Amp heat sinks are ringing

I had the same problem with a CA300 and I used MDF blocks the same length and width of the heat sinks and placed on top of the fins and then weighted down with brass cones. I painted the MDF black so it didn't look bad. The fins never got hot enough to mar the paint or the wood and the difference was dramatic, much better focus and imaging and reduced some of the glare spots through the treble.

You also try the opposite of Rhljazz's recommendation. Put the blocks under the fins so the weight of the amp rests on the blocks instead of the feet. That way the heat from the fins could rise and escape more easily than if the top is blocked. You could also try several strips with spaces between so air could get in between them. I am not familiar with your amp and don't know if the fins can hold the weight so I would proceed with caution.

I guess some of you don't realize how heat sinks work. They cool the amp by natural convection which means VERITCAL air flow around the fins. If you put blocks under (or over) the fins, you are destroying the convective flow and raising the sink temperatures exponentially. Your hand my not feel a big difference but your transistors will.

I would contact Classe and see what they have to say about this problem. If they aren't helpful, you may want to try loosening the heatsinks just a little teeny bit. It may be tough to get at mounting screws but if you can, loosen them a very little bit - no more than half a turn or else your thermal resistance from case to sink will rise too much. In no way should the sinks feel loose at all after this - if so tighten them back up some. Otherwise, you may be able to think of a way of cramming a thin piece of metal between every other pair of fins that wouldn't obstruct airflow appreciably but puts the fins in a bind. Anyway, for such an expensive amp, Classe should tell you how to fix it. I wouldn't accept no for an answer. Good luck - Arthur

All SS amps do this to varying extent. While you can cure / reduce the ringing, doing so will also change the sound of the amp. If you doubt that this could affect the sound, take some vibration readings at the output device using an accelerometer. Those that are "tweaky" have known about this for a LONG time. Nobody has mentioned it as solving this gets to be a pain in the ... You have to find a way to mass load the fins without reducing their natural convection properties. If done properly, you will solve the problem and increase cooling capacity, but it is neither pretty nor simple.

This is why i mentioned building "sound absorbing covers" to go over one's rack in a DIY rack thread. Obviously, some type of ventilation system must be used though. The other alternative is to do what both Dekay and Ernie have done and that is to mount some of your gear in a different room. Sean
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I don't know if I'm in the ballpark on this one, but I had a resonance problem with the motor on my hot-water tank system. I found these magnets at a surplus store about the size of a domino that I strategically placed on the offending ringing area and it changed the frequency enough so it is no longer a problem.