Theoretically yes, there can be a few % more drag with a heavily modulated passage, opposed to a lightly modulated one. I base this on others findings and I haven't measured this myself. The audibility of any drag really depends on the table. Platter weight, drive type and torque make all the difference. Considerations would be different for a belt drive with a light platter and low torque motor, than for a one with a heavier platter and/or speed correction etc.
Regards, |
The audibility of any drag really depends on the table If you can hear stylus drag on an otherwise accurate table, you most likely posses superhuman auditory abilities, or you simply think you hear it, but you really don't. The great majority of people cannot hear small changes in pitch so the idea that you can "hear" stylus drag is a long stretch to say the least. If your table spins at an incorrect speed to begin with, it's a different story, but I wouldn't obsess too much about stylus drag itself. |
You don't hear the change in pitch as such. You hear it as a shaky soundstage. Speed variation causes the tonearm to decrease and increase skating forces. This makes the soundstage less solid. This is why speed stability is so important. |
You really shouldn't hear any with your Raven. If you do get it repaired. |
Atmasphere is correct.
You may not consciously 'hear' stylus drag as pitch change......but there are so many subtle clues embedded in the grooves which rely on perfectly stable speed control.
Remember that only half the analogue signal is contained in the record......Amplitude.
The 'Time Domain' to complete the sine wave is provided by the turntable rotation.
Any deviation in perfect speed results in a distorted sine wave just as if your amplifier was distorting?
And yes.....I have noticed via the Timeline....that heavily modulated passages cause more stylus drag than others.
I can see this effect on my Raven AC-2 quite clearly whereas on the Victor TT-101......the quartz-controlled DD motor compensates without any visual clues. |
Not sure about Australian but a Dutchman would never buy
any Raven considering the 'speed stability' and , more in
particular, the price difference with the (victorious)
Victor TT-101 (or TT 80?). BTW the 'stylus drag' is invented
to justify megabucks TT's. I of course understand
such stories when told to our 'more beautiful halves' but
to your own friends?
Regards, |
I personally can't imagine a platter that only weights even 5-10 pounds being slowed down enough by a short complex passage, to be bothersome. These turntables weight over 150 pounds, so, a good portion of that must be platter weight.
If a record has a passage with that much drag, what happens to the soft cantilever suspension? The stylus, cantilever, suspension, and coils with pole pieces, might be moving in and out enough to possibly cause some poor sounding results too. Possibly more bad results, than a heavy platter slowing down from this intermittently.
If you drilled a hole in the record, let it play until the stylus hits the hole, I wonder how much a heavy platter would slow down when the whole stylus, cantilever, coils (magnets if MM), plus who knows what else would get ripped out?
I don't worry about a heavy platter slowing from a short complex passage myself. A cheap light platter is a different story. That's one of the reasons why better turntables have a heavier platter. I do hear variations on budget tables, but very rarely upper-end ones. Don't forget about Newton's Law about something staying in motion. |
Newton's First Law of Motion:- The velocity of a body remains constant unless the body is acted upon by an external force. 'Friction' is an 'external force'. Why do you think a motor is required to keep a platter spinning? I personally can't imagine a platter that only weights even 5-10 pounds being slowed down enough by a short complex passage, to be bothersome. Don't imagine it..........get a Timeline and SEE it! |
Dear Nikola,
Actually the Raven is not that bad.
Using the Timeline......I found that two motors (opposed) actually kept a more constant speed than the three motors.
So that's how I now use it.
I think that stylus drag is a common factor for all belt-drive TTs....even those with string-drive and very heavy platters. Read how Dover, with his Final TT had to adjust the speed controller when the cartridge hit the vinyl?
I also had to do the same on the Raven.
In other words.....the speed of the TT is different with a cartridge tracking than without.
The TT-101 however......keeps the same speed regardless of whether there is a cartridge or not.....or even if there are multiple cartridges in contact with the record.
