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Old 28th February 2013, 12:33 PM   #51
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This is good reading in the link at the bottom of the page , I don't agree with everything but who ever does ? What has to be considered is that the platter is not the sound of a turntable . If it is then someone did not finish the job . It must be sensibly damped . I have listened to master tape AB compared with the cutting ( Scully , test of cut levels ) . 33 1/3 and 45 RPM seems to be identical and not as good as the master tape ( less focused for want of a better description ) . If 45 sounds better I suspect it is EQ changes ? 78 sounds considerably better ( This Scully had it ) . It is virtually impossible to say if tape or lathe when 78 RPM . The SACD mastered from the same tape sounds like a tribute band on AB , nothing like as good as 33 1/3 even . The Scully if presented as a turntable probably would be dammed with feint praise by devotees of hi fi ( Verdier says aesthetics come too often into this ) . Big slab of metal with a cork mat , big motor . In the hands of an experienced cutting engineer I doubt if many who read this could say at 78 which is A and which is B . All the tripe you read about how the art of cutting makes the flat but accurate master tape into the jollied up LP is nonsense . There are a few tricks involved and these surprisingly amount to very little diversion from the intention of the recording engineer . There is folk-law that says some CD's were made from LP masters . It might be true and if so will present problems . The idea that every time someone prefers vinyl is like preferring instant to real coffee is nonsense . Why people like LP is that it sounds real . The resonances of an LP and it's accuracy is anyones guess . If CD had been a proper representation of an analogue master ( and it should be if it is accurate ) then fine tuning a turntable would be easy . It is not and is mostly taste that dictates opinion . Like history we know what we are told , to AB the neutrality of sound by conjecture is not truthful testament . I would suggest that the sound attributed to a platter is in fact the bearing . It is the most unsuspected source of the energy we hear . Doubtless an acyclic platter will absorb the 1.5 kHz energy better ? . The Garrard bearing side steps the problem by not being a ball .

Turntable Mat: Shape, Material, Damping, Sound Characteristics, Platter.

Last edited by nigel pearson; 28th February 2013 at 12:36 PM.
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Old 28th February 2013, 01:07 PM   #52
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Nigel, just take the mat off, hit the platter with ur finger - <ringgg>.

All I am saying is that what many people hear and like about the 301 and 401 (again somewhat different each model) appears to be the broad band resonance of the platter.

Although the case has been made for a circuit rotating from the stylus down the arm, through to the surface, over to the bearing, and to the platter.

In the case of the string suspended Schroeder arm, it's more difficult to make that case, but I suppose it may apply in many TT/arm combinations.

It makes good sense to damp the platter - i'd have considered applying damping to the bottom of the stock platter if maximum resonance control is what is desired.

I am interested in the bearing design details you mentioned.
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Old 28th February 2013, 04:43 PM   #53
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The 301 and Schroeder is complex because the vibration modes of a 301 are not subtle ( - 35 dB ) . These interfere with the arm bearing . I have used a Schroeder ( Lyra Helikon ) on a 301 and own one ( below , you might never see one like this again ) . I have a slight preference for the Hadcock 228 or Naim Aro on a 301 ( Denon 103R ? ) . 401 is a better match to the Schroeder .

The platter test is no contest , it is real and as you yourself it did not please me at first . I see only positive outcomes if it is improved . The forces that energies a platter are complex . Damping them via platter design or use of a mat will be useful . One of my better platters I used was phenolic with no mat .

Going further . A good turntable will not be significantly corrupted by the platter type common to 301 and similar types ( many other makes are similar ) . Equally the best platter in the world will do little to help a bad turntable . My assumption being that the turntable reaches correct speed when saying this . Some platters will be too heavy for some turntables . It might be enough to go from silver to gold medal in a turntable Olympics to have a good one .

TD124 seems to have a much better platter than Garrard . In a blind test one might assume TD124 to be the one with the finger tap resonance problem . The real cause is the motor and drive system . Make no mistake , I love the TD124 . LP12 has no significant resonance , yet it has quite nasty traits which again seem to be platter . It was assumed for years that a Pink Triangle turntable sounded as it did because of it's acrylic platter . Probably not .

