deHavilland Electric Company UltraVerve Line Preamplifier
Review By Dick Olsher
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  My theory is that over the years preamplifiers have been indirectly responsible for more audio grief than any other hi fi component. It is literally a stealth sonic offender, because so few audiophiles realize the mediocrity that lurks in their front end. More money has been wasted, in my estimation, in futile attempts to fix what is actually a front-end problem with downstream tweaks. Imagine the expense showered on exotic interconnects and speaker cables, when all that money could have gone toward a better sounding preamplifier. Many find comfort in owning a highly touted brand name or an audio classic. Well, please take note of the following personal observations, spanning a time frame of 35 years. With only a couple of exceptions, solid-state preamplifiers, regardless of price or prestige have failed to move me musically. Only a handful of tube designs have passed my criteria of excellence in the areas of resolution, dynamics, and transparency. And that grouping certainly does not include any vintage tube gear. Avoid McIntosh, and incidentally, I find the Marantz 7 to be more about hi fi than music.

Enter the deHavilland UltraVerve. It is, with the caveats noted below, about as sonically pure and transparent, as a line preamplifier can be. To understand its magic, one needs to reflect on the four cornerstones of its design philosophy: simplicity, Octals, power supply, and passive parts quality.

If you are looking for multiple gain stages, high part count, circuit boards, or tone controls, look somewhere else. The unit is fully hand-wired, in point-to-point fashion, and minimalist as far as parts count. There is only one gain stage, followed by a cathode follower stage. Hence, not only is the gain a modest 12dB, which should be adequate for line inputs such as CD players and FM tuners, but the unit also inverts polarity. The latter means that a positive going input appears as a negative going output. This is not something to fear or distrust and can easily be dealt with. All that is required as compensation is an additional polarity reversal in the signal path. In my system, I simply reverse the speaker leads at the power amplifier outputs. At first glance it may appear that there is no balance control. However, tucked along the rear top plate are two trimmer controls, which give Left-Right balancing adjustment, by tweaking the output of one channel relative to the other.

There are boys and there are men in tube world. Designer Kara Chafee's dictum appears to be: do not send a boy (e.g., 12AX7 miniature) to do a men's job. The eight-legged 6SN7GT is a beefy medium mu dual triode tube that dates back to pre World War II days. Its major production impetus, however, came in the 50s due to its use in television vertical sweep circuits. The GTA and GTB types, are nothing more than a GT on steroids - higher power dissipation versions of the basic 6SN7GT tweaked for TV applications. Although there are several military inventory designations (e.g., VT-231), these are essentially no different than civilian production, though they typically do imply pre-1946 vintage.

A premium member of the family is the industrial-grade 5692, the most sought after type being the RCA redbase series. A nifty feature, much appreciated by a chronic tube roller, is the ease with which octals can be substituted. Thanks to its keyed base, octals may be rolled in without sight of the socket. The popularity of the 6SN7GT is well deserved thanks to its ability to portray a vivid palette of harmonic colors and kick-butt dynamics, qualities that well suit Ms. Chaffee's musical priorities.

The power supply is well filtered and features tube rectification. The directly-heated 5AW4 rectifier tube draw an impressive 3.7A and would normally see duty in a power amplifier. But this is precisely the correct strategy for authoritative preamplifier sound: treat the thing like a power amplifier. Exceptional passive parts abound: Cardas Litz wiring, mil-spec paper-in-oil capacitors, Roederstein resistors, and a beautiful Goldpoint stepped attenuator that eliminates a few layers of soundstage veiling relative to the industry standard conductive plastic potentiometer.

The 6SN7 is driven with kid gloves at about one watt plate dissipation, so expect long tube life. Each triode section is direct coupled to a 6AH4 triode cathode follower stage. A relative of the 6BX7, 6BL7, and 6CK4, the 6AH4 is a TV vertical oscillator tube whose current drive characteristics make it a natural for cathode follower duty. There is only one blocking capacitor in the signal path.

