The necessity for absolute tt speed control

[tima]

I am not a expert, but maybe they have gotten the speed and application of feedback/correction that is so heavily relied on in this type of drivetrain just right, those very important micro variations Some of the best DD drives have until now ( MikeL. schooled me recently ) been using relative heavy platters as part of their design, maybe the Monaco has gotten the processing to the point where it can be done with a light platter.

The 2.0 is also very quiet.

The platter is magnesium with proprietary coating, so yes quite a bit lighter.

 

[microstrip]

Any idea about the exact motor type? The current model says it has a 3 phase, 8 pole, outrunner (external rotor) design that uses a microprocessor controlled feedback loop. Don't know if that is only the newest models or how far back in time that goes...how old is yours?

I think it is important to note that they are not just relying on a clean 50Hz AC with a synchronous motor...they are doing something significantly more advanced.

Funny thing was, I had a friend with a 20/2 (not sure the age) and when I first got my Allnic Speednic we measured it and found that it was not very accurate (but it was adjustable) but that with a record playing we could visibly see some fluctuations in the speed (the Speednic can be used while playing a record...quite useful to see if needle drag is affecting your speed). I think this was an older model so it could have less sophisticated motor and speed control than is current or yours...so I don't think it can necessarily be reflective of your TT.

We tried this on other TTs and only the SME was so visibly changing (others tried: Yamaha GT-2000, Voyd "The Voyd", Transrotor Turbillon with decoupled magnetic drive, Lenco L75, Luxman PD-444, Reed 1C in rim drive mode) but the Transrotor need some adjustment to get the speed correct...then it was stable under load.

What is the point of stylus drag slightly affecting the speed? It can happen with any belt driven turntable without platter feedback and is inconsequential in normal use. The expensive Allnic Speednic (usd 400, as far as I know) is a nice source of entertainment and can be used to know when it is time to replace the belt but, for example, does not tell you you need to clean the driving pulley, also a common source of wow and flutter.

I have long time experience with SME turntables and measured my SME30's (I and II) with a test LP with a 3150Hz and a professional wow and flutter meter I got for the Studer A80 maintenance and later with an audio RTA. They showed excellent performance, so my advice to anyone who has an SME measuring poorly is simply get it serviced - remember rubber belts have a limited life for best performance, I replaced it every two or three years.

 

[Solypsa]

...
Anyway, if audiophiles were really concerned with motor coupling to the platter they would ask for an hydrokinetic coupling, like those used in the old Newmann disk cutting lathes. Can we even imagine owning a Newmann VMS80 to play our cherished LPs?

VMS80 can be had for less cost than many of the turntables under discussion...it just takes time for the deal to materialize.

True story- I bought my ( long sold now ) VMS70 off of Ebay . Well not quite it didn't make reserve and was delisted, however I ended up making a private transaction: it turned out to be owned by a major label/studio but had been listed by an employee under personal account.

 

[Vienna]

What is the point of stylus drag slightly affecting the speed? It can happen with any belt driven turntable without platter feedback and is inconsequential in normal use. The expensive Allnic Speednic (usd 400, as far as I know) is a nice source of entertainment and can be used to know when it is time to replace the belt but, for example, does not tell you you need to clean the driving pulley, also a common source of wow and flutter.

I have long time experience with SME turntables and measured my SME30's (I and II) with a test LP with a 3150Hz and a professional wow and flutter meter I got for the Studer A80 maintenance and later with an audio RTA. They showed excellent performance, so my advice to anyone who has an SME measuring poorly is simply get it serviced - remember rubber belts have a limited life for best performance, I replaced it every two or three years.

SME turntables are using 8 poles motors with three integrated Hall effect sensors. At their best and most precise execution, Hall sensors are providing 1% of output error, this is translated to a speed variation from 33,002 to 33,666 rpm and 44,554 to 45.45 rpm (imprecise hall sensors‘ assembly, positioning errors -very common issues- are providing much higher output error ) . If you will insert the belt creep, belt slip, bearing issues, torque ripple and motor rumble into the equation, its easy to understand the rest; and the need to have a continuous speed correction with feedback in such a system, of course with the consequential effects on the sound (as I wrote earlier, there are many who are enjoying this sound)

P.s.There is a much more effective, more accurate, more convenient and cheaper product in the market which provides more information on the tt issues besides speed measurement (including cartridge running hours).

p.s2 Hall sensors is a very basic way to control a BLDC motor

 

[morricab]

What is the point of stylus drag slightly affecting the speed? It can happen with any belt driven turntable without platter feedback and is inconsequential in normal use. The expensive Allnic Speednic (usd 400, as far as I know) is a nice source of entertainment and can be used to know when it is time to replace the belt but, for example, does not tell you you need to clean the driving pulley, also a common source of wow and flutter.

