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Old 12th February 2012, 03:38 AM   #521
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Originally Posted by kevinkr View Post
I ordered two Schopper belts, one for each of my TD-124s, and will report back when they get here. The Swiss Franc is not as strong as I thought either which was a nice surprise.

I found Christine at Schopper extremely helpful, pleasant, and quick to deal with.. This makes it much more likely that I will spring for one of their lovely non-magnetic platters down the road a bit.

Edit: My TD-124/II came with the non-magnetic zamac platter which I have replaced with a stock cast iron platter which seems to work OK with the SPU. The cast iron platter is much more neutral sounding than the zamac platter which was brutally apparent the moment I installed it. The zamac platter does not sound bad per se with a little help, but the cast iron was a pretty big improvement in terms of unmasking detail and in getting rid of a certain zingyness that I was not fully aware of until it was gone.
There's a picture of Christine in the "Swiss Precision" td124 book, toward the back where the author makes mention of the Schopper operation. She looks very nice.

re: non-mag platter/flywheel options and the Schopper product. I'll admit to lusting after one of those myself. It looks very well made. Alternatively, Mirko makes one out of stainless steel. I know of one individual who is using one of those and says favorable things about it.

Also in the "Swiss Precision" book it was mentioned that early td124 prototypes used a bronze flywheel but that production models used cast iron to keep costs in line. Also, the iron is a very stable metal that holds its shape well. A pretty good material that doesn't seem to present any real problems with cartridge magnets that I can tell.

Still, all this makes me wonder why it wouldn't be preferable to machine a "custom" flywheel out of gunmetal bronze or similar. It's denser than iron so the same dimensions should net an even heavier flywheel and a larger moment of inertia out at the rim. And the bronze is also non-magnetic. So I wonder why not bronze! Or maybe I just haven't priced the metal lately.

-Steve
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Old 13th February 2012, 12:28 AM   #522
kevinkr is offline kevinkr  United States
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Hi Steve,
Some MC cartridges interact adversely with the iron platter, my SPU tracked about 0.7gm heavier when I changed the platter, but since I have the very simple Schick arm I just adjusted the counterweight to compensate. I do have a Merrill Mat on my table which is roughly 1/8" thick. (Not sure how that compares to the stock mat)

Decca London (not an MC cartridge) owners have told me that the cantilever will collapse if this cartridge is used with an iron platter TD-124 as the cartridge is strongly attracted even through the top platter and mat.

I'm going to save my pennies for the Schopper - I think it will be a worthwhile if rather expensive upgrade to an already great table. I'm still thrilled with this table after 14 months so...
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Old 13th February 2012, 01:26 AM   #523
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Originally Posted by kevinkr View Post
Hi Steve,
Some MC cartridges interact adversely with the iron platter, my SPU tracked about 0.7gm heavier when I changed the platter, but since I have the very simple Schick arm I just adjusted the counterweight to compensate. I do have a Merrill Mat on my table which is roughly 1/8" thick. (Not sure how that compares to the stock mat)

Decca London (not an MC cartridge) owners have told me that the cantilever will collapse if this cartridge is used with an iron platter TD-124 as the cartridge is strongly attracted even through the top platter and mat.

I'm going to save my pennies for the Schopper - I think it will be a worthwhile if rather expensive upgrade to an already great table. I'm still thrilled with this table after 14 months so...
I haven't tried that many different cartridges on the TD124. Probably the one with the strongest magnet that I've used was a Shelter 501-II (neodymium magnet). This is a cartridge that one needs to be careful with when using a regular steel screw driver around it 'lest the screw driver slam against the cart body. So I guess a Decca London has a stronger magnet that that, eh..

And the SPU, true to its reputation, does exhibit a pull toward the iron platter below...!

on the subject of SPU's I've noticed that William Thakker is selling an SPU-N MC cartridge for a somewhat modest price. If I understand correctly, this is an SPU motor minus the integrated headshell. If so, I'm tempted to use it with the black Zeta tonearm. Hmmmmm. I wonder how that might work. (just thinking outloud. Not committing...)