The 401 and 301 have very different sounds . Early 301's sound very dark ( not always my cup of tea ) . 95% of the parts are interchangeable ( 501 also ) . The sound seems to be mostly the motor differences . Motors were tweaked as stereo came in . The 301 was a mono turntable . 401 is a 301 for stereo . The same energy upsets the Schroeder as upsets stereo ( vertical vibration ) . A Schroeder can go into a gyrating oscillation with a 301 that is slightly unhappy . I must add that many use Schroeder and 301 so not condemning the choice of the two used together .

One of the people I worked with fitted a 401 platter to a modified Technics 1210 ( carefully machined to fit ) . To my astonishment it was a great improvement . I thought it would be worse ! My suspicion is it suited the servos better ? Perahps more wow and less flutter ( Roy Gandy insists that is how to make direct drives work ) ? We had many 401 platters spare as these were decks which had upgraded platters .

I will describe the Rega bearing soon . It sort of says all you need to know . I would say there is almost infinite scope with bearings to innovate . The ring magnets out of cheap speakers will not be as good as the Verdier . However to reduce bearing loads they must be a good thing . Less energy to the platter .

I was told that a big air compressor turntable was used up the Eiffel tower in perhaps the 1920's . Apparently bearing and motor rumble were very loud ( Douglas Self ) . Donald Aldous said air compressor turntables were very real sounding even allowing for the acoustic recordings ( 80 to 5000 Hz perhaps by 1926 , modern research says so ) .

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Old 1st March 2013, 04:50 AM   #54
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nigel, interesting stuff you've got!

I was only mentioning the Shroeder string/magnet bearing arm WRT the difference between it and an old school high mass arm with very solid bearings. The latter making a strong coupling, thus completing a mechanical/acoustical loop and the former, essentially being an open circuit.

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Old 1st March 2013, 07:37 AM   #55
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Well it was nice to say Schroeder is one of the many contradictions in the story . The closed loop principle was destroyed by Dave Griffiths of Logic turntables . He introduced me to the phenolic platter . He also showed me that the closed loop was a questionable principle . Dave used a massive lump of MDF on his turntable C1 . The C1 was a much better design than the closed loop DM101 ( which is better remembered ) . Dave said as long as energy is absorbed in a uniform way it will be linear . His big concern was the MDF " They won't like that , it isn't high tech enough " .

All I will say is some materials will play pin pong with energy .

I said I would describe the Rega bearing . Start with a piece of plain bronze . On a good quality lathe carefully drill the pilot hole . Use the usual tests to ensure the lathe is drilling straight . Use a carefully adjusted reamer to clean and size the hole . Use a high grade ball . Rega made to a 6 micron finish originally and 1 micron later . When I asked why he said " people for reasons best known to themselves look at the bearing " . Roy went on to say it was mostly unimportant . He also said it cost him nothing to do . How round the bearing is and the hole is a very big deal . Also the squareness of the shaft . An aircraft bearing shaft will be virtually perfect to avoid failure . It will be very cheap compared with a small quantity price of about $100 to make something better . The aircraft part is about $1 . Remember also the bearing will stop or promote platter resonance . Rega will rent a very high grade lathe ( or whatever ) to do the work . It will spit the parts out quickly . The machine can cost $1 000 000 .

This seemingly simple bearing has very little wrong with it . The Thorens TD124 is not as good in concept . The drill although crude will by averaging make the V shape very accurately on centre . The ball then is the tolerance factor . The Thorens shaft is ground on centres . A ball is then used to hide the place where it sat in the machine . The likely error is double ( >0.0001" x 2 typical ) .

Rega hinted that the shaft is an element from an SKF aircraft bearing . Cheap and very high grade . The adjustable reamer is set to get the right drag properties ( I am told it takes Reag a week to get it right , when one is right so are the next 1000 + until the tool wears out ) . This is the back art of design . Drag = excellent . Rega used EP90 . My advice is use mono-grade oils not intended for motor cars .

Verdier also thought drag a very good thing . If the motor is loaded 10 times more by drag than by the groove then the dynamic wow is reduced . Bearing clearances are very large which will surprise many . This allows the oil to do it's job . The bearing will seem very stiff . Liquids are incompressible so that would be true .

Myself I would look for a reamer in imperial stock that is about 0.001" larger than the shaft . I have a hunch if one exists then the Rega adjustment is not required . Doubtless Rega will still win because theirs is an optimum . The oil pump bearing seems a winner if asking .

