I'll worry about cartridge once I have the motor mount sorted. My leaf spring is a xerxes. Works nicely if a little oddball.
If one is building a custom plinth from scratch all aspects can be addressed. As bearing rumble and motor artifacts are at different frequencies they should be looked at seperately.
The green motor has 12 poles so any cogging (if it exists) will be around 7Hz. Not a good place to be, but if you know its there you address it in the arm/cartridge choice and setup. Would be nice to measure it but not sure how to setup something repeatable easily.
If one is building a custom plinth from scratch all aspects can be addressed. As bearing rumble and motor artifacts are at different frequencies they should be looked at seperately.
The green motor has 12 poles so any cogging (if it exists) will be around 7Hz. Not a good place to be, but if you know its there you address it in the arm/cartridge choice and setup. Would be nice to measure it but not sure how to setup something repeatable easily.
I just picked up a SL-M3, a very nice alternative to a SL-1200. Has a linear arm and a wood plinth. Better specs than a SL-1200 also.
BillWojo
BillWojo
The thing with the Thorens leaf was rotaional components or dynamic wow. It would be so sad to add that to the problems. Sorbothane whilst not ideal is cheap.
8 X SORBOTHANE 19 MM ISOLATION HEMISPHERE FEET FOR SPEAKER HI-FI TURNTABLE | eBay
SL-M3 seems like my JVC if so. Very interesting.
8 X SORBOTHANE 19 MM ISOLATION HEMISPHERE FEET FOR SPEAKER HI-FI TURNTABLE | eBay
SL-M3 seems like my JVC if so. Very interesting.
The only P-mount that I have is a AT211EP with a worn stylus. I need to save up for something better.
BillWojo
BillWojo
I will drink to that. Coral 777EX was like that. I wish I had sent a new one to Expert Pick Ups. Decca London also. I am still convinced they chew records. I do not have the money to say if I am wrong with the now examples. SE valve amps measure bad and mostly sound good. With care they can sound better. Getting distortion down to 0.2% THD at 1 watt seems to be about right. Most PU's would struggle to better an SE valve design on that. The 0.2% mostly second harmonic and no loop feedback used. Many have designs of 3 % and think it OK.
Technics SL-M3 looks like very good turntable. I know automatic turntables are not considered good but I like them. Mine is mid-fi and fully automatic and somehow it feels good that I am not touching tonearm and vinyl. For options with P mount cartridge, wouldn't a P mount adapter be useful ? For low compliance cartridge like popular Denon DL-103 it will add mass too. I am just guessing though.
Regarding cogging in direct drive turntables. I don't understand electronics but why would not a quick response electronics and platter inertia overcome it ? Atleast reduce it. Pardon me for little aberrant thinking. If we combine two precision made slim motors on axis where one motor's pole comes in the middle of other motor's two poles; would that solve the problem ? Some more abnormal 😱 thinking would be, we gladly allow all the resonance and wow (Below 10hz/20hz ?) to the phono preamp and have a digital signal processor which would not touch the analogue signal, nullify it.
Regarding cogging in direct drive turntables. I don't understand electronics but why would not a quick response electronics and platter inertia overcome it ? Atleast reduce it. Pardon me for little aberrant thinking. If we combine two precision made slim motors on axis where one motor's pole comes in the middle of other motor's two poles; would that solve the problem ? Some more abnormal 😱 thinking would be, we gladly allow all the resonance and wow (Below 10hz/20hz ?) to the phono preamp and have a digital signal processor which would not touch the analogue signal, nullify it.
Turntable speed analysis - Page 5 - pink fish media has a picture from Dave Cawley off his analyser showing the 6.6Hz signal as FM. Hardly leaping out as a huge problem. Clearly the choice of arm/cartridge is important as is any damping, but if you look at the sub 20Hz spectrum off vinyl there is a lot of energy there.
