Idler wheel "magic"...
- Thread starter DominicL
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dnewma04
The Healer
Are you talking about the video linked earlier in this thread?
dnewma04
The Healer
I would never argue that it's significant, I might not even be convinced it's audible, however, any drag you add will have some effect, no matter how miniscule. Even an engineer should be able to figure that out.
My point about drag is that having bearings with near zero friction isn't necessarily a good thing for stability. With some motor types, adding eddy current brakes leads to significantly better damping and improves speed stability.
Arkay
Lunatic Member
There is a simple answer to this. Get at least one of each! Then you can thank everybody instead of hating them, still "in the most loving way"!
nashvillebill
Super Member
I think we all can agree: we want our platters spinning at an exact 33-1/3 RPM (or 45 or 78 or whatever).
There's so many things that can cause wow and flutter though. First, are we even sure it's occurring? Take, for example, a DD quartz-locked TT with a built-in neon strobe that is running directly off of the AC line. Somebody could look at the dots on the platter and say "hey those dots are not staying constant! This direct-drive stuff is messed up!" When it's entirely possible (or probable) that the frequency of the incoming AC from the power company is drifting (evidently they've relaxed the stnadards a little lately,but that's another topic). So the platter is stil spinning correctly, but the measurement tools are inaccurate. The countermeasure is to make a neon strobe that does not depend on the AC line frequency (but then...is THAT circuit truly constant frequency?)
Then of course, the motor speed can and does change. Using a straight AC motor, whether induction or synchronous, that's dependent on AC frequency. An induction motor also operates at a "slip angle" which means it's always "dragging" so any changes in its drag, whether from the motor bearings, idler/belt,or load, also affects the motor speed. Motor bearings can and do change in their frictional drag, even if a ball bearing motor. Oil heats up and bcomes less viscous. The ball bearings don't run smoothly but can "bunch up" slightly and then relax. These effects are not insignificant, they were discovered back around World War II when gyroscopic compasses were being developed (leading to air bearings). The motor bearings can have drag measured in whole inch-ounces and the variation in drag from the motor bearings can also be very large.
But I have not addressed a factor that should be considered: unless it's a direct drive turntable, there is a speed reduction mechanism in play. For a belt drive, a small motor pulley drives a big platter. Similar with an idler wheel, the motor spindle is small and its surface speed is applied to a much larger platter. This speed reduction also means that the torque supplied by the motor is being greatly magnified. A 1750 RPM motor, going to a 33-1/3 platter, is roughly a 55 to 1 reduction in speed but a 55 to 1 magnfication in torque. This speed reduction and torque magnification also goes the other way though! Say the load on the platter changes by a whole 1 inch-ounce...it's reflected load change on the motor is 1/55th of that, or less than 0.02 inch-ounce! That is a very very tiny number.
So, we have a stylus pressure which cauases 0.04 inch-ounce of drag. (That's easily calculated, stylus pressure times coefficient of friction times radius, the only guess is the frictional coefficient) Say it varies plus or minus 50%, from 0.02 to 0.06 inch ounces. This is a variation of 0.04 inch-ounces. But its reflected change, back on the motor, is 1/55 of that or .0007 inch ounces if I haven't slipped a decimal.
THAT is extraordinarily insignificant. Compared to variations in motor bearing drag, or the idler wheel or belt drag, it is so far under the radar that it isn't even observable.
There's so many things that can cause wow and flutter though. First, are we even sure it's occurring? Take, for example, a DD quartz-locked TT with a built-in neon strobe that is running directly off of the AC line. Somebody could look at the dots on the platter and say "hey those dots are not staying constant! This direct-drive stuff is messed up!" When it's entirely possible (or probable) that the frequency of the incoming AC from the power company is drifting (evidently they've relaxed the stnadards a little lately,but that's another topic). So the platter is stil spinning correctly, but the measurement tools are inaccurate. The countermeasure is to make a neon strobe that does not depend on the AC line frequency (but then...is THAT circuit truly constant frequency?)
Then of course, the motor speed can and does change. Using a straight AC motor, whether induction or synchronous, that's dependent on AC frequency. An induction motor also operates at a "slip angle" which means it's always "dragging" so any changes in its drag, whether from the motor bearings, idler/belt,or load, also affects the motor speed. Motor bearings can and do change in their frictional drag, even if a ball bearing motor. Oil heats up and bcomes less viscous. The ball bearings don't run smoothly but can "bunch up" slightly and then relax. These effects are not insignificant, they were discovered back around World War II when gyroscopic compasses were being developed (leading to air bearings). The motor bearings can have drag measured in whole inch-ounces and the variation in drag from the motor bearings can also be very large.