Again in a rush so forgive any errors . Remember this is DIY Audio . This bearing might be possible using pillar drill . I had problems when I tried to make one , I got 90% the way there in 10 minutes .

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Old 1st March 2013, 01:49 PM   #56
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Nigel, if you haven't seen it you should check out the Turntable speed thread on Pinkfish.
Turntable speed analysis part II - pink fish media
Turntable speed analysis - pink fish media

There are a number of members there equipped to take a recording of your deck playing a test tone and hand you back accurate FR graphs but more importantly an FM speed demodulation where variance is plotted axially from the centre of the graph with time being plotted rotationally. It's a remarkable tool that allows you to see the frequency and level of every speed anomaly in your deck, of course speed stability and frequency are ying/yang.

Here's a well set-up LP12
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Here's my modded Kuzma with Lp12 bearing and silicon oil for added drag.
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The difference between the red and green on my graph was swaping the nominal 0.22uf phasing cap in the PSU for a selected 0.2uf. I've since added a DC blocker which improved things further.
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Old 2nd March 2013, 09:39 AM   #57
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That's great , yes I have seen them and like the idea . Roy Gandy and I had this conversation when I was 22 ( now 56 ) . Roy said a glass disc laser cut or photographically etched so as for once only have the measurements " truly " of the turntable would be nice ( forgive sentence length ) . The German test of 501 sort of says much the same . A single peak . Roy said he could get various wow and flutter measurements depending on how a standard test disc was positioned .

Fine tuning the phase shift of a motor is fun and very easy . I would imagine just holding the rotating motor will say plenty . DC blocking is a great idea if AC synchronous ( very cheap ) . I found a nice cheap stepper motor at Rapid Electronics UK . Did anyone convert one to synchronous ? It might be a source of cheap and excellent ? Given sine , square or triangle waves I feel all steppers work best on sine ? All the motor needs is timed pulses . That the vibration modes are related to a single frequency can not be a bad thing ? The risk is saturating the circuit and getting square waves regardless ?

The LP12 is a strange animal . A friend insisted I built a very low distortion PSU for it . What was built was a laboratory standard PSU with exact phase shift . I was very disappointed to find that it was nothing special . For fun I deliberately screwed up the phase ( 20 degrees perhaps ? ) . The turntable sound was fine . Resting my finger on the LP12 the vibration was so bad as to be throbbing . Reversing the platter I could see that the belt was thrashing about like some piece on farm machinery . One has to conclude that the Linn belt and springs do rather a good job . Too good . This is the technology for a cheap design as was the AR it is cloned off of . I found in the end voltage was the key . Linn did use 90 V , then 66 V ( Lingo ) . The motor once started will run from 20 to 130 V . Probably at high voltage low distortion has some merit ( 110 V was the best ) . In the end there was some merit in it . It sounded softer yet more forceful , a bit like getting VTA correct .

When we talked about closed loop I should point out that Linn and Pink always insisted that only the platter should be heavy . The loop should be ridged and light so as to prevent phase shift ( a bit like negative/positive feedback arguments ) . Martin Collloms proved that pin pong reflections in pick up arms also matter , the loop either helps or hinders that . Many hideously bad sounding turntables probably have this wrong . Ivor Tiefenbrun said this set up non linearity and/or phase shift ( I paraphrase ) . The LP12 is not so stupid in it's loop . Recently a high grade aluminum chassis has been fitted . I feel I should make one for my LP12 as it sounds much better . One close loop test you can try is the old garage mechanics test . Use a screwdriver to hear the music at the arm base ( bone conduction into the ear ) . On an LP12 it is difficult but not impossible . Compare lets say a Dual 505 . The Linn will sound almost the same as you would usually hear through the speakers . Somehow RIAA and mono is not an issue . The Dual = a number of clicks with music in it , like an off tune radio . It is surprising how good the Dual sounds considering .

The German reviewer who liked the 501 and I still use our LP12's . He has a 301 now to use at work . Bernhard said " compared with the 501 the Linn sounded like an old and highly accomplish cabaret performer . Far too professional to get it wrong , however old and a little bit drunk " . I paraphrase a bit . I am not in the least interested in promoting the 301/40/501/TD124 over Linn . All I would say is slightly drunk is how dynamic wow sounds . It is in my opinion related to a drive train designed for excellent low cost results using a cheap clock motor ( AR ) . The simplest cure is the best belt one can find ( I have no idea what that is ) . The thickest oil in the bearing , the motor beefed up to suit and hopefully no rumble as a penalty . The old Papst motor in the old Giro deck stands out as something excellent that should have been the minimum standard for a serious turntable . I think the multi-motor idea should have one motor contra-rotating and acting as a tentioner ( motors touching ). I will leave it to you to work out why and how ( both motors providing drive ) .