I remain unconvinced that cogging is significant and was probably invented by the belt driven flat earth mob in the 70s. but we can do things to measure it and possibly reduce it if we are starting with a motor on a bench and turning that into a turntable.
I remain unconvinced that cogging is significant and was probably invented by the belt driven flat earth mob in the 70s. but we can do things to measure it and possibly reduce it if we are starting with a motor on a bench and turning that into a turntable.
In a belt drive it is damped by the belt. Here is the graph of a stepper motor as generator into a similar load as it would consume as a motor. It's not at all bad and is very like the current waveform of the motor as a motor. I infer all stepper and synchronous motors draw current this way and the process is not completely cured by pre distortion. All the same I feel it is not a problem that one should loose sleep over. I suspect if cured the usefulness of belt drives would be in doubt. One interesting thing is the current waveform into the motor changes very little if square, triangle or sine wave. One should always adjust findings for true rms values before concluding for example sine better than square waves. I suspect sine to be marginally better. What seems to be true is that the coils are a resonant system that tends to be it's own filter. Alas not a true sine wave filter. My eyes tell me the typical motor is a victory for simplicty. The simplicty as born out by the graphs that favours a tiangle wave.
Cogging isn't real as described by the anti direct drive brigade, and as I said, with perseverance you can recover and display the effect of any motor. Or put it another way, all motors cog in one way or another, no exceptions !
Dave
Dave
Hiten, my SL-M3 is p-mount only. As far as the automatic operation goes, I'm all for it. It's to easy to damage a stylus if one isn't paying attention to the operation at hand. I do own a Pioneer PL-41D, it's fully manual. Not the table I go to if I just want to toss a record on. After I picked up my Yamaha PX-3, a full auto DD linear tracker with a regular 1/2 cartridge headshell, I put the older Pioneer aside. I just find the auto function so much more convenient.
Dave, is the AT311EP a big upgrade over the AT211EP? I need to get a stylus for the AT211EP and sometimes the whole assembly isn't a whole lot more.
Thanks
BillWojo
Dave, is the AT311EP a big upgrade over the AT211EP? I need to get a stylus for the AT211EP and sometimes the whole assembly isn't a whole lot more.
Thanks
BillWojo
Dave, I don't want to get into the motor "cogging" debate but as a machine tool service engineer I learned a long time ago that 3 phase motors are very smooth in there power delivery. Single phase motors are never used to drive precision grinding spindles, they leave marks on the work surface from the cogging effect. Looking at the DD motors commonly used, they seem to be 3 phase also. I think that maybe some of the earliest DD turntables may have suffered from it but it didn't take long to get that sorted out. Any new technology advances very fast and early examples sometimes leave a bit to be desired. Heck, some folks want a transmission in the drive path, rim drives.
BillWojo
BillWojo
Thanks for the link billshurv. Very informative. If undesirable data is creeping in while testing speed accuracy through playing test tones, can we make a strobe disk of particular frequency and optical strobe reader so we can get speed accuracy from the strobe ? If strobe disc is smaller one can get data with or without record playing also.
I am sure after certain level all these measurements are not distinguishable but as a mechanical device which produces music its quite interesting to know.
The one motor that may not cog is the hysterisis type, feel for poles and you won't find them. It needs a pure sine wave to do this to perfection ( aim for 0.1 % in the motor core and second harmonic only if possible, wind a coil to measure this, in steppers I never saw less than 10 % typical ) The phase shift is less than ideal but still has less vibration than the stepper sometimes called AC synchonous. It's speed stablity is very good long term, less so on start up ( 20 minutes to stasis, keep it running I would say as the BBC did ). This type of motor wastes power. None the less it can give very high output when using > 15 watts whilst very low vibration. The LP12 motor using about 1/30 th the power has more obvious vibration when fingers on motor. The typical speed of 4 pole type is 1500 rpm or a tad less geared down to 33 1/3 ( the tad less is the wonderful bit ). This would require 160 poles from a direct drive if the 4 x 40 poles and revs per 1 rpm of platter. A Garrard 401 is mostly a direct drive type. There is virtually no compliance in the drive wheel. The motor if you like is a W16 when the best DD a straight 4. If two DD were coupled and mechanically phase shifted a V8 might be had. The fight between servos might be excellent if understood. Another idea is to have a belt to the platter with loose coupling ( Girodek belt ? ) . The AC synchronous being hybrid drive so to speak with the DD. It might act like a viscous damper with no energy drain. I syspect the hybrid at <1 watt.