But I have not addressed a factor that should be considered: unless it's a direct drive turntable, there is a speed reduction mechanism in play. For a belt drive, a small motor pulley drives a big platter. Similar with an idler wheel, the motor spindle is small and its surface speed is applied to a much larger platter. This speed reduction also means that the torque supplied by the motor is being greatly magnified. A 1750 RPM motor, going to a 33-1/3 platter, is roughly a 55 to 1 reduction in speed but a 55 to 1 magnfication in torque. This speed reduction and torque magnification also goes the other way though! Say the load on the platter changes by a whole 1 inch-ounce...it's reflected load change on the motor is 1/55th of that, or less than 0.02 inch-ounce! That is a very very tiny number.
So, we have a stylus pressure which cauases 0.04 inch-ounce of drag. (That's easily calculated, stylus pressure times coefficient of friction times radius, the only guess is the frictional coefficient) Say it varies plus or minus 50%, from 0.02 to 0.06 inch ounces. This is a variation of 0.04 inch-ounces. But its reflected change, back on the motor, is 1/55 of that or .0007 inch ounces if I haven't slipped a decimal.
THAT is extraordinarily insignificant. Compared to variations in motor bearing drag, or the idler wheel or belt drag, it is so far under the radar that it isn't even observable.
dnewma04
The Healer
So, as established 7-8 pages ago, the drag from the stylus does play a tiny role and the debate remains, can you hear it? Both sides have their minds made up, and some of us in the middle are still trying to come up with an explanation for the sound differences. I'm leaning heavily towards the various resonances in the system playing the biggest role in a turntables sound.
mfrench
Addicted Member
Bill,
What would you suggest then, given the video footage of speed reduction, and my own experience witnessing the same? I've personally conducted this "experiment" with my own equip't (strobe mat and battery powered strobe light), on my own gear. I repeatedly dropped the needle in multiple places on the record, and witnessed a slow down as revealed by the numbers drifting. It was in such short duration that it took multiples times for me to become aware of any change, and only revealed itself when I had my wife assist me with the needle drop, so that I could devote 100% of my attention to the stroboscopic devices. It was far too short to try to formulate a percentage of variance, but you could see it by eye, with a slight jerking of the numbers away from steady - slight. The only factor that changed was the application of the needle to the record.
The decks are extremely simple decks, idler drives without drive circuitry. One being a DC powered motor, not prone to the AC sync motor/supply issue, that has a controller that dead-locks to speed. The DC deck is such a torque monster that it never showed variance. The AC motors did show variance, but as mentioned, in less time than an eye blink, were back to speed.
I trust my ears and my eyes far more than numbers.
What would you suggest then, given the video footage of speed reduction, and my own experience witnessing the same? I've personally conducted this "experiment" with my own equip't (strobe mat and battery powered strobe light), on my own gear. I repeatedly dropped the needle in multiple places on the record, and witnessed a slow down as revealed by the numbers drifting. It was in such short duration that it took multiples times for me to become aware of any change, and only revealed itself when I had my wife assist me with the needle drop, so that I could devote 100% of my attention to the stroboscopic devices. It was far too short to try to formulate a percentage of variance, but you could see it by eye, with a slight jerking of the numbers away from steady - slight. The only factor that changed was the application of the needle to the record.
The decks are extremely simple decks, idler drives without drive circuitry. One being a DC powered motor, not prone to the AC sync motor/supply issue, that has a controller that dead-locks to speed. The DC deck is such a torque monster that it never showed variance. The AC motors did show variance, but as mentioned, in less time than an eye blink, were back to speed.
I trust my ears and my eyes far more than numbers.
gusten
Addicted Member
I agree, except the coefficient of friction is more 0,2-0,3, but it doesn´t matter as a whole.
What´s being argued as very significant (by some), is stylus drag not entirely being dependent on friction, but dependent on loud passages on the record, where the platter will slow down, instantaneously, and after that it will take some time for the speed to recover. And because this is stated as a fact, this argument is used to explain why an idler is better.
gusten
dnewma04
The Healer
Just for the sake of clarity, I'm not part of the group that things it's significant. I would say that it's real, and at the same time, very insignificant.
