|
Audio Asylum Thread Printer Get a view of an entire thread on one page |
For Sale Ads |
Today, I spoke with George Merrill, a charming, outgoing southerner, now about 60 years old (he was an acquaintance from the mid-1980s when I did a little consulting for him on his turntable mods). I interviewed him a bit about the Heirloom turntable, specifically about spare parts and performance of the peripheral clamp ring. My notes:They have inventory of most everything: rings, platters, motors, etc. Ten years worth of stock, at least.
Belts are available, $21.50 each. Store spare belts in a ziplock in the Freezer. No humidity or ozone. (In Los Angeles smog, my belt deteriorated in 4 years, but in Silicon Valley, little deterioration apparent after 10 years.)
Motor damping oil is a fluid similar to what is used in a car shock absorber. Doesn't change viscosity or volume with temperature.
Bearing oil has lifetime performance, no need to replace or even replenish. Oil was tested by a pro in the business who also helped develop it, and found to have a projected life of 135 years continuous use. Also, no metal particles were found, thanks to the hardened contact surfaces in the bearing. The bearing itself should not wear out.
Arm board is part of the subchassis. If you change tonearms, you may need a new subchassis if holes for new arm are incompatible with holes for old one. Still stock plenty of these.
Clamp ring was intended not just to clamp against the lead mat, but also to terminate energy radiating across record to the periphery.
The most recent clamp ring design was black painted with a textured material. This helps damps resonances. However, this does not damp entirely.
I told him that I had used electrical tape around the edge of the lead-acrylic platter as a shim, wedging the ring over this permanently. This resulted in a very dead peripheral weight (no longer used as a peripheral clamp). He said leave it that way if it sounds good.
Alternatives: try taping outside of clamp ring with electrical tape, several layers, and use it as intended as a clamp ring. Or, paint it with Borosilicate compound - a damping material used to paint shuttle tiles with - tends to absorb and dissipate energy. Can obtain it from several people on the internet (do a search), and paint ring with it, a couple of coats. This will help even the black version of the ring. Paint all but the underside of the thin part of the inner lip, which contacts the record. This would be even better than the late production black ring; didn't use borosilicate in production because it is not as good looking or as durable to rough handling.
Clamp rings available for $230, the latest black version. They were Injection molded, then turned, the painted, many hours of labor.
Follow Ups:
Thanks for ferreting out this info! Is the newer periphery ring non-magnetic? I ask because I (as it turns out) have the older, chromed version, which quite obviously attracts unsheilded carts (e.g., Benz Glider) on the lead-in grooves. Is it the same weight as the older rings?
Jim:
Thanks for the info about George Merrill and the other goodies.
I'm using a Merrill periphery clamp (as a periphery clamp) and Merrill acrylic/lead platter on a Teres.
I've tried other damping methods on the clamp, but your suggestion of tape makes a noticeable difference. I've placed two wraps around the circumference and like the result.
I spent some time trying to find an easy borosilicate solution through Google, but came up zip. Any suggestions?
You could call George Merrill at (901) 405-0261.I tried a quick search using boro and silicate as separate terms, or as boro-silicate. Got different results. Some industries latch onto one spelling or another, so you have to be a bit creative. Try this combination .
I didn't talk to George about the paint in any further detail. But what I assume it to be is a paint that contains tiny beads of borosilicate glass in a rubber-like paint that tends to absorb high-frequency sound. The beads will scatter the sound so that (a) the paths are lengthened and thus sound is more attenuated before returning to the record, (b) the acoustical "border" of the ring is made "fuzzy" by this application so the resonances are broadened, (c) the impedance matching to the metal ring is improved so more sound enters the paint, and (d) the increased viscosity due to the presence of the beads may increase frictional losses. Of course, at audio frequencies, this all may be overkill. For ultrasound, it becomes much more important.
I would think a better material would have a higher impedance (density times velocity of sound). You would want to match the acoustical impedance of the ring. So a tungsten-loaded epoxy, for example, would work even better. George mentioned that the borosilicate was used to coat shuttle tiles, which means it is (a) low-density, (b) high-temperature, and (c) friable. None of these is good for our turntable appilication.
The trick is to apply it evenly enough (or in thin enough layers) so as not to disturb the balance of the platter. It might not be good to simply trowel some thick loaded epoxy on the ring. Spray or paint brush would be best. First, clean the ring thoroughly with clean acetone or alcohol, to enable adhesion.
At audio frequencies, any somewhat lossy material designed to have an acoustical impedance approaching metals (even less than half) that can be brushed or sprayed would work, I would think. Electrical tape is rather dense, as tapes go. There may be commercial tapes that contain particles of dense material, for example, used in contruction or other trades. These might be even better, assuming there aren't tiny air voids between the tape and the ring.
I don't know offhand if you would hear much improvement over the electrical tape, and that is removable and thus an easy way to experiment, so I'd start with that. In theory, the Qs of the ring resonances would be much better reduced by a higher-tech coating, but I'm not sure you can hear this level of improvement, in practice.
I think George's suggested material may not be best, for reasons stated above.... Plus, he mentioned that it can scratch off during handling. Not something I want on top of my nice clean records!
Jim:
Thanks much for your very detailed response. I'll do some more digging. Thanks also for the contact info.
Two layers of tape made a noticeable improvement in bass response and an increase in "blackness", which translates as the removal of "hash".
I'm using a Benz Silver 2 Reference MkII on a Tri-Planar, which is pretty responsive and revealing. The difference when using the clamp as a clamp and just using it for extra rotating mass is quite noticeable. I have no problem with the inconvenience; it's just part of the routine.
I may try some lead tennis-raquet tape between two layers of electrical tape in a constrained-layer damping configuration.
Thanks for the ideas.
... perhaps with additional layers over it of lead or electrical tape. My feeling about costrained layer damping is that it is good for reducing transmission, not so much reflection. What you want is to minimize reflection, which means matching impedance to the ring first and foremost. But, whatever sounds best is important; one can't anticipate all the tiny interactions that might occur.
Jim:
A layer of lead tape on top of the plastic tape has resulted in noticeably more bass response and even more "blackness". Detail is better. I wish I'd tried this some time ago!
This post is made possible by the generous support of people like you and our sponsors: