I don't want to re-invent the wheel, but I have a couple of ideas for a plinth for my DIY turntable, but I need some advice from others.
My thoughts are;
Solid Jarrah chopping board drilled to take the spindle and tonearm. Nice looking but expensive.
Laminated MDF plinth, painted a pretty colour. Cheap and heavy.
Laminated MDF plinth with pockets for sand or lead-shot. More labour intensive, but well damped. Sand is cheaper, but lighter. What is best?
I also have access to a nice round Jarrah chopping board that could be used as a platter. It looks like it was turned. It too is expensive, but would look great. I was thinking of adding periferal brass weights to increase inertia and reduce any likelihood of imbalance due to variations in wood density.
What do you think?
My thoughts are;
Solid Jarrah chopping board drilled to take the spindle and tonearm. Nice looking but expensive.
Laminated MDF plinth, painted a pretty colour. Cheap and heavy.
Laminated MDF plinth with pockets for sand or lead-shot. More labour intensive, but well damped. Sand is cheaper, but lighter. What is best?
I also have access to a nice round Jarrah chopping board that could be used as a platter. It looks like it was turned. It too is expensive, but would look great. I was thinking of adding periferal brass weights to increase inertia and reduce any likelihood of imbalance due to variations in wood density.
What do you think?
rookster said:
IME, this one. Mass, mass, mass.
Lead shot is reasonably expensive, about $A30/10kg in the guns shops in Fortitude Valley. Legal to buy too, but don't laugh maniacally or talk to an invisible friend when you're in the store.
My DD TT's and my suspensionless Gyro have very heavy plinths that are full of a leadshot, fine sand and mineral oil mix. When you've finished routering out the holes in the plinth, coat it inside and out wirh epoxy resin. Inside it will make it watertight for the oil, and outside, once sanded gives a great smooth finish that won't look like laminated MDF when it's done.
Forgot to mention to laminate with epoxy too.
A pic is worth a thousand words right?
http://www.teresaudio.com/haven/
Go to Teres TT, and look at the construction pix. Mine is similar, but I have a big motor assembly in the middle.
Here are some ideas
http://www.teresaudio.com/t-265.html
(check out the rest of the site too) as well as
http://www.redpoint-audio-design.com/
I don't know what you're using as a bearing, but it'd want to be good to bother with all the effort.
Do you have access to a lathe?
How about Corian
Find a kitchen contractor that installs Corian countertops. He's probably got a stack of sink cutouts in a wide variety of colors. Find one you like. Have him cut it to your dimensions and bond 2 1/2" pieces together, making a 1" plinth. Let him do the work - Corian can be dirty to cut and sand, and he's got the tools and the glue and the experience.
Enjoy,
Bob
Find a kitchen contractor that installs Corian countertops. He's probably got a stack of sink cutouts in a wide variety of colors. Find one you like. Have him cut it to your dimensions and bond 2 1/2" pieces together, making a 1" plinth. Let him do the work - Corian can be dirty to cut and sand, and he's got the tools and the glue and the experience.
Enjoy,
Bob
BobM,
I do have a friend who builds kitchens. I will ask him. I was thinking of a plinth about 50mm (2") thick at least.
Brett,
I assume you are from around Brisbane also. I think I know which gun shop you mean. I had thought of ringing them up for a quote on lead shot. I take your point about sealing and using epoxy resin.
I have purchased a Teres bearing which will fit into something about 50mm thick.
I do have access to a lathe. What did you use as a platter? I am thinking acrylic, PVC or the wooden one I mentioned. I can machine the platter here at work during lunch time.
I do have a friend who builds kitchens. I will ask him. I was thinking of a plinth about 50mm (2") thick at least.
Brett,
I assume you are from around Brisbane also. I think I know which gun shop you mean. I had thought of ringing them up for a quote on lead shot. I take your point about sealing and using epoxy resin.
I have purchased a Teres bearing which will fit into something about 50mm thick.
I do have access to a lathe. What did you use as a platter? I am thinking acrylic, PVC or the wooden one I mentioned. I can machine the platter here at work during lunch time.
