Vintage DD turntables. Are we living dangerously?

Lew,
I think there are similarities here. Have you tried the peripheral ring with the Sota clamp?

Matching the mechanical impedance of the record seems like a good idea, but only if vibrations are not reflected back. I think that's why a 5mm carbon mat is more affective than 3mm.
Griffithds likes the Funk Firm mat that purports to do just that - prevent reflections from coming back to smear the sound.

Perhaps using a metal platter or mat is a better match for slightly stressed vinyl? I use neither, but considering your and Halcro's posts, it seems logical.

Think I'll try the Achromat next. Maybe I'll take some sheet lead to a machine shop and have a thin undermat made.

Regards,

Fleib, What I wonder about is whether the stainless steel platter sheet of the L07D becomes a negative, when the LP is pressed firmly against it, since by all rights you'd think that immobilizing the LP with a ring and a weight should be a good thing to do. I probably should play with other platter surfaces, but the L07D design does not make that so easy to do. However, I can try the ring plus the Sota clamp.

On another note, I just had my SP10 Mk3 updated a la Krebs. The preliminary results are surprising, in that I really did not think much could be done to make the Mk3 sound any more lively and coherent than it does/did prior to the upgrade. Now I may be a convert. More anon, when I have had more time to listen.

Lew,
The record/platter interface seems to have so many different factors, experimentation is required, but then we have to take into account things like the sound of a particular cartridge. Assumptions can also be a problem. What works for one record might not be so great for another?

It seems that reflexing or using a vacuum changes the natural resilience of the vinyl and the way the needle is reflected off the groove. These two approaches are often thought of as a positive, but at what point does it become negative, and what kind of surface is under the record? I think using a weight and periphery clamp does the same thing, perhaps more predictably than guessing how much force to use when reflexing a record.

Because a metal platter or mat is harder than vinyl, and the mechanical match up is the opposite of a compliant mat, I would think it would be easy to make erroneous assumptions. It would be mandatory to immobilize the record anyway so you could vary center clamp weight or amount of reflex. Are there metal platters w/vacuum? You could even add weight to a periphery clamp. I doubt if that would help, but you tell me.

A compliant mat is like damping. A thick rubber mat supplied with inexpensive tables is generally more forgiving, but overdamped, smeared, and with less resolution. A very thin compliant mat like some felt or Jico thin one, seem to be the right damping for a metal or glass platter. I had an LP12 years ago and I used it with the felt mat.

The Pierre Lurne' approach is to dissipate rather than dampen, with tonearm and platter. In this respect he's probably the most copied turntable designer. The problem with dissipating vibrations is, where do they go? A hard platter/mat should be efficient transmitting, but where do they get reflected and do they come back?

My approach just copies Lurne'. Lead is very good at slowing vibrations.

Regards,

Lew, does Krebs address the mat with his modification procedure? If not, does he have a recommendation?

Thanks

Pryso, No, the Krebs mod has to do with motor and PS. You are free to choose your own mat. Richard is around here somewhere; perhaps he can weigh in on the mat question.

Fleib, I really have to say that I am so content with the L07D "as is", that I don't worry about ring vs no ring or how heavy is the record clamp. I am either getting old or lazy or both. However, I have all the doodads here, should I be moved to try the ring and heavy center weight again. I should think that a vacuum mat where the surface is metallic would be a very tricky proposition, since it would be difficult, maybe impossible, to achieve a good seal between vinyl and metal. Thus there would be a constant low grade "leak" of air and possibly not only no vacuum effect but noise added as well.

SP10 Mk3 a la Krebs is getting better from the very good baseline.