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kctess5 30th November 2012 05:15 AM

Noisy Gainclone
My gainclone (3875 kit) has been bugging me recently. It seems to be noisier than when I first built it.

It is a steady buzz, and it seems to be worse at night than during the day. I suspect that my neighbors spa pump has something to do with that.

The power supply caps are just the ones that came with the kit. Not at all upgraded. It was the first amp I ever built so the craftsman ship isn't impeccable but not terrible either. I might be able to take it into my school to test it with an O-scope but it would be a very big hassle.

Are there any common sources of noise that I could fix easily in the design? Possibly upgrading the power supply caps?

The speakers it is powering are very sensitive, they only need about 5-10 watts for very loud levels. Because of this, I am enacting a temporary fix: I got an L-pad and I plan to put it between the amp and the speakers and then turn the amp volume to a mid level (it is usually very low down) and tune it down with the L-pad. I figure this way I will lower the noise floor, hopefully enough that the buzz will become inaudible.

Thanks! Let me know what further information could be of use for a diagnosis.

zimmer64 6th April 2013 04:59 AM

You can try a filter on the AC line. Something like this perhaps :

It did the trick for me.



icyjellybean 11th April 2013 04:40 AM

"Upgrading" the power supply caps won't help.

AC filters, as suggested by Michael are usually effective and worth trying. Though speaking from personal experience, these type of devices are not always positive in regard to sound quality.

An easy-to-implement alternative would be creating an RC filter at the signal input. If you already have an input resistor, simply add a small (no more than 3 digit pfs) film capacitor after it. No negatives perceived so far (in my system).



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