The Sound
The UltraVerve's single gain stage lives and dies by the choice of 6SN7, since the preamplifier is adept at revealing differences between the good, the bad, and the ugly. Fortunately, the stock tube is a select vintage type. My unit was shipped with a Sylvania "chrome top," an excellent vintage brand, though due to limited supplies other brands may be substituted at the factory. The "chrome dome" is fairly easy to locate, and features a warm, detailed midrange. It comes close to equaling the magic of my favorite RCA smoked-glass (grey RF shield sprayed on inside of envelope) VT-231, but falls short in terms of dynamic nuances and vibrancy of timbral colors. Note that the RCA VT-231 is a 6SN7-GT type, which is my opinion is the premier type worth hunting for, as it denotes the original version of the tube, and most likely a production date prior to the TV era. Beware, there are 6SN7 types to avoid at both ends of the price spectrum. The affordable new production Russian types are definitely in the ugly category, while the much hyped RCA 5692 redbase was a definite disappointment - at least in this context - with a rather bland harmonic disposition. What follows is based on extensive auditions using the RCA VT-231.

The thing does not sound at all like a vintage tube preamplifier. Adjectives such as mellow, romantic, soft, overly liquid, or bright do not apply. There is no euphonic veil under which to hide sins of commission. Forget about sugar-coating front-end problems or mitigating loudspeaker brightness. It sounds fast and detailed without etching or exaggerating treble transients. Low-level detail retrieval is entirely a function of the front end and program material. This line stage shines in the context of a superior high-end system. Given full scope of expression, it is capable of an open, detailed, airy, and spacious presentation.

Please do not misunderstand the above characterization of the UltraVerve (UV) and its lack of obvious tube colorations to imply that it is devoid of tube virtues. Unlike silicon-based amplification, the really good tube stuff is capable of kindling reproduced music's verve. True to its name, the UV speaks directly to the heart and soul with energy and vitality. Timbral colors were painted vividly using a rich harmonic spectrum. Midrange textures ebbed and flowed with commendable neutrality, though to be perfectly honest, my preference is toward a slightly more romantic voicing. Female voice was superbly portrayed. Dynamic nuances were propelled forward with dramatic flair and subtle vocal inflections were caressed with consummate fidelity. The transition from soft to loud was especially noteworthy, zipping through a gear shift without hesitation or constriction. It stands to reason that the circuit's simplicity, tube rectification, and of course, that fabulous 6SN7 big-tone are in great measure responsible for this level of directness and musicality.

The UV had no trouble at all driving long interconnect runs. This is a consequence of its well-designed cathode follower output stage, which can be thought of as a low-impedance stage capable of adequate current drive. Surprising perhaps for a tube line stage, was the UV's convincing reproduction of bass lines. Bass impact and pitch definition were quite convincing. Bass extension scored high on the Richter scale. And best of all, the upper bass range was full-bodied, with a seamless transition to the lower midrange.

The soundstage was portrayed with excellent width and depth. Far from being tethered to the loudspeakers, massed voices were arrayed linearly across a 3-D soundstage. Closely mic'ed voices were fleshed out with almost spooky focus and palpability. The sensation of being able to reach out and touch someone was never any stronger.

Conclusion
About 20 years ago the great J. Gordon Holt pronounced the sound of the Berning TF-10 preamplifier so exemplary as to make further advances in the art unnecessary. That judgment has proved to be premature, so wisely I will not go that far. But having lived with some of the elite high-end pre-amplification from the likes of Jadis, Sonic Frontiers, and Air Tight, the deHavilland UltraVerve is currently my first choice in line amplification. At a retail price of $2,495 it upsets the ultra high-end applecart; the point being that simple, minimalist, well-engineered designs can rise to the top while being quite affordable. Low on parts count, but high on tube magic, the UltraVerve scores big in my book.

Specifications
Bandwidth: 20Hz to 80kHz

Maximum Output: 30 Volts Push-Pull

Voltage Gain: approximately 12dB

Signal Triodes: 6SN7 GT, GTA, GTB, WGT

Rectifier Tube: 5AW4 rectifier tube

Signal To Noise Ration: 85dB

Inputs: four stereo

Outputs: two stereo

Input Impedance: 50 kOhm

Output Circuit: Cathode follower; minimum 10 kOhm load recommended

Dimensions: 18 x 11 x 6 (WxDxH in inches)

Weight: 15 lbs (shipping)

Power Requirement: 115 VAC/60Hz, 40 Watt consumption

Warranty: Two-year parts; one-year labor; 90-day on tubes. Warranty is not transferable.

Price: $2,495

Company Information
deHavilland Electric Amplifier Co.
2401 NE 148th Court 
Vancouver WA 98684

Voice: (360) 891-6570
E-Mail 6sn7@abac.com
Website: www.dehavillandhifi.com