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!
A while back I read a review of the Belles 150 Hot Rod amp at in which they addressed heat sink vibration. Dont remember what they used, but you might check it out.
You may want to try placing some "felt-type" pads between the heatsinks on your amps. This should damp out some of the ringing and cost you next to nothing! However, there are probably better and more effective methods that may cost more.
Gnobber, how hot do the heatsinks normally get? If they stay cool - than you can play with some damping material. But if they run hot, anything you place on or around heatsinks will impede cooling and can cause damage to the output devices. Perhups, placing the amp in the separate room and running the cables to the speakers through the wall may be an answer.
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
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..

Unfortunately, finding someone to make a heat sink clamp out of brass or aluminum ain't gonna be cheap 'n easy.
Pm: It's not a matter of whether the change is good or bad, but that it DOES change. As such, the sound that you are used to and may have worked hard to achieve can be altered for better or worse.

Gs: Thanks for the link to Goldman's solution for this problem. Like i said, it ain't pretty or simple : ) Sean
There are a couple of alternatives that I have used succesfully:
1- Use small strips of bycicle inner tube less than 1/2 in wide rolled up to adequate thickness and push them between adjacent fins down to close to the fin base (shoot for this dimension when you roll the strips not the outside gap between fins). If you choose to do this in the lower part of thew vertical fin they'll be hardly noticed with several advantages, it´s a reversible tweak, tube is black as the fins are if needed can be done at middle height, add more etc. The effect on convection is minimal and you can kill the vibes.....
2- Use a small wire or better a small aluminum piece and adhere it to the fins with a hot melt adhesive gun in the underneath the lower portion of fins.
3- You can also bridge the fins with the holt melt adhesive and decrease the ringing acordingly.

Some options are far more effective than others and easier to implement depending on how careful you are the other too can be used but there's more potential problems So weight the options and the compromises you might get into.
I prefer the first one since it´s easy and totally reversible.
Have fun and kill the ringing.
Got it Sean-- but many of these fixes are easily reversable so I think we should plunge on in and see what happens- at least that's what I'm going to do.
Didn't read the whole thread -did anyone suggest using spring-type wooden clothes pins? Clamp the suckers ON!
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Perhaps someone suggested this and I just missed it.

The easiest thing to try first is just apply one continuous strand of electrical tape across edges of the fins connect them via the tape, which changes their ability to vibrate. You may have to run more than one layer, but if your fins are black and you use black tape, the fix is almost invisible to the eye (and cheap too).

I thought this was a fairly common tweak, but maybe not.
Before you get to the point of placing everything but the kitchen sink, french (Oops a.k.a Trader) fries, etc. in your heat sinks.

1.) Call Classe, see what they have to say?

2.) Your room needs more work, forget "Foam", & don't go crazy spending thousands of dollars on specialty acoustical panels.

A.)Tell us more about your listening room! Hardwood floors, huge bay/picture window, cathederal ceiling, etc.

B.) What kind of stands are the amps on, Metal???

Get some Homasote Fiberboard 4'x8' panels covered w/ Burlap, they are 5/8" thick & fire rated. You may have to special order these $28-50 ea. This is what radio stations & TV broadcast room walls are covered w/ instead of drywall. They cut easily (yet messy) w/ a carpet knife. You can make up your over rectangular wall panels, paint the burlap & frame the edges w/ oak edge trim from Chateu' Depot. Or cover entire walls w/ it, as once painted it looks quite attractive? Pillows, Heavier Drapes, etc.....

You won't believe this but if you search the web, you'll find interior paints w/ acoustical dampening properties, along w/ Low E, etc. at $45 a gallon.

Secondly, I would concentrate more on the base the amp is on, & dampen/isolate the heck out of it.

Placing any foreign object in my heat sinks would be the last step, Gosh the CAM-200's where actually on my auditioning list. Well not now that you need auto parts to get them to sing, oops not ring. Only Kidding :0)~

Seriously, need more info on your room itself!!!
P.S. Gnobber "STOP" Running your fingers along the heatsinks!!!
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

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.