More on Corrian
What are the thoughts about corrian instead of acrylic as a platter material? Is it easier to machine? Has anyone played with this?
Thanks,
-b
What are the thoughts about corrian instead of acrylic as a platter material? Is it easier to machine? Has anyone played with this?
Thanks,
-b
Hi,
Acrylic, AKA metacrylate as the advantage of having an impedance characteristic that's very close to vinyl.
In fact it's only slightly higher making for a good path to drain away energy from the record into the platter with little chance for back reflections.
It's not easy to work with, has to be treated with linseed oil craie to make it anti-static but has the advantage of being a monolithic polymer where as corian is much more difuse in structure and behaviour.
It would probably be O.K. as a plinth material but would be way down on my list as a platter material.
Just my 2 cents,😉
Acrylic, AKA metacrylate as the advantage of having an impedance characteristic that's very close to vinyl.
In fact it's only slightly higher making for a good path to drain away energy from the record into the platter with little chance for back reflections.
It's not easy to work with, has to be treated with linseed oil craie to make it anti-static but has the advantage of being a monolithic polymer where as corian is much more difuse in structure and behaviour.
It would probably be O.K. as a plinth material but would be way down on my list as a platter material.
Just my 2 cents,😉
fdegrove said:
PVC is available here at similar cost to acrylic, and I think that would give an even better impedance match. I use it as platter mats on two of my TT's.
Redpoint is the only manufacturer I know that uses it as a platter material.
My opinion is that acrylic looks better and that's why it's used more.
Hi,
Nope.
Better do the homework on this, Brett..
While you may want to augment perceived record mass on the top layer of the platter, this is not a material you'd want to use throughout...
We want to sink energy, not reflect it back to the stylus.
Cheers,😉
Nope.
Better do the homework on this, Brett..
While you may want to augment perceived record mass on the top layer of the platter, this is not a material you'd want to use throughout...
We want to sink energy, not reflect it back to the stylus.
Cheers,😉
Surely a better impedance match, such as offered by PVC will reduce reflections.
On a different note i've used the same thickness of PVC and Perspex as equipment shelves and greatly prefer the intrinsic sound of Perspex.
cheers
peter
Could we have a little more explication of what you all mean by 'better' impedence match? I assume that better impedence match ought to mean the impedences are similar, so that (theoretically) there isn't much of a boundary. But of course there is, in fact, a layer of air between the record and the platter, even if it is only in the grooves (this assumes a perfectly flat record and a similar platter -- we should be so lucky). What, if any, effect does this have? And why is fdgroove so dismissive of impedence matching? Am I missing something?
Hi,
Let me assure you that he's not dismissive of impedance matching.😉
What he means is that the "matching" in this case is usually understood as using a material that has the same mechanical impedance as the next or previous material.
In that case all we would have achieved is an increase in mass, not bad but not the ideal we want to achieve, namely provide an easy path for the spurious energy to go into the platter and dissipate as heat.
Ideally we should also provide for a difficult path for that energy to travel back into the vinyl record.
Using two materials with the same mechanical impedance would not provide that.
However, using a matrial with a slightly higher mechanical impedance than vinyl would, at least in theory.
Hope that clarifies it a little,😉
Let me assure you that he's not dismissive of impedance matching.😉
What he means is that the "matching" in this case is usually understood as using a material that has the same mechanical impedance as the next or previous material.
In that case all we would have achieved is an increase in mass, not bad but not the ideal we want to achieve, namely provide an easy path for the spurious energy to go into the platter and dissipate as heat.
Ideally we should also provide for a difficult path for that energy to travel back into the vinyl record.
Using two materials with the same mechanical impedance would not provide that.
However, using a matrial with a slightly higher mechanical impedance than vinyl would, at least in theory.
Hope that clarifies it a little,😉
Thanks for the clarification. I wouldn't have thought of the role of increased mass, but its and obvious issue. But it seems to me that if you want to make it easy for energy to be transported away from the record, and difficult to return, wouldn't you want lower mechanical impedence, not higher? If I am not wrong, its easier to go from high to low, so this would be benficial in both directions. I this correct? And what about the role of delay -- I assume that high impedence is related to quick transmission, whereas low impedence would be slower. Or am I using the terms incorrectly?
