This is a complex but very important area because of the almost unbelievable sensitivity of the ear to the effects of minute motions or vibrations in all components including CD transports, DACs, preamps, cables and power conditioners. CD transports, players and turntables are especially sensitive to these effects. Great sonic improvements in clarity, transparency, etc. are achievable by employing a system approach combining, where possible, mass/weight damping on top of the component, adhesive damping sheets on component chassis and support rack surfaces, both coupling and absorbing feet, and a support platform as massive, non-resonant, rigid and hard-surfaced as possible.

Detailed recommendations will not be made except regarding component feet and vibrational damping sheets. The area of component support and damping is mostly a matter of improvisation. Metal (except lead) and granite should be avoided - these materials all “ring” to some extent even when damped by elastomers. Even lead is slightly improved sonically by application of adhesive damping material.

Mail order source for lead bricks: McMaster-Carr (562) 692-5911, catalog numbers 9033K22 (15lb.), 9033KM (26lb.). Another source: 5-lb. deep-sea fishing weights sold in some fishing tackle and sporting good stores.

Adhesive damping sheets:
   
(1) McMaster-Carr catalog number 9709T18 - this inexpensive high-temp mastic adhesive-backed material is almost totally neutral sonically (no sound of its own) while significantly improving clarity. For best results stack 2-3 layers together. A very similar material, called Dynamat, is available in stores sold for auto chassis damping (doors, hood, floor, etc.). Parts Express #268-020.

(2) EAR Isodamp SD-125 and SD-40 adhesive semi-rigid damping sheets, available from Michael Percy (www.percyaudio.com). This tough PVC-based material damps micro-vibration in component chasses and electronic parts much more effectively than the above mastic/bitumen based sheets. The sonic effectiveness is greater because these sheets utilize mostly the principle of constrained-layer damping, where vibrational energy is dissipated as heat in the horizontal (shear) deformation of the adhesive between the vibrating wall and the horizontally rigid damping sheet. Viscoelastic materials such as the sheets described in (1) above less efficiently dissipate vibrational energy mainly in the compression and expansion of the material. The sonic effectiveness of this material is better also because its stiffness is a better mechanical impedance match to chassis walls. The thinner type (SD-40) is best stacked in 5-9 layers, SD-125 in 3-5 layers. Use of patches of this material on even one component will improve clarity considerably in a good system.

(3) Do-it-yourself constrained layer damping sheets. Theoretically, the effectiveness of constrained layer damping should be better if the material is very stiff in the horizontal plane, noncompressible, nonresonating and with a high mechanical impedance approximating a metal chassis wall. A damped thin metal sheet is such a material and would also effectively block external vibration. A number of commercially available damping materials utilize a sheet of aluminum or other metal. with pressure sensitive adhesive and in some cases damping elastomer backing. We found that these materials all exhibited unacceptable metallic ringings even with additional damping layers added to the back of the patches. A simple combination of off-the-shelf materials can produce very much better performance for high end audio systems. The following do-it-yourself damping pads improve resolution, imaging and general sonic clarity considerably more than even the EAR Isodamp materials.

Damping pad construction:

Apply 3M high-shear strength double-stick tape (McM.-Carr part no. 75955A673) to one side of a one to four square inch rectangle of any of the following materials:

a. 15 mil phosphor bronze sheet (shim stock, McM.-Carr # 9014K33);
b. 4 mil copper foil (McM.-Carr # 9053K13);
c. 1 mil brass foil (McM.-Carr # 9504K11);
d. copper-clad (one side) phenolic circuit board (McM.-Carr # 8521K33).

Add at least 7 layers of the adhesive-backed material to the other side of the sheet. The different materials have subtly different sonic effects, with the best all-around material being the bronze sheet. The double stick tape side of each damping square is applied to the surfaces of a component chassis after peeling off the paper backing.

This particular tape does not have an aggressive adhesive, and as a result the damping pads may not stick well to pebbled or otherwise unsmooth surfaces. It is still recommended because of its sound as a thin layer shear damping elastomer. The tape can be removed and replaced if necessary.

We have found that optimum results are obtained from using a combination of all these materials (1) - (3) essentially “tuning” the vibration reduction by ear.

Sources:
  
McMaster-Carr (562) 692-5911;
Michael Percy 530-470-8650, E-mail mpercy@pacbell.net;
Parts Express (800) 338-0531.