The necessity for absolute tt speed control

[spiritofmusic]

I've been running my Trans Fi Salvation direct rim drive tt for seven years now, and it's my keeper for life. I've wringed plenty of goodness out of it with upgrades including mag lev platter and feet, 150kg Stacore/slate stand isolation, and high quality LPS to tt motor.

Recently I've hit a fantastic level of performance. Piano in particular, but also cello, are reproduced so faithfully, I really cannot imagine significant uptick beyond this point.

However, the one area I know my tt falls behind the competition is speed accuracy. I know that it is not rock solid, probably closer to 0.3% according to the designer.

His POV, and he's adamant on this, is that he's ok on accepting some inaccuracy because the opposite, digital feedback loop speed control, brings greater accuracy, but with it deleterious SQ including graininess and greyness that he was adamant would not make the final design.

Whatever he did to improve accuracy, from feedback loop on sensor/encoding discs, or what he thought might work, measuring speed fluctuations as changes in voltage, and correcting these, never resulted in a transparent final result.

And so the designer has left speed control as a purely analog adjustment. And I fine tune every other day.

To him, some drift is ok if the alternative is colouration.

And that's how it's been for seven years. And right now I cannot fault the sound in any way. Certainly there seems no pitch or timbre issues I'm consciously aware of from speed drift.

And this brings me to a dilemma. A competent US engineer who makes his own line of amps and phonos, and who runs my tt (with Clearaudio Goldfinger cart, no less), is proposing a bespoke tt speed controller that will beef up the stock unit, and he promises way better than 0.3% accuracy.

This unit will not be cheap. I've taken punts on gear before. But this is the first one where I'd agree to buy without full confidence I'd hear an improvement and with current levels of full immersion in my analog, contemplate the uptick.

I mean, if piano feels totally vibrant, accurate and realistic to me right now, isn't this the one instrument I'd be more dubious of if speed really was an issue in my system?

 

[Lagonda]

You should have invested in the Roadrunner long ago, it would have driven your OCD to a unprecedented level. If you get this latest upgrade you have to have something to measure with Marc, or you will not know if the money was well spent

 

[tima]

I'll take this bait, lol.

I mean, if piano feels totally vibrant, accurate and realistic to me right now, isn't this the one instrument I'd be more dubious of if speed really was an issue in my system?

How well do you know what sonics a change will actually bring before you ever try it? You say: "I really cannot imagine significant uptick beyond this point." I've been there too.

I believe we don't truly know what an upgrade can do until we try it. Granted our ears and our system must be sufficiently resolving to permit detection of a change, but most recognize that virtually any change makes a difference. Whether you take it as improvment and to what degree depends on your preference.

We've been round on this topic. The two primary functions of a turntable are accurate stable rotation and keeping mechanical noise very low. Waveform frequency, the time element, comes directly from the turntable.

Imo: Wow and flutter or pitch differentiation are valid but are old school measurements. Our ears are far more sensitive to the above two critical functions than we might realize. Dynamics, tonality, timng along with clarity and realism are influenced by stable accuracy as are psycho-acoustic attributes such as image stability, vivacity, depth, back and sidewall reflections, among others.

A competent US engineer who makes his own line of amps and phonos, and who runs my tt (with Clearaudio Goldfinger cart, no less), is proposing a bespoke tt speed controller that will beef up the stock unit, and he promises way better than 0.3% accuracy.

"Way better" sounds promising. Does the US engineer quantify improvements after the fact? What is peak error from 33-1/3 rpm?

 

[howiebrou]

I've been running my Trans Fi Salvation direct rim drive tt for seven years now, and it's my keeper for life. I've wringed plenty of goodness out of it with upgrades including mag lev platter and feet, 150kg Stacore/slate stand isolation, and high quality LPS to tt motor.

Recently I've hit a fantastic level of performance. Piano in particular, but also cello, are reproduced so faithfully, I really cannot imagine significant uptick beyond this point.

However, the one area I know my tt falls behind the competition is speed accuracy. I know that it is not rock solid, probably closer to 0.3% according to the designer.

His POV, and he's adamant on this, is that he's ok on accepting some inaccuracy because the opposite, digital feedback loop speed control, brings greater accuracy, but with it deleterious SQ including graininess and greyness that he was adamant would not make the final design.

