Alternative platters ?

[Wakefield Turntables]

Mike I have your bonded copper platter and I dont have the DC mod.

[MartinT]

Martin, when you talk of warble with a heavy platter, was this before or after you removed the "motor-dynamics-mod".

The motor dynamics mod made 45rpm virtually unlistenable with your platter Mike. I removed it a long time ago after DC told me that it was designed to reduce the torque of the motor. If anyone still has the mod installed, I suggest you remove it as you're not getting the full benefit of that glorious direct drive motor.

The warble after removing the mod was very much reduced.

[Oldpinkman]

Hi Michael,
Your post beat me to it on the subject of feedback-loop mods.
Martin, when you talk of warble with a heavy platter, was this before or after you removed the "motor-dynamics-mod".
As I understand it from DC he "invented" this mod to make the SL1200 sound more like a SP12
If there are any of you who have this mod on you PCB then get rid of it.
Further when we talk about heavy platters, what weight are we talking about??
My Copper Bonded Platter weighs in at about 10Kg and as Mike says he has nothing but praise for it, and comimg from Vienna he must know!
Are there heavier platters in use?

I don't believe so. I am told funk1 is 1.4kg, standard technics 1.8, funk 2 about 2.2kg. What does etp weigh? There seem to be some very conflicting subjective assessments here. Time for someone to stick a scope on it. This can be measured surely?

[WOStantonCS100]

I don't believe so. I am told funk1 is 1.4kg, standard technics 1.8, funk 2 about 2.2kg. What does etp weigh? There seem to be some very conflicting subjective assessments here. Time for someone to stick a scope on it. This can be measured surely?

Agreed. I think it's time for some objective testing.

Let's also keep in mind that like motors were used in Technics changers/stackers where by quite possibly 6 12" vinyl records would be stacked on top of one another with the expectation that the motor would still spin all at the rated speed. My father still owns one and I can assure you, it does just that. At an average of 120g per LP, that's another 720 grams of weight spread out (not concentrated in the center) on top of the platter. So, in reference to record weights, a Techy should basically not even flinch with the use of a Stillpoints or any other similarly heavy weight, heavy record mat or outer ring stabilizer.

Here are some quotes straight from Technics for two models which essentially share the same quartz-phase-locked motor platform with heavier platters than the 1200.

SL-M3

"2.5 kg platter reaches rated speed (33-1/3 rpm) in just 0.9 sec. thanks to use of high torque direct-drive motor. The platter is driven by a powerful heteropole direct-drive motor having a very high start-up torque of 1.6 kg.cm That means the massive 2.5 kg platter reaches the 33-1/3 rpm rated speed in only 0.9 seconds. Another advantage of using the powerful motor is that variations in platter speed are zero for changes in the fixed load of up to 1 kg.cm (In other words, the correct platter speed would be maintained even if a tracking force of 200 grams were used.)

W&F .022% WRMS (JIS C5521)

SL-1500MK2

"The integral rotor platter motor delivers 1.3 lb - in (1.5 kg-cm) torque to virtually eliminate the speed fluctuations caused by tonearm or record cleaner drag. In fact, if you could fit 150 tonearms tracking at 2 grams each onto this turntable, it would still rotate at precisely the chosen speed."

W&F .025% WRMS (JIS C5521)

[MartinT]

A lot of objective testing has already been carried out in the excellent thread over at PFM. I submitted my Technics with MN Bearing / Funk Platter / Achromat test recording for analysis and the results are shown here. If others with heavy platters could do the same thing, we'll be able to make comparisons. Simon (SQ) has a test record with the correct waveform.

I hope PFM don't mind my reproducing the result here (all rights duly noted). It's a very good result when compared with several other excellent turntables.

[WOStantonCS100]

A lot of objective testing has already been carried out in the excellent thread over at PFM. I submitted my Technics with MN Bearing / Funk Platter / Achromat test recording for analysis and the results are shown here. If others with heavy platters could do the same thing, we'll be able to make comparisons. Simon (SQ) has a test record with the correct waveform.

I hope PFM don't mind my reproducing the result here (all rights duly noted). It's a very good result when compared with several other excellent turntables.

Martin,

Thanks for directing attention to that. I've read back into the PFM thread. The performance of your modded 1200 is scarily close to an SP-10MK2. I have to say that this does not surprise me from listening to and/or owning almost all the "MK2" variants for just about as long as I've been alive. And, of course, the specs between the plain jane MK2's and the SP-10 are not at all far apart (in terms of measurements and design philosophy).

