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July 2007
A Conversation With Chief Engineer, Kara Chaffee...
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.
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
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
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
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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...
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