Mains Type Hum

[snoopy]

I've two bridged AMP10 Basics. All was working fine, slight increase in noise as expected with the bridging. Then all of a sudden I get a constant mains hum in both channels after a week of perfect operation.

If I remove input to any one channel the hum goes from both. I've also noticed the right side is switching to mute faster when the power is removed but don't know if this is related.

Ideas?

[wadoka]

Do you hear hum directly from the torroid too, or just from the speakers?

[snoopy]

Just the speakers. Constant volume in both.

[snoopy]

I swapped the AC into one of the inputs on one amp and hum reduced considerably. Now trying to figure out what works best...

A.

[snoopy]

I've mirrored the AC in on both amps and the 5A@230V fuse blew, but nothing was damaged, so the power on spike must have gone over 1000W. Not sure how swapping the AC around would have caused this.

I forsee something blowing up!

A.

[snoopy]

Disaster,

When I had the power paralleled into board 1 input 1 and board 2 input 2 of amps and vice versa the bridges on board #1 ignited.

Any ideas?

[wadoka]

One idea, stop connecting amps at random and blowing them up he he he...
I suspect you have another bridge handy though, so no real damage done.
I found an interesting pdf about reducing amp hum on the net, I will look for it again and give you the link later today,

Matt.

[snoopy]

That I do, but why should it matter which primary goes into which board input?

[wadoka]

Just a joke, thats all.

http://www.psaudio.com/articles/hum.asp this may be a bit obvious, but its a bit of background. I cannot find the pdf online, but I tend to keep them so it may well be on my pc at home. I will have a look and can email you it later,

Matt.

[wadoka]

www.jaycar.com.au/images_uploaded/humloop.pdf

found it, it helped me reduce, but not eliminate the hum on my single amp10b.