turntable speed control

phoenixengr   "Agreed. But constant motor speed does not equal constant platter speed, it's basic physics. Belt creep does exist and it is measurable. "

That really depends on the turntable.

" A table driven by the SDS will have constantly changing platter speed for the first 30-45 minutes; it will either be off-speed (slow) initially then correct after 40 mins, or correct speed when cold, then off-speed (fast) after that."

Again, that depends on the turntable. It certainly is not an issue with my VPI and, yes, I've measured it.

phoenixengr " May I ask what you used to measured it? My VPI table changes speed considerably from cold to warm and so does every belt drive table I’ve measured. If you have the first belt drive table that doesn’t change speed over time, then congratulations"

I use a DIGIstrobo to measure turntable speed. It's very precise, although I find you can't use it hand-held if you want a really exact measurement.

This notion of off-speed turntables until after warmup is rather odd. Not only doesn't my VPI have this issue, but neither did my previous turntable, which was an Oracle Delphi Mk. III. (To be clear, I didn't have the DIGIstrobo when I owned the Oracle. Back then, I relied on a strobe disc to ascertain speed.)

You've claimed that " belt creep does exist and it is measurable." That's another rather odd claim. How have you measured this phenomenon? How can you be certain that whatever speed issue you may have detected is attributable to "belt creep?"

phoenixengr " ... I’d suggest you do a little more research before you decide to debate how these systems work. You seem to have little understanding of the physics involved, yet you ’know’ so much."

When phoenixengr asked how I made my measurements, I responded and the answer is above. But when asked how he substantiates his claim that " Belt creep does exist and it is measurable," he becomes argumentative. Of course, he’s trying to sell something here, and I’m not. Perhaps that accounts for the difference in our attitudes.

Not incidentally, the question isn’t only, "Is it measurable?" but, "Does it create an audible effect?" I say that because we can measure some things that we cannot hear.

" If you even lightly touch the platter while it is moving, it will drop in speed"

Not necessarily. A light touch to a 22-pound platter doesn’t effect speed - the force of the touch is insignificant compared to the moving mass of the platter. But phoenixengr already knew that.

phoenixengr, your products are highly regarded by many in the audiophile community. I’m sorry to point it out to you, but you’re really not helping yourself with the illogic you’re using here.

melm "More importantly, I believe, we can hear things that we cannot measure."

While there's no question that we can measure things we can't hear, I think it is also mostly true that we can hear things we can't measure. Oftentimes, however, I think it's not that we can't measure it, but that  we don't know how, or what, to measure.

 "That is why, despite the great (industry approved) measurements from relatively inexpensive direct drive TTs, most careful listeners know that belt drives (which may measure worse in some respects) sound better."

You'll get no argument from me on that!

anvil_turntables  "...  As the table is used the belt becomes slightly more pliable."

That's interesting! Have you noticed any difference among various belts that you attribute to either the material used to make the belt, or the cross section of the belt?

The Phoenix controller does seem to be unique and a good value.
 

last_lemmin"not it trying to offend but I own the Phoenix control and tach unit for my VPI Prime. I know for a fact that if you even lightly touch the platter the tach rpm drops instantly."


No offense taken! I guess what's at issue here regarding speed deviation is what defines a "light touch" and, of course, variations between different turntable platters. I can certainly slow down my VPI platter by touching it - I can make it stop, for that matter.

I've heard nothing but good things about the Phoenix motor control and tach, so I'm not questioning those products at all.

phoenixengr
  " Wow, you managed to get just about everything wrong on that one; from your straw man argument about my sales motive to the lack of understanding of even basic physics. You deny that belt creep exists ...  you can blame speed variations on "some other" mysterious force? ...  You are wrong on both accounts.... Apparently you not only know what you know, but now you claim to know what I know. Semantic arguments aside ...  "

You're funny, phoenixengr. I certainly never stated that belt creep didn't exist. To refresh your memory, here's what I wrote:

" How have you measured this phenomenon? How can you be certain that whatever speed issue you may have detected is attributable to 'belt creep?'"

You seem to enjoy vituperative exchange. Have fun! I'm not interested.
 

+1 stringreen!

I would add that another problem is that some come here to participate in a conversation, ask questions and exchange ideas and experiences. Others have other goals. It's usually not too difficult to distinguish one from the other, though.

lewm "Melm wrote, "...belt drives (which may measure worse in some respects) sound better." This is so so wrong and short-sighted. Yet, CLeeds agrees with him."

As melm pointed out to you, that isn't exactly what he said.

" Well designed and implemented turntables of any kind sound better than those that are not well designed and implemented. "

I agree completely! I've owned some great DD turntables even though I've been using belt drive for years. I've heard the VPI DD and it's terrific. But as melm also points out, it's an expensive and complicated undertaking to make an outstanding DD turntable. Ask Harry Weisfeld - he's made 'em all: belt, rim, DD. Who knows what he'll think of next?