Hi Chaps
Thanks for the info. The increase in speed is visible on the strobe from outer to inner part of the groove. This is matched by an increase of voltage at the motor terminals of 1-2%.
I will try to get a smaller pulley as I can see how this will improve matters. I am busy with other stuff at the moment so will probably not be able to report back anything new for a while.
Cheers for now
Matt
Thanks for the info. The increase in speed is visible on the strobe from outer to inner part of the groove. This is matched by an increase of voltage at the motor terminals of 1-2%.
I will try to get a smaller pulley as I can see how this will improve matters. I am busy with other stuff at the moment so will probably not be able to report back anything new for a while.
Cheers for now
Matt
Hi all
I’m experimenting with a Maxon RE-max29 (22W/48V) for about two years now and I was not able to find a satisfying setup so far! I have a very good quality 10mm pulley. I tried all possible combinations of belt/strings/tapes and voltage regulators (LM317, LT1083 and L200 (L200 circuit involving motor current)).
Next I will try a much weaker motor (A-max with 4W). This is an advice of the guy who gave the pulley to me and he is very pleased with his TT-drive…
I’m really tiered of experimenting with motors and if the 4w-Type won’t work as I want it, I will disassemble my old rega P3 and use the premotec motor (driven by a frequency generator)
Regards, Boris
I’m experimenting with a Maxon RE-max29 (22W/48V) for about two years now and I was not able to find a satisfying setup so far! I have a very good quality 10mm pulley. I tried all possible combinations of belt/strings/tapes and voltage regulators (LM317, LT1083 and L200 (L200 circuit involving motor current)).
Next I will try a much weaker motor (A-max with 4W). This is an advice of the guy who gave the pulley to me and he is very pleased with his TT-drive…
I’m really tiered of experimenting with motors and if the 4w-Type won’t work as I want it, I will disassemble my old rega P3 and use the premotec motor (driven by a frequency generator)
Regards, Boris
Hi planet IX,
You don't say what your problems are here, unfortunately, merely that you are not (yet) satisfied with the results.
Would you care to elaborate on this dissatisfaction, perhaps, and suggest whether this is due to speed stability difficulties, poor resultant sound, or whatever?
Otherwise, is it not possible to make any valid comments about this.
Regards,
You don't say what your problems are here, unfortunately, merely that you are not (yet) satisfied with the results.
Would you care to elaborate on this dissatisfaction, perhaps, and suggest whether this is due to speed stability difficulties, poor resultant sound, or whatever?
Otherwise, is it not possible to make any valid comments about this.
Regards,
Hi Boken,
sorry, but I thought that it was clear that we're talking about the speed stability of the platter
... and they were audible in all my setups that I tested (concerning the Maxon motor). I always checked the speed with a strobo-disc, but most of time that wasn't even necessary- on some records I could hear the speed-fluctuation immediately
...
Regards, Boris
sorry, but I thought that it was clear that we're talking about the speed stability of the platter
... and they were audible in all my setups that I tested (concerning the Maxon motor). I always checked the speed with a strobo-disc, but most of time that wasn't even necessary- on some records I could hear the speed-fluctuation immediately
...
Regards, Boris
Hi Boris,
There's absolutely no need for any apologies, and you are quite right that (most of us) have been talking about speed stability issues here.
However, whilst I (and most other posters, I think!) have been more concerned with short-term variations caused by stylus drag during heavily modulated passages on records, Matt has just surprised me with some different concerns related to speed changes across the entire record.
I wondered if your problems were similar to Matt's, as this is not a phenomenon I have come across before, and suggests to me to be due to a more serious deficiency in the motor and/or PS set-up.
Regards,
There's absolutely no need for any apologies, and you are quite right that (most of us) have been talking about speed stability issues here.
However, whilst I (and most other posters, I think!) have been more concerned with short-term variations caused by stylus drag during heavily modulated passages on records, Matt has just surprised me with some different concerns related to speed changes across the entire record.
I wondered if your problems were similar to Matt's, as this is not a phenomenon I have come across before, and suggests to me to be due to a more serious deficiency in the motor and/or PS set-up.
