Hey, I have seen alot of turntable design where they appear to have a platter system which resembles essentially the AR XA without the outer platter. Can you run an AR XA like this? I was thinking if you used a a record weight which as as heavy as the outer platter, it would balance the suspension fine and hold the record flat. What would be the advantage? None, except for I now have an XA without an outer platter, counterweight, and headshell. Just exploring alternatives. Would this work?

Hey, I have seen alot of turntable design where they appear to have a platter system which resembles essentially the AR XA without the outer platter. Can you run an AR XA like this?
Both are needed because they counter each other's resonances. Without the outer platter, the inner platter will ring like a bell.

Both are needed because they counter each other's resonances. Without the outer platter, the inner platter will ring like a bell.

Yeh, I noticed that. I guess an acrylic or wood outer platter would be best then?

Yeh, I noticed that. I guess an acrylic or wood outer platter would be best then?
I've not tried it, but I expect what you'd need to do is have a replacement for the inner platter machined out of whatever alternate material you want to use. Or you could try filling the underside with damping material and then making something that fits on top of it. As long as your record is in contact with the original platter, you will still be dealing with its resonance.

Remember also there is inertia in the platter, belt, and motor pulley all designed to keep a constant speed and was said to dampen the resonance effect. I'd say weigh an outer platter (we could do that for you) then have one made to match. Might just work!

If the only goal is to get the table running and not to explore some kind of exotic alternative platter design, I'd say just start browsing that auction site and your local Craigslist for a junker with salvageable parts.

Remember also there is inertia in the platter, belt, and motor pulley all designed to keep a constant speed and was said to dampen the resonance effect. I'd say weigh an outer platter (we could do that for you) then have one made to match. Might just work!

That was my intent, I have one here and I was gonna weigh it, and make one out of wood or acrylic of the same weight. I was gonna do the same for the counterweight.

Hey dualhead I know from the replies you got it appears to be "safety first" but I would encourage you to try the idea's you have. It might lead you to what some consider the best aspect of this hobby, DIY. Just a thought.

I went through what your thinking 20 years ago and found that things that ring and things that go around are less predictable than you might at first think. And 2 part platters are made for packing and shipping as much as anything else.

marc mc

Hey dualhead I know from the replies you got it appears to be "safety first" but I would encourage you to try the idea's you have. It might lead you to what some consider the best aspect of this hobby, DIY. Just a thought.

I went through what your thinking 20 years ago and found that things that ring and things that go around are less predictable than you might at first think. And 2 part platters are made for packing and shipping as much as anything else.

marc mc

Cool, thanks. I was kinda planning on giving it a whirl anyhow ;)

Seems to me there must be plenty of dead XAs (especially the first version with the nylon or delrin main bearing that creeps over time so that the shaft is trapped) with donor outer platters. The problem is finding them, of course...

The outer platter is needed to provide the additional weight to level the suspension, which includes the arm.

But if, as he plans, his record weight is the same as the platter (which will mean that its a massive, hence tall, weight) the suspension will be level. The rotational inertia, of course will be dramatically less, with unpredictable results. Probably mostly negative.
But I hope he tries -- I remember the Meitner table in the early 80s which had no platter and was based on the idea that air was a better medium to contact the vinyl than any platter (I think the idea was that vibrations would be very quickly reflected, limiting smearing compared with vibrations travelling through the mat and platter and then being reflected).

I don't know how I missed that from the OP...but I did! :dunno:

But if, as he plans, his record weight is the same as the platter (which will mean that its a massive, hence tall, weight) the suspension will be level. The rotational inertia, of course will be dramatically less, with unpredictable results. Probably mostly negative.
But I hope he tries -- I remember the Meitner table in the early 80s which had no platter and was based on the idea that air was a better medium to contact the vinyl than any platter (I think the idea was that vibrations would be very quickly reflected, limiting smearing compared with vibrations travelling through the mat and platter and then being reflected).

I replaced the platter weight 20 years ago with the metal inside the hub visable in the top picture. It was Ed's articles all those years ago that got me going. I do have the options of with or without the platter on this table I made. But I prefer it without the platter. The rotation would seem to be different but you could never hear it. It acts like a table with the belt around the entire platter.

Just food for thought.

http://i65.photobucket.com/albums/h214/marcstoolshed/oracle005.jpg
http://i65.photobucket.com/albums/h214/marcstoolshed/oracle011.jpg
http://i65.photobucket.com/albums/h214/marcstoolshed/oracle025.jpg
http://i65.photobucket.com/albums/h214/marcstoolshed/turntable2a012.jpg

marc mc

I'll let everyone know what my results are.

Seems to me there must be plenty of dead XAs (especially the first version with the nylon or delrin main bearing that creeps over time so that the shaft is trapped) with donor outer platters. The problem is finding them, of course...

I had new Delrim thrust washers made for my XA correct tolerance. If the platter bearing is deburred and polished it will not be trapped. Nice upgrade btw.