Incidentally......I also find that low compliance cartridges like most LOMCs.....have more stylus drag than high compliance MM s.
This may be why I hear less distortion with most MMs than I do with LOMCs?
Regards |
06-04-12: Halcro
Newton's First Law of Motion:-
The velocity of a body remains constant unless the body is acted upon by an external force.
'Friction' is an 'external force'. Why do you think a motor is required to keep a platter spinning? Step into the path of a person on a bicycle, and see how much measurable speed is lost. Then try stepping in front of a freight train, and see how much the train slows. Big difference. More mass. That short heavy passage is more like the bicycle IMO. Also, if the groove has that much information, there is probably a lot more tracking distortion problems, stylus suspension distortion, and other problems going on that would be more noticeable IMO. If your listening to something recorded on a an analog master, there is a lot more speed variation. Their flywheel has just a tiny bit of mass. You could hear this on a $99 record changer. You may be seeing more record slippage with the Timeline, than the actual platter speed error. How much error does the Timeline clock and circuit have? The hole in the records are off-center quite often. More constant speed error here too. I hear a lot more of errors on the records, in comparison to a good turntable. You could get a custom made multimillion dollar table, but you still have the same records, with their problems. |
Regarding the greater stylus drag with low compliance MC cartridges......I suspect it is also related to the higher tracking forces generally required with those over the MMs? |
The logic and our hobby don't fit together. I have no clue
why the low compliance carts are produced which is the same
(in my case)as that they make no sense to me. Despite of
this (subjective) fact I own 2 or 3 of those. I know that something
is wrong with me but have no idea what is wrong
with the low compliance MC's. Can someone explain to me why
those are still produced?
Regards, |
Good question my friend.
J Carr would certainly have an answer if he was lurking? |
Dear Henry, 'J.Carr would...'. Since when my Aussie friend
become diplomatic? J. Carr is a very nice guy so one need
only to ask? J. Carr WILL you be so kind?
Regards, |
Hi Folks, thanks for your comments so far. Some comments from me:
I agree with Halcro that the Raven slows down when the needle hits the groove. I base this on the shift in speed as observed with the KAB strobe disk. So I usually set speed with the needle in the groove. So clearly stylus drag is impacting speed, but I can't tell if it deviates based on the fluctuations in modulation of the actual record on speed has been set taking average drag into account. But it apprears Halcro has observed changes in speed with havily modulated sections of the record using the TimeLine. The key question is whether or not this small change is audible.
I agree with Atmasphere and Mosin (in the other thread on turntable speed accuracy) that the best way to listen for speed stability is by assessing the soundstage expansiveness and the small, faint micro-dynmaic and timberal details in the recording, in addition to the sheer dynamics. These come across more clearly than possibly changes in pitch.
The best description I heard about TT's is that they are "rotating resonance machines". Very true! We need to worry about both speed and resonance.
Andrew |
Yes, the only way to set the speed is with the needle in the groove. You are trying to make it perfect for the conditions in which you listen. You don't listen with the stylus on the tonearm mount, do you?
As for MC's having more drag ... I can only surmise that, since most MC's have Shibata or a fine line stylus, they sit lower in the groove than MM's which have more rounded tips. So there is expected to be more drag for MC's. At least that makes sense to me. |
Yes, technically there is drag that will vary but practically I would not worry about it if speed is set properly with a quality table like yours that appears to have a massive platter. The drive mechanism combined with inertia of a heavy platter rotating should make any variable stylus drag effects insignificant practically I would expect.
If it does not sound good or good enough for some reason, I would look for a problem elsewhere before worrying at all about this. If it sounds good enough to you, then just enjoy and don't sweat any details that do not matter.
Also a good point above to make sure that the record itself is not the culprit with a speed variation issue. Try looking head on at the cart as it tracks near the outer edge and try to detect any cyclical lateral motion as the record spins. That is the indicator of an off-center cut record that will likely produce speed/pitch/other sonic variations as it rotates that may or may not be audible depending.
