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Old 28th December 2016, 09:29 AM   #211
sq225917 is offline sq225917  United Kingdom
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Nigel what do you mean in your "belt does the same with stylus and motor vibration comment?"
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Old 28th December 2016, 10:41 AM   #212
nigel pearson is offline nigel pearson  United Kingdom
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That's easy. When building a Linn LP12 power supply for a friend I was interested as to the phase angle on the blue phase ( 220 nF ). I was very surprised to find it wasn't a big deal so tried all options including 130VAC and 66VAC as per Lingo ( 66V not my taste, too thin ). The really big deal was the voltage ( 80 to 90 ). I had the phase capacitor so bad at one point that the plinth of the LP12 was vibrating, yet the sound was very OK.

The step that changed my thinking was inverting the LP12 outer platter to see the belt working. It was flapping in a very controlled way on the dreadful phase cap. This means the LP12 has a remarkable spring and belt set up for this problem. The next part of the understanding came from owning a Garrard 401. It is very much like the LP12 in the good and the bad of it. The bad is very small in my view. Better than LP12 is the solidity of images and a sound usually only heard on first class analogue tape decks. As someone said the LP12 sounds like a slightly drunk yet polished performer who never makes it obvious as he is a pro. The Garrard motor is about 20 times larger in power output if taking the Lingo solution and 16 watt ( 28 in reality ) Garrard motor. The Garrard is almost DD in how it works except to have the advantage of gearing. LP12 250 RPM , Garrard Circa 1350 ( 1/4 inch to 10 1/2 inch ), DD real speed.

It isn't a big leap to say the belt removing the flap vibation must also do the same to the LP vibrations. It isn't hard to come up with cures for this. Stiffer belt, better motor ( Old Papst ? ). More bearing drag. And the 1954 Philips idea of a belt tensioner. The idea that the flywheel is a cure seems not to be the whole story. My thinking is belt drive is for very cheap high quality turntables ( AR ). However to take it to the highest grade is very hard. Whilst DD's are not perfect they answer the question of Verve. The Lenco is near perfect. I suspect it could be made much better for very little money.

I have been using an LP12 for about a year now ( Ekos, DL110, own preamp ). It's great, still hear the drunkeness. Have a 401 I must build.

If the cut of an LP is played on it's cutting lathe the sound is more like a 401. The little JVC has a similar sound. My girlfriend has one I found. At times I am jealous. Unlike most DD's it has no obvious high frequency problems and an excellent midband. Even the arm is ultra solid. It looks awful and cheaply made, which it isn't.

Back to the vibrations on LP. These are not constant. Sometimes called dynamic wow when slowing slightly under load. If the speed when LP12 is checked at 66V or 130V there is no change in speed as it has a synchronous motor, yet the sound is very different. Thus the flywheel is not the store of energy for this problem. LP12 has a supurb flywheel and bearing if asking.
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Old 29th December 2016, 06:34 AM   #213
andyr is offline andyr  Australia
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Very interesting post, Nigel - my comments are interposed:

Quote:
Originally Posted by nigel pearson View Post
That's easy. When building a Linn LP12 power supply for a friend I was interested as to the phase angle on the blue phase ( 220 nF ).
AIUI, it is not so much the value of this phasing cap which sets the phase difference between the red & blue wires on a Premotec but the fact that it is a cap ... hence delivers 90 deg phase difference.

Unfortunately, the optimum phase difference for Premotec motors - which produces the minimum motor vibration - is not 90 deg!

How do I know this? Bcoz for the last 12 months I've been running a prototype of the 'Number9' motor speed controller - which is about to have its Production release. This allows you to adjust the phase angle in 0.01 deg increments ... you simply hold the motor in your hand and adjust the phase angle - so you can feel when you have selected the right value.

