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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
jtimothya
612 posts
 
The belt v direct drive battle has swung to and fro over many decades but is the tide finally about to turn for good in the favour of the latter?

Should anyone in 2019 really leave the vital matter of turntable speed control precision depending upon a rubber belt?

A rubber belt who’s main purpose seems to be an attempt to dampen and isolate motor vibrations at the cost of significantly measurable imprecision.

@cd318
The tide has turned.

Read Moncrieff's article part 1 article on the Rockport Sirius III
http://www.iar-80.com/page12.html
 
It thoroughly lays out the issues with belt drive and other drive systems with a view from several years back.  Those issues still hold today.

Then to get a perspective on where modern direct drive is today, read Roy Gregory's review of the Monaco 2.0 turntable.http://www.theaudiobeat.com/equipment/grand_prix_monaco_20.htm or a different take here:http://www.theaudiobeat.com/blog/grand_prix_monaco_20.htm  The stable speed accuracy of this table is stunning. 

While stylus drag cannot be denied (physics), there are ways to deal with it.

apologies to H for going off topic...
halcro's avatar
halcro OP
2,664 posts
 
Not off Topic JT...😃
I read that Peter Moncrieff article 10 years ago....in fact it has a permanent place on my Desktop.
I even wrote to Peter (RIP) to ask him where I could find Part II of the article....but he never got around to finishing it 😥
As you say....
It thoroughly lays out the issues with belt drive and other drive systems 
So thoroughly (and understandable) in fact....that it should be required reading for every 'wannabe' turntable designer and every 'practicing' turntable designer who I'm sure, have little in-depth knowledge of the science and physics espoused in that article 🤯
jnorris2005
185 posts
 
I have a Luxman PD-277 direct-drive turntable and have seen the strobe slow down very slightly when the stylus is dropped.  The effect is more noticeable at the outer edge of the record.
rodman99999
5,981 posts
 
@tablejockey - The Denon DD table(DP75), I purchased in 1980(still have it, in a closet), has a Quartz referenced/AC servo motor speed control system, that reads 1000 precisely recorded pulses, from what amounts to magnetic tape, imprinted on it’s platter’s circumference, via a tape head(like in a cassette deck or RTR). That particular tech’s been out there, for decades. I’d be using the new version of the Roadrunner/Falcon system, with my VPI, if it didn’t require a redesign of my homemade SAMA(remachining, to fit their motor). I waited too long, when the original Phoenix pieces(excellent concept) were available(then: poof, gone). That system would have worked, with my VPI motor. Not that I’ve had any speed issues anyway. Easy to adjust, via my SDS. Long as I keep the belt talced; I measure/hear no drift or pitch change, whether with my LASER tach or strobe .
rodman99999
5,981 posts
 
@tooblue :   +1
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