TO eliminate all nasty potential snafus with vinyl playback, which was invented over a century ago, go digital. Nowadays, jitter is practically the main noise related issue to deal with and technology is to the point these days where that can be easily rendered a non issue with most any decent digital source. With noise issues practically non existent, all you have to worry about is finding the DAC that sounds good to you. SOme can even come pretty close to sounding like vinyl depending! |
..just for the halibut, I checked the speed of my VPI Superscoutmaster/Rim drive with and without the arm playing the record. I put on a record with a wide dynamic swing, and the hash lines of the strob remain in place...not moving forward or backward no matter if the record was played or not. Id be interested in the results of a belt drive, and a direct drive table if anyone with those pieces should be inclined to test them. |
If you search the forums you will find that all 'tables, regardless of drive choice, have to deal with stylus drag. Don't take my word, search. It has been reported by several designers/manufacturers. Also, as several designers have schooled me, there is no such flywheel effect from heavy platters that compensates for this. |
IT's been awhile, but with many older belt and DD tables from the 70's, back when I dealt with many, I do not recall the strobe indicating any measured slowdown in speed with record playing versus not with units in good condition. WIth units with worn or dirty belts, measured speed fluctuations with the strobes were often apparent and resolved with a belt change or good cleaning. I recall many of these did use servo motors of various types. |
"Also, as several designers have schooled me, there is no such flywheel effect from heavy platters that compensates for this. "
Its basically inertia. A heavier mass in motion will require greater force (friction in case of stylus tracking a record)to change speed than otherwise.
That's why I would expect greater mass platters in motion to be less susceptible to small changes in drag/friction as the stylus tracks than otherwise.
ALso I suppose higher tracking force would result in greater drag/friction than less tracking force, so of course as in most things it all depends. Drag/friction is a fact but how significant it is is more up to debate I suppose and could vary widely case by case. It all depends....
For me, if the speed measures as accurate an stays that way and I do not hear any ill effects, I would not worry about it.
Of course, that will not stop some who really really care from fretting...... |
Yes, a platter does store energy. Apparently, that alone is not enough to counter stylus drag. |
My Final Audio TT has a 19kg platter and very sophisticated motor drive, basically a huge AC motor driven by oscillator preamp and power amplifier which reconstructs sine and cosine waves for the motor and provides precise adjustability for both speed and torque applied to the motor.
As Halcro alluded to above when setting speed, I have to do that with the stylus in the groove.
Once set though it is very stable. In recent tests with the Timeline and KAB there was no speed change from heavily modulated passages both inner groove and outer groove.
Arm and cartridge were Naim Aro/Koetsu Black tracking a 1.8g |
Andrew,
I have checked my speed on my BN with a digital readout through my computer using a program that is free called iSpectrum. What I do is play test frequencies and checked the Waterfall plot and it is spot on. My biggest factor is the belt. They need to be replaced when they get old otherwise you get a sling effect. But this has been by ear. I have excellent speed stability which I can watch on a screen. I don't use a strobe but instead the computer to set my speed. Seems to match the strobe though. Once set it stays put. I have checked it often and my speed stays steady. |
Stringreen, If you check the other, older thread on speed stability, you will find many reports from many owners of results for many different kinds of turntables. Most were using the Sutherland Timeline as a criterion for speed stability. The sentiment was that the Timeline is superior to what is probably the best of the strobe devices, the KAB, in the sense that the Timeline could show speed errors where the KAB showed none. A disturbing number of tt's were unstable even with no stylus drag factor added, using the Timeline. That's why this thread is completely redundant. |
I'm not sure the discussion is staying on topic. The fact that a platter slows when the stylus is in the groove is not the same as what as referred to as stylus drag. As I understand it, I don't think it has ever been measured quantitatively. |
The problem I envisage with the timeline is that if there is a regular (emphasis on regular) slowing down and speeding up of the platter between flashes the timeline will show perfect speed where the reality in realtime will be very different....a bit like the teacher who checks on a class every 2 minutes and sees a class of perfect angels but as soon as he/she goes out of the room the kids start running amok.
