-- Bandwidth

      Another challenge faced by SET power amps is bandwidth. The de Havilland reaches to both frequency extremes much better than most other SET power amps.
      SET power amps are famous for their rich, musical midranges, but most are notoriously weak at capably extending their reach up into the trebles and down into the bass. SET power amp topology faces difficult challenges here. For example, output transformers like being fed in a balanced or push-pull mode, but they dislike being fed in a single ended mode, and they present some special limitations when the SET power amp designer forces them to operate in this single ended mode. These limitations imposed by the output transformer can act to worsen distortion and to limit bandwidth, perhaps at both ends of the musical spectrum. Most SET power amps have bass that's weak and/or poorly controlled, and trebles that are dull, rounded, and soft (as well as distorted).
      The de Havilland employs expensive custom Electra-Print transformers, and these, combined with the de Havilland's unique circuitry, give the de Havilland its ability to reach toward the frequency extremes of the audio bandwidth better than other SET amps.

   -- Tonal Neutrality

      Another challenge faced by SET power amps is tonal neutrality. The de Havilland sounds more tonally neutral and accurate than most other SET power amps, which are tonally colored. Indeed, for many listeners the rich, warm midrange bloom that SET power amps bestow upon music is part of the charm that makes them attractive.
      However, there is more to music than midrange bloom, and these other SET power amps usually shortchange the rest of the music in various ways. Common problems among them are that music's trebles are to tonally recessed and not articulate enough, and that music's bass is too warm, prominent, and flabby in the upper bass while being too weak in the lower bass.
      The de Havilland has the midrange bloom that SET lovers crave, but it then balances this with a much more neutral rendition of music's treble and bass spectral regions than most other SET power amps can manage. Thus, the overall musical portrait from the de Havilland is much more balanced, accurate, and neutral.

Construction and Controls

      The de Havilland's construction features a number of costly aspects, which are all oriented toward producing better sound. Parts are expensive and oversize. Point to point 3D wiring is used throughout, to avoid the sonic limitations of PC boards. These are big and heavy (55 pounds) amplifiers, and you're clearly getting your money's worth in parts alone. It's also worth noting that your money is not wasted on cosmetic window dressing. You won't find chrome plated potting cans on the transformers, or a fancy milled chassis box, etc. The front control panel is a simple handsome thick plate of brushed aluminum, and that's it.
      The de Havilland has some interesting and useful controls. An optional stepped attenuator (not simply a cheap pot) allows you to control the input volume level. We found this very useful for being able to run our DAC directly into the power amp, for optimum fidelity. It was also useful to be able to turn down the input volume to zero for safety while changing system connections upstream.
      A feedback pot allows you to experiment with the sonic changes wrought by changing the feedback, from zero up to a maximum of 8 db. We far preferred the zero feedback setting, and our sonic report above is based on this zero feedback setting. With this amp we found that even a slight bit of loop feedback degraded the sound in a number of ways. With feedback, the music sounded more closed in and less open and airy, as expected. But, unexpectedly, with feedback the amp also sounded less tonally neutral, and also more distorted. So we strongly recommend that you use the zero feedback setting (fully CCW).
      The de Havilland is also designed to accept a variety of tubes as the driver tube, including the KT88, 6550, and 6L6GC. You can choose an alternate type of tube to alter the tonal personality of this amp. The above report is based on this amp used with the KT88 that comes standard. You could also deliberately adjust the de Havilland's bias control away from the recommended optimum  .52 volts measured at the test points, to make the sound warmer or leaner (note though that increasing the bias will probably shorten tube life).
      This power amp is easy to sum up. The de Havilland Aries gives you more than any other SET power amp at up to 6 times to 10 times its $3995 price [now $6000]. The de Havilland Aries gives you two crucially important things that these other SET power amps don't: better intrinsic sound (lower distortion, wider bandwidth, better neutrality); plus the invaluable ability to pick and choose the best sounding speakers to mate with the amp.
      The de Havilland Electric Amplifier Company is located at: 1701 Santa Rosa Ave, Santa Rosa CA 95404; phone 707-527-6980. Website address is www.dehavillandhifi.com.

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