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Chassis Damping the TD160
Above photo #1. 'Dynamat Extreme' is put to use by cutting out the shape with scissors, removing the waxed paper cover and pressing the sticky tar side where you want the Dynamat to go. Work it in by pressing with fingers or other suitable soft instruments. BTW, Dynamat the product is expensive. I paid $35 for a single 4 sq. ft. piece. Other, more affordable similar products are available under many different names. The stuff we are talking about is a visco-elastic tar with a heavy foil top cover to it.
Above photo #2. The sub-platter is damped using Dynamat. This proved to be worth the effort. Listening tests revealed an obviously decreased background noise and an increase in musical detail. This makes sense considering proximity to the spindle bearing. Careful consideration was given to cutting and placement of the damping material with regards to concentricity. Care must be taken to avoid a dynamic imbalance of the platter assembly.
Nothing was gained from placing Dynamat to the --outer-- platter however. This was tried. Then, after removing the Dynamat from the outer platter, no difference was noticed except that the platter was now riding slightly higher. Dynamat is heavy.
Above photo #3. Dynamat is placed onto the underside of the top motor plate. Naturally, considerable attention is given to placing this damping material in the vicinity of the motor mounting. The whole object of damping the motor plate is to kill, or at least reduce, the motor vibes running through this sheet metal.
Above photo #4. Not included in the above Chadwick recipe, but mentioned as having by done by some of the Thorens tuners at the asylum, is damping the sprung sub-chassis. This is an area that is damped in the improved model of the TD160, the TD160 Super. Cork is chosen for it's damping qualities as well as relative light weight. Note the 3 rubber bump stops. The top surface of this sub-chassis will be covered with a layer of automotive cork gasket material that will clear the bump rubber by .06 inches. Meaning the cork won't interfere against the underside of the motor plate.
Above photo 5. Upper side of sub-chassis is seen to be covered in cork. Bottom side of sub-chassis is also covered in the same cork material. The cork is glued to the sub-chassis plate with Blue RTV Silicone (Permatex). Edges are also sealed with this silicone.
Notes about damping the sub-chassis: Photo #6 shows that the sub-chassis had been previously covered in Dynamat. Dynamat is quite heavy and added too much total weight to the suspension. Goodness knows what this extra weight did to the resonant frequency of the suspension. The Dynamat was subsequently removed and cork was then substituted as the damping material. The stamped sheet metal of this sub-chassis, while not flimsy, is not rigid enough to suit me. The addition of damping material to this piece will not increase rigidity but may serve to reduce or eliminate some bearing vibrations coming off the spindle. More evaluation will be given to this sub-chassis as time permits. At the moment I do not 'hear' a substantial benefit from damping this part, but have not noticed any negatives effects from having done it. For the time being , cork damping will do. If you are wondering whether or not to damp this piece consider that no great benefit has been noticed from damping this part. In the future, I will substitute an altogether different sub-chassis design that will feature greater rigidity and better inherent damping in the material and construction. But for now, it is cork damping.
Above photo #6. It is easier and more efficient to add damping material to the motor plate if it is removed from the base cabinet:
Above photo #7. Additional damping to the plinth is done with Blue-Tack and a Blue-Tack substitute which can be found in department stores in a variety of guises and locations: shown here: This Blue-Tack substitute is made by Elmers. It is a visco-elastic substance. A very stiff putty that does not harden or dry out.
Above photo #8. This clay like material is added liberally to the corners of the cabinet and plinth as is shown to add damping to the plinth. The end result is a much more 'inert' base cabinet. The Blue-Tack material is also used around the mounting spacers between the cabinet base and the motor-plate to fill in every conceivable void.
Above photo #9. Damping the --upper-- side of the motor-plate with Dynamat. Note that the motor is mounted to the underside of this same plate and in the immediate vicinity.
Above photo #10. If you do nothing else, this is the mod that will gain you the most. A much more solid bottom plate cut out from 1/2 inch birch plywood. I used grade-A lumber here. The original flimsy hardboard was used as a trace pattern. The board is a tight fit to the under side of the cabinetry. The result is a more solid and rigid cabinet structure.
Above photo #11. A side by side comparison between the standard hardboard bottom plate and the one I've added. I also added much heavier rubber feet in the standard location. The feet can be seen in photo 12.
Above photo #12. Later, I cut a hole in the bottom with a jig saw to allow any wayward, air-born resonance to escape rather than bounce around inside the box. I can't say I noticed any 'sonic improvement' due to this extra measure, but there was nothing lost but a little wood.