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Old 11th September 2005, 08:54 AM   #1
dome406 is offline dome406  United Kingdom
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Exclamation 8V on outputs

I have just finished making a gainclone which sound good at the moment however buzzes/hisses so need to look at grounding etc. The dc offset with noload and inputs shorted is 25mv and 7mv.

However I was measuring the dc offset or something like that on my old amp (a panasonic thing which has an integrated tuner cassette deck and balancer it is combined 30W) that I am using at the moment for my speakers and it gives out 8V on its output !!! I am measiring with no load and inputs shorted. It doesn't change when I turn the volume up or down or unshort the input.

Is this the way I am measuring it, or is this true with some amps, I don' want to damage my speakers but I will be using my gainclone soon so it won't matter too much until it explodes .

Thanks
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Old 11th September 2005, 09:15 AM   #2
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If it's a very old amp, it may well be single ended. In that case, the output electro may well have gone leaky with age and is passing dc from the biasing.
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Old 11th September 2005, 09:19 AM   #3
dome406 is offline dome406  United Kingdom
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It is very old it may be over 10years old because I have had it for 6 years and my uncle had it in his garage , is it damaging my speakers because that is the last thing I want
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Old 11th September 2005, 03:16 PM   #4
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It could damage your speakers,if the caps are really leaky,but you'd probably notice the speaker cones moving in or out when you turn the amp on?
They probably aren't leaky enough to cause major damage right away,but it's something you want to check out

Try measuring the voltage across the output with a couple 8ohm resistors in place of the speakers as a 'dummy load'.
There should be very little (if any) voltage across the output with a load on it.
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