DominicL
Active Member
Originally Posted by marc mc
The issue of rumble keeps coming up with discussions about idlers. I thought I would add another quote from Arthur on this issue since sound floor is his obsession.
My most important observation is that the Lenco did not fail in those areas where I originally expected it to fail. Based on my prior experiences with idler-drives, I was concerned that I may hear "rumble", and even if the rumble was no longer itself directly audible, I still expected the higher sound-floor of the Lenco to obscure low-level musical information. As an audiophile whose entire system was designed to have the lowest sound-floor theoretically possible, any component that noticeably compromises this area would be unacceptable to me, regardless of its other virtues.
As it turned out, the Lenco's sound-floor was basically as low as the Forsell's (which has an air-bearing platter). In fact, I couldn't distinguish them. Since the Forsell had the lowest sound-floor I ever experienced, the Lenco's (highly welcome) achievement in this area is both surprising and unexplainable (at this time). In any event, with this highest of hurdles successfully breached, the next challenge was the Forsell's neutrality and/or lack of coloration/character. Once again, to my surprise, the Lenco matched the Forsell in this critical area (especially for those serious audiophiles who don't want a relentless "editorializing" or "bias" in what they hear). Further, in the area of transparency, the two turntables were also indistinguishable to me. In short, the two turntables sounded very similar in "the basics", which is something I hadn't experienced before at this high level.
Marc mc
+1! Less rubber =less rumble. No need to ask how I know!
I see this thread took a turn for the better. Lots of good info. I'm back again. I see a lot of "self opinionated and not afraid to show it" folks are making sense. Digging in now!
The issue of rumble keeps coming up with discussions about idlers. I thought I would add another quote from Arthur on this issue since sound floor is his obsession.
My most important observation is that the Lenco did not fail in those areas where I originally expected it to fail. Based on my prior experiences with idler-drives, I was concerned that I may hear "rumble", and even if the rumble was no longer itself directly audible, I still expected the higher sound-floor of the Lenco to obscure low-level musical information. As an audiophile whose entire system was designed to have the lowest sound-floor theoretically possible, any component that noticeably compromises this area would be unacceptable to me, regardless of its other virtues.
As it turned out, the Lenco's sound-floor was basically as low as the Forsell's (which has an air-bearing platter). In fact, I couldn't distinguish them. Since the Forsell had the lowest sound-floor I ever experienced, the Lenco's (highly welcome) achievement in this area is both surprising and unexplainable (at this time). In any event, with this highest of hurdles successfully breached, the next challenge was the Forsell's neutrality and/or lack of coloration/character. Once again, to my surprise, the Lenco matched the Forsell in this critical area (especially for those serious audiophiles who don't want a relentless "editorializing" or "bias" in what they hear). Further, in the area of transparency, the two turntables were also indistinguishable to me. In short, the two turntables sounded very similar in "the basics", which is something I hadn't experienced before at this high level.
Marc mc
+1! Less rubber =less rumble. No need to ask how I know!
I see this thread took a turn for the better. Lots of good info. I'm back again. I see a lot of "self opinionated and not afraid to show it" folks are making sense. Digging in now!
ejman
Super Member
Not at the lofty levels of equipment that you mention but in my own set up I have a Lenco L75 in a modified plinth along side a Rega P3 both feeding through a Mapletree preamp and Conrad Johnson amp to Magneplanar speakers. I also have an HSU sw 12va subwoofer that I've tested in my own room with a sound meter to have a fairly flat response down to 20 HZ and I hear no rumble - either from the Lenco or the Rega.
Pio1980
AK Member
It's fairly simple to establish drag on a BD with adjustable speed by zeroing a strobe disc with it cued up and checking it cued down. For dynamic drag, again, it will be a relatively slow process overcoming the momentum of the platter during a prolonged heavy passage with a subsequent pitch rise of the sustained decaying note afterward, a fixed-pitch instrument like a piano is particularly telling when this occurs. If you never hear this then the TT probably doesn't have a problem with dynamic drag pitch droop.
While I'm referring primarily to platter speed rather than motor speed, it is well-known that some motors free-wheel at a somewhat higher speed than when loaded. Some will stabilize to load at a certain threshold until the torque is overcome by sufficient further drag and the speed again drops.
While I'm referring primarily to platter speed rather than motor speed, it is well-known that some motors free-wheel at a somewhat higher speed than when loaded. Some will stabilize to load at a certain threshold until the torque is overcome by sufficient further drag and the speed again drops.