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!
I agree with Audiobugged. It sounds like you've got a lot of work ahead of you. The ringing of the heatsinks is but a very small piece of the puzzle at this point in time.

My thoughts are that you should work with room acoustics first and then move in the area of your racks / stands. All of the sound bouncing around that type of room will overwhelm any system improvements that you can make. Start with the big stuff and work your way down the list. From the looks of what you've posted, you've got a long list. Then again, don't get disparaged. If you like what you are hearing now, it can only get a LOT better : ) Sean
FYI, most general use electrical tape is UL Listed and certified to 176 degrees. I SERIOUSLY doubt the claims by those who say it will melt and "make a mess" by being attached to the edge of an amplifier heatsink fin.

Anyway, it worked first-hand for me and several others in my neck of the woods. It's not clear whether those who claimed otherwise have actually tried it or not, so perhaps there have been actual bad experiences. I just don't see how it is possible.
Labtec: I deal with electrical tape every day. There are various grades that hold up to varying degrees over time. Some of this stuff won't even stick to itself after a while. Either way, i will GUARANTEE that putting tape on the heatsink fins of a high bias amp will end up leaving "adhesive gunk" on them. This is true even if you use something like 3M brand tape, which is good tape.

If you were to use something along the lines of high voltage / high temperature tape, that is another story. The problem with this is that, if you had to resort to using this type of product, the amp is already running hot. As such, adding such a compound to the heat sinks will only reduce the already limited convection that is taking place. Not a good thing.

As far as the 176* spec that you quote, what time period is involved in this level of exposure and how long is the tape supposed to hold up after being exposed to this type of temperature ? Sean

PS... Would you like to hear from a manufacturer regarding "horror stories" that involve heat build-up and carpet being melted into the heatsink fins ?

Let us know what Classe says-- the last time I emailed them a question, it took about a day and a half until a very helpful guy called me up with a reply.

As for my amps, I can make the heatsinks ring if I run my finger on or across them, but due to the lucky fact that they're sort of "buried" in my room and off to the side, I'll never hear the noise they make. Playing the system as loud as my loudest ever is I couldn't hear any appreciable ringing with the naked ear or a mechanic's stethoscope. I'll damp them with something anyhow, likely a rubber/cork/rubber sandwich pad used for electric motor isolation cut into little pucks. I have to talk to the sales rep and see what density he thinks would work best in this non-standard app of his products.
I wonder if one of Herbie's products (Hal-o) could be cut to work for you. They are at least tube-heat proof. I've never used them to hear how effective they are, but others seem to really like them.

Yours are not the only amps with this problem; at a shop long time ago, I had clapped in an audition room to check for slap echo. Something else was ringing - metallic, too. After a few test claps to narrow down who was talking back, we found a pair of Mark Levenson ML-2s on the other side of the room with some huge, lively heat sinks.

Good Luck!
To Pmkalby:

I received a reply from Armin at Classe, who says

"We have done some testing with regards to this concern, and I can tell you that the ringing is Not transposed into the sound from the speakers.

It is also very difficult to make the heatsinks ring when playing music unless the CAM-200 is directly in front of the speaker, and even in that scenario the ringing is very limited, and is not transposed to the speakers."

Nonetheless, I did cut up some wine corks into small trapezoidal wedges, and pushed them into the top and bottom of each heat sink pair. It seems to cut down the ringing when I clap, and has so far survived a loud listening session where the amps got quite hot. There is still a substantial airflow path to allow convection to work. This should take care of any noise that might have come through the amp and speakers, as well as any ringing that comes straight through the air to me.

thanks again for everyone's great ideas on this question!
Excellent idea Gnobber, I would continue to acquire wine corks. Even if it doesn't stop the ringing you won't care!
Very FUNNY Herman, but oh so true!