2. analog
  3. 151541-486

Stylus-Drag..Fact or Fiction?

Most audiophiles can't seem to believe that a tiny stylus tracking the record groove on a heavy platter could possibly 'slow-down' the rotating speed of a turntable.
I must admit that proving this 'visually' or scientifically has been somewhat difficult until Sutherland brought out the Timeline.
The Timeline sits over the spindle of the rotating disc and flashes a laser signal at precisely the correct timing for either 33.33rpm or 45rpm.
By projecting these 'flashes' onto a nearby wall (with a marker attached)....one can visualise in real-time, whether the platter is 'speed-perfect' (hitting the mark at every revolution), losing speed (moving to the left of the mark) or gaining speed (moving to the right of the mark).

RAVEN BELT-DRIVE TT vs TIMELINE 
Watch here how the laser hits the mark each revolution until the stylus hits the groove and it instantly starts losing speed (moving to the left).
You can track its movement once it leaves the wall by seeing it on the Copperhead Tonearm.
Watch how it then speeds up when the tonearms are removed one by one....and then again, loses speed as the arms are dropped.

RAVEN BELT-DRIVE TT vs TIMELINE
Watch here how the laser is 'spot-on' each revolution with a single stylus in the groove and then loses speed as each additional stylus is added.
Then observe how....with NO styli in the groove.....the speed increases with each revolution (laser moves to the right) until it 'hits' the mark and then continues moving to the right until it has passed the mark.

Here is the 35 year-old Direct Drive Victor TT-81 turntable (with Bi-Directional Servo Control) undergoing the same examination:-
VICTOR TT-81 DD TT vs TIMELINE 
128x128halcro
atmasphere's avatar
atmasphere
11,983 posts
 
Pardon me, but can we let this cogging thing go with respect to synchronous motors? Because its totally not a thing. Synchronous motors (seen in idler drives and some belt drive machines) are locked to the line frequency and don't really have power surges or the like regardless of line voltage.


Idler drives can work just fine if the turntable is designed fairly well. This is why some older vintage designs have a following- Lenco and Thorens (TD124) in particular.

If you look at the best of the vintage 'tables that have a modern following you will see one thing that they all have in common- a robust drive. This is true of belt drive machines- like the Empires, and direct drive machines like the Technics SP10, in particular the SP-1 MkIII which has so much torque its suitable for LP mastering lathe use.
I will gladly accept minor speed variation versus my tonearm hopping across the record when someone walks into the room.
@mijostyn
This can be solved with a proper stand. I have a custom Sound Anchors stand but what really did the job was placing the stand on a set of bearings which relieve side to side pressures caused by foot falls. I lived in an older house and this was a very effective solution to that problem! Sorry for the Off Topic bit...

richardkrebs
422 posts
 
Halcro. Thanks for posting the videos. I have seen tests like this before and the thing which startles is how quickly the platter slows down. All due to the drag induced by a tiny diamond thrashing about in a plastic groove. Others have said that a high moment of  inertia platter will save the day. Don't know what the inertia figure for the Raven is but the platter itself does look substantial, so it is reasonable to assume that it isn't a feather weight. 
A  high inertia platter simply changes the time constant for a given motor torque. Sure, its deceleration rate will be slower but it will also take longer to recover. There doesn't seem to be any free lunch here.
Also agree totally with atmasphere. "a robust drive" is a common thread through most of the collectable vintage TTs  
richardkrebs
422 posts
 
Wouldn't setting the speed with the arm lowered be, at best, a compromise?
What record do you choose? Surely the stylus drag is modulation dependant, so if you choose to set the speed at a 'medium modulation' level record, the platter will run fast some of the time and slow some of the time. This, purely dependant on what is going on with the music. Add in the radius where you lowered the arm and it becomes a lottery. 
lewm
13,373 posts
 
Ralph, In my understanding, cogging and synchronicity are two different things.  Cogging is a function of the number of poles; the rotor experiences a regularly irregular rotational force due to the naturally varying intensity of the magnetic fields produced by the stator.  The rotor is therefore constantly inconstant in its speed.  There is a regularity to it that is said to be audible to some, and that's "cogging".  The tendency can be ameliorated by using a stator with a lot of poles, the more the better. Coreless motors may do away with the issue altogether. (No matter how much I search on that last topic, I have never found a satisfactory treatise on the subject of coreless motors vis a vis cogging, but most talk about coreless motors as if they are free of it.)  On the other hand, an AC synchronous motor does lock onto the line frequency, and this can keep the speed steady, absent drag, etc.  But an AC synchronous motor could still exhibit cogging, if it is poorly designed with an inadequate number of poles.  Maybe Richard can comment on my thoughts.
halcro's avatar
halcro OP
2,664 posts
 
Hi Richard,
I hoped you would see this Thread...😃
the thing which startles is how quickly the platter slows down. All due to the drag induced by a tiny diamond thrashing about in a plastic groove. 
I first saw this demonstrated on a Transrotor FatBob Turntable which has an even heavier platter than the Raven, and the 'slowdown' was even more dramatic and faster.
I like you....was similarly 'startled' 🤯

I agree totally with your 'conundrum' about which record to choose to set speed with the stylus playing...?
Apart from massed symphonic performances with both highly and lightly  modulated passages....I think that Rodman's insightful and practical habit will work well.
RAVEN AC-2 TT vs TIMELINE

The question is.....how audible is this phenomenon in the 'real world'?
I can still happily listen to the Raven in my system although I can hear the differences in presentation on the Victors with complex orchestral works.
The Raven has a slightly more 'relaxed' sound and whilst we know from reading Peter Moncrieff's treatise.....the effects of 'Stylus Drag' are 'distortions' of the musical waveform.....there are many many more distortions (from cartridges, tonearms, headshells, turntables, speakers etc) that probably have greater consequences.

Whilst all this sounds 'gloomy' for those outside the vinyl/analogue 'True-Believers Brethren'.....none of it stops vinyl from sounding infinitely better than digital 😝👍
More to discover