View Full Version : Bitumen sound deadening pads

mega lord
15-03-07, 01:11 AM

After reading Les W's book of mods i thought i might try using these pads on the inners of my naim electronics. Les suggests that putting a pad on the top inner surface of the cases reduces the ringing and bennefits microphonic components such as semiconductors.

Has anyone tried this approach. There are different sorts of pads available such as self adhesive bitumen and products used in cars such as Brown Bread and Damplifier pro. These car products whilst being expensive and resistant to heat, have a foil layer on them. I am concerned that this metal foil will cause problems - is this so ? The ordinary bitumen pads called dedeshete (wilmslow) look good but as they are stated for use in speakers, will they be resistant to the sort of heat which my nap140, hicaps and cd3.5 kick out ? Obviously i dont want to limit the heat sink capabilities of the case or have black sludge leaking all over the place. If people here tell me its ok, i will go ahead and place it on inner top of cases and maybe cut some small strips to go in unused spaces on nac72 motherboard and speaker xover boards.

Thanks for any advice stu

15-03-07, 01:55 AM
I noticed that the higher end amps and cd players tend to use a little bit of plastic folded over the top of back plate. When the lid is slid on, it is pressed snug against the plastic and dampens vibration. My own solution was to buy a length of clear 3mm plasticy/rubbery tubing from a diy store @ 49p/metre and cut a couple of four inch lengths off, slit 'em down the middle and slip 'em over the edges of the back plates on my cd3.5 and 62 (now starfish). Works a treat!

15-03-07, 02:11 AM
The foil won't be an issue.
The heat generated by your amps is minimal.
Adding pads of any sort will have absolutely 0 effects upon the heat sinking capabilities of your amps.
If you want to get an idea of the effect the pads will have put a paperback book on your amp with a weight on top of that. If you can't hear a difference doesn’t bother with the damping pads.
On a similarly pragmatic note, the inner chassis of all Naim amps are a surprisingly tight fit in the outer sleeve. There may well be insufficient gap to allow you to slide the inner section back inside the outer sleeve once a damping pad is fixed.

I have used the type of damping sheet that Wilmslow Audio sell (I suspect it is this type that Les is thinking of). They do, on occasion, have a bit of a tendency to become un-stuck over time - especially if gently warmed. Make sure all surfaces are nice and clean before sticking them on and warm them up with a hairdryer first to make them a little more flexible.

Also, there aren't any unused areas inside your Nac72 worth putting tiny bits of bitumen pad on.

15-03-07, 02:48 AM
As an alternative ...try bitumen roof flashing ..this is 2mm thick and comes on various length rolls..cost is about 6 from wilko's

I've not heard a cdp or amp that has not benefited .....thought you need to be careful where heat dissipation is required.

Just placing a sheet on the base of the nac 72s sharpened up its act ..also its accompanying flatcap. Big gains on cdp if you cover the inside of the lid and case on say an AA5 or cd67 [both of which I own] you can feel the extra mass and hear the change in resonance if you hold the edge of the lid and tap with a screw driver before and after treatment. I also damp the chip in cdp's and add a copper foil screen below the bitumen [grounded to earth].

15-03-07, 12:35 PM
Soundcoat. Not expensive, easy to use and very effective. I get mine from the nice people at the PartsConnexion.