Platter material
Would brass not be a better alternative to S/S and cast iron. On any substitute TD-124 platter one could (with a bit of machining) be able to have the upper platter "standoffs" made to the thickness of the platter main bed + 0.04" and then press fit them into the holes in the main platter thus helping to break resonances.
Would brass not be a better alternative to S/S and cast iron. On any substitute TD-124 platter one could (with a bit of machining) be able to have the upper platter "standoffs" made to the thickness of the platter main bed + 0.04" and then press fit them into the holes in the main platter thus helping to break resonances.
The platter is aircraft grade aluminium. It is pulled like transistors to get a good structure, ideal for platters as the billet is round. I dare say there is some copper in it ( 2% ? ). We use two 11 inch O rings in the platter grooves. The cork-neoprene mat finishes the job. We did try other things. I fancy acrylic in the same weight would be good, phenolic resin my number one love. Like Linn and Garrard I suspect the mass is about right . The chassis is non magnetic stainless and weighs a ton. That really makes a night and day difference and must help the -79 db rumble. That's where you need mass. Not in the plinth I should add.
When you say "pulled" I presume you mean that the aluminum* 'billet' is a forging. Aluminum forgings are still preferred in aircraft manufacture because the process can manipulate 'grain' direction within the metal and at the molecular level.
Interesting comment; chassis mass versus plinth mass, where chassis mass is more important. That seems logical to me.
re: phenolic resin. It is common to find phenolic resin reinforced with different types of fibers. Canvas phenolic is commonly used in many applications. It machines easily enough. Although the cutting process releases a strong odor of ammonia.
re: O-rings at periphery of platter to reduce the 'ringing' effect. Has this been verified via measurements or is it a subjective evaluation?
When it comes to more massive chassis in combination with Garrard 301-401 models, I am reminded of some work being done at Classic Turntables and this link: Solid Chassis 301
Classic turntables was reproducing Garrard 301 chassis via cnc milling and making them somewhat thicker in comparison to the original cast chassis produced by Garrard.
I always wondered if there was any cooperation between Ray Clark (director of Classic turntables) and Loricraft; owner of the Garrard name? Just curious.
And this effort tends to bring up the idea of producing a TD124 chassis similarly to what Classic Turntables has done...ie: more massive chassis and cnc machined from a forged aluminum billet versus the die-cast aluminum chassis as produced for Thorens back then.
Another thought. Last year I had contact with an individual in the U.S. who had rebuilt a TD124 in a rather elaborate fashion. One of his 'mods' was to strip the TD124 cast chassis completely of all fastened parts, chemically strip the paint and then sent it to a plate shop that coated (electroplated) the chassis in a generous layer of copper all over.
I never did hear back about how well this project turned out, but I presume that the additional layer of copper on that chassis might have had some effect on the way vibrational energy migrates across that copper clad chassis.
-Steve
* note: North American spelling results in a slightly different pronunciation of the word.
There is also working of materials to improve them although I have no specialist knowlegde in aircraft except a very healthy love of them. My maths teacher built the first examples of the UK jet engine, Chris Bartrum. We had our own Vampire Jet. Chris's example is in the science museum. I went to a RAF funded college. The first job interview I got was via college at Garrard in Newcastle Street, I now have the factory plate from the building I went into ( and the test gear from that room ).
The metal we use is cast and then has a refinement process which the supplier said to be not unlike making transistors. I would imagine the impurities are left at the end of the section. One gets told various stories from salesmen so who knows. We did also use this.
ALCA 5 Precision Aluminum Plate | AA5083 - Cast Tool and Jig Plate | Aluminium Mold & Cast Tooling Plate - PCP ALUMINIUM
In Oxford we have the original body scanner companies. I worked for Magnex for a while as the quality control engineer on gradient coils ( Using a 3000 watt Amcron amp to test X,Y,Z of the coils ). I never asked why we used non magnetic steel rather than aluminium, pretty and tough I guess. It was greatly helpful to Loricraft that I had these contacts. The unique problem Loricraft has is above 10 inches few have the lathes now. We often use an old Colchester lathe as it can do the work ( and soft jaws ). The link with the scanners helps as they also want larger pieces. We also have the Fomula One suppliers. These are surprisingly not the people we should use. They really don't seem to understand what we need or think we are bonkers. SME help with that. We only have to say make it as if for yourselves. Linn offered also.