Some guy tried to tell me the LP12 " using " 0.5 watts had a surplus of power. That is interesting. If so why do all the high power turntables sound better than the LP12 ? With some care the Garrard SP 25 does. Most of it needs to be junked to find that alas, the bearing is a joke. The Lab 80 is a better one. BSR HT 70 also.
Roy Gandy felt that if the DD system was optimised for lower flutter and gave a less than perfect wow figure ( 0.2% ) that might be best. The cogging we talk about is really the massaging of wow and flutter as a lumped term. Some of the German magazines show this better than the UK ones . They use a test not unlike for tape decks. The Garrard 501 was pointed out as the only example to look like a tape deck ( one steady peak ). - 79 dB rumble also. A world record for idler by a long way ( 401 - 57 dB ). A Thorens reference was 3 dB worse. The test by the Thorens coupler. Transrotor is - 90 dB. Not a deck I love as it sounds a bit bland. Although in hi fi terms much worse I have heard a 1210 against it and prefered the 1210. If I understand correctly the Transrotor was hurried out to win back the rumble test for Germany. The cost is two houses in Stoke on Trent. The Lenco will make all of them look poor value as it does to nearly all. With rumble one must remember - 60 dB is about the cutting limit. Surprisingly - 80 dB is noticably quieter than - 60 dB. All the same one should think CD if this matters so much. David Price has me saying CD is ideal to hum to whilst vacuum cleaning. He swears I did. I like digital, but don't like CD. No idea why. A guy I met uses a 401 to test CD players. He said the sound of the 401 is changed via CD. He went on to say it shouldn't be and he works from there. His idea being it is like a live performance that can be repeated and be mostly be identical years later. No live thing can do that. So 401 is better than live in that way. The Transrotor regardless of right or wrong would make it harder to tell.
One guy in Germany came to pick my brains about 401's. He was being a bit naughty as he said he wanted to do all the work himself. I was honest and said what he should do. I then asked what turntable he had. A Verdier his proud face said as the words came out. To be equally naughty I said " Well you won't be using that when I next see you ". I think he said " Don't be crazy ". I forgot about it and perhaps 5 years latter it was my long lost cousin coming to see me. " Nigel, you were so right. I have sold the Verdier". I felt a bit bad as the Verdier is something that does what Transrotor hints at ( my oppinion only before anyone rightly says so ). All the belt drives I like mostly look like Verdiers. My ERA mk6 was one of his I think ( SME V15 circa 1974, £77 + 29 from Lasky's, LP12 was about the same without arm ). It used blocks of acoustic foam as suspension. It was fantastic, PRAT and low colouration. Better than the now LP12 ? Perhaps. Sort of the same sound. If you want to rememeber sounds think of what is wrong and when you heard it before like that. It is like putting books in the library. Not perfect, but helpful.
Some guy tried to tell me the LP12 " using " 0.5 watts had a surplus of power. That is interesting. If so why do all the high power turntables sound better than the LP12 ? With some care the Garrard SP 25 does. Most of it needs to be junked to find that alas, the bearing is a joke. The Lab 80 is a better one. BSR HT 70 also.
