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.
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.
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