I have even considered a turbine in the bearing if a cheap source could be found ( undersized reamer ? a 401 bearing has a dead section ideal for that ) .

I said 1 micron finishes are a jewelery aspect of turntables . Not so with motor spindles .

Last edited by nigel pearson; 2nd March 2013 at 10:04 AM.
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Old 2nd March 2013, 07:48 PM   #58
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Interesting thoughts Nigel. I'd agree that the motor runs best on higher voltage, certainly you need it if running into a draggy bearing. The improvement with added viscous drag isn't trivial. I think the LP12's greatest flaw is that the motor can wag the suspension somewhat, certainly defeating the suspension improves speed stability, at the cost of some increase in coupled noise.

I have a friend who designs and sells an alloy LP12 sub--chassis, the Rubikon so I've heard all variants out there over time. He runs a magnetic bearing with no point contact, this breaks the 'closed loop', the only difference to my ears is a reduction in the noise floor, I think the closed loop theory is just marketing rhetoric, sure you need a sink, but anywhere will do.

Slightly drunk, yeh that's accurate, and why i use an LP12 bearing and platter on a Kuzma Stabi chassis. At some point I will get round to adding my second motor, but there's a host of other projects to got at first
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Old 2nd March 2013, 09:03 PM   #59
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Nigel, I've been looking at the Rega bearing myself recently and yes it does everything required and yet it really can't get much simpler can it? A decent mounting collar would be nice but I think RG would disagree with the amount of extra work required and the cost of course. My own thought was to start with a large diameter piece for the housing and leave it like that so that the mounting holes can be drilled and tapped into the top face. The extra mass would help damp the bearing?

Thanks for sharing so much of your knowledge, it's inspirational to say the least!
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Old 3rd March 2013, 10:38 AM   #60
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The magnetic bearing is interesting . I have had difficulties with it . The magnetic levitation bearing " seems " very easy . Even the cheapest speakers have decent magnets in the useful doughnut shape .

I am sure the closed loop is correct . Some cheap contact mics on the LP12 chassis will tell all . Dave Griffiths linear dissipation also .

The higher voltage to motors is a compromise between power to the platter and vibration in the system . Although I have only tried it with a hysteresis motors I found that vibration between motors can be made to cancel as in petrol engines . The sharp kick of a stepper be might be less helpful ? Phases like 45 degrees need electronic solutions . The DC stepper converted to AC seems ideal as a TDA 2040 ( L165 ) will drive it .

My total interest started in 1974 in a house 200 metres from where I live now on the same little path ( almost by accident ) . My friend Stewart said I could take a copy of Hi Fi news home belonging to his brother ( Feb 1972 I think ? ) . Inside it talked of JFET's and the Thorens TD125 . The reviewer falsely described the TD125 . He should have said a special low voltage motor driven by a Wein Bridge oscillator . It is outrageous that no one ever said that both Thorens and Linn were AR clones . The LP12 a TD150 clone . The Lingo a TD125 PSU clone . All they could say was that Linn was an Ariston . It was and it wasn't and 95% unimportant , however to airbrush out the others is unforgivable . The airbrushing completely excluded France ! Airbrushing the technical into the bargain .

The 10% I found difficult was the reaming of my Rega clone bearing . I was calculating between imperial and metric sizes today looking for an imperial size slightly larger than a metric size . If I use a 11 mm drill shank and 7/16 I have something that might work . The drill bit can be snapped easily enough to make it shorter . The end could be capped by a standard 10 mm Pyrex window ( pyrometer ) . With a little care it could be placed with a suitable adhesive square on the end . When I tried such a bearing my thrust plate was of electrical grade graphite shaped to a dome by eye on the lathe . Under the Garrard platter it lasted well , no signs of wear after months of 24 hour use . A little soft sounding . I must stress , do not use motorcar oils that are intended for pressurized bearings especially if using sintered phosphor bronze . If you use sintered shells they are cheap and of superb tolerance .
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