Whatever he did to improve accuracy, from feedback loop on sensor/encoding discs, or what he thought might work, measuring speed fluctuations as changes in voltage, and correcting these, never resulted in a transparent final result.

And so the designer has left speed control as a purely analog adjustment. And I fine tune every other day.

To him, some drift is ok if the alternative is colouration.

And that's how it's been for seven years. And right now I cannot fault the sound in any way. Certainly there seems no pitch or timbre issues I'm consciously aware of from speed drift.

And this brings me to a dilemma. A competent US engineer who makes his own line of amps and phonos, and who runs my tt (with Clearaudio Goldfinger cart, no less), is proposing a bespoke tt speed controller that will beef up the stock unit, and he promises way better than 0.3% accuracy.

This unit will not be cheap. I've taken punts on gear before. But this is the first one where I'd agree to buy without full confidence I'd hear an improvement and with current levels of full immersion in my analog, contemplate the uptick.

I mean, if piano feels totally vibrant, accurate and realistic to me right now, isn't this the one instrument I'd be more dubious of if speed really was an issue in my system?

I have been using a strobe disc for the first time to check my tt speed. Use it too much and you will go blind as everything becomes one continuous blob after a while but it's good to know that my speed is spot on.

 

[Vienna]

I've been running my Trans Fi Salvation direct rim drive tt for seven years now, and it's my keeper for life. I've wringed plenty of goodness out of it with upgrades including mag lev platter and feet, 150kg Stacore/slate stand isolation, and high quality LPS to tt motor.

Recently I've hit a fantastic level of performance. Piano in particular, but also cello, are reproduced so faithfully, I really cannot imagine significant uptick beyond this point.

However, the one area I know my tt falls behind the competition is speed accuracy. I know that it is not rock solid, probably closer to 0.3% according to the designer.

His POV, and he's adamant on this, is that he's ok on accepting some inaccuracy because the opposite, digital feedback loop speed control, brings greater accuracy, but with it deleterious SQ including graininess and greyness that he was adamant would not make the final design.

Whatever he did to improve accuracy, from feedback loop on sensor/encoding discs, or what he thought might work, measuring speed fluctuations as changes in voltage, and correcting these, never resulted in a transparent final result.

And so the designer has left speed control as a purely analog adjustment. And I fine tune every other day.

To him, some drift is ok if the alternative is colouration.

And that's how it's been for seven years. And right now I cannot fault the sound in any way. Certainly there seems no pitch or timbre issues I'm consciously aware of from speed drift.

And this brings me to a dilemma. A competent US engineer who makes his own line of amps and phonos, and who runs my tt (with Clearaudio Goldfinger cart, no less), is proposing a bespoke tt speed controller that will beef up the stock unit, and he promises way better than 0.3% accuracy.

This unit will not be cheap. I've taken punts on gear before. But this is the first one where I'd agree to buy without full confidence I'd hear an improvement and with current levels of full immersion in my analog, contemplate the uptick.

I mean, if piano feels totally vibrant, accurate and realistic to me right now, isn't this the one instrument I'd be more dubious of if speed really was an issue in my system?

I agree with @Lagonda, I would get first the Phoenix Engineering Roadrunner (an inexpensive Tacho geniously made, with very simple installation). This device would give you a real time picture of all of your speed issues, if any; and of course the degree of the speed improvement with a new motor or controller.

You own a very impressive turntable with my favorite transmission (rim drive) but I think that you would be surprised with the degree of sound improvement that a good motor and controller will provide. The platter, plinth and bearing are very important , but the motor is more important due to the fact that it’s the only active element. As such it has the most demanding job.

