Just an idle question, do any of you listen to the music, or do you just sit there watching rev counters? Absolute speed is not usually an issue unless you have perfect pitch, and few do; speed variation is the bigger worry.
What a drag!
Hi Neil,
No, unfortunately I don't have any way of 'quantifying' this effect, or at least so far I have not attempted to do this.
However, two points I raised on the Forum recently are that when I polished off no more than a thousandth or two of an inch from a pulley which was (IIRC) about 3/8" to 1/2" in diameter, I could clearly hear the change in pitch with the same synchronous motor I was then using.
This simply confirms my comments that this area of interest is incredibly sensitive to even quite minute differences, as the nominal speed of this motor was, of course, governed by the mains frequency and shouldn't have changed.
The other point was that a few years ago I purchased an extremely accurate self-contained stroboscope/tachometer, which did not rely on mains frequency, or whatever, for its operation.
It has a series of maybe 50+ leds around its circumference, which light up (flash) at pre-determined frequencies, controlled by an accurate quartz crystal clock, and this is very revealing when used whilst records are being played.
It then became easy to 'see' what effect the heavily modulated passages have on the TT's speed, and to watch how things change, and it was only after obtaining this device that I made any further real progress with my PS designs.
This finally confirmed precisely the effects I was earlier hearing, but previously the reasons for these abberations were not quite so clear, and still left some doubts in my mind, as the degree of these effects were not initially at all intuitive to me.
Maybe a good analogy here would be with viewing signals on a 'scope, where it is infinitely more clear what is happening to a signal, which subjectively does not sound as good as it might.
I have ended up with a fairly high mass platter, with a lot of the mass concentrated at the outer periphery, to deliberately encourage a flywheel effect, and this tends to 'plough through' any short-term attempts for the stylus drag to reduce the overall speed.
With this arrangement, allied to a high torque motor fed with a very smooth and clean DC voltage, which is also extremely accurately regulated, I have achieved the best results so far.
I still have serious reservations over using very low DC voltages here, as expressed earlier in this thread, as I found that keeping extremely low voltages so well regulated is less easy than higher voltages, all else being equal.
Hi Harwoodspark,
I hadn't read your post when I last contributed in response to Pjotr, but you will now see that I agree entirely with your comments on the relatively elastic nature of flexible belts, and their own attendant problems.
I have also experimented with duplex belts, in an effort to reduce any 'stretching' abberations, and this does help, somewhat.
However, nothing in life is free, and although this gave some benefits, I generally preferred the single belt, overall, in listening tests.
As they say, the jury is still out on this one, though, and I will try some more with this arrangement at a future time, as it is one way of reducing the otherwise (albeit minor) inevitable belt-stretching effects. I cannot hear any pitch changing effects with my current set-up due to any belt stretching, but common-sense tells me that on longer term heavily modulated passages, this must happen to some degree, and I would like to eliminate this possibility.
Presently, I am inclined to try out some other belt materials first, of a less stretchy variety like nylon cords, but joining these is not the easiest thing to do I have found, without ending up with a lump somewhere on the belt where it is joined.
This, unfortunately, tends to give the platter a minute 'kick' every time it passes around the quite small motor pulley.
As you will also have seen, your comments about using a TT with "sufficient mass", and a "rock steady output" from the DC supply make a lot of sense, and to me these are far more important attributes to the sound than any feedback or servo attempts.
Incidentally, as with preferring not using very low voltages, I don't see any reason to restrict the motor's torque, as in my book, the more torque you have (within sensible bounds), the less any stylus drag will affect the resultant speed.
I now need to pinch my TT's belt (when it is running between my fingers) quite hard before there is any noticeable speed reduction, and this is entirely down to the higher torque motors I have progressed to.
Any such pinching needed to affect the TT's speed is many times (orders of magnitude, I suspect) greater than any stylus-induced drag, I believe.
Hi Neil,
No, unfortunately I don't have any way of 'quantifying' this effect, or at least so far I have not attempted to do this.
However, two points I raised on the Forum recently are that when I polished off no more than a thousandth or two of an inch from a pulley which was (IIRC) about 3/8" to 1/2" in diameter, I could clearly hear the change in pitch with the same synchronous motor I was then using.
This simply confirms my comments that this area of interest is incredibly sensitive to even quite minute differences, as the nominal speed of this motor was, of course, governed by the mains frequency and shouldn't have changed.
The other point was that a few years ago I purchased an extremely accurate self-contained stroboscope/tachometer, which did not rely on mains frequency, or whatever, for its operation.
