advertisement


Thorens TD125/160/150 etc upgrade platter - Interest check

Mike P

Mike P

Trade: Pickwell Audio
I apologise in advance for the slightly vague nature of this post.

Basically I'm trying to gauge how much interest there might be in an upgrade platter for the Thorens belt drive models in the TD150/160/125 'family' of turntables.

I own both a Thorens TD125mk2 and a TD124 mk2 and a couple of months ago I swapped the Zamak alloy platter on my TD124 for an original cast iron platter. The difference between the Zamak alloy platter and the iron platter was huge. It was a total game changer.

The iron platter is heavier and so has a greater flywheel effect, thus improving speed stability and pitch stability significantly. It is also MUCH less resonant. The Zamak platter literally rings like a bell for 10+ seconds when struck! Try it for yourself and you'll see what I mean!

I'm planning to have an iron platter made for my own TD125 and if there is sufficient interest I will have a small production run done and offer them out to others as a product for sale.

Cast iron really is a brilliant material for this. Stainless steel and brass and bronze platter all ring like the Zamak platter and for that reason are a poor choice of material. The only downside to iron as a platter material is that it is magnetic and this can preclude the use of certain cartridges. With many cartridges it's simply a case of taking the magnetic attraction into account when setting the VFT and this is easy to do with a cheap digital VTF scale. On my own TD124 for example I found I did not need to make any VTF adjustment at all when using an Ortofon VMS30 with the iron platter. MM carts will be fine, I would think some MC carts will be OK but anything like a Decca would be impossible to use. The easiest way to reduce the magnetic attraction is to increase the distance between the cartridge and the platter, so anyone wanting to use a cartridge that has strong magnets and exhibits too strong an attraction to the iron platter may be able to get around it simply by adding an extra platter mat/spacer. For the sake of simplicity and to be very cautious and conservative about this, I want people to assume this platter would be for MM carts only.

The new platter would be made to better tolerances that the original and fully machined on all faces. I've carefully measured a number of original platters and the tolerances are quite sloppy with significant variation between examples.

With the TD125/160/150 etc being sprung designs it isn't going to be possible to increase the mass of the platter a huge amount but a modest increase in mass should be still be very beneficial to speed stability and can be compensated for by adjusting the spring preload. Using a 3D CAD model the calculate the mass of the cast iron platter it should come out at around 2.6kg, which is around 600g heavier than the Zamak platter. I've experimented on my TD125 and 600g extra weight on the platter only needs a small adjustment to the suspension springs.

I can't give you a price for the finished article yet but my best guess would be something in the region of £350 - £550, which I appreciate is a rather loose estimate but the costs scale down massively as the production quantity increases, so the more people want one the cheaper they'll be.

This is all in the early stages but if you might be interested please let me know as I'll soon be getting quotes for the materials machining.
 
Last edited:
I'm now Thorens-free so not in the market but wanted to wish you well with this Mike, sounds great.
 
Sounds very interesting! Will you have a loaner so people can get a feel for what it does sound wise?
 
I have the non-ferrous Swissonor heavy platter for the TD124 which is used in the Schopper set of upgrades. It's well worth it over the standard MkII alloy platter. But an idler is a very different proposition to a bouncy suspended deck - not just in terms of suspension but also the design of the bearing generally a much more lightweight thing than generally found in an idler. I have a TD160 MkII here and replacement of the platter with a solid iron one would surely bottom out the suspension?

I wonder if some heavy solid 'top mat' option, the thickness of a rubber mat, might be a better proposition? If it could be a non-ferrous metal so much the better, adding weight and reducing resonance but without the potential overkill.

I suspect at least some of the improvement from using Funk mats and the like on an LP12/TD126/150/160/Systemdek etc over the felt mat is about adding mass, but the amount is way short of what an iron platter would add. My old Voyd 3-motor used a Lexan platter - again, quite high-mass compared to standard acrylic - to achieve similar. Perhaps it might be sensible to do something closer to solutions already known to work on suspended decks, rather than applying the logic of an idler?

