turntable speed control


VPI sds vs. Phoenix engineering PSU speed control

1litespeed
Personally I find the SDS quite adequate.  On paper, the Phoenix is better, but I couldn't hear a difference.  The digital ouput is quite nice if you're an anal type.  I am a pro violinist and am pretty sensitive to pitch deviation, and find the SDS working for me. Of coarse, I live in the Arizona desert with little power problems....you should listen for yourself.
@stringreen

I agree, the VPI SDS works great.

The Phoenix does no AC regeneration, or lower the motor voltage after startup like the SDS. More noise.

We sometimes agree. LOL!
don
The Phoenix does no AC regeneration, or lower the motor voltage after startup like the SDS. More noise.

Thought this question was asked prior and it was concluded
that the Phoenix does in fact lower the voltage .
SDS is better as once you set a speed it is locked to that. Phoenix corrects speed so it would be constantly changing which could be audible. 
SDS is better as once you set a speed it is locked to that. Phoenix corrects speed so it would be constantly changing which could be audible.

This is a common misconception and is actual the opposite of reality. The SDS does not change its output frequency once it is manually set so the speed of the motor will remain the same, however the platter speed will constantly increase 0.2-0.4 RPM as the belt and bearing warm up over the first 30-45 minutes of play and it is audible to many listeners.

The Falcon/Eagle PSU does not correct "constantly"; there is a window of error that the PSU responds to (only if connected to the tachometer). When the platter speed drifts outside the window, the PSU applies extremely small corrections** evenly over the next revolution to keep the platter on speed. The correction is not audible. Once the table speed is stable, it is not uncommon to see 20-50 revs without correction, but if the PSU did not correct, the speed error would build up and it would be audible.  Of course, if feedback is something you are opposed to, then don't connect the cable between the tach and PSU and adjust the speed manually.

** The SDS uses a PLL circuit and the output is constantly wobbling a minute amount. The amount of correction the Falcon/Eagle PSU applies is smaller than the constant wobbling of the SDS:
https://www.youtube.com/watch?v=QOs7oB8N9Zs&nohtml5=False
The Phoenix does no AC regeneration, or lower the motor voltage after startup like the SDS. More noise.

This of course is also incorrect. The Falcon/Eagle are AC regenerative power supplies and they use DDS technology to create AC regeneration which has much lower distortion and noise as well as being hundreds of times more accurate than the PLL circuit the SDS uses (see link above).

The Eagle/Falcon also has reduced voltage output which is front panel programmable.

The Eagle is capable of 230VAC output so it works with tables worldwide. It will also work with 50Hz motors where the SDS does not. The Eagle/Falcon works with the RoadRunner tachometer to automatically correct for long term drift which the SDS cannot.

The Eagle also delivers more output power than the SDS:
https://www.youtube.com/watch?v=tt9AuTg3QXA
phoenixengr

Thanks for dropping in, pretty much sums it up.


I was looking at buying an SDS for my Prime, but after reading this and comparing the price ($525 for the Eagle vs $1399 for the SDS) it seems like a no brainer.
If the motor on the sds system is always turning the same speed the platter will not go faster because the bearing is warm. That's a load of hooey. And I think the affects of belt creep are also greatly exaggerated. You could always go to tape, silk, or thread if you are concerned about that. To me a a constant stable speed is always better than a changing one. 
The best belt would be a endless rubberized steel cable style belt like the old micro seikis. Quiet and they can't stretch. Micro did things right
To me a a constant stable speed is always better than a changing one.
Agreed.  But constant motor speed does not equal constant platter speed, it's basic physics.  Belt creep does exist and it is measurable.  With an elastic drive belt, it cannot be cured, but the effects can be mitigated by holding the platter speed constant as we do.

By your own assertion, a constantly changing speed could affect the audio.  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. 

With  the Eagle PSU and  tachometer feed back, the platter speed will always be constant, therefore, it will sound correct both when started and after the table warms up.

Thanks for helping make my point.
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.

It certainly is not an issue with my VPI and, yes, I’ve measured it.
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.

If a particular turntable platter truly doesn’t change speed over time, then the argument is moot: The Eagle would not apply correction so there would be no perceived issue either from "constant correction" or constant drift. End of problem.

As far as the rest of the tables that do drift over time, would you agree that constant platter speed is better than a slow drift upwards in speed?
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?"

You’ve claimed that " belt creep does exist and it is measurable." That’s another rather odd claim. How have you measured this phenomenon?
Are you denying that belt creep exists? That’s not only an odd claim, it’s counterfactual. Without belt creep, elastic belt drives could not transmit torque to the platter; it is undesirable, but necessary for these systems to work.