It has a series of maybe 50+ leds around its circumference, which light up (flash) at pre-determined frequencies, controlled by an accurate quartz crystal clock, and this is very revealing when used whilst records are being played.
It then became easy to 'see' what effect the heavily modulated passages have on the TT's speed, and to watch how things change, and it was only after obtaining this device that I made any further real progress with my PS designs.
This finally confirmed precisely the effects I was earlier hearing, but previously the reasons for these abberations were not quite so clear, and still left some doubts in my mind, as the degree of these effects were not initially at all intuitive to me.
Maybe a good analogy here would be with viewing signals on a 'scope, where it is infinitely more clear what is happening to a signal, which subjectively does not sound as good as it might.
I have ended up with a fairly high mass platter, with a lot of the mass concentrated at the outer periphery, to deliberately encourage a flywheel effect, and this tends to 'plough through' any short-term attempts for the stylus drag to reduce the overall speed.
With this arrangement, allied to a high torque motor fed with a very smooth and clean DC voltage, which is also extremely accurately regulated, I have achieved the best results so far.
I still have serious reservations over using very low DC voltages here, as expressed earlier in this thread, as I found that keeping extremely low voltages so well regulated is less easy than higher voltages, all else being equal.
Hi Harwoodspark,
I hadn't read your post when I last contributed in response to Pjotr, but you will now see that I agree entirely with your comments on the relatively elastic nature of flexible belts, and their own attendant problems.
I have also experimented with duplex belts, in an effort to reduce any 'stretching' abberations, and this does help, somewhat.
However, nothing in life is free, and although this gave some benefits, I generally preferred the single belt, overall, in listening tests.
As they say, the jury is still out on this one, though, and I will try some more with this arrangement at a future time, as it is one way of reducing the otherwise (albeit minor) inevitable belt-stretching effects. I cannot hear any pitch changing effects with my current set-up due to any belt stretching, but common-sense tells me that on longer term heavily modulated passages, this must happen to some degree, and I would like to eliminate this possibility.
Presently, I am inclined to try out some other belt materials first, of a less stretchy variety like nylon cords, but joining these is not the easiest thing to do I have found, without ending up with a lump somewhere on the belt where it is joined.
This, unfortunately, tends to give the platter a minute 'kick' every time it passes around the quite small motor pulley.
As you will also have seen, your comments about using a TT with "sufficient mass", and a "rock steady output" from the DC supply make a lot of sense, and to me these are far more important attributes to the sound than any feedback or servo attempts.
Incidentally, as with preferring not using very low voltages, I don't see any reason to restrict the motor's torque, as in my book, the more torque you have (within sensible bounds), the less any stylus drag will affect the resultant speed.
I now need to pinch my TT's belt (when it is running between my fingers) quite hard before there is any noticeable speed reduction, and this is entirely down to the higher torque motors I have progressed to.
Any such pinching needed to affect the TT's speed is many times (orders of magnitude, I suspect) greater than any stylus-induced drag, I believe.
Hi Jo,
Its a relief to see that you have been paying such close attention, as it makes the effort all worthwhile!
"Speed variation", mainly due to stylus drag, and trying to eliminate it, is precisely what most of this has been about for several days.
Personally, I haven't been able to enjoy listening to a record for many years due to all the flashing leds I need to keep a close eye on!
Regards, 😉
Its a relief to see that you have been paying such close attention, as it makes the effort all worthwhile!
"Speed variation", mainly due to stylus drag, and trying to eliminate it, is precisely what most of this has been about for several days.
Personally, I haven't been able to enjoy listening to a record for many years due to all the flashing leds I need to keep a close eye on!
Regards, 😉
Bob,
with your LED strobe, do the bars on the strobe disc have sharp edges?
I've been using a traditional neon strobe, synced to the AC line. You can tell if the bars are moving left or right, but you cannot use it for detecting flutter, as there is too much jitter in the flash of light, which makes the edges of the bars appear blurred. I've been toying with the idea of making a strobe with LEDs, maybe now is the time. I notice a few such DIY projects on the web.
with your LED strobe, do the bars on the strobe disc have sharp edges?
I've been using a traditional neon strobe, synced to the AC line. You can tell if the bars are moving left or right, but you cannot use it for detecting flutter, as there is too much jitter in the flash of light, which makes the edges of the bars appear blurred. I've been toying with the idea of making a strobe with LEDs, maybe now is the time. I notice a few such DIY projects on the web.