The O-rings pass the customer test of reducing bell resonance. The bigger deal is the cork-neopreen. James Walker sent out some apprentices to see us. Mostly to please them I tested an idea they had. I was very surprised how well it works. There are many fakes now selling. Talking with my musician / scientist friend he said this. Cork is already chaotic, grid it up to be more so. This reduces the Q of the neoprene so as not to have a marked resonant frequency ( damping is not unlike the problem it solves ) . Chaos is in fact linear when talking damping. The more interesting thing is an aluminium platter sound becomes more neutral with one of these mats. An acylic platter which is more neutral remains so. What the mat of this sort seems not to spoil is the anvil effect. The stylus seems to give more dynamic range if encountering a metal platter. Some say that's resonance. I doubt it is that simple.
The old 301 chassis you show was made from recycled aircraft mostly. Above 60C the gasses still come out. The Hammerite finish is to cover the problems. The Japanesse like this Garrard best. They work at 100 V being the bigger reason, latter ones 117 V. The bearing converted to oil to do 100 V. The latter ones were more for stereo. Terry of Loricraft is still in contact with Brian Mortimer who's dad designed the 301 ( I seem to remember he interviewed me ). Brian was head of quality control at Garrard. The latter 301'd die cast from higher grade aluminium. Japan is not so happy with the 401 as 4 is a bit like 13 to us Brits ( When our Knights of old were defeated on Friday 13 th ). Many more modern Japanesse love 401. Mr Kondo was one.
As for Ray Clark. No comment.
The metal we use is cast and then has a refinement process which the supplier said to be not unlike making transistors. I would imagine the impurities are left at the end of the section. One gets told various stories from salesmen so who knows. We did also use this.
ALCA 5 Precision Aluminum Plate | AA5083 - Cast Tool and Jig Plate | Aluminium Mold & Cast Tooling Plate - PCP ALUMINIUM
In Oxford we have the original body scanner companies. I worked for Magnex for a while as the quality control engineer on gradient coils ( Using a 3000 watt Amcron amp to test X,Y,Z of the coils ). I never asked why we used non magnetic steel rather than aluminium, pretty and tough I guess. It was greatly helpful to Loricraft that I had these contacts. The unique problem Loricraft has is above 10 inches few have the lathes now. We often use an old Colchester lathe as it can do the work ( and soft jaws ). The link with the scanners helps as they also want larger pieces. We also have the Fomula One suppliers. These are surprisingly not the people we should use. They really don't seem to understand what we need or think we are bonkers. SME help with that. We only have to say make it as if for yourselves. Linn offered also.
The O-rings pass the customer test of reducing bell resonance. The bigger deal is the cork-neopreen. James Walker sent out some apprentices to see us. Mostly to please them I tested an idea they had. I was very surprised how well it works. There are many fakes now selling. Talking with my musician / scientist friend he said this. Cork is already chaotic, grid it up to be more so. This reduces the Q of the neoprene so as not to have a marked resonant frequency ( damping is not unlike the problem it solves ) . Chaos is in fact linear when talking damping. The more interesting thing is an aluminium platter sound becomes more neutral with one of these mats. An acylic platter which is more neutral remains so. What the mat of this sort seems not to spoil is the anvil effect. The stylus seems to give more dynamic range if encountering a metal platter. Some say that's resonance. I doubt it is that simple.
The old 301 chassis you show was made from recycled aircraft mostly. Above 60C the gasses still come out. The Hammerite finish is to cover the problems. The Japanesse like this Garrard best. They work at 100 V being the bigger reason, latter ones 117 V. The bearing converted to oil to do 100 V. The latter ones were more for stereo. Terry of Loricraft is still in contact with Brian Mortimer who's dad designed the 301 ( I seem to remember he interviewed me ). Brian was head of quality control at Garrard. The latter 301'd die cast from higher grade aluminium. Japan is not so happy with the 401 as 4 is a bit like 13 to us Brits ( When our Knights of old were defeated on Friday 13 th ). Many more modern Japanesse love 401. Mr Kondo was one.
As for Ray Clark. No comment.
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I wonder: are there any of you that have tried to substitute the steel ball in the main bearing with a sapphire ball, and the thrust plate with a sapphire disc? having owned a SOTA Star sapphire in the past, I realise they are very brittle but the slow rate of descent of the main axle would seem to take care of that.
I have tried one of those silicon ceramic bearing balls. But with a delrin thrust pad.
