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Vinyl record clamp

Sal1950

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have a TT that clamps the record to an acrylic platter with no mat. This reduces the vibration of the vinyl LP itself, removing some of the distortions inherent in LP playback. Putting a weight on an LP that is sitting on a mat probably helps too but I suspect not as much.
That's the part that makes me scratch my head. The engineer in me says the platter mat should be of some material that will dampen the vibrations. Back in the day I experimented with a few different mats made of cork, rubber, etc. The one I felt most effective was a rubber mat with raised ridges all around that came with my HK table. As to the other, I always used an inexpensive clamp that served the purpose of pushing the record against the mat without adding weight to the bearing and drive components. Now happily out of LP's for over a decade. ;)
Just my 2 cents
 

rwortman

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That's the part that makes me scratch my head. The engineer in me says the platter mat should be of some material that will dampen the vibrations. Back in the day I experimented with a few different mats made of cork, rubber, etc. The one I felt most effective was a rubber mat with raised ridges all around that came with my HK table. As to the other, I always used an inexpensive clamp that served the purpose of pushing the record against the mat without adding weight to the bearing and drive components. Now happily out of LP's for over a decade. ;)
Just my 2 cents
Clamping the vinyl hard against the bare acrylic platter couples them together so now the whole thing acts like one piece with a lot more mass that is much harder for the stylus to vibrate. The acrylic is used because it is close to the same physical properties as the vinyl so the vibrations won't reflect back from the interface. Sitting a vibrating thing on top of an elastomer mat isolates the vibrating thing from the platter below. Pushing the thing against the mat may reduce the vibrations but not as effectively as effectively coupling it to something much more massive. Which works best depends on the mass of the platter and what it's made of. Some folks would rather let the record vibrate because they like the way it sounds or because vibrating the lightweight platter below sounds worse, hence felt mats on glass and steel platters.
 

Deacon Blues

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I use the Douk Audio clamp (Mitchell clone). It was a great small investment. Not worried about my tonearm dancing all over the place. I had a DMM Beatles White album on colored vinyl that looked like a roller coaster. No more.

Vinyl does have a special place in my heart, although I'm not down with the new costs associated with it. I'm cheap. Being cheap and an audiophile do not go hand in hand usually. But, I try to make smart purchases and differentiate what makes sense, and what does not.
 

Sal1950

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Which works best depends on the mass of the platter and what it's made of
Interesting, I appreciate your point. I guess best answered thru measurement if you cared to pursue the answer.

I'm cheap. Being cheap and an audiophile do not go hand in hand usually. But, I try to make smart purchases and differentiate what makes sense, and what does not.
Actually times have never been better for the cheapskate audiophile. Transparent components can be purchased for ridiculously little money these days. If your audio shrine doesn't have to gleam with machined metals, acrylic and piano finished woods, things are real good. Hell, you don't even have to invest a penny in music ownership, a small monthly streaming subscription can get you access to a library that would make even the richest collection look lacking.
I guess that's the number one reason why audio as a hobby is falling off a cliff.
 

rwortman

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Interesting, I appreciate your point. I guess best answered thru measurement if you cared to pursue the answer.
The concepts are mechanical engineering. Measurements would quantify the effect but aren't necessary to prove that the effect exists. I listen to music as a hobby, not measure equipment so none will be forthcoming. Think of it like this. Pick up tuning fork that is tuned to A above middle C. Lay it on a rubber mat and tap it. It still rings at 440hz but the ringing is damped so it doesn't ring as loud or as long. Now bolt the tuning fork to another much more massive piece of steel like a 3 foot 2" x 4" bar. Mechanically now you have a new assembly with a much different resonant frequency that is also more massive. Now it takes much more mechanical energy to vibrate it and you may have moved the resonance to an either inaudible or less objectionable frequency.
 

Sal1950

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The concepts are mechanical engineering. Measurements would quantify the effect but aren't necessary to prove that the effect exists. I listen to music as a hobby, not measure equipment so none will be forthcoming. Think of it like this. Pick up tuning fork that is tuned to A above middle C. Lay it on a rubber mat and tap it. It still rings at 440hz but the ringing is damped so it doesn't ring as loud or as long. Now bolt the tuning fork to another much more massive piece of steel like a 3 foot 2" x 4" bar. Mechanically now you have a new assembly with a much different resonant frequency that is also more massive. Now it takes much more mechanical energy to vibrate it and you may have moved the resonance to an either inaudible or less objectionable frequency.
Once more you've provided an interesting hypothesis. But once again if you want to prove which approach really will reduce the resonance's influence on the output of the phono cartridge more, measurements must be made.
I also listen to music for the love of it. That is why my playback has been 100% digital for over a decade now. I don't care to stress over technical details that were made obsolete over 4 decades ago. ;)
 

watchnerd

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For many years in my vinyl days I used a record clamp. Better than the weight types, they grab the spindle with a collet and put pressure on the disc when tightened. Doesn't load the platter bearing like weights but can supply a positive interface with the mat. Normally quite inexpensive to boot.
http://www.audioadvisor.com/prodinfo.asp?number=RDRC

I have a collet type.

