A Conversation With Chief Engineer, Kara Chaffee...
Or, Why Consider deHavilland?
This month we highlight dehavilland
Electric Amplifier Company. With four pieces of equipment highlighted, we
also felt many of our readers would like to learn more about the company. While concentrating on parts and build quality over
putting money into super fancy cabinetry, deHavilland Electric Amplifier
Company offers very reliable, excellent sounding products. And so our
question and answer session begins...
Q: What is "pure Class A"?
A: "Pure Class A" means that 100% of the music
signal is handled by a single output device. Most amplifiers divide the
music signal and feed it to multiple tubes or transistors. The signal is
then reconstructed later. It is like trying to focus several movie
projectors on a single screen, and have all the images line up exactly.
The Aries amplifier never takes the music signal apart, so it does not
have the problem of putting it back together again. No engineer, if they
were being honest, would deny that this is the best way to handle a music
signal, given you could get enough watts. And we do. Through experience I
have found that single-ended is its own thing, it does not sound like a
multi-tube design, and it doesn't sound remotely like solid-state. It is
its own entity.
Q: If a single tube is such a good engineering approach,
why doesn't everyone use single-ended designs?
A: Fair question. The historical limitation to single
ended sound has been the lack of power. The classic single-ended amplifier
is the 300-B type amp, which is good for about seven watts. People have
gotten around the power problem by utilizing horn-loaded loudspeakers,
which is fine if:
A) you like horn sound, and
B) you have a big livingroom.
Q: Why a deHavilland?
A: It was our goal to build a single-ended amplifier
that would drive medium efficiency , as well as high efficiency
loudspeakers -- and still deliver the midrange magic that single-ended is
justly famous for. Much of the research and development was done using a
pair of B&W 805 minimonitors, which are about 86dB efficient. Many
non-horn type speakers are 90dB efficient or greater, and the Aries -- 845
drives them beautifully. As the Aries design matured, we ourselves were
impressed that the amp sounds like a much bigger amplifier than the
numbers would suggest. There is something very important about the quality
of the watts, that gives the music a free and dynamic quality, having less
to do with the maximum power output, than you might imagine.
Q: What is the story with the 845 tube?
A: The 845 is an exceptional audio tube built like a
radio transmitting tube. The plate on this tube is machined out of a bar
of solid graphite, and can withstand very high power dissipation and
voltages. There is no way to get large amounts of power out of a SE amp
without a tube like this. The 845 is also one of the most linear triodes
available. The inherent linearity of a tube like this helps to give the
music that three dimensional magic that we all love so much.
Q: And what about the GM-70 tube?
A: It's a big Russian power triode which is getting
popular in the Far East- its similar to 845 but bigger. You can get a few
more watts out of it and it can drive more speakers. Sonically it is a
higher gain tube than the 845 -- which gives it a little more forward
sound. It gives us the option of really tailoring the amplifier and
speaker sonics to best advantage.
Q: The 6AU5 is an unusual tube isn't it?
A: We tried all kinds of driver tubes and finally found
the 6AU5. It is an early television sweep tube, and is wonderful sonic
complement to the 845. The 6AU5 has the midrange sweetness we were looking
for, and also had the sense of drive and pace that gets you emotionally
involved with the music. The 6AU5 is classed as a "high
purveyance" tube which means that the tube is willing to deliver
current to the grid of the 845 on demand. If you look at the grid of an
845 it looks like a kitchen toaster element.
Q: And the 6SN7?
A: The 6SN7 is a tube that single-ended people describe
as having "BigTone". It is a dual triode that has a very open,
relaxed and graceful sound, without sacrificing detail. Introduced by RCA
in 1939, it is hard to find a driver tube that is more rugged, and
sonically consistent.
Q: What is the story with zero feedback?
A: The Aries 845 amplifier uses no feedback loop or
"negative feedback" at all. This is probably the most difficult
way to design an amplifier, because the amp has to sound good just the way
it is. Feedback was traditionally used to lower distortion and improve the
tone of an amplifier-for example if you remove the feedback from most
audio amplifiers, they sound "yelly" or have a tunnel kind of
tone. With a carefully designed triode amplifier you spend endless hours
matching and understanding the strengths and weaknesses of each component
in the amplifier, until it sounds balanced and natural without adding
feedback. The benefit then is that the amplifier sounds more open,
immediate, dynamic and natural. Feedback tends to homogenize the sound.
Q: What do you mean by voicing?
A: Ah, my favorite subject. Voicing is what takes a pile
of electronic
parts and molds it into a musical instrument. Electronics textbooks
describe basic circuits well enough, but rarely address what the things
really sound like. There are endless subtle variations of components and
circuitry that make a difference in a good amplifier. This becomes
especially important in a low-feedback design. You can't depend on
feedback to fix the circuit if it sounds bad. You must work with the basic
circuit until it is well behaved on its own.
Q: Isn't single-ended performance compromised at the
frequency extremes?
A: In many single-ended amplifiers this seems to be the
case, but I think this is mainly due to a lack of power. Listeners are
usually shocked by the bass performance of our amplifier. The bass is
crisp and powerful. A jazz recording with a well recorded double bass will
astonish you. There is no bloopy halo surrounding the bass.
Q: The imaging is exceptional. What does this?
A: The single output tube is part of the story. All the
musical information is happening in the same time and phase. Your ears
then have an easier time reconstructing the image. Also the power supply
in the Aries is very overbuilt. A good amplifier is like a pyramid. Nine
tenths of the amp is really power supply, and one tenth is the audio
circuit proper. You want the power supply wagging the audio, rather than
the audio wagging the power supply. Our power transformer , for example,
could easily run two amplifiers. By overbuilding here, the supply voltage
sags very little when large demands are put on the amplifier.
Q: What about distortion?
A: The Aries amplifier measures 0.1% distortion at 1
watt, and around 0.2% at 5 watts. Although all single-ended amplifiers
measure higher distortion as they approach maximum output, this doesn't
seem to be a big problem. I have compared the Aries with amplifiers which
had far more power output, and the Aries sounded cleaner, more dynamic,
and more listenable.
Q: Where is the chrome trim and gold plated metal?
A: The amplifier is not supposed to look like a Wall
Street bank. We put considerable effort into the front plate, but overall
the chassis is functional. It may sound like a cliché, but I spend the
money on the circuitry and components. People who are going to buy an
amplifier like this have probably owned a couple of tube amplifiers
before, and want more of what they love about tubes. We are a company of
tube nuts and build amps that we like to listen to. The amplifiers I
listen to at home are a dead-stock pair of production Aries. We have put
everything we know how to do, into this amp.
Q: How do you sum it up?
A: After thirty years of building amplifiers and
listening to hi-fi systems, what I really want is a piece of equipment
that gets out of the road. I want to kick off my shoes and forget that I
am listening to a machine. The Aries is remarkably un-mechanical in sound,
and yet has superb clarity. It just does not throw this clarity in your
face all the time, like a teenager saying, "look at me! look at
me!". One last point is this. The audiophile world often competes on
the basis of an arcane checklist of sonic technicalities. The real acid
test of an audio component is whether the owner listens to it. A good
audio component has to beat out the television, video game, and the
computer." Its a real "John Henry" test against the steam
hammer!
Company Information
deHavilland Electric Amplifier Company
332 Alamo Square
Alamo, CA 94507
Voice: (925) 837-7201
E-mail: 6sn7@abac.com
Website: www.dehavillandhifi.com