I have long time experience with SME turntables and measured my SME30's (I and II) with a test LP with a 3150Hz and a professional wow and flutter meter I got for the Studer A80 maintenance and later with an audio RTA. They showed excellent performance, so my advice to anyone who has an SME measuring poorly is simply get it serviced - remember rubber belts have a limited life for best performance, I replaced it every two or three years.

Speed being modulated by the signal would introduce rapid and random speed changes that would almost certainly be detrimental to SQ.

 

[tima]

If you will insert the belt creep, belt slip, bearing issues, torque ripple and motor rumble into the equation, its easy to understand the rest; and the need to have a continuous speed correction with feedback in such a system, of course with the consequential effects on the sound (as I wrote earlier, there are many who are enjoying this sound)

P.s.There is a much more effective, more accurate, more convenient and cheaper product in the market which provides more information on the tt issues besides speed measurement (including cartridge running hours).

p.s2 Hall sensors is a very basic way to control a BLDC motor

Care and accuracy in feedback design and implementation is critical. Beyond the Hall sensor and other readers, the encoder disc, control circuitry and software are extremely important to establishing accuracy and to holding it. How many lines are on an encoder disc and how they are read and at what frequency, along with how quickly that data is processed, how it is processed, the algorithms used and computer speed required take the implementation well beyond the mere electro-mechanical. The breadth of talent and depth of skill set required is pretty amazing.

 

[tima]

Speed being modulated by the signal would introduce rapid and random speed changes that would almost certainly be detrimental to SQ.

Test records? Among other things you end up creating a signal with the wow and flutter of the cutter that made the test record.

 

[morricab]

Care and accuracy in feedback design and implementation is critical. Beyond the Hall sensor and other readers, the encoder disc, control circuitry and software are extremely important to establishing accuracy and to holding it. How many lines are on an encoder disc and how they are read and at what frequency, along with how quickly that data is processed, how it is processed, the algorithms used and computer speed required take the implementation well beyond the mere electro-mechanical. The breadth of talent and depth of skill set required is pretty amazing.

Exactly, but the designs of the 70s and 80s didn't use computers to process the encoder signal. They used PLL with quartz oscillators and some type of lock-in amplifier concepts...stuff right out of a physics lab from that same era. I only have a sketchy idea about how that works.

 

[tima]

Exactly, but the designs of the 70s and 80s didn't use computers to process the encoder signal. They used PLL with quartz oscillators and some type of lock-in amplifier concepts...stuff right out of a physics lab from that same era. I only have a sketchy idea about how that works.

Me neither - I should read up on that.

I speculate that use of a computer (the Monaco's is 40MIPS) increases what is possible within a given increment of time - more reads per second, more responses per second. The platter is controlled rather than driven. With software and so much data, prediction becomes possible and peak error further reduced.

Some of the designs of the 70's and 80's were quite sophisticated for their time.
Computers were of course available then - don't know if they were used for TT design and likely not for production and not for table control. It was late 70's / early 80's that the microprocessor brought the start of a revolution. Coming later, computer controlled machining has raised the quality and precision of parts. Miniaturization allowed GPA's Parabolica to eliminate an external controller and place it in the plinth.

 

[Solypsa]

Creating an ideal 'correction response' seems to be one of the 'arts' the designer practices. The high mass belt drive resisting change and the direct drive active change both do this in one way or another it seems to me. It is clear that speed modulation kills tone as can easily be seen in many tables, not only direct-drive. With ~50 years of direct drive development the fact that only a few come close to the top level shows how difficult this is to design. This despite the fact that a great number of modern records are cut on direct drive but that of course is a different beast.

Even in the case of the lower cost STST direct-drive tables I work with, the 'soft response' was what Stefan worked so hard on.

, the encoder disc, control circuitry and software are extremely important to establishing accuracy and to holding it. How many lines are on an encoder disc and how they are read and at what frequency, along with how quickly that data is processed, how it is processed, the algorithms used and computer speed required take the implementation well beyond the mere electro-mechanical. ...

 

[microstrip]

SME turntables are using 8 poles motors with three integrated Hall effect sensors. At their best and most precise execution, Hall sensors are providing 1% of output error, this is translated to a speed variation from 33,002 to 33,666 rpm and 44,554 to 45.45 rpm (imprecise hall sensors‘ assembly, positioning errors -very common issues- are providing much higher output error ) . If you will insert the belt creep, belt slip, bearing issues, torque ripple and motor rumble into the equation, its easy to understand the rest; and the need to have a continuous speed correction with feedback in such a system, of course with the consequential effects on the sound (as I wrote earlier, there are many who are enjoying this sound)

P.s.There is a much more effective, more accurate, more convenient and cheaper product in the market which provides more information on the tt issues besides speed measurement (including cartridge running hours).

p.s2 Hall sensors is a very basic way to control a BLDC motor

Hall sensors are not used to control speed - just to determine the position of the motor to control the coils current and phases, as in most brushless motors. All you say concerning hall sensors is not relevant to the speed accuracy of the motor, that is synchronized to an ultra stable oscillator. BTW, the Brinkmann also uses such kind of device in a similar way, but calls them a funny name.

