[chillysalsa]

I recall reading some specs. regarding Alkelines having high impedance, and this being undesirable from the point of view of supplying an amp, because of common mode noise.

If so, how do NiMH and sealed lead acid compare, if we want to achieve the lowest noise?

Can anyone find specs. to compare? I found 750mAh NiMH as being "0.02 ohm internal impedance".

 

[BlazerFRS]

I might be wrong here, but I believe that measurement is the output impedance of the battery.

Output impedance affects how 'stiff' the battery voltage (or any source of voltage) is in the face of low impedance loads. A battery with an internal impedance of .02 ohms is VERY stiff; you ought to be able to drive a load resistance down to .2 ohms w/o any loss of voltage due to loading... but .2ohms would drain your battery awful fast!

An example:
I think the battery in a cmoy sees about 2K35 ohms looking into the amp. If this is correct (back me up anyone?) you'd have to string about 30,000 of those .02 ohm batteries together in series before it'd be an effect worth worrying about.

Basically, don't worry about it; the power rails of most amps aren't anywhere near demanding enough for this spec to matter. I've used alkiline 9v in cmoy's before with no difference in sound quality; so I wouldn't worry about it.