Power Amplifiers

Mystere pa21 Stereo Tube Power Amplifier

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I tested the Mysterè pa21 with a McIntosh MCD500 SACD player, OPPO BDP-83SE/NuForce universal player, Lamm LL1 Reference preamplifier, and Carver Amazing Mark IV ribbon speakers. Cables were Emotiva and Legenburg.

One of the first things I noticed about the pa21 was that it did not roll off at the high frequencies or the deep bass. Many tube amps do roll off in these areas, and it is just something we put up with. The pa21 handled the natural harmonics of violins, and the lowest notes on a piano with ease. This is something I am not used to with tube components. Tubes themselves have a linear response into the megahertz, but it is the output transformer that limits the overall frequency response. In the case of the pa21, it has a huge output transformer, and this results in a better, deeper bass response.

The pa21 had a midrange lushness that I have come to expect. This is due to a tube amp's natural tendency to produce mostly 2nd order harmonics, which you will see in the bench tests. It produced more distortion overall than a solid state amplifier might, and the argument never ends about why consumers are happy with that higher level of harmonics, even though they are "euphonic", which means having a "sweet" sound. I am a huge fan of tubes myself, and love the characteristic that the high level of 2nd order harmonics imparts on the sound. The reason for this is that we can never really come up with an audio system that will truly reproduce the sound of a live orchestra in our listening room. It can come close, but no cigar. For a single instrument or a jazz quartet, maybe really close. Still no cigar though.

So, tubeophiles enjoy the addition of the sensory experience that 2nd order harmonics give us. This is not a term that fits within the framework of high fidelity. It is simply a sensation, and it is very pleasurable. You have to keep in mind that bench test graphs show harmonic peaks that look really big, but in fact, the Y axis is graphed exponentially, so those high peaks actually only represent about 1% distortion, or less. We would never tolerate that amount from a solid state amplifier because solid state tends to have more odd-order distortion, which is very unpleasant. Remember, all amplifiers have distortion. It is a matter of choosing your poison, so to speak - how much distortion and what type of distortion you are willing to accept. But you don't have the choice of purchasing an amplifier with no distortion.

I listened to a lot of CDs and SACDs with the Mysterè, and I think what I enjoyed most was easy listening music with female singers. There was something about that midrange sweetness that made their voices just waft through my temporal lobe (the part of the brain's cerebral cortext that is involved with emotion and hearing, among other things). Like I said, the sound was giving me not only her words and voice inflection, with piano, bass, and drums, but a sensation, and it was a sense of inner calm.

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