Study carefully the pictures on my system page. Especially the platter and record clamp. https://systems.audiogon.com/systems/8367 Nobody makes a proper clamp so I had to build one myself. It has been improved since these pictures were taken but the key features are the same.
Two main features: the thick washer that fits over the spindle, and the under side of the clamp is dished out. Really need to take more and better pictures because this subject keeps coming up.
Look at the thick black washer placed around the spindle. This holds the record up about 1mm above the platter surface. The clamp is dished on the under side. Clamping the record down causes it to bend very slightly, forcing the outer edge of the record down onto the platter. Because of this virtually all records, unless they are pretty obviously warped, they lay perfectly flat. In fact they are so flat and flush with the platter that when the clamp is removed after playing they continue to be held down by atmospheric pressure until gently raised at the edges. So freaking cool you have to see it to believe it!
To the best of my knowledge the only other one to figure this out is Paul Beckett. He designed a variation of this into his Onkk Cue platter. The Cue platter is very slightly dished so that as the record is clamped down it contacts the outer edge first. A better engineered approach, I must say. If I had a machine shop with a lathe it is what I would do. But I don't, so we make do with what we have.
So that's what you do. Take my washer/clamp idea and figure out how to make it work for you.
You provide no actual information. How heavy is your record weight? What type of turntable do you use, belt-, idler- or direct-drive? Does the motor incorporate a speed control? What type? Have you actually measured speed with vs without the weight? If not, how do you know that the speed is not affected at a level you cannot detect simply by listening for pitch, which is what I presume you do? If you are concerned about your own record weight, you might consider switching to a record clamp, like the SOTA. A clamp applies pressure to the LP against the platter mat surface but adds very minimally to the weight supported by the bearing. Some don't like clamps because there is the potential to transmit noise from the bearing into the LP surface.
Nobody makes a proper clamp so I had to build one myself. It has been improved since these pictures were taken but the key features are the same.
Dont know where you've been for the past 40 years, but reflex style clamps/washers have been around since the 80's - SOTA, Goldmund and others. My Japanese turntable built in 1971 had a massive dished weight as standard along with a selection of washers of verying thickness to optimise for each record.
The big joke with many ultra expensive record weights like the Dalby is that they have a flat bottom and do absolutely nothing for slightly warped records. The biggest laugh for me was the stillpoints which I tried - all it did was muddy the sound.
Don't know where you've been for the past 400 years, dover, but "proper" never has meant "reflex" not in any dictionary I have ever seen. But I tell you what, since you want to argue so much, find me the clamp you think is "proper" as described above. One that clamps the record down so flat and secure it has to be lifted by the edges after playing. You find that one for me, post a link like I did for mine. That way I can explain in detail what you missed and why it is, compared to mine, not a proper record clamp.
There is a series of posts on the VPI discussion site that tells of a modification where you use 2 dimes opposite the spindle on the record, then put the weight on, then put the ring clamp on. I do that with mine....makes a significant step up.
Yes. I started out with tricks like that.
One of my early tweaks was ordinary washers. The inside of most platters is so dished out that records can't be clamped much or the center depresses and the outer edge gets jacked up. My first Basis reflex clamp (that dover somehow thinks I don't know about, even though I owned one, 30 years ago) used an O-ring around the spindle. That allowed a little bit of clamping, but not much or the O-ring compressed and the edge pushed up. So one of the first mods I tried was different washers. Larger O-rings, plastic, brass, steel. Tried them with tape, Blu-tack, etc.
The one now is carbon fiber, with fO.q tape on either side. There's also a ring of fO.q tape around the edge of the clamp. The clamp is also carbon fiber. So when clamped records are held in place with this eminently advanced vibration control tape and carbon fiber, tight and perfectly flat on the platter.
So all dover has to do is find another proper carbon fiber clamp. Not cheap aluminum, plastic, or wood. Carbon fiber. With advanced vibration control hold-down. Not O-rings, not dimes and washers. That works in a system that fastens records as securely as a vacuum hold down system.
Vaguely Asian/mystical New Age name full of cache and no real meaning. This combined with nobody having the faintest idea what is going on even if it's laid out in detail, is more than enough to capture a few sales from people with that kind of scratch burning a hole in their trust fund. After all it is only $5k. Putin has a $144,000 toilet brush in a guest bathroom he's never even been in. Don't have to sell many at those prices now do you?
The first table I saw with a reflex clamp was the Oracle Delphi. As described above, a thin (1/16") washer is slid down the spindle and onto the platter---under the LP, which of course raises the LP off the surface of the platter by the same height. The reflex clamp is then tightened down onto the LP, slightly bending it and securing it to the platter, in the process removing all but the worst warps.
VPI’s first table---the HW-19, was of the same design. Both the Oracle and VPI clamps were threaded (as were the top of the platter spindles), and the underside of the clamps dished (raised around the perimeter on the underside).
BDR made a reflex clamp with the same threading as VPI: 1/4-20, both as a 1-piece and a 2-piece. Both also had a dished underside. @slaw decided using a clamp provides a pathway for bearing noise to make it into the PVC of the LP. so sold his BDR clamp. I still have my 1-piece.
Herbies makes a washer specifically for use with reflex clamps, made of their proprietary damping material. 1/16" thick, 1-1/4" diameter.
Get an Ap called "RPM" on your phone and see for yourself. If your turntable is DD or using an AC synchronous motor it should not matter.
It should also not matter with a well controlled DC motor. In Short, If it does change your turntable's speed it is junk, throw it away and start over. If the weight is changing speed so is groove friction which varies.