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Pio1980
AK Member
Quartz-clocked DD Strobes are almost always keyed to the clock and not line freq, to confirm PLL locking. Earlier DD tachometer regulated TTs used line freq neon lamps to ref exact speed setting and they were somewhat less stable than their quartz-clocked offspring aside from the issues being discussed. Either one has to sense error to correct rotational rate, the relationship of the time constants in the various parts of the system including torque-to-platter mass ratio determine how smoothly it takes place and it's audible detectability.
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gusten
Addicted Member
What I can say so far, is that I have not been able to detect any difference in platter spin down time between very highly modulated grooves and silent grooves. And this is for a period of more than 25sec, which in music context is very long, I think.
So even if stated as a fact that platter is really slowing down, I have yet to see it. And this is for a fairly light platter.
I would be interested in others trying to measure this.
gusten
So even if stated as a fact that platter is really slowing down, I have yet to see it. And this is for a fairly light platter.
I would be interested in others trying to measure this.
gusten
marc mc
Super Member
All a person has to do to confirm the ideas that are theorized in this thread is hear a reference Lenco. That's it.
I learned more about what vinyl playback is, what it's capable of, and what all the other tables I have heard were doing wrong in 2 albums than I had in 25 years. I can say the same for my Delta 15 speakers.
When you hear something right. It makes the wrong far more obvious.
BTW gusten, these things are microscopic. What I think happens is the Lenco gets everything right in the area of pace and the accumulative effect is therefore easily detected. The same for my Delta speakers. With these 2 products what they do better is easily detected with only ears.
Marc mc
I'd be astonished if there was a clearly measurable difference, or an audible one, assuming blind testing.
Gusten, Marc mc (I know is goes against your subjective bias) and anyone else who is interested, have a look at the 'Turntable speed analysis' thread over at pinkfish. Very interesting figures and discussion, also
Gusten, Marc mc (I know is goes against your subjective bias) and anyone else who is interested, have a look at the 'Turntable speed analysis' thread over at pinkfish. Very interesting figures and discussion, also
Apoplectic
Well-Known Member
I've got an idea. Someone with a super slow motion camera can tell us whether stylus drag is significant or not. Put a dot on the outside of a fairly bass heavy record and another dot on the top of the turntable. Have the platter spin without the stlus on the record. Starting when the two dots meet count 100 revolutions. This should take exactly 180 seconds, if not adjust pitch so it does. Next do it with the stylus in the groove. Does it take any longer than exactly 180 seconds? If so then stylus drag is real, ad depending on how much of a difference, it may be audible.
Unfortunately money and space constraints inhibit my audiophile aspirations, but c'est la vie.
There is a simple answer to this. Get at least one of each! Then you can thank everybody instead of hating them, still "in the most loving way"!
Unfortunately money and space constraints inhibit my audiophile aspirations, but c'est la vie.
dnewma04
The Healer
No, it's not that simple. I've heard heavily modded Lenco's. They were nice, sure. Perhaps even very good. I'd pick one up if I ever found a deal on one, in fact. However, hearing them never made me think that I had just encountered something I hadn't heard with direct drives and belt drives.
I think it would be interesting to hear a Teres tape drive system compared to their idler and their new DD motor.
marc mc
Super Member
Maybe I should have stressed a person requires the hearing. I was talking to a guy the other day that told me all speakers sound pretty much the same to him. While one of my sons can nail any change I make in one of my systems in seconds without the slightest hint from me. He's right every single time, instantly.
You said earlier that as you get closer to the top you felt gear is harder to tell apart. And maybe for you that's true. Maybe as the bigger problems are taken care of by good designs you can't hear the subtle differences. Audiophiles assume everyone hears or does not hear like they hear. I mean I don't know, maybe you worked around loud equipment or shot firearms all your life.
Arthur got me into audio, and I remember that while we listened to top end gear I did not have the vocabulary for subtle things I noticed, he still knew and agreed with what I was saying. I was with a friend the other day that owns some Tannoy Westminsters and he was laughing as I described things these speakers did. All were very very subtle refinements in sound like pace, composure, simplification, contrast and scale. He told me these were also his favorite things and they were also not things everyone who hears them notices.
We are talking about things that are microscopic in size and audibility. Maybe not everyone can hear it? Maybe that's how simple it is?
Marc mc
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