Would you change your amp selection knowing...?


OK - so this thread was promted by some comments on another thread - not wanting to hijack that thread I created this one...

ISSUE: some high current designed amps have an issue with speaker cables that have a high capacitance.
- the amp can be driven to self destruction because of internal oscilation caused by the high capacitance of the speaker cable
- this does NOT apply to Tube amps - i.e. to my knowledge

The amps I know of that are affected in this way are Ayre, Gryphon and NAIM
- only NAIM warns of this up front AND instruct their dealers to let customers know about it

So why don’t other brands warn about the possibility?

QUESTION:
- would it put you off?
- would you select a different amp if the manufacturer warned of this "issue" up front?

Cheers



williewonka
The point about ESL speakers and the significant capacitive load, as compared to the load from the cable, they present to the amplifiers has been mentioned twice and I see no explanation as why amplifiers seem to be able to suck that (load) up without self destruction. what gives?
@unsound re:...
and know that I use a wide bandwidth ss amp with high capacitance speaker cables
Which amp and which cables - I'm curious 8-).

Thanks

Kalali, that’s an excellent question, and I’ve wondered the same thing myself. While I’ve seen a number of reports over the years of solid state amplifiers self-destructing as a result of having to drive cables having ultra-high capacitance, I don’t think I’ve ever seen a report of an amp being damaged from having to drive an electrostatic speaker.

But while I’m not sure how to explain that, if I were to hazard a guess I’m thinking it may be related to the presence of the step-up transformer that I believe is used at the input of nearly all ESLs. Perhaps the bandwidth limitations and/or other characteristics of the transformer cause the amp to see a load impedance that is much less capacitive at ultrasonic and RF frequencies than it is at audible frequencies, and in comparison with the impedance of a highly capacitive cable at ultrasonic and RF frequencies.

And my suspicion is that the destructive oscillations which have been reported to result from the use of high capacitance cables typically occur at ultrasonic or RF frequencies, not at audible frequencies.

Also, I believe that the few ESL designs which don’t have a step-up transformer at their input, such as some older Acoustat models, have a built-in amplifier to step up the input voltage. In those cases presumably the built-in amp provides a relatively non-capacitive input impedance.

Best regards,
-- Al

In the old days Quad esl 57s could happily destroy less than stable amplifiers.
Williewonka,:
Threshold S 500 Series II
Goertz Alpha-core MI 3’s with free supplied RC networks