AC synch motors operate at 2 different speeds: 100.00% of rated speed determined solely by the drive frequency or 0% when the cogging torque is exceeded and the motor stalls. There is nothing in between. If you even lightly touch the platter while it is moving, it will drop in speed, yet the motor maintains its speed at 100%. How do you account for that if there is no belt creep, a phenomenon that is well documented in physics?

It’s trivial to measure the difference in platter speed caused by stylus drag (if you have the right equipment i.e. a tach with 3 decimals of resolution; a hand-held tach with 1 decimal is a poor indicator, strobe discs are even worse). The difference in drag at the beginning of a record is even different than when the stylus is closer to the spindle. Anything that creates drag on the platter, including changes in bearing friction, will increase the torque demand on the drive system, increase belt creep and reduce platter speed.

If I let the platter speed stabilize at 33 RPM for several hours where little or no correction is applied, switch to 45 RPM for even one side of an LP, then switch back to 33 RPM, the speed will be 0.15-0.2RPM higher while using the exact same frequency as when I left 33 RPM. The difference is due to changes in the belt and bearing.

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.
As far as measuring the consistency of turntable platter speed - I have found nothing better than the Timeline form Sutherland Engineering, its a device that emits a laser beam pulse at very precise time intervals.  This is placed on the spindle of the turntable and a dot appears on the wall of the room the turntable is placed in.  If this dot does not move the speed of the turntable is exact - and I have yet to find any belt drive turntable thats been able to hold the position of the spot over the entire length of a LP playback.  I have run many VPI based tables with and without a SDS unit and while SDS certainly makes it a lot more speed stable it simply cannot hold absolute precise speed.  I have not tried the Phoenix unit but will some time in the future.

However, once you get a Direct Drive turntable it becomes very obvious that these are far better at maintaining the correct speed The Denon drives which we retrofit,  rebuild and sell are quite precise.  The Technics SP 10 MK2 and 3 are exceedingly more accurate in maintaining correct speed.   And by accurate I mean the laser dot emitted by the Timeline does not move on a wall 23 feet away from the turntable.

Halcro whom posts on this site frequently posted a video on youtube a while back indicating the speed accuracy of his Victor TT101 Direct Drive turntable to indicated if Stylus Drag is an issue on a Direct Drive Table
The results of this are quite obvious.


https://www.youtube.com/watch?v=RE52bsIh_ZA

  
Good listening

Peter

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.
Post removed 
"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".

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

""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"

Well, I have a 20 lb.TNT platter + a flywheel and the reduction in speed when given even a very light touch is undeniable to all who can hear . . or measure.

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!

..just wondering if anyone has data about the accuracy of VPI's rim drive Superscout.
Let me clarify if I may.  The potential slightly fast speed of a "warmed up" turntable is caused by BOTH the belt and bearing.  As the table is used the belt becomes slightly more pliable.  In some bearing designs this allows the bearing to more precisely align itself and work as it was designed.  The "cold" stiffer belt pulls on the platter harder which can create a chaotic situation in the bearing and reduce its performance.  My turntables avoid this, however I have measured this increase in speed myself, in some designs.  My tables btw, often use the Phoenix controllers and they are excellent and great value.  Drift on my tables, with Phoenix controllers is essentially non existent.

Bruce
Anvil Turntables
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.
 
Hi again. My favorite? Surgical silk thread with a light application of instrument string rosin ( applied while table is spinning ). Sounds best and you also feel very cool when your finished. I also like light test fishing line although its a little noisy on the platter and the knot makes a little ticking sound ( which I have not heard through playback). Belt circumference  affects speed so you need a variable controller.
Why not rubber? Rubber belts get micro tears in them ( meaning pliancy is all over the place) and along with wear can really mess up your W&F. The more friction you have in your bearing the more pronounced this is.

Rubber belts have a bigger "fatter" sound, and less pliable belts tend to sound "crisper" and cleaner, generally throughout the frequency range.
Hope this helps.

Bruce
Mr. Creeds, 

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. Also - before I powdered my belt - on start up the tension side of the belt was taught but after the belt passed the pulley you could visibly see the band vibrating due to the slack. This was only obvious for a second until the platter speed stabilized, but I would still think this is happening albeit to a much smaller degree once the platter is up to speed.  Wouldn't this be some indication that belt creep is happening to one degree or another?

All i I know is that the system works flawlessly and tach reads 33.33x where x fluctuates up or down .001+/- rpm.  And I definately hear very stable sustained piano notes. So belt creep aside, it does a magnificent job at keeping the platter stable and at a significantly lower price than the SDS. 

Cudos to PE!
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.