Bill Carlin (@Phoenix Engineering), recently made for me a new 11.8 kilos (26 lbs) rim drive by using BLDC motors which are frequency controlled, through a cleverly designed controller and high Biased Class AB amplifier, fed by a quality linear power supply. The BLDC motors are driven as a 3 phase AC synch motor. The rotors are aligned with the rotating field created by 3 extremely accurate and clean sine waves, spaced 120° apart and the speed is controlled very accurately by the frequency of the sine waves, just as any AC synch motor.
Through his sophisticated controller and algorithm the motors‘ torque is being controlled too, through voltage regulation. To be noted that the drive is not using Hall sensors and provides me with the options, either for auto Or for manual speed correction. The speed options are 33.33, 45.00 and 78.00 rpm.

i can’t describe you the degree of the sound improvement (In all sound aspects) which I am currently experiencing. Its going without saying that vibration and noise measurements are dramatically reduced too with direct impact on the sound quality.
Through this BLDC rim drive I realized what accuracy and correct timing is offering to the analogue reproduction. I will never forget the moment I have experienced this and how , in a moment, my soundstage acquired so much detail, depth and dimensionality with wonderful dynamics.

what kind of motor do you currently have ? DC or BLDC? please write some details for the proposed system

 

[spiritofmusic]

I'll take this bait, lol.



How well do you know what sonics a change will actually bring before you ever try it? You say: "I really cannot imagine significant uptick beyond this point." I've been there too.

I believe we don't truly know what an upgrade can do until we try it. Granted our ears and our system must be sufficiently resolving to permit detection of a change, but most recognize that virtually any change makes a difference. Whether you take it as improvment and to what degree depends on your preference.

We've been round on this topic. The two primary functions of a turntable are accurate stable rotation and keeping mechanical noise very low. Waveform frequency, the time element, comes directly from the turntable.

Imo: Wow and flutter or pitch differentiation are valid but are old school measurements. Our ears are far more sensitive to the above two critical functions than we might realize. Dynamics, tonality, timng along with clarity and realism are influenced by stable accuracy as are psycho-acoustic attributes such as image stability, vivacity, depth, back and sidewall reflections, among others.



"Way better" sounds promising. Does the US engineer quantify improvements after the fact? What is peak error from 33-1/3 rpm?

I totally agree Tim. All I'm relaying is a real sense of "rightness" on piano, it's never been this vibrant and present in my system. And I know that rock solid speed often reflects thru piano reproduction in particular.

Details on the speed controller are sketch. It will use a digital loop to get to speed and then revert to pure analog/no feedback. And be battery powered.

 

[spiritofmusic]

I agree with @Lagonda, I would get first the Phoenix Engineering Roadrunner (an inexpensive Tacho geniously made, with very simple installation). This device would give you a real time picture of all of your speed issues, if any; and of course the degree of the speed improvement with a new motor or controller.

You own a very impressive turntable with my favorite transmission (rim drive) but I think that you would be surprised with the degree of sound improvement that a good motor and controller will provide. The platter, plinth and bearing are very important , but the motor is more important due to the fact that it’s the only active element. As such it has the most demanding job.

Bill Carlin (@Phoenix Engineering), recently made for me a new 11.8 kilos (26 lbs) rim drive by using BLDC motors which are frequency controlled, through a cleverly designed controller and high Biased Class AB amplifier, fed by a quality linear power supply. The BLDC motors are driven as a 3 phase AC synch motor. The rotors are aligned with the rotating field created by 3 extremely accurate and clean sine waves, spaced 120° apart and the speed is controlled very accurately by the frequency of the sine waves, just as any AC synch motor.
Through his sophisticated controller and algorithm the motors‘ torque is being controlled too, through voltage regulation. To be noted that the drive is not using Hall sensors and aprovides me with the options, either for auto Or for manual speed correction. The speed options are 33.33, 45.00 and 78.00 rpm.

i can’t describe you the degree of the sound improvement (In all sound aspects) which I am currently experiencing. Its going without saying that vibration and noise measurements are dramatically reduced too with direct impact on the sound quality.
Through this BLDC rim drive I realized what accuracy and correct timing is offering to the analogue reproduction. I will never forget the moment I have experienced this and how , in a moment, my soundstage acquired so much detail, depth and dimensionality with wonderful dynamics.

what kind of motor do you currently have ? DC or BLDC? please write some details for the proposed system

What is a BLDC motor?

 

[spiritofmusic]

All I know is my current speed controller is "simple" voltage regulated. I've then replaced the stock SMPS with a beefy LPSU, aftermkt pwr cord and fuse.
It's specced as accurate to 0.3%, and needs minor tweaking via strobe disc every other day. Ambient temperature seems to be a factor.
The new device? I have no details yet. Other than the designer is an amps guy who has built a line, owns the tt, and is very familiar with the existing controller.