Quote:
Originally Posted by nigel pearson View Post
That's easy. When building a Linn LP12 power supply for a friend I was interested as to the phase angle on the blue phase ( 220 nF ). I was very surprised to find it wasn't a big deal so tried all options including 130VAC and 66VAC as per Lingo ( 66V not my taste, too thin ). The really big deal was the voltage ( 80 to 90 ). I had the phase capacitor so bad at one point that the plinth of the LP12 was vibrating, yet the sound was very OK.
The 'Number9' also allows you to increase the voltage being fed to the motor. My understanding is that Linn chose 80v for the Lingo in order to minimise motor vibration. The higher the voltage fed to the motor, the more it vibrates ... and because they were not using the optimum phase difference for the motor windings (as I said, not 90 deg), they had to reduce the voltage from the nominal 110v.

I agree the Lingo delivers thin sound - that's the penalty for low motor voltage! What Steve (the designer of the ' Number9') and I found is that increasing the voltage increases the motor's "drive" ... torque ... whatever - and this produces a definite increase in SQ. I'm feeding 30v to a 24v (Rega) Premotec atm - so equivalent to feeding 140v to a 110v (Linn) Premotec.

Quote:
Originally Posted by nigel pearson View Post
The step that changed my thinking was inverting the LP12 outer platter to see the belt working. It was flapping in a very controlled way on the dreadful phase cap. This means the LP12 has a remarkable spring and belt set up for this problem. The next part of the understanding came from owning a Garrard 401. It is very much like the LP12 in the good and the bad of it. The bad is very small in my view. Better than LP12 is the solidity of images and a sound usually only heard on first class analogue tape decks. As someone said the LP12 sounds like a slightly drunk yet polished performer who never makes it obvious as he is a pro. The Garrard motor is about 20 times larger in power output if taking the Lingo solution and 16 watt ( 28 in reality ) Garrard motor. The Garrard is almost DD in how it works except to have the advantage of gearing. LP12 250 RPM , Garrard Circa 1350 ( 1/4 inch to 10 1/2 inch ), DD real speed.
Absolutely agree - but you need to try an LP12 running a standard 110v Premotec at 140v ... when using a 'Number9' to get the phase angle optimised.

In my own " SkeletaLinn" I run 2 motors (the 'Number9' controls 2 motors independently, with a selectable phase angle between them) - and Steve and I reckon the result is almost DD in delivery!

Quote:
Originally Posted by nigel pearson View Post
Stiffer belt, better motor
With the 'Number9' I've always used silicone O-ring belts (D70) about the same circular diameter as a Linn flat belt. Have no idea whether they are in fact stiffer than a Linn flat belt ... or not. However, next experiment is to use a pair of 300rpm / 60Hz Hurst motors that Steve has located (not the ones that VPI use). These are double the horsepower of the Premotecs I've been using so, if the voltage experiments are anything to go by, they should deliver even better SQ than I'm getting at present.

Andy
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Old 29th December 2016, 09:05 AM   #214
nigel pearson is offline nigel pearson  United Kingdom
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I'm happy with my looks like new 1989 LP12. I never updated it above the glued chassis point as the drive system is not good enough. I heard the later LP12 a year or two ago and realised it has moved nearer to lets say the Lenco sound. Cost says Lenco is the better option, even the Lenco arm is OK for entry level PU's.

I measured the LP12 motor as a current waveform. From memory about 10% THD. This is what needs to be better if vibration is to be far lower. I did consider recording the waveform and then constructing a mirror image version as if the output of negative feedback. As the wave is repetetive any full wave sample would be enough. This is called predistortion. If a square wave is fed to the LP12 motor the current waveform looks very similar. Both look like triangle waves. Even Valhalla is only 0.05%THD at the drive end so not the reason for doubt ( voltage waveform ). This sort of suggests the predistortion won't do much, without trying it is hard to say. This motor is a resonant device which for normal mains helps, for improved power it holds it back. Valhalla's 47 uF 250V are too small and 220 uF works better ( Hetrodynes of mains and 50Hz at circa - 40 dB, - 57 dB at 220 uF ). A floating 230 or 115 V gets 6 dB when worst case. In the UK 110V is cheaper to buy as a rule and Valhalla has the option. Centre grounding ( 55-0-55 ) makes it worse!

