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acrylic platter mat

DENNYDOG

DENNYDOG

Addicted Member
I had been searching for a table to mount my early Pioneer PA-100 arm on when all of you guys started talking about how awesome the Pioneer PL-41 is with it's 4-pole hysteresis synchronous motor. I thought this should be a great match up between the two.

I finally found a super nice one. The only problem is the stock tonearm sits super low compared to the platter. There really isn't a good way to raise the platter without screwing up the motor and belt alignment. I know a few of you ran into this same problem. My idea is to machine a 3/4" piece of acrylic to act as the new platter mat so the PA-100 matches up with the height of the record.

I have read that the solid acrylic platters are great performers on some tt's. I am hoping the two jive well. Paired together with the original platter it should bring it up to where it will work with the new tonearm and not have to modify anything else on the table.

I found a site called freckleface.com that has awesome prices on acrylic. I just received my order for a 24x24x3/4" piece. It looks like I will be able to get two platters out of it. I figure if I screw up the first one I will still have enough left over to make another.

All I need to do now is figure out the best way to machine it to what I want. I do have access to a lathe and would think the acrylic should cut fairly easily. I may also have to make a new spindle as the original will be too short. That or make a stub that fits in the top of the mat.

Has anyone else done anything like this? Good idea or not? Any suggestions or comments are welcome.
 
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A little confusing, because at first, you say the Arm sits super low compared to the Platter. You mean super high, don't you?

I gather there's bee some sort of an arm change? Can the Arm mount be remade, or machined down? Pics would sure help, and hopefully, some other PL-41 owners can chime in to help. Mark
 
I guess it's a little confusing the way I wrote it. The stock arm sits super low but the PA-100 arm is quite a bit higher than the original arm. This is why i need to bring the platter or the mat up to get everything aligned. Edited original post.
 
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From what little info I could find about this arm on a google search, it says this is a universal arm, usable with various platters, etc.

Hmm. Are you sure something cannot be altered-changed at the Arm Mount, thus lowering the Arm? Sure there isn't a combination of Arm mount Parts that you applied, that maybe doesn't need to be there? I see the Cueing Cylinder on the Arm, and provided that doesn't hit the base, one could perhaps have a machinist make a lower profile Arm Mount. This sounds easier than the Platter mat, spindle, etc route.

If you can do that, the sheet of acrylic could be turned into a shelf mount perhaps, or a isolation base for the Table to sit on? Mark
 
IMG_4696.jpg

It might be a little hard to tell in the pictures but stock arm on the left sits quite a bit lower than the new arm that's replacing it.

I will be machining a groove in the bottom of the acrylic to match up with the groove in the original platter so it sits all the way down on the platter and then machine grooves in the top of the acrylic like the original platter mat had.

I won't be using a rubber platter mat other than just the acrylic.

Here you can see how the original platter uses a two piece mat. Mine was missing the inner piece.

IMG_4697.jpg
 
Ok, you are wishing to use the Arm on the lower right of the picture, right?

Now on that arm's Mounting shaft post, I see two circular rings. Does that lower circular ring have a allen set screw, that that lower ring can be slid off the Mounting shaft? Mark
 
Yes it is the lower right arm. The bottom ring is the nut to hold the arm in place. The top "ring" could be removed but that would only let me bring it down about a 1/4". I am still higher than the other arm by about 1/2" even without the trim collar.

I figured I would keep the collar on it so I don't lose it and go with the 3/4" mat. I can't really get the arm any lower than that without doing heavy modifications to the turntable which I am trying to keep away from doing. I might be a little higher with the mat than I need to be but that gives me some room for adjustment for different cartridges. The PA-100 arm has built in vta.
 
Hmm, I was fearing that you'd say that about that being the bottom retaining nut. :-(

I;m tring hard to figure some way, as I know you must be stumped as well about a solution. The Platter seems like it could possibly incur a whole nother can of worms issues, that you'll perhaps cure one issue, but maybe cause some other problems?

The one possible easy way out is another Arm, but I take it you are already drilled for that S-P Distance, right? Mark
 
Thank you for the link. The only problem with buying one is it won't be near the thickness I need. I guess it can't be too bad of an idea if someone is making something like this already.
 
Here's some brain farts about this type of mod.

First, how would one attach the Acrylic Sheet to the top of the Alu platter? Glue? Screws? ?

The other thought that came to mind, is since this is a sheet of acrylic, it may not be true/flat enough to produce acceptable results? With the Platter, and thus the Arm-Cartridge bobbing up, and down, this will be a problem.

Just lathing the sheet into a circle may not do it. Any manufacturers that make acrylic, or other material platters generally machine the entire affair, to attain the needed precision. Mark
 
markd51 said:
Here's some brain farts about this type of mod.

First, how would one attach the Acrylic Sheet to the top of the Alu platter? Glue? Screws? ?

The other thought that came to mind, is since this is a sheet of acrylic, it may not be true/flat enough to produce acceptable results? With the Platter, and thus the Arm-Cartridge bobbing up, and down, this will be a problem.

Just lathing the sheet into a circle may not do it. Any manufacturers that make acrylic, or other material platters generally machine the entire affair, to attain the needed precision. Mark
Click to expand...

Why would I need to permanently attach the mat to the platter? The mat would sit on the platter just like the original mat and like the acrylic one ripblade gave a link to. It sure is heavy enough so I have no reason to believe there should be any need to attach it in any way.

I put a strait edge on the piece of 3/4" acrylic I got and it's perfectly flat. Surely not even close to being as bad as you suggest to make the arm "bob up and down". I plan to machine the ridges into the top surface just like the original mat to give it the same look. I will have it chucked up in the lathe so even if it was off even slightly it wouldn't be a big deal to fix that.

