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Old 1st June 2014, 11:48 AM   #11
AJT is offline AJT  Philippines
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Location: Palatiw, Pasig City
Quote:
Originally Posted by Mr Onion View Post
I shorted the input and the voltage dropped to 0VAC

When I removed the short, it rose to a stable 1.5VAC

Turning the amp off and on again initially it was ~40VAC which quickly dropped to a stable 1.5VAC without the input shorted. Shorting the input gave 0VAC as before.

My DMM lowest ranges are 20VDC and 200VAC


the input cap should have a 100k to ground connected...
another option is a 50k pot to connect that input cap to,
that way you can mute the amp at turn on...
Click the image to open in full size.


the other hum issue you are having can be due to layout and wiring....

this is how i did my gainclone...
Click the image to open in full size.
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Old 1st June 2014, 12:02 PM   #12
AndrewT is offline AndrewT  Scotland
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R5 and R3 are both shown as 22k.
Why should he change one to 100k?
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Old 1st June 2014, 12:06 PM   #13
AJT is offline AJT  Philippines
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the input cap is hanging on one side, it must not be left open like that...
100k? not critical, other values are fine, just do not leave that cap hanging
on one side...
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Old 1st June 2014, 12:11 PM   #14
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Thanks all. I'll take that board out and play with it tomorrow
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Old 9th June 2014, 12:02 PM   #15
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Thanks for all the pointers. I have re routed the cables and I am getting 0VAC at both outputs.

I'll tidy it all up later and make sure they all stay in place.

Thanks again.
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Old 14th June 2014, 10:56 AM   #16
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Its all measuring and sounding good now, thankyou all
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