The Lenco motor at my best guess is 0.5% THD current wave distortion. The Garrard 501 is < 0.1% at the third harmonic which includes all distortions of the power unit. The 2nd is less than 1%, this is a good trade off as this type of vibration is almost unimportant and does not show in the -79dB weighted rumble ( LP12 about -72 dB ). A very good Garrrard 401 is about -60 dB, the 501 has the same drive system. This shows attention to detail pays off. I doubt the LP12 would show +/-3 dB regardless of trying very hard. The 501 idler is nearly solid as are it's motor mountings ( pure madness to do that, worth it ). If the mounting of a 401 were made solid I suspect the -60 dB would not be possible. The 501 motor is built in house. The 501 prototype had a 301 motor. It was good for two weeks before noise showed up even after a careful rebuild. The 501 looked at that problem and cured it. To my astonishment the Lenco is good in this regard. However the Lenco makes new problems with it's solution. I could live with that.
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Old 29th December 2016, 09:43 AM   #215
nigel pearson is offline nigel pearson  United Kingdom
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Click the image to open in full size.

This is a high grade motor as used by Avid. I have always speculated that the triangle current wave is a result of the triangular magnetic window seen in this and the LP12 motor. How one would change this is hard to say.
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Old 30th December 2016, 10:35 AM   #216
Hiten is offline Hiten  India
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Belt flapping : If we use precision round belt and turn the motor 90 degrees with respective to platter the flapping will reduce. Isn't it ?
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Old 30th December 2016, 01:08 PM   #217
volken is offline volken  Netherlands
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Quote:
Originally Posted by andyr View Post
Very interesting post, Nigel - my comments are interposed:



AIUI, it is not so much the value of this phasing cap which sets the phase difference between the red & blue wires on a Premotec but the fact that it is a cap ... hence delivers 90 deg phase difference.

Unfortunately, the optimum phase difference for Premotec motors - which produces the minimum motor vibration - is not 90 deg!

How do I know this? Bcoz for the last 12 months I've been running a prototype of the 'Number9' motor speed controller - which is about to have its Production release. This allows you to adjust the phase angle in 0.01 deg increments ... you simply hold the motor in your hand and adjust the phase angle - so you can feel when you have selected the right value.



The 'Number9' also allows you to increase the voltage being fed to the motor. My understanding is that Linn chose 80v for the Lingo in order to minimise motor vibration. The higher the voltage fed to the motor, the more it vibrates ... and because they were not using the optimum phase difference for the motor windings (as I said, not 90 deg), they had to reduce the voltage from the nominal 110v.

I agree the Lingo delivers thin sound - that's the penalty for low motor voltage! What Steve (the designer of the ' Number9') and I found is that increasing the voltage increases the motor's "drive" ... torque ... whatever - and this produces a definite increase in SQ. I'm feeding 30v to a 24v (Rega) Premotec atm - so equivalent to feeding 140v to a 110v (Linn) Premotec.



Absolutely agree - but you need to try an LP12 running a standard 110v Premotec at 140v ... when using a 'Number9' to get the phase angle optimised.

In my own " SkeletaLinn" I run 2 motors (the 'Number9' controls 2 motors independently, with a selectable phase angle between them) - and Steve and I reckon the result is almost DD in delivery!



With the 'Number9' I've always used silicone O-ring belts (D70) about the same circular diameter as a Linn flat belt. Have no idea whether they are in fact stiffer than a Linn flat belt ... or not. However, next experiment is to use a pair of 300rpm / 60Hz Hurst motors that Steve has located (not the ones that VPI use). These are double the horsepower of the Premotecs I've been using so, if the voltage experiments are anything to go by, they should deliver even better SQ than I'm getting at present.

Andy

Yes all these motors are different I have done more then 250 Thorens TD160 motors for tuning on min.vibration some are the same but most times the phase cap need individual tuning. A two phase supply is the best solution.

IMG_6108.jpg
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Old 31st December 2016, 01:22 PM   #218
nigel pearson is offline nigel pearson  United Kingdom
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I think belts are a very worthy subject for debate. The old Grundig fabric backed ones seem a good idea.

The quality DD and 301/401/Lenco have is a more solid stereo image as most obvious trait.
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