Cheers,
Denny
 
I put an acrylic mat (different brand) on my Oracle almost 20 years ago. This particular one had a peel and stick adhesive that covered the entire bottom surface in narrow ribbons only 1/8" apart. These ribbons ensured no air gaps were formed between the mat and platter.

I have a friend who has the XTM1 mat I linked to above who uses no adhesive at all. These mats seems to work either way. He does however strongly recommend the use of a clamp.
 
DENNYDOG said:
Why would I need to permanently attach the mat to the platter? The mat would sit on the platter just like the original mat and like the acrylic one ripblade gave a link to. It sure is heavy enough so I have no reason to believe there should be any need to attach it in any way.

I put a strait edge on the piece of 3/4" acrylic I got and it's perfectly flat. Surely not even close to being as bad as you suggest to make the arm "bob up and down". I plan to machine the ridges into the top surface just like the original mat to give it the same look. I will have it chucked up in the lathe so even if it was off even slightly it wouldn't be a big deal to fix that.

Cheers,
Denny
Click to expand...

True, a 3/4" thick sheet of acrylic that size should not slip by just the drag of a Stylus.

I was actually thinking more about the possibility of variance in thickness of the sheet, that could cause up-down errors. Mark
 
As a cabinetmaker I often work with acrylic sheets and can state confidently that the material tolerances are quite close...more than likely bettter than an Lp.

I would avoid turning a heavier thickness down on a lathe as it would probably be impossible to match the tolerance of a thinner sheet. If 1/8 is insufficient, consider 3/16 or heavier and just cut the outer diameter and label recess.
 
DENNYDOG said:
I had been searching for a table to mount my early Pioneer PA-100 arm on when all of you guys started talking about how awesome the Pioneer PL-41 is with it's 4-pole hysteresis synchronous motor. I thought this should be a great match up between the two.

I finally found a super nice one. The only problem is the stock tonearm sits super low compared to the platter. There really isn't a good way to raise the platter without screwing up the motor and belt alignment. I know a few of you ran into this same problem. My idea is to machine a 3/4" piece of acrylic to act as the new platter mat so the PA-100 matches up with the height of the record.

I have read that the solid acrylic platters are great performers on some tt's. I am hoping the two jive well. Paired together with the original platter it should bring it up to where it will work with the new tonearm and not have to modify anything else on the table.

I found a site called freckleface.com that has awesome prices on acrylic. I just received my order for a 24x24x3/4" piece. It looks like I will be able to get two platters out of it. I figure if I screw up the first one I will still have enough left over to make another.

All I need to do now is figure out the best way to machine it to what I want. I do have access to a lathe and would think the acrylic should cut fairly easily. I may also have to make a new spindle as the original will be too short. That or make a stub that fits in the top of the mat.

Has anyone else done anything like this? Good idea or not? Any suggestions or comments are welcome.
Click to expand...

I completely understand the problem. I retrofitted a Sumiko FT-3 tonearm to my Pioneer PL-41 and encountered the very same issue. I have the VTA adjustment down to its lowest setting and it is barely correct. The only way I can think of to fix the problem is to do a custom armboard (recessed?), add spacers to the headshell, or do what you are thinking of doing.
 
I know I have other projects I have started before this and should finish first, but I've been wanting to get this arm mounted on a PL-41 ever since I got it in the mail.

I ordered a couple short pieces of stainless round to see if I can turn a new taller spindle to accommodate the thicker mat. The lathe we have at work is an old worn out piece of crap so we will see how well that goes. If it doesn't, I think a short stub pressed into the top of the acrylic will work just fine for centering the records.

We will see how long this takes me. I haven't been known for being speedy with some of my projects.

Mark, hopefully this will work and give us both a solution to the problem we are having. The way it sounds you might be able to get by with a slightly thinner mat if this does work.
 
DENNYDOG said:
I know I have other projects I have started before this and should finish first, but I've been wanting to get this arm mounted on a PL-41 ever since I got it in the mail.

I ordered a couple short pieces of stainless round to see if I can turn a new taller spindle to accommodate the thicker mat. The lathe we have at work is an old worn out piece of crap so we will see how well that goes. If it doesn't, I think a short stub pressed into the top of the acrylic will work just fine for centering the records.

We will see how long this takes me. I haven't been known for being speedy with some of my projects.

Mark, hopefully this will work and give us both a solution to the problem we are having. The way it sounds you might be able to get by with a slightly thinner mat if this does work.
Click to expand...

How did you plan to address the ridge in the platter? Are you making the platter mat a two piece design like the oem rubber one? Also, if you raise the mat a lot, won't you run out of spindle? Or, are you adding spacers under the thrust washer to raise it.

If I had the skill, I would build a recesssed arm plate, something along the lines of the way my Technics SL 1200 MK II's arm plate looks. That way, you would never have to worry about your arm height.
 
The mat will be a single piece since it's 3/4" thick. I will machine a groove in the bottom of the acrylic so it sits flat on the platter. I ordered some stainless shaft to turn a longer spindle. We will see how that goes.

If I can't get that to come out right I will most likely just make a short stub that is pressed into the acrylic. This may be the easiest and best solution. There probably would be no real benefit in having a long spindle anyways.

If I went any thinner with the mat there wouldn't be enough room to press in the short stub. I guess that would be another benefit of the thicker mat. It would be easy to retrofit tables that need a higher platter height without having to modify the spindle. If the mat is higher than it needs to be, it would be very easy to shim the arm to where it should be also.

Do you have pics of the recessed arm plate for your Technics? I am trying to figure out how that would work on the PL-41 without cutting the mounting base for the arm. This is one of the things I was trying to stay away from by making the thicker mat.
 
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