This is an interesting topic, and I appreciate your help thinking through it.
This is an interesting topic, and I appreciate your help thinking through it.
All,
Thanks for the advice. I agree that impedance matching is important, but perhaps not something that we all agree upon as it is not an eaxct science, but neither is turntable building. As with anything it is a mix of theory, luck and experience.
Should a record clamp or weight be used? How does that affect impedance matching?
For convenience sake I have obatined a 2" thick disc of acrylic, approx 13" in diameter. I will add peripheral weights to it for inertia reasons, but they should not alter the impedance match.
I have the Teres bearing ready to fit the platter. I believe I will use a laminated MDF plinth with pockets for lead, oil, sand mix. This should add about 20lbs to the plinth and the whole assembly minus the motor pod should weigh about 60lbs or so.
I will try and veneer the plinth instead of paint, but it depends how well the veneer sticks down.
The motor pod will be an outboard unit weighing around 10lbs and made mainly of brass.
I will take photos as I go and post them, but this will take a couple of months to make any real progress.
Thanks for the advice. I agree that impedance matching is important, but perhaps not something that we all agree upon as it is not an eaxct science, but neither is turntable building. As with anything it is a mix of theory, luck and experience.
Should a record clamp or weight be used? How does that affect impedance matching?
For convenience sake I have obatined a 2" thick disc of acrylic, approx 13" in diameter. I will add peripheral weights to it for inertia reasons, but they should not alter the impedance match.
I have the Teres bearing ready to fit the platter. I believe I will use a laminated MDF plinth with pockets for lead, oil, sand mix. This should add about 20lbs to the plinth and the whole assembly minus the motor pod should weigh about 60lbs or so.
I will try and veneer the plinth instead of paint, but it depends how well the veneer sticks down.
The motor pod will be an outboard unit weighing around 10lbs and made mainly of brass.
I will take photos as I go and post them, but this will take a couple of months to make any real progress.
Hi,
You could but; lower mechanical impedance material will also be softer materials.
Note also that the impedance "mismatch" between record vinyl and metacrylate is really small and there other reasons than just theoritical ones for chosing it that may not necessarily apply to DIY designs.
Putting a record on a softer than its own material will tend to diminish dynamic range and micro-detail.
An analogy I often use to allow people to picture what's going on is to compare writing on a solid fixed surface or writing on a cushion.
Viewed by the cartridge this would amount to the same.
There's alot more to tell and I'm trying to collect as much info as possible...
Cheers,😉
You could but; lower mechanical impedance material will also be softer materials.
Note also that the impedance "mismatch" between record vinyl and metacrylate is really small and there other reasons than just theoritical ones for chosing it that may not necessarily apply to DIY designs.
Putting a record on a softer than its own material will tend to diminish dynamic range and micro-detail.
An analogy I often use to allow people to picture what's going on is to compare writing on a solid fixed surface or writing on a cushion.
Viewed by the cartridge this would amount to the same.
There's alot more to tell and I'm trying to collect as much info as possible...
Cheers,😉
Hi,
A record clamp is imperative IMO and the better ones apply the same principles as applied to platters with the added goals of keeping the record from slippling on the platter and flatten the record by applying pressure on the outer rim of the label.
One of the best I had was a Goldmund which was really well thought out.
Be careful with oversized platters, some tonerams are really hard to put on those.
If you insert them at the bottom of the platter they'll also help to absorb energy from the bearing.
Cheers and keep us posted,😉
A record clamp is imperative IMO and the better ones apply the same principles as applied to platters with the added goals of keeping the record from slippling on the platter and flatten the record by applying pressure on the outer rim of the label.
One of the best I had was a Goldmund which was really well thought out.
Be careful with oversized platters, some tonerams are really hard to put on those.
If you insert them at the bottom of the platter they'll also help to absorb energy from the bearing.
Cheers and keep us posted,😉
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