Mechanical buzz coming from the chassis


I have noticed a mechnical vibration causing a low level buzz eminating from the chassis of one of my monoblocks. The buzz is not audible through the system. It is only audible when your ear is close to the amp. Also if I squeeze the chassis the vibration stops.

The amp is a Quicksilver mid-mono with KT88 tubes.

Any ideas on how to solve the problem?
nick_sr

Showing 3 responses by nick_sr

I checked the screws on the power transformer, they were loose. I tightned them and the hum is nearly gone. I really have to get my ear in close to hear it now.

Do I need to be concerned that there is an underlying problem with the transformer or incoming power? I have a dedicated 20amp line for the system so there is not much I can do to improve the power.
I have the amps sitting on 1/4" thick cork mats. This helps, but regardless the hum is not audible from my listening position.

The other strange thing is that only one amp hums but both amps had relatively loose screws.

Also, soft mats and tightnening screws will eliminate the symptoms but do not address the root cause.
It appears that the hum is due to the bottom plate on the chassis casing vibrating against the side wall. I placed something underneatht the amp to pressure on the bottom cover and this has eliminating the hum.

I guess I could also loosen the screws and place a bit of blue tack between the two surfaces and then tighten everything again.