The phenomenon of amplifier is buzzing

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Hello friends!
I have a vintage ALBA 700A amplifier bought on eBay, I discovered the phenomenon of buzzing, the louder the louder the buzzing sound, I checked the transistors that they work normally, the capacitors did not There are any bad signs. What should I do?
 

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Hi there,

Have you looked at the amount of ripple voltage on the power supply feed. If it is high, it may indicate a faulty power supply rectifier or capacitor. The sound being a 'buzzzzzz' more that a hum would confirm that. Do you have another power supply you could test it with to check this?

Hope this helps,

Mike
 
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When you buy an old piece of equipment (this one looks to be at least 40 years old), some if not all of those electrolytic capacitors will be original and probably well past their useful lifetime. Replace them - all of them, including the little coupling capacitors, because the buzz is most likely due to their failure.
 
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I think this may be a language / semantics thing. I assume buzzing (from speakers) may be what is normally called “hum” from the mains. Hum from mains might be due to PSU caps or bad rectifiers - but as the caps were replaced, it may be from a ground loop or inadvertently contacting signal ground to chassis ground somewhere. A few more closeup photos at oblique angles rather than straight rectilinear may show us more detail to help debug.

It is not clear that the aluminum chassis has a connection to earth/mains ground. Try grounding the chassis and see if it helps. Maybe use a 10ohm resistor ground loop breaker.
 
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Mooly has provided a link which gives the amplifier specs. The line level input SN ratio is only 63db. The buzzing if its a low level might be normal. Is the buzzing noise the same on all inputs? You mentioned the buzzing gets louder as you turn up the volume. Check the shielded cable ground connections.
 
Mooly has provided a link which gives the amplifier specs. The line level input SN ratio is only 63db. The buzzing if its a low level might be normal. Is the buzzing noise the same on all inputs? You mentioned the buzzing gets louder as you turn up the volume. Check the shielded cable ground connections.

"hum" sounds when not connected to input devices. I broadcast the loudness floor got "hum"
 
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