Presently I'm using very hard steel bearing ball (72 hrc) with a torlon 4301 thrust pad. Wear rate is reduced at the pad in comparison to original nylatron pad material. Otherwise, there is no perceivable difference in sound.
Not really a magic bullet.
-Steve
+
The thing about using hard rigid thrust pads is that they don't indent from the pressure above. Therefore, the bearing ball never centers. This, over time allows the shaft to work against the bushing walls more so than it would if the shaft were well centered over the indentation in the pad.
I suspect that there is more noise generation to be dealt with at the bushing walls than there is noise at the thrust....providing that the thrust isn't damaged in any way.
-Steve
We tried a graphite and glass design. It worked and didn't wear! It sounded very different and not sure I liked it, very dark. In my heart it should be ideal and doubtless was doing the right job. The graphite was motor brush grade and pyrex window from a lab oven. The graphite made to look like a Garrard 401 dome. I made it in the lathe in a few seconds by eye. The idea was the contact would become polished in use. 6 months later it hadn't changed much. The idea came from Garrard notes to the directors circa 1953 where Mr Mortimer used glass to calibrate measuring devices in his " power point " presentation of the day . This was him setting out why 201 could not continue for LP transcription. Many things Linn quoted are to be found in these notes. 1/10000th inch centering for example.
I dug up some section views of the Thorens, Linn and Garrard bearing types. I thought this might help to visualize parts of the recent discussion. I note that the Linn bearing is very similar to the bearing type used in the Thorens TD16x, TD14x and those that came later. Except Thorens, for its bottom plate, tended to use a swaged-on plate for those belt drive models. And this makes giving maintenance to the thrust pad quite a bit more difficult....but possible.
I note that the Garrard brg does not use a ball and thrust plate. Instead it appears to be two flat, or nearly flat, smooth surfaces one directly over the other. The scheme there must be that both upper and lower thrust pads must mate to have a low coefficient of friction and, presumably, a steady source of lube.
The TD124 bearing should be familiar to all in this thread.
-Steve
Somebody somewhere might as I think they were sent to the Gramophone. Word for word what Ivor Tiefenbrun of Linn stated were in this Garrard presentaion. Linn reinterpreted the 1/10000" as for Garrard it was squareness at the bearing thrust on the 301. The 401 has a soft dome that allows a less tight spec which new owners Plessey wanted one guesses ( it's their style ). In about 1960 there was a fire at Garrard. Plessey a failed 1930's radio maker who went on to do defence work lent Garrard a factory. Out of kindness it became a buy out. Alas the dead hand of Plessey took control as it had when they last failed in the consumer market. Didn't take them long to poke off the USA importer who had just got Porsche their first big USA title in the 1973 Garrard Porshce. The result B.I.C a rival product.
Garrard and Porsche
Linn aged their platters 7 months with 4 outside and 3 inside machinings. The metal was from Birmingham Master Casters part of Garrard rival BSR who I nearly got a chance to run ( too late and me too much trouble as you might guess ). What Garrard did is mature the parts outside in the rain. Ford do this with brake parts or did when I saw then lined up at W Lucy and Co where I parked my car for years. Next to nuclear waste it turns out ( medical )! Lucy about the same age as Robert Garrard and Co. Terry and I are now in the RG&Co history book.
I asked Thorens what war work they did as Garrard did plenty. The guys said if only they knew and really begged me to find out. If you haven't guess Thorens are my buddies and we would do anything to have them make the 124 again. Whilst I have a small feeling the TD124 could have been better if the belt wasn't their it is a stunning piece of engineering. Somethings you guys want to change are in engineering terms perfection. That isn't total precission. It is as near as it needs to be and the tollerences to cope. For example grinding on centres and adding a ball bearing is two tollerences whereas Line is one. Rega side stepped all of that and use the errors to cancel and they did it for less than $1, although it looks cheap and is too small it isn't junk. Roy was from Ford and it tells. BTW. No one says this. How Thorens make the TD124 work is the running clearance is exactly right to work with the engineering compromises. The oil if you like the real engineering. I could imagine if the bushing was replaced with engineering plastics the reduced vibration transmission would be a small bonus, don't whatever you do change the size to be " better ". Logic turntable went this route. They showed me how tapping the chassis with stylus on platter the two bushing types was noticably better when PTFE ( ask an expert if you do about the shaft, PTFE is not without problems and other newer choices could be better ). As the Logic bearing took a minute to go down there was time to test this. It should be said it was louder when fully down and may be questionable. Time was anything Linn did was copied.