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 pre-amplifier. 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 pre-amplifiers,
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 pre-amplifier 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
pre-amplifier 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
pre-amplifier 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 pre-amplifier. 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
pre-amplifier 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.
= Poor Performance
= Under average
= Average
= Very Good
= Excellent Performance
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 Company
108 Wallace Lane
Cloverdale, CA 95425
Voice: (707)894-0176
E-mail: 6sn7@abac.com
Website: www.dehavillandhifi.com
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