The link worked for me.
I see that your device doesn't even use the strobe disc. You just look directly at the LEDs. Very clever.
I see that your device doesn't even use the strobe disc. You just look directly at the LEDs. Very clever.
Hi pixpop,
You will see the device I use in the thread above.
I know exactly what you mean here, and I gave up a long while ago with any mains controlled devices, as the mains is not sufficiently accurate quite a lot of the time.
In the UK this is especially so late at night (which is my preferred listening-time) when the Electricity Authorities make up any 'lost time' (during the daytime) so that clocks still keep good time, overall!
Copying a Gyrascope would not be an easy DIY effort, I regret to say, and the blue led version I have cost about £350 ($600+), several years ago.
This cost was only justifiable as I was involved in a commercial development at that time.
Edit for Pinkmouse. It works OK for me, as I just tried it out immediately after I posted it.
You will see the device I use in the thread above.
I know exactly what you mean here, and I gave up a long while ago with any mains controlled devices, as the mains is not sufficiently accurate quite a lot of the time.
In the UK this is especially so late at night (which is my preferred listening-time) when the Electricity Authorities make up any 'lost time' (during the daytime) so that clocks still keep good time, overall!
Copying a Gyrascope would not be an easy DIY effort, I regret to say, and the blue led version I have cost about £350 ($600+), several years ago.
This cost was only justifiable as I was involved in a commercial development at that time.
Edit for Pinkmouse. It works OK for me, as I just tried it out immediately after I posted it.
Hi PM,
Have you cracked it OK now? I just tried the link again, and it seems fine to me.
Hi Arne,
Yes, that is certainly a lot less costly, as you say. I wouldn't like to speculate whether or not the abberations I was concerned with could be readily seen on this tacho/strobe, although I am sure it would enable accurate overall speed settings to be made.
I wasn't aware of the Hagtech device when I bought the Gyrascope, but I was under pressure to finalise a design, and I went for the most accurate device I could find, anywhere.
It did the job well!
Have you cracked it OK now? I just tried the link again, and it seems fine to me.
Hi Arne,
Yes, that is certainly a lot less costly, as you say. I wouldn't like to speculate whether or not the abberations I was concerned with could be readily seen on this tacho/strobe, although I am sure it would enable accurate overall speed settings to be made.
I wasn't aware of the Hagtech device when I bought the Gyrascope, but I was under pressure to finalise a design, and I went for the most accurate device I could find, anywhere.
It did the job well!
Gyrascope
I guess the Gyrascope also function as a clamp/weight, it looks good, and would be an interesting option for older (non-quartz) DC-motorized TT's, like MicroSeiki...
Arne K
For speed-variation checking, you will find wow & flutter-meters on ebay for "next to nothing"
I guess the Gyrascope also function as a clamp/weight, it looks good, and would be an interesting option for older (non-quartz) DC-motorized TT's, like MicroSeiki...
Arne K
For speed-variation checking, you will find wow & flutter-meters on ebay for "next to nothing"
Wow & flutter meters
Hi Arne,
The last time I used one of these meters, it was necessary to also use a test record with accurately recorded sine waves on it.
Otherwise, I don't know how you can get any meaningfull readings from a TT set-up to measure with a wow & flutter meter, but perhaps you can enlighten me.
Irrespective of the levels and frequencies of these test signals, they are recorded effectively as 'steady-state' signals, and therefore their modulation does not vary during each track.
The problem with this arrangement is that it precludes you from carrying out the kind of tests I am interested in and have been discussing, which are mainly how the TT speed is affected *during heavily modulated passages* on 'normal' recordings.
I have looked at waveforms etc. on 'scopes, and tried several other ideas, but so far, the Gyrascope has proved to be the most illuminating tool I have used in this connection.
Regards,
Hi Arne,
The last time I used one of these meters, it was necessary to also use a test record with accurately recorded sine waves on it.
Otherwise, I don't know how you can get any meaningfull readings from a TT set-up to measure with a wow & flutter meter, but perhaps you can enlighten me.
Irrespective of the levels and frequencies of these test signals, they are recorded effectively as 'steady-state' signals, and therefore their modulation does not vary during each track.
The problem with this arrangement is that it precludes you from carrying out the kind of tests I am interested in and have been discussing, which are mainly how the TT speed is affected *during heavily modulated passages* on 'normal' recordings.
I have looked at waveforms etc. on 'scopes, and tried several other ideas, but so far, the Gyrascope has proved to be the most illuminating tool I have used in this connection.