Having said that, if there's one doing the rounds I'd be keen to try it out, and as it happens I've switched to MM anyway on my TD160. (Not necessarily a permanent state of affairs though).
 
montesquieu said:
I have the non-ferrous Swissonor heavy platter for the TD124 which is used in the Schopper set of upgrades. It's well worth it over the standard MkII alloy platter. But an idler is a very different proposition to a bouncy suspended deck - not just in terms of suspension but also the design of the bearing generally a much more lightweight thing than generally found in an idler. I have a TD160 MkII here and replacement of the platter with a solid iron one would surely bottom out the suspension?

I wonder if some heavy solid 'top mat' option, the thickness of a rubber mat, might be a better proposition? If it could be a non-ferrous metal so much the better, adding weight and reducing resonance but without the potential overkill.

I suspect at least some of the improvement from using Funk mats and the like on an LP12/TD126/150/160/Systemdek etc over the felt mat is about adding mass, but the amount is way short of what an iron platter would add. My old Voyd 3-motor used a Lexan platter - again, quite high-mass compared to standard acrylic - to achieve similar. Perhaps it might be sensible to do something closer to solutions already known to work on suspended decks, rather than applying the logic of an idler?

Having said that, if there's one doing the rounds I'd be keen to try it out, and as it happens I've switched to MM anyway on my TD160. (Not necessarily a permanent state of affairs though).
Click to expand...

Making the platter to the same dimensions as the original but in grey cast iron adds about 600g by our calculations (we'll see how accurate that is when I get the prototype made). I've tried adding 600g of mass on my TD125 and it makes very little difference to the suspension and only causes the suspension to sag 2-3mm. Easily compensated for with a small adjustment of the spring preload.
 
That's not too bad, but I'm surprised its as little as that - I just weighed the alloy platter on my TD160 MkII and it's a whisker over 2kg. Interestingly the Thorens-branded stock thick rubber mat is almost 500g. That's a fair amount of weight already on the suspension.

The Swissonor platter is 5.5kg which is a different proposition! I think the Mk II alloy TD124 platter is something like 3kg, vs 4.5kg for the MkI iron one, so a 50% uplift ... but doubt in this context an extra 400g worst case would kill the idea. Useful to think through the actual numbers.
 
Tarzan said:
This was my first thought having tried to pick up a cast iron Nottingham Analogue Mentor platter..........:eek:
Click to expand...
Please read the posts above. We're not talking about a 5kg+ platter here.

I don't know exactly which zinc alloy Thorens used but zamak 5 and zamak 3 have a density of 6.6g/cm3

Grey cast iron has a density of 7.15g/cm3

We have created a 3D CAD model of the proposed platter and the software allows you to input the density of the material and it will calculate the mass. It results in an estimated mass of give or take 2.6kg and this amount of extra weight can easily be compensated for by a small adjustment of the spring preload, at least it can on a TD125, I've tried it.

The proof of the pudding will be in the eating. I'll update the thread when I have the finished prototype.
 
Interesting. The first pictures of the finished product will be decisive for many I suspect.
You might want to lower the price a bit too.
 
chartz said:
Interesting. The first pictures of the finished product will be decisive for many I suspect.
You might want to lower the price a bit too.
Click to expand...

Given the extremely reasonable price of Mike's blue belt, I suspect the price of the platter will be whatever it costs him to develop and have made with a bit on top for his trouble. I doubt he is in it to get rich.
 
chartz said:
Interesting. The first pictures of the finished product will be decisive for many I suspect.
You might want to lower the price a bit too.
Click to expand...
The only way to lower the price is to make a much larger production run.
 
matt j said:
Given the extremely reasonable price of Mike's blue belt, I suspect the price of the platter will be whatever it costs him to develop and have made with a bit on top for his trouble. I doubt he is in it to get rich.
Click to expand...
Yes, no doubt about this. I for one can’t wait to picture it.
 
You must log in or register to reply here.


advertisement


Back
Top