2. amps-preamps
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Tube Ampp Almarro low level hum

My Almarro 318B amp has recently developed a low level hum that comes and goes. I have swapped out all 4 tubes at one point or another and that does not change it. Once the hum stopped for a few days while I was breaking in a new paid (NOS) of 6C33C tubes. But it keeps coming and going. It gets a bit louder and then softer. If I tap the base of the amp, the hum stops. If I pick up the amp, it stops. If I knock the table where the amp sits, it stops.

I run the amp about 6-8 hours a day. Once a week I foget and leave it on all night.

Any ideas?

Thanks

Dan
mcmanus

Showing 4 responses by mcmanus

mcmanus OP
82 posts
 
The transformers are very secure on the chassis. With the suggestion of the current, I checked my circuit and found some other appliances (a laser printer and scanner) that were plugged into different plugs on the same circuit. I moved those and had no hum for two days. Now it is back but much much lower so I believe it is a current issue. I can live with the current hum but I'll send an email to Almarro to see if they have any ideas. Thanks to all for the great advice.
mcmanus OP
82 posts
 
Jax2 - good thinking. If it is a transformer, is it humming because it is aging? Malfunctioning? Or is that just how transformers are? Can I address the source of the problem or just deal with the symptom? Thanks for your comment.
mcmanus OP
82 posts
 
I placed weights on the transfomers and indeed that solved the hum problem. Then I tried using springs under the amp to isolate it and that solved the hum problem without the weights. Thanks for all the great advice to solve the problem.
mcmanus OP
82 posts
 
The hum came back after a few days on the springs. So the weight is the ultimate answer to this problem. I just need to find one that matches the ascetics of the amp :) Thanks.
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