 

[Audiophile Bill]

Marc. Imho you should download RPM app for your phone. Calibrate the app with your current strobe and measure the absolute speed stability and wow/flutter.

As everyone else as said, you need to establish a baseline to know where you are at.

 

[spiritofmusic]

Agreed. This will be my first App, wish me luck Lol.

Let's say Vic's data is right, 0.3%. And the new controller, with no digital servo loop, gets it down to 0.1%. Or if I'm lucky 0.05%. Is there any way I wouldn't perceive/benefit from this?

I ask because I don't detect much at all if I listen to an lp w some drift on strobe disc versus straight after corrected.

Does that revoke my analog/audiophile privilege card? Lol

 

[Vienna]

I totally agree Tim. All I'm relaying is a real sense of "rightness" on piano, it's never been this vibrant and present in my system. And I know that rock solid speed often reflects thru piano reproduction in particular.

Details on the speed controller are sketch. It will use a digital loop to get to speed and then revert to pure analog/no feedback. And be battery powered.

What is a BLDC motor?

Its a type of DC motor. The main difference is that the BLDC motors are brushless with no cogging and can be driven by controlling the frequency, thus maintaining the virtues of an AC synchronous motors without the noise and vibration.

BLDC motors present linear hi torque too.

 

[tima]

I totally agree Tim. All I'm relaying is a real sense of "rightness" on piano, it's never been this vibrant and present in my system. And I know that rock solid speed often reflects thru piano reproduction in particular.

I understand and agree that piano reproduction is where many of us look first or notice first for speed related impact. It was there I noticed improvements over tape drive when I switched to a Verus rim-drive with my Teres 320 table. Easily the most notable improvement in going to my Monaco 1.5 was not just an improvement in pitch but a sense of ease and flow - noticeable attributes that words don't capture well. A total surprise came - the only time I've ever used the words 'goose bumps' in a review - with the sense of dynamic control, a sense of grip no less, that improved accuracy brought with the Monaco 2. Granted this was my personal reaction based on prior experience with my various systems, but it told me about how big an influence stable accuracy could make. I realized my system was much better than I thought it was - which was pretty neat.

I ask because I don't detect much at all if I listen to an lp w some drift on strobe disc versus straight after corrected.

A strobe disc is better than no strobe disc, but I consider it a very gross level measurement because it is based on how stable is your electricity from millisecond to millisecond and based on the acuity of our visual perception to detect absolute dead stop movement of the strobe markings. Turn away and look at an object you know is not moving - do you have the same sense of certainty with the strobe markings? Be that as it may, I'm confident you will hear the difference if the implementation is right.

 

[spiritofmusic]

Vienna, I'm not in much contact with the original designer. He's retired from audio. All I know is it's a tiny deck of cards sized box that sets speed based on voltage regulation, set and forget, zero feedback loop, adjust every other day, pwrd now by LPS.

The proposed new controller? Again, scant details. Maybe more in the way of your system.

My question is not so much the tech, more the concept. Is it possible for me to seemingly be a little insensitive to drift...solve that drift with the new device...and then notice all the benefits of rock solid speed?

 

[Audiophile Bill]

Agreed. This will be my first App, wish me luck Lol.

Let's say Vic's data is right, 0.3%. And the new controller, with no digital servo loop, gets it down to 0.1%. Or if I'm lucky 0.05%. Is there any way I wouldn't perceive/benefit from this?

I ask because I don't detect much at all if I listen to an lp w some drift on strobe disc versus straight after corrected.

Does that revoke my analog/audiophile privilege card? Lol

0.3% is what though? Is this the absolute speed accuracy to 33.33 and 45 or composite wow&flutter? Need to know details.

 

[Vienna]

Vienna, I'm not in much contact with the original designer. He's retired from audio. All I know is it's a tiny deck of cards sized box that sets speed based on voltage regulation, set and forget, zero feedback loop, adjust every other day, pwrd now by LPS.

The proposed new controller? Again, scant details. Maybe more in the way of your system.

