and a modified Audio Alchemy DAC 1 with the output stripped out, coupled to a Loesch-Wiesner tubed preamp. I found the sound with the bias switch in the front position more subtle sounding and natural, though punchier with the switch in the back position. I’ll describe my listening with the switch in the front position and the volume pot all the way up.

Piano was very well resolved, with good tonality and clarity. I heard some dynamic compression, but no gross clipping distortion, even on peaks. On Ravel’s Jeux d’eau on the Conifer label (75605 51755 2), played by the superb Kathryn Stott, the feeling is laid back, relaxed, but playful and appropriate to the music. Earl Wild’s transcriptions of Gershwin on Chesky CD 32 is one of my favorite CDs. Imagine Gershwin as nineteenth century romantic/classical music and you’ll have a rough idea! Track 11, "There’s a Boat Dat’s Leavin’ Soon For New York," from the Fantasy on Porgy and Bess, has complex runs that can test the resolution of even a fine system, as well as microdynamic shadings that give the music much of its character. With this amp, I didn’t find the typical midrange bloom of my single-ended 300 B amps. I heard a sweet, clear presentation with no blurring of piano lines. Impact, tone, and decay were all dead on. Presentation remained polite, with the image more between the speakers than in front, and always enjoyable.

I use the title track of Bela Fleck’s Flight of the Cosmic Hippo CD (WB 9 26562-2) to check out bass performance. Small tube amps aren’t generally known for good bass. On the easier-to-drive Tannoys, the bass was solid and well defined and didn’t fade out as the synth growled deeper. At the same time, the banjo plucks were clear and musical.  Compared to my 300B SE amps, the presentation again had less midrange bloom, less impact at similar volume, but better detail and clarity.

The Dorian release of the JS Bach Secular Cantatas (DOR 90199) features soprano Dorothea Roschmann as the daughter in the humorous Coffee Cantata. It’s easy to forget that Bach wrote some fun, light music. The "Coffee Cantata" has a tenor introduce the piece, followed by the baritone-voiced father lamenting his daughter’s coffee addiction, a commentary on the new (to Bach) coffee craze that was sweeping Europe. This is followed by the daughter trying to negotiate her right to drink coffee, pretending to concede but planning to get her beloved caffeine-laden beverage anyway. This musical dialog is accompanied by the excellent Les Violins du Roy and harpsichord. While an enjoyable CD in its own right, it’s also a great way to hear tenor, soprano, and baritone voices realistically portrayed. With the Decware, the soaring flute in track 12 had proper breathiness and detail. Voices were quite realistic in all ranges, with no excessive sibilance. The baritone was a bit less chesty than I’m used to, but still believable. The background harpsichord and orchestra were in proper perspective.

On an experimental Lowther design, the amp was excellent on simple material, but not as good at resolving detail in complex orchestral material as a much more expensive E.A.R. push/pull triode amp. On a pair of Tannoy Monitor Gold 12s in custom five cubic foot cabinets, the amp performed similarly to the Tannoys in the Lockwood cabinets—very nicely.

The Decware SE84B is not for everyone, but it is an amp for those with easy-to-drive speakers, i.e., flattish impedance curve with no dips in the bass (like my Saturn 8s), a 92-93 dB/watt efficiency or better, and few drivers. The amp does convey some of the single-ended "magic" without the midrange exaggeration common to 300B SE amps. This amplifier is a genuine bargain if you have the right speakers. Mark Katz





Reimer Wind Rivers.

Clayton Audio M70 monoblock amplifiers. HRS unit and Taddeo Digital Antidote Two. E.A.R. 834P phono stage. Blue Circle BC3 preamp w/Amperex BB tubes, and BCG3.1 power supply.

EAD T1000 transport and 1000 Series II DAC with Audient Technologies’ Tactic and Audi, Nordost Moonglo digital cable. Linn Axiss turntable with K9 cartridge and Basik Plus arm.

