Belt stretch

Hi again,

If you are trying to gather a result from two samples of different drive types, that may be your first error because the simple fact that they are different drive types cannot possibly be used as a standard for any sort of test to measure the effectiveness of the drive type. Are all other parameters the same? Of course, not. The platters, spindles, plinths, etc. are not the same. So, how do you separate sonic differences? Are you saying that you never hear speed differences, regardless of the nature of them? Is the difference merely one of pitch, or could a lack of openness or a smearing of various tones be due to a speed difference? Could there be some other cause? Or, do you never hear such differences?

If you are saying that the precision of a given turntable, or the lack thereof, when it comes to speed control makes no difference, I'm not sure what Doug or I can possibly say to change your opinion. In fact, I'm not really sure what else can be said. What I do know is that I most definitely hear it, and so do many others. Why you wouldn't is something I do not know.

The technology necessary to measure the effects of stylus drag and belt stretch exists today, but the people that have access to such equipment don't give a damn about it. They're probably too busy smashing atoms together and sending things to space.

The technology that was around when most records were cut was primitive at best and probably exhibited major speed fluctuations. Achieving super accurate speed precision today probably just enables one to better hear the inaccuracies of yesterdays equipment, but what do I know. I own a stupid belt driven turntable :)

Stylus drag and belt stretch is an idea (something, such as a thought or conception, that potentially or actually exists in the mind as a product of mental activity).

I have an idea. Perfect speed precision will guarantee slow transients.

I think we might be better off if we tried to figure out the inaccuracies of yesterday's equipment (such as how it reacted to cutter drag) and compensated for it. If a lathe slows down while the cutting head cuts a big transient on a lacquer, our TTs need to speed up the disc for the same transient. If you disagree that a lathe slows down when cutting a big transient on a lacquer, you might be indirectly saying that a cutting lathe has perfect speed precision while cutting a lacquer. Buy one and mount a tonearm to it and you should hear more accurate speed precision than any TT can provide. I don't know, but I bet that a cutting head on lacquer produces more friction than our styli do on vinyl.

Rccc you can believe whatever you like but you should do so in the face of the available evidence:

1. Belt creep exists (see Mosin's post for one argument, there are several others)

2. I can measure it.

3. Doug Deacon can hear it.

Ketchup, if the lathe slowed down for a transient the recorded signal would rise in frequency. The playback would need to slow down by an equivalent amount to replicate the "original" signal.

The folks at Pristine Classical in the UK have extensive digital files of works which they have taken off disc and have performed analyses of the changes of frequency within sustained notes. They do this so they can find artefacts of the recording process and correct for them. From what I have seen there is no great effect attributable to the lathe slowing down under cutter drag.

I can think of two reasons why this might be: firstly, don't forget that the cutter head was heated and used on a relatively soft acetate formulation - very much like a hot knife through butter.

Secondly, modulation drag exists because the hysteresis of the cartridge suspension removes energy from the system, the larger the modulations the larger the energy lost. The only source of "make up" energy is the motor (everything else is passive).

The cutter on the other hand is actively driven so the larger the modulations the larger the amount of energy being put into the system. If the energy lost through frictional heating equals the energy inserted into the system we'd be in net balance.

Dougdeacon, great post!

I don't think you even need high quality equipment or perfect pitch to hear the effects under discussion. I owned a Well Tempered Record Player (belt drive), and now own a Technics SP-15 (direct drive) in the heavy Technics base. I definitely don't have perfect pitch, but I could easily tell the difference between the cheap stretchy 3rd party belt on the WTRP, the outrageously expensive precision ground flat plastic-like OEM belt, and the Technics, with the Technics easily besting the WTRP on all measures of speed stability. If you have better equipment, or ears like Dougdeacon's partner Paul, I'm sure the differences are both more readily apparent and probably really irritating.

Ketchup, as far as mastering goes, here's some interesting reading:

http://www.kabusa.com/1200agon.htm

Of course, the Technics wouldn't be factor for older recordings, which might very well exhibit the effect you postulate. These guys:

http://www.trutone.com/mastering.html

claim the Technics drive motors are way better the the original Neumann. I have no idea whether stylus drag was audible on the old lathes. Your theory has been discussed before here on Audiogon.

Anyway, I'm firmly in the camp that says belt stretch is audible, because I've heard it.

David