[Ned Carlson]

flipper wrote:

It did make me wonder what position on the volume knob people design
their 'Hi-Fi' power amps around. Nominal power (whatever that means)
at 'mid scale'? Max power at pot maxed? And vs what input level?

If there's a volume control on a *power amp* at all, it's there
simply to pad down the input. The specs are given at a given
voltage input level (eg: "Sensitivity 1.5V input for 35 W output",
etc) to the amp itself.

Guitar amps are different as having the pots maxed typically would
have the amp clipping at the input levels a guitar pickup would
put out, and frankly, few people give a hoot about the numerical
distortion specs of a guitar amp. The pots are centered so with a
typical signal, you can check the AC signal level at various points,
without the signal being clipped and giving erroneous readings on
the kind of AC voltmeter they expected techs to use.
Probably something like a Simpson 260, often on old amp schematics
there will be a note on the diagram as to what kind of meter was used,
like "Measured with 5,000 ohm per volt meter" or "Measured with VTVM",
in some cases there may be a note that one needs to use a VTVM to get
accurate readings.



Makes for a significant gain issue as 'mid scale' to full open is
20dB.

Depends on the pot taper or how the attenuator is set up, mid
scale might be -30 dB. Still, it's irrelevant to measuring
power amp specs unless it's internal rather than simply padding
down the input, which would only be useful if the power amp in
question amp has no overall negative feedback.

--
Ned Carlson
SW side of Chicago, USA
www.tubezone.net