Nordost Blue Heaven and SPM interconnects, and SPM bi-wired speaker cables.

API 116 Power Wedge and Coherent Systems Electraclear EAU-1 parrallel conditioner. Dedicated 20 amp ac circuit. BDR cones and board, DH cones, Vibrapods, various hard woods, etc.


two.jpg (6646 bytes)Do 8-ohm, 94dB sensitivity speakers imply an easy load for a 2- to 5-watt SET amplifier? Our Reimer Tetons are just such speakers, but an easy load on paper does not necessarily lead to a happy mating with a very low-powered amp. I believe the issue goes further than ohms and dBs. Two speakers with the same specs may differ widely in terms of design. An 8-ohm, 94 dB two-way is not the same as an 8-ohm, 94dB three-way, much less a speaker like the Teton, which has seven drivers per side (two front-firing woofers, two internal isobaric-chambered woofers, along with two midrange drivers and one tweeter). The issue is the number of drivers (and the type of crossover), not just the sensitivity and load. You can use a go-kart engine to power a racing car, but it may not work very well. This is pretty much what I experienced with the ZEN 84B triode. The Tetons were not the speakers in mind when the 84B was conceivedsingle driver Lowthers or more likely horns! The Tetons have the right specifications, but not the right execution. As such with the number of drivers requiring power and control, the 84B is at a distinct disadvantage.

The 84B is a cute little amp, and one in which simplicity is the name of the game. It has the minimum number of parts inside to get the job done. To the end of keeping things simple, it also sports a volume pot, allowing the user to avoid the need for a preamp, assuming that only one source is used and that the amplifier’s input impedance is compatible with the source.

You already know that this was not a match made in musical heaven, but neither was it musical hell. Amazingly, the ZEN drove the Tetons to very reasonable levels and never embarrassed itself, sonically or musically. I sat there day after day, mumbling to myself, "Two watts, only two watts!" Alright, so the bass was not even close to that of the Claytons, but bass there was—more amorphous than textured, loose than tight, rolled-off than extended, but still appreciated musically. And the music was dynamically restricted, but not glaringly so, though you could tell that this many drivers was just too many for the ZEN to control. But, the essence of the music was still there. A little closed-in? Sure. But I still enjoyed disc after disc, LP after LP.

Not extended? Of course. Rather soft at the top and bottom? Naturally. Rhythmically constricted? Yeah. A lot less? Perhaps, but again, music through the ZEN was quite enjoyable. No tonal aberrations, no drastic signs of stress, just less of what we hear with amplifiers possessing greater horsepower. What do you expect with two watts?! Using music that is more of the middle ground sonically (as opposed to bass/dance driven titles) the 84B really showed its stuff. Even so, most music came across with enough musical "essence" to let me hear what the SET mantra is saying.

I am certain that the Reimers were not what the ZEN designer had in mind, but the fact that I spent several weeks enjoying it with them speaks volumes about how the amp might work with friendlier speakers. Would I buy this amplifier if I had speakers to match? Yes, certainly, it was just too cool. Can it be made better? Well, there appear to be many available parts modifications, allowing for greater transparency and drive. Better caps, resistors, and transformers might do the trick, and hey, what about tubes as well? The ZEN is a bargain at the price! Dave Clark





Magneplanar .5.

Sonic Frontiers Anthem 1 amplifier.

Audio Electronics CD1 player.

Kimber PBJ interconnects and Tara Labs RSC Prime Bi-wire speaker cable.


three.jpg (8484 bytes)High fidelity audio exists in two universes, one occupied by boutique brands, multinational corporations, and specialty companies, the other a Twilight Zone in which audio experimenters are limited only by their imaginations and the laws of physics. Decware is firmly within the Twilight Zone. The Decware Zen Triode SE84B is a single-ended stereo amp which features point-to-point silver wiring, class A1 operation, tube rectification, ATOM capacitors, a 6922 input tube, and SV83 output tubes for three watts of power. It is small enough to fit atop my B&W DM 302 monitors.