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.
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, yet you can blame speed variations on "some other" mysterious force? If you reread my post above, you will see that I did answer your question. Belt creep manifests itself as reduced speed, and I measured it with a digital tachometer. But even simpler than that, you can do as melm has indicated and just listen when you touch the moving platter while a record is playing.

Not incidentally, the question isn’t only, "Is it measurable?" but, "Does it create an audible effect?"
Yes. See above.

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.
You are wrong on both accounts. Inertia will only affect the rate at which it slows, but it will slow down. And, I know the opposite of what you said to be true. Apparently you not only know what you know, but now you claim to know what I know.

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.
There is nothing illogical about my posts. Everything I've posted about the operation of belt drives is correct and easily verified not only by application of simple physics, but also by empirical testing (listening) and simple measurements.

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.
Semantic arguments aside, if you put a digital tach on your 22 lb platter you will see that the speed slows down even when the stylus makes contact with the record (I'd consider 1.75 grams to be a light touch).

As far as the rest of the tables that do drift over time, would you agree that constant platter speed is better than a slow drift upwards in speed?
You still have never answered this question.
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.
 
The problem on these (and all audiophile) posts is that too many people think they know it all. What these pages should be is a forum of people’s experiences and beliefs in their own systems and others’ that they know well. ....a friendly exchange of experiences ..delights, and disappoints. There are few absolutes in audiophilium.
+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.
+1 stringreen!

I would add that another problem is some people can’t debate issues using facts and data, so they try to impugn someone’s character with innuendo:
Others have other goals.
and try to make their point with straw-man arguments:
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?’"


What you actually preceded that statement with was this:
You’ve claimed that " belt creep does exist and it is measurable." That’s another rather odd claim.

I took that to mean you questioned the existence of belt creep or that it couldn’t be detected or measured. When I asked you if that was the case, you didn’t respond, so I proceeded with that understanding (you still haven't denied it).

I see no other purpose to any of your posts other than to start an argument, a rather simple and tiring one at that, and one that I’m done with.
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. Well designed and implemented turntables of any kind sound better than those that are not well designed and implemented. (I am not going to say that one drive system is per se better than the other; they all [3] have trade-offs.) But an advantage for us direct-drive aficionados is that we don't have to engage in snippy contretemps with each other about belt creep.  From what I know about it, Phoenix engineer is basically correct on all counts, and I would choose their products over the SDS, at this point in time. In fact, I might buy into the technology for my Lenco L75.
If you're going to quote me, please quote enough for it to make sense.  What I wrote was:

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

Problem is that it takes quite an expensive DD with a heavy and non-resonant platter to approach and even surpass well designed belt drives.  There are a few you can buy today, including the VPI.  But the run-of-the-mill DDs with lightweight and ringing platters just don't do it.
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?

Melm and cleeds, My apologies.  I was to some degree playing for laughs.

Anyone tired of fiddling with belts and belt tension might want to consider any of several vintage Japanese direct-drive turntables, the creme de la creme, not the bargain basement ones, as an alternative.  Examples include Denon DP80, Victor TT101 or TT81, Kenwood L07D, Technics SP10 Mk2 or Mk3.  Only the Mk3 would cost anywhere near $10K. The rest are typically cost less than $5K, ready to roll. In a modern plinth, these turntables can be bulletproofed and made to sing.

I’ve owned both these products and am commenting from direct personal experience. When I owned a VPI Classic 3, I purchased a used SDS (for about $750) and noticed a definite improvement in sound quality. I was in an upgrade phase and that set-up was soon the weak link in the system so it was replaced by, in my opinion, the greatly superior Basis 2800 with vacuum, stabilizer base and placed on a Vibraplane. As good as it sounded , the speed was off. 5k for the Basis Synchrowave was not sounding appetizing and with a bit of research I found the Phoenix gear. SDS, new about $1200+/- and inferior, Phoenix gear new, about $600 and superior. For me it was a no brainer and it works perfectly. I’m no engineer or physicist but it seems pretty simple: most LPs were designed to be played at 33 1/3 or 45 rpms. Anything other than that is outside of design spec. The Phoenix gear delivers a clean regenerated power source to the motor and the link between the Roadrunner Tach and PSU insures proper platter speed. Since the minute fluctuations in speed are restrained to a mere .005 rpm window, I would defy anyone or any measuring device to detect any pitch or tonal variations because of speed issues. It seems like there’s a lot of flat earth "thinking" and "reasoning" going on in this discussion. Yes, it possible and useful to use digital and engineering advancements to improve analog systems.
Also, why this constant hijacking of topics? Nobody was asking about DD tts. This was a direct question about two specific products. Start a different discussion if you want to argue the merits of DD vs Belt drive tables, geez :)