I like the idea of the Feickert app better BUT, in playing a steady tone on the test disc there is no way to really test differences in groove modulation and it's effect on stylus drag.
An experiment for those of you with multi-arm tables would be to play an LP with heavily modulated grooves with one arm and then have the 7" (3150Hz tone) Feickert disc sitting on top of the LP being played at the same time by the other arm. Obviously with only the test tone selected to play through the speakers using the app you could see the exact effects of stylus drag in realtime.
My own observation is that a centre hole that is even a tiny bit off centre (most records and IME especially modern 'audiophile' repressings) will cause audible pitch variations that totally SWAMP inherent differences between turntables. In testing my own turntables(both belt and direct drive)with the Feickert app this was certainly the case. |
The fact that a platter slows when the stylus is in the groove is not the same as what as referred to as stylus drag. That is how I define stylus drag. What else would it be?? |
Stylus drag is defined by the coefficient of friction between the stylus and the vinyl groove multiplied by the normal force (tracking force) of the stylus. I found some old technical papers that measured and evaluated the coefficient of friction of vinyl records comparing different vinyls as well as cleaners and lubricants. Surprisingly, the coefficient of friction can vary quite a bit. They showed numbers ranging from 0.2 to 0.4. Multiply that by your tracking force, eg. 2 grams and the stylus drag can range from 0.4 to 0.8 grams. That drag is what generates the skating force component on the tonearm. So your anti-skating setting is an indicator of just how much stylus drag you have- less bearing friction in your tonearm. As an aside, if your tt sounds better with no anti-skating applied, then perhaps the tonearm bearing has some significant friction.
As for speed control: I have shown some calculations in other threads for information and inspiration purposes. Observations with the timeline show that the speed shifts on some tt's when the needle is dropped onto the record. That doesn't mean it is a bad tt. Any external force applied to a platter must be reacted to by the motor/speed control system. Dropping the needle onto the record can add about 0.011-0.021 in-lbf (120-240 g-mm) of torque to the platter. How much that changes the speed, if any is dependent entirely on the tt.
So let's say someone using the timeline with a 500mm radius to the wall observes a 2mm shift in the red line when they drop the needle onto the record. At 500mm that is a 0.06% change or 0.02 rpm shift. If you were playing a 3150Hz test tone, that would cause a 1.9Hz change. Now what I thought I read was that the red line on the wall shifted one time as the needle hit the record but then did not drift while playing the record. What is wrong with that? So the speed shifted ever so slightly due to the torque change. The motor/control system compensated and the record platter speed remained stable afterward. Seems fine to me. The timeline accuracy is good to three decimal places and almost all turntables are good out to two decimal places. Record runout is good only to one decimal place. Ref my calculations in the other thread. I can hear record runout. That is the real problem. I cannot hear my turntable's 0.02%/0.03% Wow and Flutter- not even in the soundstage or other subtle cues. And my analog soundstage is superior to CD. |
Tonywinsc,
Good stuff! Thanks for adding some well thought out metrics to the discussion!
