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Measuring "Stylus Drag" with the RPM Speed and Wow app

33.33>33.40

I recently spent what I considered way too much for a Lenco L75S. But I was tired of waiting to score a bargain; and I figured life is too short; and a nice unit came available on my favourite audio website. Sold!

I won’t start another thread about how the idler drive system is the absolute best turntable system; instead I will just report that even before improvements (DIY plinth, upgraded arm), the stock Lenco sounds very fine indeed. Talk about speed stability! Talk about defined beginnings of musical attacks! Talk about lack of smear (Did I mention speed stability?)!

And it has got me thinking: maybe there is something to this concept of the importance of "stylus drag", and its effect on vinyl playback.

Which also got me thinking: why don’t we start measuring this phenomenon (seeing as it is one of the biggest issues a turntable has to deal with - after speed stability).

So then I thought, "why not use the RPM Speed and Wow app, and take readings with a record playing, and without?

And have done just that. I understand the app is considered "not accurate", but I would assume it is "consistently not accurate", or thereabouts (can anyone with more technical knowledge of a phone’s gyroscope corroborate or deny this?). And since it is a RELATIVE PROPORTION we are looking for, this app might just work for all of us to create a database of "Stylus Drag" relative measurements for all of our turntables.

With a chosen track, my Lenco’s readings are:

Playing a record: 33.33 (0.03% W & F)
Not playing a record: 33.40 (0.04% W & F)

The difference on a Lenco is 0.07. I call this figure the "Stylus Drag Coefficient Number".

Next I will do readings for a Mission 775S, a Thorens TD160, and a Technics SL-D2.

Oh, the fun that can be had after rehearsing Mahler’s 9th Symphony, and drinking a couple of beers while listening to vinyl on a new-to-you turntable!

fusian
mijostyn's avatar
mijostyn
8,570 posts
 
While theoretically true there is an important variable that will differ from one table to the next and that is the inertia of the platter. The increase in friction heavy modulation would cause is transient and it takes a certain amount of time to change the rotational speed of the platter depending on how heavy the platter is. Short increases in friction will have little effect on a heavy platter. Longer increases will be countered by a good turntable's drive system. This is the reason most turntable manufacturers use AC synchronous motors. Any slowing of the motor causes an instantaneous increase in torque maintaining platter speed. 

fusian, if you want to be accurate about it you have to make a "puck" that fits on the platter's spindle just 2-3" in diameter so that your phone can lie flat over the platter. Then, you have to mark the phone and puck to index  the position of the phone so that you are putting it down in the exact same position every time. 
totem395
390 posts
 
Many threads regarding exactly what your talking about
a few years ago. Whats old is new again.

https://sutherlandengineering.com/products/timeline/
chakster's avatar
chakster
6,144 posts
 
Thanks Jonathan @jcarr for posting video in Russian :) This time only I can fully understand it without goodle translate or subtitles :) Interesting.


He’s using Soviet Melodiya test record and Soviet Corvette cartridge with elliptical tip (1.5g tracking force).
lewm
13,718 posts
 
The inertia of the platter, the torque available from the motor, the particular musical passage, the position of the stylus on the LP surface relative to the spindle, the cartridge, etc., etc. These are all factors that would influence any measurement of stylus drag. So to begin with, we would all have to agree on one particular LP pressing and on one particular passage on that LP surface. Then, since it is impossible for us all to be using the same cartridge, at least we could agree on one stylus shape for all of us. VTF Also affects friction.  These are all things that we would need to agree upon a priori to obtain data that are remotely comparable, and there’s more I haven’t thought of yet. But, Mijostyn, platter inertia is a variable that figures in to the result. Of course it would make a difference, but of course that is what we are looking for.
billstevenson
592 posts
 
At the risk of ruining everyone's fun it seems to me that the desired outcomes for this set of measurements could easily be overcome by the simple expedient of a simple listen.  If our ears can discern some sort of smearing or loss of detail, then the matter is resolved.  If not, then it does not matter.  One word of caution.  The OP mentioned lubrication via beer, and the music of Mahler.  I see no problem with the lube, but too much Mahler could obfuscate the veracity of the outcome.  ;-)
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