Regards,
Got it now, don't know what happened there.
It's certainly an impressive piece of kit, but the Hagtech one looks a little more feasable for home construction. 🙂
It's certainly an impressive piece of kit, but the Hagtech one looks a little more feasable for home construction. 🙂
Hi Al,
Glad you made it!
Actually, I tried the link again this AM, and I had difficulty navigating the site, so it looks like they may be having some intermittent problems.
As you say, it is a very well-made piece of kit, but so it should be at the price!
It does, however, exactly as Lys claim "takes into account the drag of the stylus attached to the cartridge", and I have not (yet!) found anything better for this purpose.
Its a silly cost for DIY'ers, and maybe the Hagtech device would be worth experimenting with. It all depends on how clearly the strobe effects can be seen, as Neil previously discovered.
Also, with any unit which has quite heavy batteries etc. within, it is important to ensure that the final 'set-up' is statically balanced as well as possible. Otherwise, when it is rotating on the platter, out of balance rotational/centrifugal forces will tend to induce wow on its own, and this will very likely adversely affect the results.
Regards,
Glad you made it!
Actually, I tried the link again this AM, and I had difficulty navigating the site, so it looks like they may be having some intermittent problems.
As you say, it is a very well-made piece of kit, but so it should be at the price!
It does, however, exactly as Lys claim "takes into account the drag of the stylus attached to the cartridge", and I have not (yet!) found anything better for this purpose.
Its a silly cost for DIY'ers, and maybe the Hagtech device would be worth experimenting with. It all depends on how clearly the strobe effects can be seen, as Neil previously discovered.
Also, with any unit which has quite heavy batteries etc. within, it is important to ensure that the final 'set-up' is statically balanced as well as possible. Otherwise, when it is rotating on the platter, out of balance rotational/centrifugal forces will tend to induce wow on its own, and this will very likely adversely affect the results.
Regards,
Hi folks
I've just caught up with the latest postings which interestingly reflect my recent experiences- stylus drag etc.
I just got my new motor, REMax 226756. Its quieter than the premotec which is a good start! As I still haven't got a good quality 10mm pulley I'm using the Linn 20mm one and running the motor at 1.6v. I am using a 317 reg mounted right at the motor terminals. The sound is good, however, the speed is not constant when viewed using a strobe disc. I estimate that there is a increase in speed of about 1.5-2% from the first to last track of the record as reflected in a voltage increase at the motor terminals of this magnetude. I was suprised as I expected the regulator to easily cope with any current the motor was likely to draw, also I thought that given the heavy platter of the Linn stylus drag would be smoothed out. I'll try a better regulator, as the 317 is down near its lower operating limit (1.2v).
Cheers
Matt
I've just caught up with the latest postings which interestingly reflect my recent experiences- stylus drag etc.
I just got my new motor, REMax 226756. Its quieter than the premotec which is a good start! As I still haven't got a good quality 10mm pulley I'm using the Linn 20mm one and running the motor at 1.6v. I am using a 317 reg mounted right at the motor terminals. The sound is good, however, the speed is not constant when viewed using a strobe disc. I estimate that there is a increase in speed of about 1.5-2% from the first to last track of the record as reflected in a voltage increase at the motor terminals of this magnetude. I was suprised as I expected the regulator to easily cope with any current the motor was likely to draw, also I thought that given the heavy platter of the Linn stylus drag would be smoothed out. I'll try a better regulator, as the 317 is down near its lower operating limit (1.2v).
Cheers
Matt
Matt,
did you measure the speed difference with the stylus in contact with the record, and not in contact?
Also, do you know the mass of the rotating parts?
did you measure the speed difference with the stylus in contact with the record, and not in contact?
Also, do you know the mass of the rotating parts?
Hi Matt,
Sorry to hear of these speed drift problems, but I am not entirely surprised.
Inconvenient though it may be, I am still quite certain that you will have better results with a smaller pulley and using higher voltages.
As I suggested in post #62, such low voltages are not so easy to control accurately in my experience. Also, and more importantly, whatever regulator you end up with, it will not be perfect (nothing in life ever is!) and it will have some inherent degree of accuracy in maintaining a set speed etc, and a 'noise' level, neither of which are good for the best results.
Suppose for argument's sake, the output accuracy of the regulator will allow a drift of 10mV, and you are running at 1volt nominal for the motor. This is a 1% variation here.