Roy Gandy felt that if the DD system was optimised for lower flutter and gave a less than perfect wow figure ( 0.2% ) that might be best. The cogging we talk about is really the massaging of wow and flutter as a lumped term. Some of the German magazines show this better than the UK ones . They use a test not unlike for tape decks. The Garrard 501 was pointed out as the only example to look like a tape deck ( one steady peak ). - 79 dB rumble also. A world record for idler by a long way ( 401 - 57 dB ). A Thorens reference was 3 dB worse. The test by the Thorens coupler. Transrotor is - 90 dB. Not a deck I love as it sounds a bit bland. Although in hi fi terms much worse I have heard a 1210 against it and prefered the 1210. If I understand correctly the Transrotor was hurried out to win back the rumble test for Germany. The cost is two houses in Stoke on Trent. The Lenco will make all of them look poor value as it does to nearly all. With rumble one must remember - 60 dB is about the cutting limit. Surprisingly - 80 dB is noticably quieter than - 60 dB. All the same one should think CD if this matters so much. David Price has me saying CD is ideal to hum to whilst vacuum cleaning. He swears I did. I like digital, but don't like CD. No idea why. A guy I met uses a 401 to test CD players. He said the sound of the 401 is changed via CD. He went on to say it shouldn't be and he works from there. His idea being it is like a live performance that can be repeated and be mostly be identical years later. No live thing can do that. So 401 is better than live in that way. The Transrotor regardless of right or wrong would make it harder to tell.
One guy in Germany came to pick my brains about 401's. He was being a bit naughty as he said he wanted to do all the work himself. I was honest and said what he should do. I then asked what turntable he had. A Verdier his proud face said as the words came out. To be equally naughty I said " Well you won't be using that when I next see you ". I think he said " Don't be crazy ". I forgot about it and perhaps 5 years latter it was my long lost cousin coming to see me. " Nigel, you were so right. I have sold the Verdier". I felt a bit bad as the Verdier is something that does what Transrotor hints at ( my oppinion only before anyone rightly says so ). All the belt drives I like mostly look like Verdiers. My ERA mk6 was one of his I think ( SME V15 circa 1974, £77 + 29 from Lasky's, LP12 was about the same without arm ). It used blocks of acoustic foam as suspension. It was fantastic, PRAT and low colouration. Better than the now LP12 ? Perhaps. Sort of the same sound. If you want to rememeber sounds think of what is wrong and when you heard it before like that. It is like putting books in the library. Not perfect, but helpful.
As the test disk is not measuring speed accuracy in the traditional sense, and it gives you data you cannot get with an optical reader I don't think so. cheap PCs and new test disks is a real boon to getting under the surface of what is happening.
Yes you are right. And yet it is unhelpful to say it as the truth that was to come out is then hidden. Keep an open mind I would say and when music comes second to science one should be asking if the train has left the rails?
As someone said to me. One should look at the energy flows and not the outcomes. If the flows look suspect some adjustment might bring nice results. Pre distortion seems to be an idea. One way would be to do the current waveform into a motor and put the distortion into a subtractor ( op amp differential output ). The differential fed into a CD R machine. The motor could be fed from this wave if the motor is no worse than a 401 for stability. This might be impossible as the mark space ratios come into it as the motor resonce might be miles from 33 1/3. Even so if the motor is at stasis it should be able to accept a repetitve waveform. The conjection is 3 db lower rumble by statistical cancellation as a wild guess. If the motor is unhapppy like this it would raise questions as to what dirt is under it's door mat.
As someone said to me. One should look at the energy flows and not the outcomes. If the flows look suspect some adjustment might bring nice results. Pre distortion seems to be an idea. One way would be to do the current waveform into a motor and put the distortion into a subtractor ( op amp differential output ). The differential fed into a CD R machine. The motor could be fed from this wave if the motor is no worse than a 401 for stability. This might be impossible as the mark space ratios come into it as the motor resonce might be miles from 33 1/3. Even so if the motor is at stasis it should be able to accept a repetitve waveform. The conjection is 3 db lower rumble by statistical cancellation as a wild guess. If the motor is unhapppy like this it would raise questions as to what dirt is under it's door mat.
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