If any specific turntable is able to maintain speed adequately when a record of mass N (N would vary from record to record) is placed on the platter, isn't it reasonable to think that adjusting for stylus drag as well once that comes into play as well is not a problem? |
As far as stylus drag's affect on speed control, let me also explain that platter mass is part of the entire speed control system. The speed control system is designed around the motor and platter inertia. Turntable designers, especially belt drive tt's use platter mass for dampening. Mass is commonly used for dampening. Your car engine and even your car body has mass dampers to minimize the vibrations that you feel and hear in the car. A massive platter requires more torque to control speed- and so belt drive tables use the small motor pulley and large platter outside diameter as a torque multiplier. A direct drive tt has a relatively low mass platter and as many on this forum will attest, also has excellent speed control. The speed control system is different for the low mass DD tables as compared to a belt drive table. DD turntables simply use a different control system for the lower inertia platter. DD turntables were originally designed for DJs so they could stop/start the platter quickly. My personal preference is the massive platter on a belt drive table because the mass doesn't just dampen torque variations, but also external vibrations from the floor and the air. The massive platter makes a great sink for the record. DD turntable users have to admit that they must work hard to isolate their DD turntables and platters from vibrations. |
Dear Toniwinsc, I nearly sold my Kuzma Stabi Reference (8kgr platter, two motors, one belt) in order not 'to stay behind'. Lucky me there was no Kenwood 07D available during
my 'intention time' otherwise I would make a mistake. Thanks for your 'grounded' explanation. I want mention the the packaging and posting of the 'monster from Slovenia'.
Regards, |
Hi,
As this is verging on speed stability, i'll post some new comments on the turntable speed accuracy thread.
Andrew |
****But it apprears Halcro has observed changes in speed with havily modulated sections of the record using the TimeLine. The key question is whether or not this small change is audible.****
Well, Halcro is correct, but I suppose that the key question is wether this "small" change is audible to YOU, and wether you are particularly sensitive to the effects of subtle speed instability effects. I disagree with Atmasphere that these changes are heard only as effects on sound staging as opposed to speed stability. Yes, there can be decreased sound staging stability, but also (and more important to me) varying degrees of instability in the swagger or groove of the music compared to the rock-
solid stability of live music; that is, assuming that the musicians were playing with a rock-solid groove.
To put this in a musical perspective look at some of Tonywinsc's great comments and stats:
****So let's say someone using the timeline with a 500mm radius to the wall observes a 2mm shift in the red line when they drop the needle onto the record. At 500mm that is a 0.06% change or 0.02 rpm shift. If you were playing a 3150Hz test tone, that would cause a 1.9Hz change.****
When an orchestra tunes to A:440 it is not uncommon for musicians to comment among themselves that the pitch being given (usually the oboe) sounds a bit high or a bit low. This, even though the digital tuner being used tell the oboist that the A he/she is playing is a true 440. What is the point? That the trained ear can hear subtle pitch changes that even the TYPICAL PORTABLE digital tuner can not identify. Now, consider Tonywinsc's comment, and I realize that the comment doesn't address the effects of heavily modulated passages on stylus drag. A change in pitch of 1.9Hz is easily audible. Orchestras make the choice to tune to A:440 or 441, 442, etc. for very real, and musically important reasons. Additionally, players are constantly making minute changes in their respective pitch centers. So, when one considers that due to the mechanical nature of LP playback a change in speed stability means a change in pitch and a change in the musical impetus of the music, it is not difficult to understand how stylus drag can be an important issue. Now, where we choose to try and perfect our very imperfect sound systems, and which of these imperfections we are each most sensitive to is a very personal matter, but there is no doubt that the music is very vulnerable to all these effects. |
I had used my little strobodisc for years on my turntable. When I used the 3150Hz tone and the iPad app, I found that my speed was low by a few Hz. I didn't hear it as a pitch change, but as a rhythm and pace improvement. I'm hearing all of my records as new just from getting the speed dialed in correctly. That was a learning experience; don't rely on the little stobodiscs. I hear a pitch variation only when playing a pure sinewave. The record runout causes a small but noticable warbling in the pure tone. Improving record runout (filed the hole out and centered the record on the platter) directly reduced the pitch variation. |
