2. amps-preamps
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Need help to trouble shoot the noisy amp.

Gentlemen,

Not too long ago, I bought a pair of hybrid monoblock amp. One is dead quiet and the other is noisy but still plays good music. 90% of the amp is point to point wired so very easy to compaire the two. The noisy one is also running bit hotter and vibrates bit more on my touch.

Upon careful inspection, I've noticed that the power supply wires are connected (bunched up) differently. The quiet one is joined with (thick red + brown + black) & (thick white + white + light brown) combination. The noisy one is joined with (thick white + brown + black) & (thick red + white + light brown) combination. It has one big toroidal transformer and on small one connected to the input tube.

Could this be the problem? All other wirings are same on both. I'm tempting to re-wire the noisy one to see what happen. However, I don't want to distroy the amp either.

Big TIA for your kind advise....
zt000
marakanetz's avatar
marakanetz
5,473 posts
 
remove the output fuse.
fatparrot
1,314 posts
 
Try swapping tubes, as a microphonic tube might just be your problem.
chuck
201 posts
 
Zt000,

Unless you are a qualified technician i would not recommend rewiring the amp yourself. As stated by others power supply capacitors can store electricity for months. Unless you know how to drain them i would recommend you defer to someone else. As for the amps noise problem. Have you switched IC inputs to verify that it is the amp you are describing. My point is have you verified that the stated amp is noisy or not?? Also you may want to check your grounds on your fusebox to verify that it has a ground rod. Also, as others have stated call the manufacturer and see if they can offer ideas. It may be possible to "lift" the ground on the amp.

hope this helps,

Johnny
cleopatra52's avatar
cleopatra52
81 posts
 
Do you hear this noise through the speakers or is it just the amp (tranformer(s)) buzzing. If the former, it is almost always associated with a ground loop. If the later, it could be the transfomer but more likely it is a bad capacitor in the power supply. I am not a technician - just going on a similar experience not too long ago.
zt000 OP
30 posts
 
Thanks All!!
I wasn't getting a response back from the manufacturer. But, finally got the response back from the original builder.

Here is what he says:
I dont know what sort of transformer they are using now. But it seems that would be the cause of it. You could rewire the noisy trans same as the quiet one, use a 3-5A fuse , and monitor the amp as you switch it on. If it blows the fuse, or is even noisier, then turn it off immediately. If it is quiet, you can call yourself a fine detective. MickMN

Though, I have a felling that I can do this task, if a qualified tech is near So. Cal. area I'd rather take it to him. Any one of you know of any tech around So. Cal. area?

Big thanks to all your kind reply......
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