Regards,
Hi Bobken
No, I have never had any problems with speed stability over the side of a record, like Matt reported. This sounds very curious…
My anger are the short-term variations. But funnily enough I could not say that they appear only at heavily modulated passages… They seem to appear coincidental, regardless what record is playing and if the passage is quiet or loud or so.
The output-voltage of the LT1083 is absolutely constant and I believe that a LM317 will do the job just as well.
Boris
No, I have never had any problems with speed stability over the side of a record, like Matt reported. This sounds very curious…
My anger are the short-term variations. But funnily enough I could not say that they appear only at heavily modulated passages… They seem to appear coincidental, regardless what record is playing and if the passage is quiet or loud or so.
The output-voltage of the LT1083 is absolutely constant and I believe that a LM317 will do the job just as well.
Boris
Hi Boris,
Point is that virtually all motors exhibit some torque ripple, the one more than the other. Problem is to find one with the lowest ripple at the speed needed. The properties of the belt are crucial to dampen the ripple. Not only should the belt have a proper springiness but also a proper damping to absorb the short time speed irregularities. The more poles a motor has, the higher the ripple frequency and as such it is better absorbed by the belt and platter inertia. Has anyone ever looked at the PML pancake motors?
http://www.pmlflightlink.com/motors/GP.html
And all for all a synchronous motor with its 50/60 Hz ripple frequency is still a pretty good one but lacks simple speedcontrol.
Cheers
Point is that virtually all motors exhibit some torque ripple, the one more than the other. Problem is to find one with the lowest ripple at the speed needed. The properties of the belt are crucial to dampen the ripple. Not only should the belt have a proper springiness but also a proper damping to absorb the short time speed irregularities. The more poles a motor has, the higher the ripple frequency and as such it is better absorbed by the belt and platter inertia. Has anyone ever looked at the PML pancake motors?
http://www.pmlflightlink.com/motors/GP.html
And all for all a synchronous motor with its 50/60 Hz ripple frequency is still a pretty good one but lacks simple speedcontrol.
Cheers
Hi Boris,
Now I see.
Certainly the LT1083 should be adequate for this job, and these LTs are generally better than LM regs., so this is a real puzzle, especially as you suggest it is not consistent.
It still suggests to me that there is either a lack of adequate torque here, or is it possible there is some 'outside' influence, perhaps?
Does the TT (without any belt to the motor) spin freely and run on for a long time if you rotate it by hand?
Also, have you tried 'braking' the TT by hand (gently) when it is running to see how much drag needs to be applied to replicate this effect? This might indicate how much drag is occurring (if it is drag which is the cause) because if a lot of braking effect is necessary, it would look more like a PS problem to me.
The amount of drag caused by any stylus, should be very little in reality, and in my experience it will tend to increase consistently when playing heavily modulated passages.
I don't know what else to suggest right now, but I will give it some more thought.
Regards
Now I see.
Certainly the LT1083 should be adequate for this job, and these LTs are generally better than LM regs., so this is a real puzzle, especially as you suggest it is not consistent.
It still suggests to me that there is either a lack of adequate torque here, or is it possible there is some 'outside' influence, perhaps?
Does the TT (without any belt to the motor) spin freely and run on for a long time if you rotate it by hand?
Also, have you tried 'braking' the TT by hand (gently) when it is running to see how much drag needs to be applied to replicate this effect? This might indicate how much drag is occurring (if it is drag which is the cause) because if a lot of braking effect is necessary, it would look more like a PS problem to me.
The amount of drag caused by any stylus, should be very little in reality, and in my experience it will tend to increase consistently when playing heavily modulated passages.
I don't know what else to suggest right now, but I will give it some more thought.
Regards
Hi Pjotr,
I read this thing with the low torque ripple in a german dissertation (!) about turntables once. But no motor-manufacturer mentions its value in the motor-datasheets…
Furthermore I read in this dissertation, that one way to lower torque-ripple is to drive a motor with a very low voltage.