Benefits seem to be:

1. Flattens slightly warped records (hopeless for seriously warped)

2. Couples the LP more securely to the platter, which seems to help bass a bit and *maybe* lower the groove noise floor

3. Looks cool
 

Deacon Blues

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Once more you've provided an interesting hypothesis. But once again if you want to prove which approach really will reduce the resonance's influence on the output of the phono cartridge more, measurements must be made.
I also listen to music for the love of it. That is why my playback has been 100% digital for over a decade now. I don't care to stress over technical details that were made obsolete over 4 decades ago. ;)
Yeah, but if I gave up LP's - I would be giving up so many beautiful masterings of my favorite records. You can't stream everything.
 

rwortman

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Once more you've provided an interesting hypothesis. But once again if you want to prove which approach really will reduce the resonance's influence on the output of the phono cartridge more, measurements must be made.
I also listen to music for the love of it. That is why my playback has been 100% digital for over a decade now. I don't care to stress over technical details that were made obsolete over 4 decades ago. ;)
Earlier you said "the engineer in me". Accepting nothing as true without an experiment isn't engineering, it's dicking around.
 

bobhol

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Earlier you said "the engineer in me". Accepting nothing as true without an experiment isn't engineering, it's dicking around.

Well there is a little bit of truth in what you say. But what is "engineering" and who is an Engineer has been a moving target over the decades since the start of the Industrial Revolution. Going back to the thirties I've watched movies where the Engineer is some know-it all college graduate that designs things by the book. But its the master mechanic who learned by getting his hands dirty who can really design the best carburetor and wins the big race.
In modern days the current Boeing problems show what modern engineering looks like. Engineers have to do what marketing and management tells them. Boeing did not have the time to design a whole new plane to compete with its main competitor. The design engineer does the best he can to graft a bigger engine on an existing frame. And it is up to the Software engineer to get it all to work adequately. But somewhere between the Software design and the pilot training things went astray.

My apologizes if this is off topic. Being an engineer I couldn't not answer.
 

Frank Dernie

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I dicked about with record/platter interfaces when I worked for Garrard.
It certainly made a difference to the cartridge output (we used to look at the cartridge output measurement as the principle indicator since if something did not cause a problem here it wasn't an actual problem for the playback).

A lot of people, including some engineers, use static thinking for dynamic subjects. This leads to wrong conclusions.

For example, who knows how a "crankshaft damper" works in an IC engine? Basically it isn't a damper at all it is a mode-shape changer. By attaching a torsional spring and rotational inertia to the crank tuned to the same frequency as the torsional mode to be changed what happens is that at the frequency at which the crank used to resonate the little flywheel is resonating on its rubber spring so the mode shape of that resonance has been changed such that even though there is something resonating away like mad it isn't felt by the engine/transmission/bodyshell/driver.

I found that things could resonate on a record player without giving any output to the cartridge, and sometimes simple solutions, like a carefully placed punched hole in the top plate, could stop a particular structural resonance getting to the arm base and hence to the headshell (of course the cartridge output doesn't know whether it is the stylus or its body that is vibrating - both give an output).

I digress, the difficulty with record clamps is one of basic production engineering. All the theory is pointless if you don't have a perfectly flat record - which you don't. Non-flat, ie all, records only touch the mat or platter at a few points so a clamp will vary in effectiveness from disc to disc.
My own record player has a -0.060" cone for a top platter surface such that the disc sits with only its periphery touching the platter when it is dropped on but when the clamp is applied the whole disc is in contact as long as any warps are less than 0.060 high.
There may be other well thought through record players or solid mats which do this but most don't and a weight or clamp is therefore of limited and varied efficacy. I don't bother with one with my other 3 record players.
 

Sal1950

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My own record player has a -0.060" cone for a top platter surface such that the disc sits with only its periphery touching the platter when it is dropped on but when the clamp is applied the whole disc is in contact as long as any warps are less than 0.060 high.
Frank, did you custom machine that platter profile?
 

Frank Dernie

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Frank, did you custom machine that platter profile?
No it is a well thought through aspect of the original design. I did do a prototype design similar to this in 1976 but it was not thought to be appropriate for production by the management :(
It is the only turntable I know of like this and why I bought it.
It would be easy to do a metal “mat” and clamp to achieve the same result - re-arranging the arm and base such that the playing arc is horizontal would be more difficult.
 

pozz

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My own record player has a -0.060" cone for a top platter surface such that the disc sits with only its periphery touching the platter when it is dropped on but when the clamp is applied the whole disc is in contact as long as any warps are less than 0.060 high.
Could the same effect be achieved with a shallow cone cut into a thick acrylic or cork mat?
 

Thomas_A

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If you want to reduce warp-related noise, a weight-related clamp works poorly without an outer ring clamp. It can reduce warp-related noise on the average 5-6 dB according to measurements, and it of course varies with how badly warped a record is from start. Messing with clamps and rings is just to much work, IMO. A vacuum platter would be the best solution to this. You can also reduce warp-related noise by having higher resonance of the arm-cartridge, see link below.

https://www.dropbox.com/s/c47wosw9ux38nij/Tonearm mass and noise LP playback.pdf?dl=0
 
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