My question is not so much the tech, more the concept. Is it possible for me to seemingly be a little insensitive to drift...solve that drift with the new device...and then notice all the benefits of rock solid speed?

At my case it has made a huge difference, like getting a new turntable, tonearm, cartridge and phono stage together, but again i had serious speed issues

 

[analogsa]

What is a BLDC motor?

Something i am willing to bet you won't like much.

There is a wide spread misconception that it is a kind of a DC motor. It is not. In the majority of tt applications it is controlled by pure sinewaves as if it were a normal synchronous AC motor . The original design brief assumed a trapezoidal drive, which was externally powered from a DC source.

Tried several BLDC motors, one of which from a Continuum, but none could reach the musicality of a cheap brushed Maxon or an outer rotor Papst. Yes, excellent speed stability but also a substantial and undesired in my system transformation of sound towards greyness.

 

[spiritofmusic]

Well Vienna, I would get that. I'll follow Bill's advice soon re the App. All I can say is that on any two consecutive days, there is some minor wavering to and fro on my strobe disc. This suggests absolute speed can be fixed, but some wow moment to moment.

My guess is that sort out this tendency to fluctuate, and the aggregate change will be dramatically better. Maybe less grain and better transparency, less veils.

What I need to do is listen to albums that require maximum fidelity of reproduction...solo piano, string quartets. Listen to them after a couple of days of not adjusting when strobe indicates I should. Then again straight after speed is tweaked. And see if there is perceptible uptick in resolution, microdynamics and transparency.

My tt has always benefitted from the aftermarket changes I've made. Good likelihood it will again with this. It's just that those areas that would seem to be most at risk from speed issues, like piano, are absolutely convincing at the moment.

 

[spiritofmusic]

Something i am willing to bet you won't like much.

There is a wide spread misconception that it is a kind of a DC motor. It is not. In the majority of tt applications it is controlled by pure sinewaves as if it were a normal synchronous AC motor . The original design brief assumed a trapezoidal drive, which was externally powered from a DC source.

Tried several BLDC motors, one of which from a Continuum, but none could reach the musicality of a cheap brushed Maxon or an outer rotor Papst. Yes, excellent speed stability but also a substantial and undesired in my system transformation of sound towards greyness.

Does this BLDC use a feedback loop to measure speed and adjust?
Vic, my tt designer, tore his hair out trying to square the circle on measure/adjust speed, and never could. Even feedback involving speed variations leading to voltage fluctuations, and his prototype adjusting those to maintain speed, led to unacceptable grey colouration.
For him, he decided to settle for compromise on absolute speed stability via 100% analog/zero feedback control, and thus the necessity to tweak every other day.

 

[analogsa]

Does this BLDC use a feedback loop to measure speed and adjust?

Not necessarily. Some of the BLDC motors in turntables are used exactly as proper synchronous AC motors which never use any feedback and rely on the motor locking onto the driving frequency. Yet others have a tacho coil and do use a feedback control. Long term speed stability is really not an issue with BLDC motors even without feedback.

Not sure feedback alone is bad as there are too many ways it can be applied. The old Teres belt driven tt used a brushed Maxon dc motor and a very slow integrator in a feedback loop, which would slowly adjust the speed after a number of revolutions. Pretty much like what you do by hand, only automated. No reason this would be audible in any negative sense. Some of the top tts using BLDC motors and feedback take a different approach and correct the speed thousand of times per second. The correction algo becomes crucial to how well this works. Unfortunately the tacho coil is typically inside the motor and the feedback corrects the motor rotation, rather than the platter.

Btw, direct drive motors are very close in principle to BLDC. Due to the low rotational speed and usually lowish platter inertia a feedback loop is essential. If DD turntables can be made to sound great, so in theory should be possible for belt drives using BLDC motors. It is just that in practice it does not happen often.

 

[analogsa]

Even feedback involving speed variations leading to voltage fluctuations, and his prototype adjusting those to maintain speed, led to unacceptable grey colouration.

If i read between the lines your designer seems to have chosen an unregulated PS. Hmmm, never tried this, but it is an interesting suggestion. It clearly makes the average speed even more prone to fluctuations. Do you know what motor is being used?