On Tue, 19 Oct 2004 17:36:56 GMT, (Don Pearce)
wrote:

On 19 Oct 2004 16:58:30 GMT, ohawker (Andy
Evans) wrote:

I would be more inclined to find out what the variac is doing to the amplifier
and fix that. Not to experiment

I don't have measurement equipment unfortunately, apart from my usual DVM. what
is the actual construction of a variac? I had imagined it was an isolation
toroid with a large series of taps off the secondary. Andy


Pretty much - except there is no secondary. It is a big tapped choke
rather than a transformer. The turns ratio still applies to get the
output voltage, though. Picture the way a volume control works, and
substitute an inductor for the resistor and you have it.

You beat me to it! But you have to imagine an olde worlde wirewound
volume control. :-)
--

Stewart Pinkerton | Music is Art - Audio is Engineering