Audible "buzzing" from amplifier case.. any experience?

[as labs]

Question for those more knowledgeable about amplifiers than me:

I have been hording power amps that i find for cheap (ie used) over the years and a few of them have an audible "buzz" radiating from the case.

I do not hear the buzzing through the speakers, just the case.

Any idea what this could be? I suspect some degraded components in the power supply... not an expert.

My newest is a 10-20 year old bryston 7B that sounds normal enough through speakers, but the buzz from the case is actually pretty loud. The buzzing starts immediately when powered on whether it is connected to a source, speakers or nothing. it is not volume dependent, just ac mains on or off.

Any thoughts?

 

[AudiOhm]

Have you removed the covers to look inside?

Older transformer laminations can be a problem...

Ohms

 

[DVDdoug]

It's probably the main power transformer. I think these things always vibrate to some extent so it's a matter of trying to find & stop the rattling.

And there has been some discussion here about it being worse when there is DC on the power line and there was least one solution for removing the DC. (I couldn't find it in a quick search.)

 

[Doodski]

My newest is a 10-20 year old bryston 7B that sounds normal enough through speakers, but the buzz from the case is actually pretty loud. The buzzing starts immediately when powered on whether it is connected to a source, speakers or nothing. it is not volume dependent, just ac mains on or off.

Any thoughts?

Bryston offers a 20 year warranty. Have you approached Bryston?

"Proof of purchase in the form of a copy of the bill of sale from an authorized Bryston Dealer/Distributor must be presented to obtain warranty service."

There is mention of a series of serial numbers that do not require a bill of sale? It's best to read the warranty webpage if you are looking for warranty service.

 

[Chrispy]

Might try adjusting tension on screws holding power supply to the chassis....

 

[Nonick]

Thats the power transformer lamination buzzing. Ive had it with Denon DRA800H.
You can try to solve it with:
- open case and adjust screw pressure of power transformer to case base
- remove screws and insert a rubber bottom circle paddings on holes, under power transformer.
- if this doesnt solve buzzing, you can tighten lamination with metal "squeezer"

 

[sergeauckland]

All mains transformers buzz, due to magnetostriction. https://en.wikipedia.org/wiki/Magnetostriction
However, whether it's audible depends on how the transformer is encapsulated or varnished, and how it is mounted on the amplifier chassis, and whether the chassis panels are well damped or can resonate to the transformer buzz. What the amplifier sits on may also resonate.

As has been mentioned above, any DC on the mains will worsen the buzz, especially in toroidal transformers, so a DC blocker can be useful.

If it's the panel(s) resonating, you can try damping pads, you can also try changing what the amp sits on, and as has already been suggested, check the transformer clamping. Sometimes slackening the mounting screws slightly helps, other times tightening them does, and at other times, nothing helps! There's no one solution, a case of try it and see what works best.

S.

 

[as labs]

I tightened the transformers and it actually worked! I have to be honest here, i'm surprised!
The model is a 2B-LP, not a 7B.

I knew one channel was out, so I checked for the fuse when i was inside and the "bad" channel had a burned fuse.
Swapped the fuse from the other channel, turned it back on, and it blew immediately. I guess it is going in for service after all unless someone has a tips for things to look out for!

I have checked with Bryston, but they are severely back-logged and I don't know if I will get service in any reasonable amount of time. I just haven't even gotten a response, but I just tried again. I consult and design music studios and (at least 6 mo ago) our AV integrator couldn't buy a new bryston for a project even if he brought cash to the factory.

 

[Katji]

However, whether it's audible depends on how the transformer is encapsulated or varnished, and how it is mounted on the amplifier chassis, and whether the chassis panels are well damped or can resonate to the transformer buzz.

Isn't Bryston a quite expensive brand?

 

[as labs]

Isn't Bryston a quite expensive brand?

yes, and they're built like tanks
one perk of working in studios is getting some of the castoffs

 

[as labs]

update - i got in touch with a tech and they think the main issue is a transistor shorting and it's going in for repair... under warrantee

 

[Doodski]

update - i got in touch with a tech and they think the main issue is a transistor shorting and it's going in for repair... under warrantee

Well done! Let them manage everything. Service bulletins and MODs can sometimes occur and a general service technician with no knowledge of those bulletins and MODs will simply attempt a repair without them.