[Amps] Acoustic Noise Comparison

[Jim Brown]

On 6/21/2012 10:12 AM, Jerry Kaidor wrote:
>    Still playing with my "new" Alpha 78.

No experience with that amp, but some components of motor noise are 
vibrationally coupled to the desk or shelf that the amp sits on. I've 
reduce that component of the fan noise in my Titan 425 amps by setting 
the RF deck on soft foam padding. There are no vents on the underside of 
that amp, so I'm not interfering with cooling.

I bought all of my 425s used, and one of them came with a power 
transformer that made a lot of noise. The problem was loose windings, so 
I jammed some shims between the windings and the frame to kill the 
vibration.

Another component of fan noise is air turbulence, and the components are 
higher in frequency.  Higher frequency components bounce off of hard 
surfaces (like walls and shelves) and into the room. We can kill those 
reflections (and thus some of that noise)  by placing soft materials 
(what we acoustic consultants generically call "fuzz") on those 
surfaces.  Obviously this should be done in a manner that doesn't 
interfere with cooling.

73, Jim K9YC