Amp heat sinks are ringing

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.

This is the first I've heard of this problem with the CAM-200s-- I'll have to go home tonight and see if mine do it, although where they are located I would never hear the heatsinks ringing, but I should hear their effect on the sound coming out of my speakers.

As for putting something over or under the heatsinks I think they get too hot to make that an option.

I would think that it would be a fairly simple matter of "wedging" a piece of appropriately size rubber (maybe a 1/4" long piece of the appropriate diameter automotive heater hose?) in between fins at their midpoint-- you'd not really adversely affect airflow or cooling area, and you should greatly reduce or eliminate ringing since you've just effectively halved the unsupported length of the fin-- this would have to alter its resonant frequency substantially.

Maybe 2 rows, one 1/3 of the way down, one 1/3 of the way up, of small pieces of appropriately size rubber (or cork) material would be more effective.

What effect this would have on the amp's sound is debatable, I guess-- although I can't see how eliminating a resonance there that's being excited by room sound would be anything but a positive for sound quality.

Goldmund understands and addresses this problem..

http://www.goldmund.com/old/Millennium/mechanics.html

Unfortunately, finding someone to make a heat sink clamp out of brass or aluminum ain't gonna be cheap 'n easy.