Belt stretch

I dont doubt the theoretical possibility or even likelihood of differential belt tension what Im saying is that it isnt audible. I dont tune pianos but I do have perfect pitch and have spent much of my life in concert halls and enjoying Hi Fi. Its possible Mozart would have been able to hear those anomalies in a belt drive table, how many Mozarts are there on this forum? So let me rephrase what I stated. Aside from the esteemed genius's mentioned above no mortal can hear the effects of belt tension as has been reported in the audio forums and press. Why I started this thread is that knowledgeable people in the audio business have made reference to belt stretch,stylus drag etc but never quantifying it in any way but theoretical. I have both belt and direct drive and have never heard any speed related differences. Since this comes up from time to time I have asked freinds and associates in the music industry if they have and no one has been able to actually demonstrate the audibility of this variance. Im simply trying to debunk this myth or hear from someone whom can demonstrate that it is in fact audible to someone besides Mozart. I appreciate the thoughtful reponses but we have only addressed the possibility of some pitch shift not that it in fact exists and is audible.

Rccc, Assuming you own high quality examples of belt-drive and direct-drive turntables, have you done the experiment of listening to each one with the same tonearm and cartridge? If so, do you hear any differences that could therefore be ascribed to one or the other turntable? What are the differences if any? If you have not done that experiment, then maybe you are premature in declaring that the inherent mechanical differences between belt-drive, dd, and idler-drive are irrelevant or inaudible.

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.