It occurred to me re-reading some of these threads that no one has mentioned some turntables have closed loop speed control systems while the rest are open loop. That means if you put your finger on the rim of the platter ever so slightly just to add some drag and you hear/see the speed drop and stay low, then your tt is an open loop speed control. A closed loop system has a speed sensor and the control system will add/subtract torque as needed to maintain the set speed. If you touch the rim of a closed loop table you might see/hear the speed change momentarily but then correct itself. My turntable is open loop. I have a speed dial to adjust the speed and I adjusted it while playing a record, but any changes in load on an open loop turntable will affect the speed of the platter. If the friction varies from one record to another, then our open loop tt's will have slight variations in speed. Probably too small to notice, but it is there. I don't know which tables are closed loop design vs. open loop, but I think just about all DD turntables are closed loop. The timeline device probably seperates out the closed loop tt's from the open loop systems. That's because the closed loop tt's are going to maintain a constant speed by adjusting torque as the needle is dropped onto the record and as the friction/drag varies while playing the record. Again, I don't necessarily hear it as a pitch change but more as rhythm and pace. |
Tony, Thanks for your very informative comments on this thread. I was not aware of difference between open and closed loop systems. According to the manual, my SME turntable uses a closed loop speed control system. Perhaps it is one of the few belt-drive tables that does. I've found the speed is constant and stable, but I've only tested with the KAB strobe. I plan to use a digital tachometer and perhaps also try a test tone. |
Probably my own "dictionary". :-) I think of "stylus drag" as the potential for minute changes due to congested passages, rather than just simply friction, which is more noticeable on sustained notes. The kind of changes those of use who use mylar belts hear between a belt with the metal still on, and one that has had it removed with etching solution. Same cartridge and feedback controller, but there is more clarity through congested passes due to improved drive, contact, etc. |
Peterayer, the SME table embodies to me, everything a turntable should be- massive platter, state of the art speed control, great sound and great looks. If I had the means I'd let SME spin my records. Happy listening. |
I assert that small changes in speed caused by stylus drag can be heard. Frogman is heading in the right direction.
I would also agree with Tonywinsc that pace/rythm is another way to gauge the effect of speed stability. In my experience, a table which is less sensitive to speed variation caused by stylus drag during heavily modulated passages tends to preserve both the dynamics and timberal aspects of crecendos and dynamic passages.
I believe it also preseves the detail of micro-dynamics...and i think this is where Atmasphere and Mosin may be referring to.
Andrew |
Tonywinsc,
The closed loop open loop is not as simple as implied. They are inextricably linked to the motor technology used, AC or DC.
DC motors require a feedback or speed control system to actually run. They will not run without it unless you use a computator type DC motor.
Now it is my understanding that AC motors only require the frequency to be locked in order to run at the correct speed.
The fundamental difference as I understand it is that when changes in load, eg stylus drag variations, occur, the DC motor does not respond and the speed will vary - hence the need for a feedback or speed correction system.
However when there is a change in load, eg stylus drag variation, on a synchronous AC motor, the AC motor will self correct as the motor speed is determined by frequency, not load.
Now most, but not all direct drives are using DC motors, the big exception being the Denon DP100. There appear to be 2 camps on how the speed is maintained. I believe the L07D & Halcro's Victor have soft recovery speed control, whereas others such as the Technics have a faster recovery. I think this explains some of the sonic differences between these DD's. In my view the LO7D and Victor 101 are simulating an AC motor in how they respond to load variations.
You cannot compare DC and AC motor driven turntables as such because all DC motor driven TT's have speed controllers. Unfortunately in my view most TT's that use AC motors have little or no speed control and rely on incoming mains frequency being stable which is simply not true. Examples of this are the VPI Classic series, which even at the US$6000 price point, they only have 1 capacitor between the mains and the motor to split the phase. There is no provision for mains frequency fluctuation.
The only conclusion that I can see is that mass in the platter will assist in maintaining constant speed under load variation in both AC & DC motor applications.
I note that in a recent post Atmasphere checked a cutter lathe for speed accuracy whilst cutting. The formula here was massive motor, way in excess of domestic TT's coupled with 'direct drive' via driveshafts not connected to the bearing and by implication a massive gearing down from motor speed to platter speed.