The Zen has a sweet, non-fatiguing sound that will give you more than a glimpse of what single-ended triode is all about. It sounds similar to the Welborne Apollo monoblocks we reviewed recently. Both amplifiers envelop the listener with harmonic richness, especially in the midband. Both excel at portraying microdynamics and dimensionality. However, the Apollos’ mighty 300XBR output tubes, massive transformers, and hefty power supplies produce uncommon amounts of bass and thunder, while the little Zen can barely muster enough steam to blow out a candle.

Let me give some examples. I listened to Ibrahim Ferrer’s Bruca Manigu. His voice sounded harmonious and emotional. I could perceive the shape of his mouth and warm resonant chest. The violin balanced just the right amount of metal and wood. The band was correctly placed around the vocalist at center stage. The music was pleasing, except for one key element—scale. I could sense the presence of real performers, but they lacked drama and impact  Also, convincing bass was only hinted at. Another example is Santana’s much-lauded Supernatural CD. The Zen went a long way toward softening the hard textures on this up-front pop recording Congas sounded less slappy and more organic, timbales less clangy, more resonant. Santana’s guitar also sang more sweetly, but bass beats and pacing lacked force.

My B&W DM302s are fairly efficient at 91dB, but I think 100dB would be a better match for the Zen. For this amplifier to perform its best, it needs a second stage of amplification, by which I mean a high-sensitivity horn. This would allow the Zen to operate within its comfort zone. Otherwise, I can only recommend the Zen as part of a small bookshelf system.  Victor Chavira





On behalf of myself and the entire staff here at Decware, we would like to thank all of you for your time and efforts!

Over the past couple years we have been approached by several popular hi-fi mags with an interest in this amplifier. We have even sent a few off for reviews and received glowing phone calls about its sound—only to be later forgotten for a lack of willingness on our part to advertise with them. We think this amp is good enough to stand on its own without "paying" for glowing reviews. It is a real pleasure to see that yor publication is not like this, because as you well know, we have made no effort whatsoever to advertise in your magazine.

On that positive note, Id like to make a couple brief comments about your reviews;

First off, the obvious issue with this amplifier is speaker matching. For many, like yourselves as a good example, "normal" speakers give you a wonderful taste of high fidelity at lower listening levels. Victor is correct when he comments that a high sensitivity horn system would be ideal for listening without any restrictions.

We anticipated this and address the issue by personally consulting each customer prior to purchase, and then after the sale. We also help those with less than ideal speakers to find affordable speakers that do work well. We also designed the amp to be bridgeable into mono blocks with the pair adding another 6dB of headroom. (Usually a cost-effective option)

Mark and Dave both mentioned that speakers with an easy to drive load (i.e.. no dips in the bass) would be a better match for this amplifier. An easy assumption to make, however untrue. You see the SE84B puts out more power into lower impedance loads.

For example 4 ohm speakers usually work much better than 8 ohm. In fact this amplifier has no problem driving loads to less than 1 ohm. On the flip side, a 16 ohm load (like the Lowthers that Mark tried) only see about � a watt RMS of output from this amplifier.  Hence the break-up during complex passages i.e.. clipping.

What this amplifier does not like is complex speakers and or crossovers. For example, a Zobel impedance network in a crossover, or complex multi-driver speakers usually cause pre-mature compression limiting the entire performance. The reason is simple, when you have a complex crossover a large percentage of that first magical watt is spent as heat before it reaches the drivers.

That said, we did a minor revision on the amp in April of this year (SE84C) and recently in October we have started selling a new SELECT version of the amp which sonically pushes the envelope by using the same parts as found in our more powerful Signature Gear. At the same time we re-introduced our original $499 price for the SE84C and even have some used SE84B amps that were traded-in.

Steve, Dave, Larry, DeVon & Bill
Decware/High Fidelity Engineering Co.

Zen SE84C amplifier
Retail $499

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