Would you change your amp selection knowing...?

Hi Steve (Williewonka),

I suspect that **many** high end solid state amplifiers are prone to adverse effects from speaker cables having ultra-high capacitance, at least if a Zobel network is not used with the cable. (My understanding, btw, is that if requested Goertz will supply such networks for use with their ultra-high capacitance cables).

In extreme cases those effects may include destructive oscillations, as you indicated and as several members here have reported experiencing. In less extreme cases, though, there may be subtle but significant adverse effects on sonics, including things like overshoot, ringing, or low level ultra-sonic or RF oscillations that are not directly perceivable as such. Whether or not such effects occur will depend in part on how much feedback the amp uses, and on its gain, bandwidth, and output impedance.

I’m somewhat surprised to see Ayre on your list of susceptible amps, btw, since most or all of their amps are zero feedback designs. In general I would expect lack of feedback to minimize or eliminate such sensitivity.

To answer your question, though, the possibility of this issue, whether mentioned by the manufacturer or not, would have no influence whatsoever on my selection of an amplifier. It would certainly influence my selection of a cable, though. A cable having extreme and /or unusual parameters would be a non-starter for me. And if as is often the case basic parameters such as inductance, capacitance, and resistance are not specified for a particular cable, and if the manufacturer can’t or won’t supply that information, and if a rough idea of these parameters can’t be inferred from the cable’s description, I would look elsewhere.

Best regards,
-- Al

Oscillation can self destroy the amp and might damage tweeters. 

I assume that amplifier can safely drive all typical cables and speakers unless manufacturer specifies limitations - like maximum load capacitance.

Since preventing oscillation usually reduces bandwidth of the amp, either thru Zobel network, shallower negative feedback, limiting bandwidth at the input or frequency compensation, then amp that oscillates was likely designed with shortcuts to improve specifications (or poorly designed).

@almarg - you bring up anothre very interesting point...

In less extreme cases, though, there may be subtle but significant adverse effects on sonics, including things like overshoot, ringing, or low level ultra-sonic or RF oscillations that are not directly perceivable as such

So another question one could ask - are members aware their amp could be suffering a less severe effect that may be degrading audio quality due to the speaker cables they have selected?

We hear so many times people finding a particular speaker cable sounds nicer with their amp - was the old cable causing issues within the amp?

@newbee ...

How come cable manufacturers don’t warn potential customers?

Well - for starters ...
- it does not apply to Tube amps (as far as I know)
- it does not happen with every solid dstate amp - high current only
- the length of speaker cable increases capacitance.
- it might even depend on the added capacitance of the speakers.

So from a cable perspective it’s not an exact science

However - i do think the amp manufacturer should make customers aware - just like NAIM does.

After spending 40 years as an audio enthusiast there still are so many variables that the customer is expected to consider - thank goodness for Audiogon :-)

Because the NAIM dealer told me up front - it made no difference to my amp selection - but if the amp had self destructed - I might be taking a different view on this question.

I would change my amp selection to favor a designer that actually knows what they're doing.  If they are clueless enough to design an amp that would go into oscillation under a cap load, then they aren't worth owning, don't qualify in the marketplace.