-Steve
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Old 13th February 2012, 04:07 AM   #524
kevinkr is offline kevinkr  United States
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Quote:
Originally Posted by user510 View Post
I haven't tried that many different cartridges on the TD124. Probably the one with the strongest magnet that I've used was a Shelter 501-II (neodymium magnet). This is a cartridge that one needs to be careful with when using a regular steel screw driver around it 'lest the screw driver slam against the cart body. So I guess a Decca London has a stronger magnet that that, eh..

And the SPU, true to its reputation, does exhibit a pull toward the iron platter below...!

on the subject of SPU's I've noticed that William Thakker is selling an SPU-N MC cartridge for a somewhat modest price. If I understand correctly, this is an SPU motor minus the integrated headshell. If so, I'm tempted to use it with the black Zeta tonearm. Hmmmmm. I wonder how that might work. (just thinking outloud. Not committing...)

-Steve
Hi Steve,
I've tried a small number I am surprised to admit, but the SPU is by far the best of the ones I have tried - I have a modern Classic GM E II which I track at 4gms according to my trusty electronic stylus gauge.

I've had a Zu Denon DL-103, DL-103D, DL-103SA, Stanton 380 Flux Valve, SPU G/TE, SPU GM E II, a certain Shure I am sworn to secrecy not to reveal, and a Pickering 681EE in either the Schick or SME 3009 Series II as appropriate for mass and compliance.

Yes, the SPU - N is the same one that goes into the SPU Classic GM II, note Thakker is not authorized to sell Ortofon cartridges here in the USA, and Ortofon considers any cartridge acquired this way as gray market and sans warranty - your sole recourse would be with Thakker. Needle Doctor does sell it for significantly more here: Ortofon SPU Classic N Phono Cartridge

The N is a very low compliance type and tracks at 3 - 5 gms and likes high mass arms like the 3012 and Schick.

I have to admit I really like the SPU (in general) and will acquire other models in the line as resources permit.
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Old 14th February 2012, 06:45 PM   #525
volken is offline volken  Netherlands
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Steve the difference in sound between the iron platter and Schopper platter is amazing and between the alu.platter huge.
When you change the platters you hear it immediately in the first note"s on the record .
It is the first upgrade with a big sound improvement the second is the Schopper mainbearing !!
You hear more details improvement in low and high frequencies and dropping from noise between the music.
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Old 17th February 2012, 11:48 PM   #526
kevinkr is offline kevinkr  United States
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One of these days I will check my copy, always nice to see who you are dealing with.. Anyway the belts arrived today and I have installed one on the TD-124/II, and when I next work on the TD-124/I I will install one on that table as well.

First observation is that dimensionally it is very similar to the FLA belt I have commented on in early posts, however it is much more pliable, and runs MUCH quieter right out of the bag.. Where there was a very slight amount of belt noise audible from a foot or so away now almost nothing is audible now - probably the room noise floor is currently higher than the noise generated by this belt.

The old belt has been on the table for about six months now and was running as quietly as it ever will, the new belt may get even quieter with some use.
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Old 17th February 2012, 11:50 PM   #527
kevinkr is offline kevinkr  United States
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Quote:
Originally Posted by volken View Post
Steve the difference in sound between the iron platter and Schopper platter is amazing and between the alu.platter huge.
When you change the platters you hear it immediately in the first note"s on the record .
It is the first upgrade with a big sound improvement the second is the Schopper mainbearing !!
You hear more details improvement in low and high frequencies and dropping from noise between the music.
I can believe it, the difference between the zamac (zinc alloy) platter that came new with my TD-124/II and the cast iron platter I replaced it with was not subtle. I expect a pretty substantial further improvement with the Schopper.
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Old 18th February 2012, 01:13 PM   #528
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Default Cast Iron Vs Zimac

I agree, Kevin, the Zimac platter is in my mind, terrible. Rings like a bell also.




Quote:
Originally Posted by kevinkr View Post
I can believe it, the difference between the zamac (zinc alloy) platter that came new with my TD-124/II and the cast iron platter I replaced it with was not subtle. I expect a pretty substantial further improvement with the Schopper.
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Old 19th February 2012, 08:00 PM   #529
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Default So just what is this alloy used in the Schopper TD124 platter...?

Beyond its reduced magnetic attraction tendencies, just what are the properties of this Schopper platter that make it such a sonic miracle in comparison to the original iron platter? Perhaps that is a subject worth looking into?

