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

Showing 5 responses by lewm

Yes, the tachometer will show you the frequency of speed correction that is needed to maintain 33.333 rpm in spite of stylus drag, in addition to actual platter speed. The Eclipse add on is constantly correcting for such forces. When there is a lot of drag, the indicator LED blinks more frequently and the speed momentarily sags. But usually by less than 1.0 rpm. At least that’s how my Phoenix Eagle plus Roadrunner works.
Better to buy the KAB strobe disc and the battery powered strobe light that goes with. Can use with any TT and is much more accurate than any built in strobe on our vintage DD TTs. But that will only give you a qualitative answer that you can verbally relate to others, not hard data.The KAB strobe disc is about 7 inches in diameter. So, you can run the strobe disc on top of a 12 inch LP with the stylus in the outer grooves of the LP, to get an idea of the effect of stylus drag.
Not that I care a lot, but I disagree that actual data would be worthless. I think it would be interesting. However I do not think it will ever happen because of the necessary controls that we really as a group cannot put into affect.
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.