As I said, I tried out a non-slippery and stiff tape instead of a rubber-belt. The idea behind it is (as I was told), that a dc-motor has some kind of self regulation: when the platter is slowed down caused by the stylus drag, the motor-current will increase coevally, what in turn increases the torque. In this way the platter-speed should be constant when using a tape. But in my case this didn’t work…
These PML-motors look very good. Probably I will try to get one, if they fit to my pulley.
Boris
I read this thing with the low torque ripple in a german dissertation (!) about turntables once. But no motor-manufacturer mentions its value in the motor-datasheets…
Furthermore I read in this dissertation, that one way to lower torque-ripple is to drive a motor with a very low voltage.
As I said, I tried out a non-slippery and stiff tape instead of a rubber-belt. The idea behind it is (as I was told), that a dc-motor has some kind of self regulation: when the platter is slowed down caused by the stylus drag, the motor-current will increase coevally, what in turn increases the torque. In this way the platter-speed should be constant when using a tape. But in my case this didn’t work…
These PML-motors look very good. Probably I will try to get one, if they fit to my pulley.
Boris
Hi Bobken,
the motor I use has plenty of torque and the platter spins for minutes if I rotate it by hand without the belt (It’s a Scheu Platter and bearing).
If I break down the platter by hand it speeds up relatively quick and if I do it to heavy, the tape or belt slips over the pulley… So far everything as it should be.
the motor I use has plenty of torque and the platter spins for minutes if I rotate it by hand without the belt (It’s a Scheu Platter and bearing).
If I break down the platter by hand it speeds up relatively quick and if I do it to heavy, the tape or belt slips over the pulley… So far everything as it should be.
Hi Bob,
Do you have any idea how much the drag of the stylus is? I did some simulation with a 4 kg platter and an ideal running motor (that is, with a rock solid speed). The temporarily speed deviation due to the inertia and the belt will be then app 0.1% at a change of the drag of 1 gram (at the outside of the record where the effect is strongest). With a heavier platter the speed change will be lower but the duration will also be longer. To halve the speed change you will need a 4 times heavier platter, this relation goes with the square root of the mass of the platter.
@Boris,
Yes, that pancake motors look very interesting but these are quite expensive. They are available from Farnell and will cost around 130 eu
Regards
Do you have any idea how much the drag of the stylus is? I did some simulation with a 4 kg platter and an ideal running motor (that is, with a rock solid speed). The temporarily speed deviation due to the inertia and the belt will be then app 0.1% at a change of the drag of 1 gram (at the outside of the record where the effect is strongest). With a heavier platter the speed change will be lower but the duration will also be longer. To halve the speed change you will need a 4 times heavier platter, this relation goes with the square root of the mass of the platter.
@Boris,
Yes, that pancake motors look very interesting but these are quite expensive. They are available from Farnell and will cost around 130 eu
Regards
Boris,
do you see rapid speed variations (flutter) or slow speed variations (wow) or both?
Do you also see the same speed variations when no record is playing, or only when a record is playing?
Can you try driving the motor directly from some batteries, to eliminate the regulator as a problem?
Neil
do you see rapid speed variations (flutter) or slow speed variations (wow) or both?
Do you also see the same speed variations when no record is playing, or only when a record is playing?
Can you try driving the motor directly from some batteries, to eliminate the regulator as a problem?
Neil
less talk more action...
will someone post a decent DC motor controller PCB? Pick a decent brushless motor, somewhat strong to drive a 3+ kg platter and accompany it with a good controller. Let's build it then and then comment on it... we can improve it later. you need 500 euros to get something decent from the market. its ridiculous...
will someone post a decent DC motor controller PCB? Pick a decent brushless motor, somewhat strong to drive a 3+ kg platter and accompany it with a good controller. Let's build it then and then comment on it... we can improve it later. you need 500 euros to get something decent from the market. its ridiculous...