Now, I'm even more curious to see the plot for a heavier platter (with the same or nearly the same other mods).

[Mike_New]

Martin,
What are the units on you polar graph plot? and what is the centre point?, or has the polar plot been mathematically corrected for any out-of-centre rotation of the test record?
The variations are probably due to the efects of the interaction between the 12 driver coils and the 16 poles of the isotropic radially magnetised ferite rotor.

Here is another test that I have devised, perhaps Paul Stewart might be interested in this one as well.

There is or was available a center weight fitted with a crystal controlled laser this is mounted onto your record/platter and swithed on for 33/45
The idea being that the laser projects a spot on a wall or white board which can be marked and observed for deviation longitudinally/radially.
Now if a setup is devised to record these pulses onto a digital camera focused onto a screen in total darkness then we should be able to see either a single spot or a line which will be proportional the total speed deviation over a given period of time say 10 minutes or more.
This should settle the issues once and for all time.
I did not buy one at the time the device was announced as it was a bit expensive about $600 if I recall.

[MartinT]

What are the units on you polar graph plot? and what is the centre point?, or has the polar plot been mathematically corrected for any out-of-centre rotation of the test record?
The variations are probably due to the efects of the interaction between the 12 driver coils and the 16 poles of the isotropic radially magnetised ferite rotor.

Hi Mike

You need to fully read the PFM thread. Essentially, a 3.15kHz test tone from a test record is played back and recorded digitally. This is then analysed and the data plotted polar-wise as shown, with the amplification greatly magnified to show any bearing or drive inconsistencies. A spectrum graph is also plotted to get an idea of motor cogging or other frequency modes affecting rotation.

Paul R is the chap who has the software to do the plots. It would be worth your joining PFM and having a chat with him directly.

[NRG]

The scaling doesn't mean anything in reality. Its an exaggerated scale for 5 revolutions of a 3150hz test tone recorded from a test record. Each revolution is overlaid onto of each other, the smaller the circular plots the slow the deck is running, it can highlight some very interesting things about your deck. In the PFM thread somewhere there is a standard 1210 plot and it was not good, the deck or test record could have been at fault. Simons plot for his modified Kuzma was excellent.

This is one of my SP-10s before and after I matched the drive transistors after I took out one drive phase Hint: The green plot is the good one! Its also scaled to show the difference.

[Oldpinkman]

Am I missing something? I confess to scanning through the earlier thread http://theartofsound.net/forum/showt...o-Towers/page2 but it appears Marco and others are trying a MUCH heavier and higher inertia platter, weight and a new bearing, and greatly prefering the sound to the standard technics, with no mention of the adverse affect on the motor causing "wibble". Marco talks of the strain on his Amex this vast improvement necessitates. Nobody has posted "even with the noticeable wibble caused by the heavier platters, we prefer the Oyaide / Mike New to the stock Techie". And these are platters approaching 10Kg

Now the Funk2 platter comes along, and the Mike New ETP sits in the wings, weighing 2.2Kg and it has a motor trashing effect that nobody troubled to mention before. Doesn't ring true. Of course - brilliant news for Funk if it is, since Funk 2 and ETP are too heavy to work, and everyone can buy Funk 1 instead. But doesn't ring true. I heard the "strata" platter against the standard technics, and, unprimed for a motor problem, heard none. I am down to Newhaven on Tuesday and will get a chance to hear strata against acrylic and will do so. Now - my only interest is whether to make Arthur do me a prototype strata for my PT - which is a considerable faff, since although there are no motor servo issues, the springs, sliders, and centre of mass are all affected. If Techie acrylic (which I haven't heard) is clearly better than Techie strata (which I have) I can save him the bother of the PT prototype. Unless the "problem" with the strata is motor wibble which wouldn't repeat on the Pink Triangle.

I hae me doots.

And Martin - what do your plots tell us about this platter mass/inertia issue? They don't measure any of the heavy platters. So we still need some measurements of the alleged phenomena. I am hoping Arthur will get his silly scope out, but anyway I will take my Nimbus records 45rpm Dvorak 9th down with me, and Little Jimmie Osmond "Tweedle de dee" which Sue has kindly agreed to lend me