First off, for a reference Schopper offers an article written by Richard Foster in Hi-fi+ magazine. Issue #37

In the article, Foster recounts how how Jerg Schopper and some "Swiss Metallurgists" conducted some research and come up with a cast iron alloy invented during WWII that was used by the U.S. Marines on their mine-sweeper vessels. But he doesn't go into deep detail on this and so doesn't actually explain much about it. The reader is just left to assume that the hull of a mine sweeper vessel needs to not attract magnetic sensors within a particular type of mine. Pretty vague stuff.

In an article written by Art Dudley we also have some clues offered to us as to what this alloy actually is. And we can thank Art for not offering up some bull S&it story about WWII mine sweepers. Art just tells us that the metal in question is simply grey cast iron that has been in common use for ages and that grey iron, which has a considerable graphite flake content, is less attracted to magnetic pull than other iron alloys.
Here's a link to the Dudley "no BS" article:
Listening #65 | Stereophile.com

So far I haven't answered the question in my subject title box. What is the exact alloy in use.... and apart from its lowered magnetic properties, what makes it so desirable as a platter material?

I recall from an earlier life as a machinist that in one shop that I worked in, I did some lathe turning on grey cast iron. Grey cast iron does have a high graphite content which makes it fairly machinable and also makes a big mess on the shop floor that puts black graphite dust over everything in the building. Very dirty stuff that gets everywhere and follows you home.

The material is stable in that it does not change its shape during the manufacturing process. It doesn't warp like some stainless and aluminum alloys. It holds size nicely.

Other properties are:
High damping properties....in that it is excellent at vibration damping!

Good wear resistance......so the inner rim that takes its drive from the idler wheel should keep its size and shape over the years and does not suffer any worn grooves from the idler tracking.

A low modulus of elasticity!! Grey iron tends to be somewhat brittle and can break into pieces if subjected to any serious shocking force. But this can be adjusted by various heat treating processes. Still. In fact the alloy is brittle. So don't drop one of these platters to the hard concrete floor. Not that we would.

What I can't remember from my previous life is whether or not I ever put a magnet to grey cast iron. I probably did since we used magnetic dial indicator stands to support a dial indicator while measuring run-out and other dimensions. My guess, if this is the same stuff Schopper is using, the magnetic holder would not hold very well against grey iron. Too bad my memory doesn't resolve that far back.

In the mean time as I search the web for properties of grey iron, I see no mention of magnetic attraction among the descriptions of the metal. I see no mention of magnetic properties in combination with grey iron.

"Machinery's Handbook" does not speak to the magnetic properties of iron either. It does, however mention another different category of irons; "Alloy Cast Iron". This category allows the use of various different alloying elements such as nickel, chrome, copper, manganese, etc. These can be added in varying amounts to achieve different mechanical properties. So I wonder if Schopper doesn't use something more specific than just plain old grey cast iron. If so, they don't tell us.

But then I suppose that would come under the heading of "trade secrets".

One thing I notice while looking at the various descriptions of different iron alloys; grey iron is the only metal that is described as having good damping properties. The other irons (white iron, Chilled cast iron, malleable iron, etc) make no mention of this damping property. With that in mind, I suspect a rather soft brittle grey iron with its high graphite flake content may be very desirable just from the dampening properties it offers!


Q: so just what iron alloy is the standard Thorens TD124 platter?
A: unknown. In Bung's book he calls the standard platter material "stabilized cast iron".

I do know that the TD124 platter attracts even the weakest of magnets quite strongly.

-Steve
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Old 19th February 2012, 09:05 PM   #530
brianco is offline brianco  Ireland
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A possible property of such metal which causes the mentioned 'damping' effect is that the larger-flake graphite content is responsible. It is reasonably well known that carbon will turn vibration into heat. If this is in fact the reason then some vibration will be dispersed. [I have two purest-carbon platter blanks waiting for use: one will certainly be bonded to the existing platter of my Lenco, whilst the other will be used on a simple string drive DIY TT.]

Thank you for the link to Art Dudley's article; from there I travelled to his review of Mr Schick's tonearm. It was most interesting.

Last edited by brianco; 19th February 2012 at 09:07 PM.
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