Hey all. So today I thought for the first time if having a substantial weight or clamp on the spindle affects the platter rotation speed. It doesn't for me, as far as I can tell, but if not, why would that be so?
It can happen ONLY with belt drive turntable!
For Direct Drive this problem is irrelevant and not exist even with high mass platter mat + heavy record weight or clamp.
This is by far the best clamp/weight I even owned!
@chakster , speed fluctuations can happen just as easily with a poorly designed DD table as with a poorly designed belt drive. Well designed tables of either type do not have this problem at all. The only thing you can say about the DD turntable is it will start up almost instantaneously and sound universally horrible:-)
It is not at all a matter or torque. It might take a little longer for a low torque table to get to speed but that is all. Once the platter is in motion it takes very little torque to keep it going. Even the lowly AR XA runs just fine with a record clamp.
@mijostyn The “sound” of a turntable drive is BS, you hear the sound of cartridge/tonearm mainly. The rest is speculations. Speed must be stable, period.
Even very cheap direct drive can’t be affected by the weight of a record clamp.
Not every Direct Drive have a high torque and immediate start at constant speed. Not every DD have a high mass platter. My luxman pd-444 or Victor TT-101 are not high torque turntables.
Technics is a high torque turntable, even if you put 3kg on the platter the rotation will be stable with immediate start!
Belt drive can be affected by many factors and the speed is the main issue, read tons of comments on audiogon from BD turntable owners, those type of drive is notorius for not stable rotation. Most of BD turntables on the market is junk and people love it!
Heavy clamps increase the wear on the bearing.
There is no reason for them to be heavy if they have correct mechanical design. Screwing onto a threaded centre pin is a much better approach than using mass to hold the record down.
@simao It's really quite difficult to get a TT to run at 33.333333 rpm.
And a cogging computer controlled direct drive is not the way to do it.
@chakster 3kg??? Many TTs have platters weighing 25kg, some much more.
Over-engineered glitzy TTs with extra bling are one of my pet hates.
Simao, there are many things that can push the speed a little one way or the other such as temperature and AC line drift. Very few turntables are right on unless you can adjust the speed. Some modern turntables actually have a computer monitoring the speed and making the adjustments for you in unnoticeable increments.
@chakster , you are right. It is the tonearm and cartridge that produce the sound and DD turntables make them sound lousy which I can easily demonstrate to you in person. The last thing you want in close proximity to a cartridge is a pulsating magnetic device. Not to mention that I know of no DD turntable that is adequately isolated making matters even worse. But everyone knows by now how the two of us feel and neither is going to change the others mind without a demonstration that can not be performed. So it is a moot point.
Clearthinker Theoretically I agree. The more weight you place on a bearing, the shorter will be it's life span. (except for magnetic and air bearings). Threaded reflex clamps are the way to go for sure unless you have vacuum. However the bearings of most good turntables are very over-engineered and unless subjected to trauma you could measure their lifespan in centuries. My Sota Sapphire was as quiet when I sold it as the day I bought it 40 years previously. That is listening to the sub chassis with a stethoscope. I also agree on your bling thing. Turntables are meant to be heard, not looked at. They only need to be tidy and well built/finished, just one of the reasons I like Sota's and Dohmann's. Tricking one out to make it look like Star Wars is a waste of money, money that could be better spent elsewhere.
Mijo, I am getting a little excited about the idea of a "pulsating" anything, anywhere in my vicinity, given the dearth of human to human contact that characterizes my day to day existence during the pandemic. Anyway, I have to disagree with my DD co-conspirator, Chakster, on at least one issue. I do think that each type of drive system has its own sonic signature. Guess which drive system I prefer. I also think you ought to see someone about your fear of pulsating magnetic fields. You are surrounded by magnetic fields, unless you live in a cave. But seriously folks, I bought an EMI meter just to satisfy my curiosity about EMI in the vicinity of the cartridge that might be generated by the motor of a DD turntable. Detected nothing at the platter surface. This was with a Technics SP10 Mk3 which sports the largest iron-core motor of any vintage DD and probably at least as large as that of any modern DD. I also checked my Kenwood L07D, which uses a coreless motor. Nada. Of course this observation is subject to the sensitivity of my meter. The fact that you personally may fear the negative effect of a DD motor on cartridge performance is not per se proof that there is any appreciable effect in reality. The engineers that designed DD turntables in the first place were not unaware of the potential problem and were aware of how to use shielding and motor orientation in order to eliminate the problem. They did a good job. Now, can there be a cheap, poorly designed DD turntable that adds its own noise to the audio signal? Maybe. Can there also be a cheap poorly designed BD turntable that is wildly inaccurate speed-wise? Absolutely yes.
@chakster 3kg??? Many TTs have platters weighing 25kg, some much more. Over-engineered glitzy TTs with extra bling are one of my pet hates.
I’m talking about additional platter mat and additional record weight, not about stock platter weight.
Some modern belt drive weight a ton, looks like a bunch of heavymetal, cost like a house and still ugly as hell. This is what you’re talking about?
A mass market belt drive turntables are very light and if you will put 3kg in the platter you will burn the motor probably.
The weight of additional platter or clamp is irrelevant for Technics direct drive, no harm for the bearings and everyone knows it. Been using SP-10mk2 with Micro Seiki CU-500 mat and ST-10 weight (about 4 kg additional weight all together). Still immediate start with Technics DD motor. New SP-10R is even better!