However, with an identical 10mV drift with the same regulator, if one is using 10 volts to drive the motor, this inaccuracy reduces by a factor of 10, down to merely 0.1%.
Have you tried out deliberately braking the platter gently by hand, either by pinching the belt (if it is accessible when the TT is in use) or perhaps with a finger on the platter's edge?
This is crude, but should give you some idea of how resistant the arrangement is to drag effects generally, together with some rough idea of how much torque you have currently.
Sorry to hear of these speed drift problems, but I am not entirely surprised.
Inconvenient though it may be, I am still quite certain that you will have better results with a smaller pulley and using higher voltages.
As I suggested in post #62, such low voltages are not so easy to control accurately in my experience. Also, and more importantly, whatever regulator you end up with, it will not be perfect (nothing in life ever is!) and it will have some inherent degree of accuracy in maintaining a set speed etc, and a 'noise' level, neither of which are good for the best results.
Suppose for argument's sake, the output accuracy of the regulator will allow a drift of 10mV, and you are running at 1volt nominal for the motor. This is a 1% variation here.
However, with an identical 10mV drift with the same regulator, if one is using 10 volts to drive the motor, this inaccuracy reduces by a factor of 10, down to merely 0.1%.
Have you tried out deliberately braking the platter gently by hand, either by pinching the belt (if it is accessible when the TT is in use) or perhaps with a finger on the platter's edge?
This is crude, but should give you some idea of how resistant the arrangement is to drag effects generally, together with some rough idea of how much torque you have currently.
Bobken said:
Hi Bob,
Yes a smaller pulley will help a lot here. The smaller the better, I would opt for a 8 mm one.
The LM317 regulators are pretty good with quite low noise. Long term stability is not that an issue when properly heat sinked. What is important when driving a motor is that these regulators do not “starve of current”. That can be a result of motor irregularities especially due to the back EMF. When they starve of current they present a high impedance to the motor and electric motor damping is lost. It is best to load the regulator with a bleeder resistor (in parallel with the motor) that draws a current of app. 1/2 the steady motor current.
Cheers 😉
Hi Pjotr,
Yes, that's a good point about pre-loading (any) regulators with a resistor at the output, which I omitted to mention, myself, even though I use them and find them beneficial.
I confess to being puzzled by some of Matt's comments though, as an increase in RPM of 1.5 to 2% simply across a record is horrendous in my opinion, and suggests almost negligible torque from the motor, or something similar. I have never encountered anything like that in my many years of experimentation. The surface velocity at the inner grooves will, of course, be less than at the outer rim (smaller circumference here but the same RPM) and consequently the stylus drag would be marginally less here.
However, for this to noticeably affect the speed at all would cause me to think that something is very wrong, somewhere. I even wonder if I have understood what Matt said correctly here.
I would guess that any changes in drag would be far more prevalent during heavily modulated passages, than any overall differences in drag across the record, so goodness what this will be doing to the pitch of music when replaying 'enthusiastic' passages!
Unless Matt is using a 317*L* (100mA max.) the other suffix 317s should provide somewhere between 500mA, and 1.5A, which should be plenty of current available for such motors.
Off the top of my head, my present motor takes only a few tens of mA during normal running, although it does draw a substantially higher current momentarily during start-up, as I mentioned as a caveat earlier on in this thread.
Regards,
Yes, that's a good point about pre-loading (any) regulators with a resistor at the output, which I omitted to mention, myself, even though I use them and find them beneficial.
I confess to being puzzled by some of Matt's comments though, as an increase in RPM of 1.5 to 2% simply across a record is horrendous in my opinion, and suggests almost negligible torque from the motor, or something similar. I have never encountered anything like that in my many years of experimentation. The surface velocity at the inner grooves will, of course, be less than at the outer rim (smaller circumference here but the same RPM) and consequently the stylus drag would be marginally less here.
However, for this to noticeably affect the speed at all would cause me to think that something is very wrong, somewhere. I even wonder if I have understood what Matt said correctly here.
I would guess that any changes in drag would be far more prevalent during heavily modulated passages, than any overall differences in drag across the record, so goodness what this will be doing to the pitch of music when replaying 'enthusiastic' passages!
Unless Matt is using a 317*L* (100mA max.) the other suffix 317s should provide somewhere between 500mA, and 1.5A, which should be plenty of current available for such motors.
Off the top of my head, my present motor takes only a few tens of mA during normal running, although it does draw a substantially higher current momentarily during start-up, as I mentioned as a caveat earlier on in this thread.
Regards,
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