Hi Pjotr, if I’d know the problem eliminated with this motor, I would buy one. But at least I have no pulley for the axis of this size…
What you say about platter-mass and speed deviations might lead us to lightweight platter in combination with a strong motor, doesn’t it? But then the torque-ripple of the motor becomes more a problem, if I understand right…
Hi Pixpop, particularly I hear these speed variations. So far I never listened to the music and simultaneously observed the strobe-disc.
There are no speed variations without a needle on the platter (possibly they are there, but then much lower).
The same is for battery-supply. I’ve tried really everything possible.
But now... finishing time for me today and time for a beer
What you say about platter-mass and speed deviations might lead us to lightweight platter in combination with a strong motor, doesn’t it? But then the torque-ripple of the motor becomes more a problem, if I understand right…
Hi Pixpop, particularly I hear these speed variations. So far I never listened to the music and simultaneously observed the strobe-disc.
There are no speed variations without a needle on the platter (possibly they are there, but then much lower).
The same is for battery-supply. I’ve tried really everything possible.
But now... finishing time for me today and time for a beer
Hi Pjota,
No, unfortunately I don't, or at least I haven't measured it for myself (yet!).
Actually I have been thinking about this issue for a day or so, and I wonder if the following would be worthwhile trying out.
Fortunately, I don't have any of these problems, and right now I have rather too many other matters to attend to, to try out such an experiment, myself.
However, what I would suggest is to obtain (or maybe make!) a spring letter-balance, the kind which used to be in use for weighing individual letters before posting. I haven't seen one for some years, but basically it consists of a suitably weak coil-spring with a hook at the ends, and one end is fixed relative to a slide along which the spring extends.
This slide has graduations marked along it, and according to Hooks Law, the extension of the spring (within sensible boundaries) will be in proprtion to the force (the weight of the letter) acting upon it. Something similar could quite readily be made by a DIYer, I think, and calibrated using gravity by reference to some known weights.
I would then attach a long piece of thin nylon fishing line/sewing nylon, or whatever, to the rim of the TT with some adhesive tape, and wind this several times around the outer rim of the TT, possibly where the belt rides normally.
Then, by attaching the balance to the other end of the nylon, one could rotate the platter by pulling on the nylon, by way of the balance, to see how much 'pull' is needed (read off the scale) to rotate the TT with the cartridge in place.
This is rather crude and probably not very accurate, but I still suspect it would be quite revealing, and the biggest problem to overcome is the inertia of the set-up until the TT gains speed to 33.3 RPM.
Accordingly, it would possibly need maybe ten or so windings of nylon to enable the TT to be got up to speed (check this with a strobe) and a helper to keep an eye on things to avoid too many tangles! Clearly some practice would be needed too.
The tester would need to walk steadily away from the set-up with the balance held carefully in his hand and watching the scale, while the helper reads the strobe, and gives instructions about the TT's speed.
Depending on how this initial exercise turns out, it might also be possible to make a comparison without any stylus pressure as well, and this could provide a 'difference' which would indicate the true stylus drag, itself. However, this may be expecting rather too much of this basic idea.
Before you laugh too much at all this, it would be (almost?) free to try, except for needing a lot of patience, and I have had some success with several similar situations in the past, believe it or not. After all, we are talking about DIY, aren't we?
Doubtless I will try it myself at some future date, but if anyone else does so in the meantime, I would be interested to learn if it was successful.
Regards,
No, unfortunately I don't, or at least I haven't measured it for myself (yet!).
Actually I have been thinking about this issue for a day or so, and I wonder if the following would be worthwhile trying out.
Fortunately, I don't have any of these problems, and right now I have rather too many other matters to attend to, to try out such an experiment, myself.
However, what I would suggest is to obtain (or maybe make!) a spring letter-balance, the kind which used to be in use for weighing individual letters before posting. I haven't seen one for some years, but basically it consists of a suitably weak coil-spring with a hook at the ends, and one end is fixed relative to a slide along which the spring extends.
This slide has graduations marked along it, and according to Hooks Law, the extension of the spring (within sensible boundaries) will be in proprtion to the force (the weight of the letter) acting upon it. Something similar could quite readily be made by a DIYer, I think, and calibrated using gravity by reference to some known weights.
