Mrtennis 02-07-11: So, you are saying that a tube amp would have a different frequency response than a ss amp, when driving an electrostatic speaker.Yes. The ss amp will produce a brighter and more extended top end than the tube amp with an electrostatic (which may or may not be preferable, depending on the particular components, the room, the listener, etc). The same ss amp will produce a weaker and less extended top end than the same tube amp, when used with dynamic speakers having an impedance curve similar to Bryon's Focals.
In other words, one amp can be either more bright or less bright than another amp, depending on the speaker that is being used!
Would you expect the difference to be as much as 5 db difference at frequencies exceeding 3 db, or what difference in spl would you expect and at what frequenciesIt depends on the damping factor/output impedance of the tube amp, and the impedance curve of the speaker. I did a quick calculation based on the impedance characteristic of the original Quad ESL, and based on a 2 ohm output impedance (damping factor 4) for the tube amp, and a 0 ohm output impedance for the ss amp. The ss amp in that case would be about 6db stronger in the 15 to 20kHz area than the tube amp. The 6db number would be smaller if the damping factor of the tube amp were higher.
How might the frequency response change if the amp was a hybrid (tube input stage), such as the aria amp, designed by mike elliot? I have quad esls and am considering the aria wt 100. It has a tube front end and bipolar transistors.With respect to the effect we are discussing, that amp would behave the same as a purely ss amp. What counts is the type of output stage, which is ss in this case. Consistent with that, the amp has a damping factor of 44 according to the specs shown in this review.
An important consideration with many electrostatics, also, is that the amp not be weak in terms of its current capability, because current requirements will be increased as a result of the capacitive nature of the speaker's impedance. The WT100 certainly appears to meet that requirement, based on the specs and description shown in the review linked to above.
Learsfool -- just saw your comments. Thanks! Your perspectives on these kinds of questions are always particularly valuable.
Best regards,
-- Al