A $300-$400 turntable tweak

Oh come on Lew.......we have agreed on other occasions methinks :^)

Rockitman and I are in agreement :)

I most frequently use a Marantz TT-1000 direct-drive turntable with a bonded-on graphite mat and a Graham Phantom II tonearm.

In the past I tried a variety of clamps of varying construction, material and weight on this turntable, and have found that heavier isn't always better. In fact, usually it wasn't.

Today I am using a clamp that has adjustable clamping force. The clamp itself is fairly light and simply drops onto the record label (like a gravity clamp). Internally, however, there is a neodymium magnet which is positioned above the turntable spindle (which is normally steel). The magnet is mounted on a fine-pitch screw mechanism which allows the distance between the magnet and the turntable spindle to be adjusted in very fine increments. If the distance between magnet and spindle increases, the clamping force decreases, and if the distance decreases, the clamping force increases.

Since the screw mechanism that adjusts the magnet has nothing that binds directly to the turntable spindle, the clamping force doesn't need to be reset every time the clamp is removed from the record (unlike a normal threaded clamp).

With this clamp I have been able to experiment with clamping force and sound quality. I find that I prefer the sound when the total clamping force isn't so high. I'd guess that the clamp weighs about 200~250 grams, and I usually have the magnet set so that it adds another 250 grams or so (estimated). The clamp can be set for much higher clamping force that what I typically have it at, but I find that the sound quality starts becoming compressed both in dynamics and timbre when the clamping force is too high. Maybe someone who can't stomach any trace of edginess at all in their sound would like this. Me, I find it the sound less emotionally involving, less intellectually interesting, and far too polite.

Sonically, the difference can be pretty big. Enough to make you come to different conclusions about the same piece of equipment (or LP pressing).

I also find that some LPs benefit from less clamping force than others - it seems to vary according to label and production era.

OTOH, I have not found that leaving the clamp off completely is better - a certain amount of clamping force, but in moderation, is what I find to work best (in my audio system).

If any of you have a clamp which allows fine adjustments to the clamping force, I encourage you to experiment and experience for yourself how the sound changes.

cheers, jonathan carr

Interesting Jonathan,
Have you also ever tried a peripheral rim weight?
Cheers
Henry

Hi Henry:

Yes, I've tried various peripheral rim clamps and vacuum clamps (both add-ons and integral). In this case I found that I usually preferred the sound without peripheral or vacuum clamps. Even on my Micro-Seiki SZ-1S, which has a 28kg machined stainless-steel platter and integral vacuum clamp as well as air bearings for the platter and motor/flywheel, I ended up keeping the air bearings engaged and defeating the vacuum clamp (although I did prefer to insert a mat between LP and platter surface).

However, this is probably due to the fact that I own very few warped LPs. If I had more warped discs, I suspect that I would feel a greater fondness for peripheral or vacuum clamps.

In fairness, none of the peripheral or vacuum clamps that I have used offered such fine-grained control over the clamping force as my adjustable magnetic center clamp. I suppose that I could design such a peripheral clamp, but I have far too much on my design plate already!

cheers, jonathan