PE 500 and 250 amp DC volts?

[scp53]

i have both the 500(calss d one with a parametric eq) and 250 watt(unboosted version) plate amp from pe. i ran a dc volt test on it today with a muli meter i have. i set it to dc volts on 200mV. i was getting 50-130 or 150 mV with music on teh 250. that was running it low level so it was NOT clipping. i ran it with just the test leads touching the amp leads. for the 500 it was runnging similar and puting out 10 or so mV. is this normal? do all amps leak like this or what? thanks, scp53

[bill]

You measure DC offset with the input to the amp shorted, not with program material playing.

DC offset is caused primarily by bias differences on the amp's output transistors or their drivers. Anything over 100 mV is excessive. You're more likely to see this on a Class AB amp than a Class D, because in a Class AB amp, both sides of the output stage are biased on with the output at zero. It's not leakage.

Try measuring again with the input shorted and see what you measure.

HTH,
Bill

> i have both the 500(calss d one with a
> parametric eq) and 250 watt(unboosted
> version) plate amp from pe. i ran a dc volt
> test on it today with a muli meter i have. i
> set it to dc volts on 200mV. i was getting
> 50-130 or 150 mV with music on teh 250. that
> was running it low level so it was NOT
> clipping. i ran it with just the test leads
> touching the amp leads. for the 500 it was
> runnging similar and puting out 10 or so mV.
> is this normal? do all amps leak like this
> or what? thanks, scp53

[envisionelec]

> i have both the 500(calss d one with a
> parametric eq) and 250 watt(unboosted
> version) plate amp from pe. i ran a dc volt
> test on it today with a muli meter i have. i
> set it to dc volts on 200mV. i was getting
> 50-130 or 150 mV with music on teh 250. that
> was running it low level so it was NOT
> clipping. i ran it with just the test leads
> touching the amp leads. for the 500 it was
> runnging similar and puting out 10 or so mV.
> is this normal? do all amps leak like this
> or what? thanks, scp53

First, you cannot reliably test DC offset with a signal. Your meter will not accurately see residual DC voltage while looking at a comparatively high AC voltage. If it was the opposite (AC on a DC bias) then your meter has a better chance of reading properly.

Remember, 100mV is only 1.25milliwatts into an 8 ohm load. 10mV is 12.5 microwatts.

I wouldn't worry about it.