Having overhauled and upgraded my crossovers recently I have been re-listening to a lot of piano music lately and it is clear that, in my particular TT/system, there is no instability induced by stylus drag, but there is on eccentric records, this now seems to be the larger issue, as you have suggested. Hope your needle file is still doing the business.
|
Dover,
If belt drive DC motor driven TT's use a closed loop, why do Halcro and I observe that the speed changes on the Raven AC TT with the needle in the groove?
Andrew |
Aoliviero -
I can only surmise that the power supply and feedback mechanism of the Raven AC is inadequate if it cannot hold the speed. I certainly wouldn't be happy spending that sort of money on a TT and it not being able to hold the speed accurately whilst playing. Have you asked the manufacturer ? |
Even in a closed loop system some speed variation will occur. An error must exist between the setpoint and actual before the system will react. A certain deadband around the setpoint exists or else the sytsem would hunt, ie. cycle about the setpont which would be much worse. That is the theory. I do not know the details of the actual tt design. It is analogous to the cruise control on your car. You are at a set speed and come to a hill. Notice the speed drops one or two mph as the engine increases torque to compensate. The same happens as you go down a hill; the speed increases one or two mph as the engine torque decreases. But in the case of our high end turntables, I think the designers have the platter speed held to within 2 decimal places under moderate load variations due to needle drag. |
Where is the feedback mechanism in a Raven turntable? |
Bottom line is measuring rotation speed is not rocket science. ANyone who is in question how well their table maintains proper speed should be able to measure and confirm as needed and put the issue to rest.
"How does one measure "rhythm and pace" again? That is totally subjective, which is fine if that works for you but has no real meaning or use to others accordingly.
I'd be willing to bet that practically imperfections in record manufacturing, warping over the years, etc. is a much bigger real issue than stylus drag with most any well designed and executed turntable. Of course, we have little control over that, so probably more practical to fret the details of stylus drag assuming those who created our SOTA turntables did not?
My records sound fantastic, so I see little value for me personally. |
I have an older VPI MKIII with the stand alone motor assembly. Stylus drag is exactly what tells me when my belt is getting too stretched out and the motor needs to be re-positioned.
It is especially apparent when there is a loud sustained line (kraftwerk or other electronica). The pitch sags when the volume increases. This is the 9lbs platter btw. |
In any motor, AC or DC, if the load increases the current in the motor will increase too. This provides a feedback mechanism that functions well even on open loop systems. For an AC motor that runs off the line, if the motor has any torque at all it will be able to compensate for stylus drag with ease (the voltage of the AC line contributes to torque while the frequency determines the speed) as it might just draw a little more current to stay on speed and with the AC line, there is essentially an infinite supply.
With a DC motor (open loop- not sure if that is the right term as many DC motors have internal electro-mechanical speed controls) the limitation *can* be the stability of the power supply. There are a lot of variables here depending on design so calling out generalizations can be risky. |
I do agree with Dover......that the better your TT becomes at maintaining accurate and constant speed under heavily modulated passages.....the more you tend to hear the imperfections of the record pressings such as off-centre holes?
For every solution.....another problem is revealed :^( |
I call it record runout. Runout is the periodic side to side motion that can be seen in the record and even the tonearm as the record is spinning on the platter. It is caused by the centerline of the record hole being offset to the centerline of the record grooves. When it is visible with your eye and in many cases even the tonearm is seen swinging side to side, that is near the maximum tolerance; but still within tolerance! In the other thread I posted the industry tolerances for the center hole position and its impact on WoW & Flutter. The higher quality pressings I found, have pretty low runout but some old Columbia pressings from the 70s are probably the worse that I have seen. Ironically, my stereo test record had pretty bad runout which I corrected by filing the hole out; but now I have to center the record on the platter. |
