[AMPS] RMS POWER

[siezzi@starband.net (Steve Iezzi)]

I spent several years on a repair and test line for audio amplifiers in the
seventies.

Here's what we did to certify amplifiers to the published specs for RMS
power:

We placed the unit with cover on in the normal horizontal position.
Two loads were attached (8 ohms if we were testing for the 8 ohm spec).
The input was driven with a two tone Intermodulation Distortion waveform
(600 Hz/2KHz or the like).
The gain was adjusted to get the RMS voltage such that the rated power =
(Vrms)^2/8 ohms.
The bias current was adjusted for the minimum that would meet the published
IM distortion spec.

Then we left the amplifer running like this for 30 minutes.  To pass, the
unit had to still be running and the temperature of the heatsinks and the
transformer had to be less than 50C over ambient.

This was considered a torture test for most pieces.  If they weren't
repaired properly or set up properly, you generally would know in short
order.

I remember shipping cases of power transistors back to Phase Linear during
those days......

Steve KT4FY




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