I would then attach a long piece of thin nylon fishing line/sewing nylon, or whatever, to the rim of the TT with some adhesive tape, and wind this several times around the outer rim of the TT, possibly where the belt rides normally.
Then, by attaching the balance to the other end of the nylon, one could rotate the platter by pulling on the nylon, by way of the balance, to see how much 'pull' is needed (read off the scale) to rotate the TT with the cartridge in place.
This is rather crude and probably not very accurate, but I still suspect it would be quite revealing, and the biggest problem to overcome is the inertia of the set-up until the TT gains speed to 33.3 RPM.
Accordingly, it would possibly need maybe ten or so windings of nylon to enable the TT to be got up to speed (check this with a strobe) and a helper to keep an eye on things to avoid too many tangles! Clearly some practice would be needed too.
The tester would need to walk steadily away from the set-up with the balance held carefully in his hand and watching the scale, while the helper reads the strobe, and gives instructions about the TT's speed.
Depending on how this initial exercise turns out, it might also be possible to make a comparison without any stylus pressure as well, and this could provide a 'difference' which would indicate the true stylus drag, itself. However, this may be expecting rather too much of this basic idea.
Before you laugh too much at all this, it would be (almost?) free to try, except for needing a lot of patience, and I have had some success with several similar situations in the past, believe it or not. After all, we are talking about DIY, aren't we?
Doubtless I will try it myself at some future date, but if anyone else does so in the meantime, I would be interested to learn if it was successful.
Regards,
Hi Pixpop, I don’t use a mat on the platter. I put the records directly on the platter (it’s made of vinyl). Also I don’t like weights on the record. This all didn’t sound good for my ears. And I’m sure that the record doesn’t slip on the platter. (Is this really possible? I can not believe it).
I’ve been using the original Scheu-Motor, before I started playing with the maxon. There were no speed deviations in this setup. Since I haven’t changed anything else but the motor, I can be sure that the platter and bearing were okay.
Then I got the maxon. First setup: tape-drive (from a normal audio-tape) and L200 voltage regulator. The sound was much better then with the Scheu-Motor, but I had some little speed deviations sometimes. I have the voltage regulator circuit from the L200 designers guide(Dc-motor-regulator involving the motor-current). Since the tape was very slippery, I got me a tape, that didn’t slip. I thought that I need a very inelastic/rigid coupling for this kind of regulation. But with the new tape I really noticed speed deviation through dynamic passages in the music.
Then I tried out the LT1083 voltage regulator circuit and with this I have the unpredictable speed deviations I was talking about. When the speed keeps constant for a few minutes, the sound is better than in all other setups.
So at least I believe that there is something wrong with the motor (although it is very smooth running, if I turn the axis by hand) and I will try a weaker maxon type next. Also I started looking for a small and stable frequency-generator circuit, which can drive the premotec-motor from my old Rega…
Regards, Boris
I’ve been using the original Scheu-Motor, before I started playing with the maxon. There were no speed deviations in this setup. Since I haven’t changed anything else but the motor, I can be sure that the platter and bearing were okay.
Then I got the maxon. First setup: tape-drive (from a normal audio-tape) and L200 voltage regulator. The sound was much better then with the Scheu-Motor, but I had some little speed deviations sometimes. I have the voltage regulator circuit from the L200 designers guide(Dc-motor-regulator involving the motor-current). Since the tape was very slippery, I got me a tape, that didn’t slip. I thought that I need a very inelastic/rigid coupling for this kind of regulation. But with the new tape I really noticed speed deviation through dynamic passages in the music.
Then I tried out the LT1083 voltage regulator circuit and with this I have the unpredictable speed deviations I was talking about. When the speed keeps constant for a few minutes, the sound is better than in all other setups.
So at least I believe that there is something wrong with the motor (although it is very smooth running, if I turn the axis by hand) and I will try a weaker maxon type next. Also I started looking for a small and stable frequency-generator circuit, which can drive the premotec-motor from my old Rega…
Regards, Boris
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