Amp heat sinks are ringing


I have been working to reduce the slap echo in my room by using quick hand claps, and various foam panels to attenuate the noise. I have discovered that my Classe CAM 200 monoblock heat sinks are actually ringing- they can be excited by handclaps, and heard across the room. There are 10 heat sinks per amp, about 2" deep by 8" high. Running my fingers along the heatsinks makes them ring like a bell!

I am concerned that this ringing might be excited when I am listening to the system, and may add extra treble noise.

Does anyone have any suggestions for damping out the noise? I am concerned about using a material that can withstand the heat, and not impede the airflow?

thanks for your help!
gnobber
Electrical Tape adhesive won't work w/ heat, you would have a MAJOR MESS on your heat sinks & hands!
Call Classe and let us know what they recommend you do. I am curious as to what they come up with. Goldmund's style is fantastic - even their accent comes through their text. I need to buy a Goldmund amp. Arthur
If you really want to do this right ( the Goldmund method is "partially there" ), it will require drilling holes or being very creative in using threaded holes that are already in the chassis. These holes are used to anchor the multiple metal damping strips that clamp against the outer edges of the heat sinks. By using multiple clamps ( ala multiple versions of the Goldmund method ) and staggering their spacing, you not only reduce the amplitude of each resonance, but spread the points of resonance out at various intervals. This means that you no longer have one large "ringer" but several smaller, different sized "ringers" of much lower amplitude.

The problem with this approach is that it is not "universal" i.e. what does one do with heat sinks that are staggered in height or depth ? While the manufacturer may have gone to staggered heatsinks to spread out the resonance / reduce the amplitude of the ringing taking place, there really is no easy solution if one wants to try and "damp" such designs.

As several folks noted, using something that is heat sensitive or will melt is NOT a good idea. That is, if you have a good quality amp that is of high bias. You have to remember that some of these amps have their heatsinks running at well over 130* and hitting 150* - 165* at the heatsink in the summer with a room that has no air-conditioning is not uncommon. As such, the smell of cooking wood aka having a "kiln" in your house is not something that i would look forward to. Using soft rubber or some type of material with adhesive is also a no-no as it may melt / produce fumes.

Elizabeth's idea of using the "stoppers" from "chemical beakers" or test tubes may work pretty well as these are designed to be exposed to high heats when "making potions" in the lab as the beakers / test tubes are heated over Bunsen ( sp ??? ) burners. The fact that she's running them on an a Class A amp that does get QUITE hot and has had no problems with them verifies that. As mentioned though, i would be careful with how / where you place them. The further out towards the end of the heatsink that you can get them, the lower the temperature they will be exposed to and the less airflow blocked.

With amps that run cool to the touch, you might not run into many problems using some of the other methods described. Just remember that if you did want to remove your "mod" at a later date, you may have to scrape the goo / gunk that was used to adhere your "damper" from the heatsinks. AS such, use something that is relatively easily reversible or get ready to pull your hair out trying to clean between the heatsinks.

Audiobugged: While one can work on optimizing room acoustics and "draining" the energy from the amp into the stand, the vibration of the heatsinks has to pass through the entire chassis prior to being "drained". There's just no way around the ringing unless you directly address the problem. Sean
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PS... To those "fans" of Goldmund products, i apologize for calling them "Goldman". I must have been fantasizing about Oscar from the Six Million Dollar Man again : )
Hi everyone,

thanks for your many responses- there are a lot of interesting ideas out there!

To answer a few questions:

-the amps are on homemade stands (2 3/4" sheets of particle board, screws running through them to provide spiking to the the floor, screws extending ~1.5" beyond the particle board)

- the room is 20x27, speakers both on the 20' wall. Drywall construction, cathedral ceiling, berber carpet on the floor. The wall behind the speakers has around 16' of windows, 4' high (that is mostly what I was trying to cover with the temporary use of foam as an experiment)

-I have written to Classe about this yesterday- no response yet.

-I am not sure if the ringing is audible through the speakers. The ringing IS audible directly through the air (i.e. hand clap excited the heat sinks, they ring, and are audible 10 feet away).

thanks for everyone's help! At this point I think I will try some rubber (stoppers, bicycle tube) to see if that helps as a quick experiment.

Bill
Bill,

WOW, you have a lot of things going on in this room! Cathederal Ceiling will cause echo-ing.

First off your stand!!! Particle Board IS TOO DENSE!!!If you only have 4 screws going through the 2 pieces, then there might be vibration in the stand itself. Did you use wood glue to laminate the 2 boards together???

Lose the DIY Particle board stands, look into maple for a stand top. Stay away from metal, mdf, & glass! Metal bases are ok as long as they can be filled to be dampened. You just don't want the top to be metal.

16' of Glass, try heavy Drapes, or if older windows?
Look into (in time) replacing them w/ triple glazed, foam filled vinyl or wood windows, w/ argon gas.

Take apart the stands, glue them, & re-screw them w/ more than just 4 screws that hold the whole base together. Them get back to us about Ringing!