 

[morricab]

Creating an ideal 'correction response' seems to be one of the 'arts' the designer practices. The high mass belt drive resisting change and the direct drive active change both do this in one way or another it seems to me. It is clear that speed modulation kills tone as can easily be seen in many tables, not only direct-drive. With ~50 years of direct drive development the fact that only a few come close to the top level shows how difficult this is to design. This despite the fact that a great number of modern records are cut on direct drive but that of course is a different beast.

Even in the case of the lower cost STST direct-drive tables I work with, the 'soft response' was what Stefan worked so hard on.

There are just as many mediocre/poor belt and idler drives as there are poor DD. It is hard to make a good sounding anything as most gear/speakers are not so good.

Is there a belt drive cutter?
The STST is supposed to sound good...I will have to hear it someday. The Dutch brand Primary Control has a “soft” DD concept that sounds good.

 

[microstrip]

Care and accuracy in feedback design and implementation is critical. Beyond the Hall sensor and other readers, the encoder disc, control circuitry and software are extremely important to establishing accuracy and to holding it. How many lines are on an encoder disc and how they are read and at what frequency, along with how quickly that data is processed, how it is processed, the algorithms used and computer speed required take the implementation well beyond the mere electro-mechanical. The breadth of talent and depth of skill set required is pretty amazing.

Motor control is not rocket science, but implementation compromises affect the subjective sound quality of the turntable. Having read the excellent white papers of Monaco sometime ago we understand some of them. But again, remember audiophiles do not want perfection in vinyl, they want something personnel and different to get their magic.

 

[microstrip]

Speed being modulated by the signal would introduce rapid and random speed changes that would almost certainly be detrimental to SQ.

The point is that speed in not being modulated. See my previous post on metal lacquer cutting.
Remember that Newmann disk cutting lathes used vacuum to couple the lacquer to the platter.

If the speed was being modulated it would be very easily detected - many studies were carried with two tonearms playing simultaneously different tracks, including test tracks, and analyzing them. Turntable, tonearm and cartridge designers and manufacturers of the past spend a lifetime studying such problems. Unfortunately these studies predate digital press and are ignored as google can't find them.

 

[Solypsa]

There are just as many mediocre/poor belt and idler drives as there are poor DD. It is hard to make a good sounding anything as most gear/speakers are not so good.

Is there a belt drive cutter?
The STST is supposed to sound good...I will have to hear it someday. The Dutch brand Primary Control has a “soft” DD concept that sounds good.

Agreed. I've heard the Kinea a few years ago and it sounded great.

 

[Vienna]

Hall sensors are not used to control speed - just to determine the position of the motor to control the coils current and phases, as in most brushless motors. All you say concerning hall sensors is not relevant to the speed accuracy of the motor, that is synchronized to an ultra stable oscillator. BTW, the Brinkmann also uses such kind of device in a similar way, but calls them a funny name.

You are completely wrong I am sorry: :,https://www.embitel.com/blog/embedded-blog/hall-effect-sensor-and-its-role-in-a-motor-controller, hall sensors are a part of the speed regulation and control; and their error output is affecting the poor controlling and speed performance. You are presenting the facts the way you always prefer, like the ‘perfect turntables ‘ you suggested but they all need a repair To perform.

Using Hall sensors is the most basic way to control a BLDC motor; it is unsophisticated, but easy to do. The motor behaves just as a DC motor, with the amplitude of the square waves being switched on/off controlling the speed. Only 2 of the 3 windings are energized at any phase of the rotor and the square wave signal has limited rise time, so they appear more like trapezoids (which is why this is sometimes called trapezoidal commutation). Speed control is poor, unless you use a feedback mechanism. Using Hall Sensors (like SME, Dereneville etc), the controller does block commutation aka square waves. Block commutation also produces torque ripple and vibration.

Another wrong assumption and misrepresentation of yours is related to the Brinkmann motors which are not BLDC but DC and hall sensors are not only absent but have no use at all

 

[tima]

Even in the case of the lower cost STST direct-drive tables I work with, the 'soft response' was what Stefan worked so hard on.

What is "soft response"?

The high mass belt drive resisting change and the direct drive active change both do this in one way or another it seems to me. It is clear that speed modulation kills tone as can easily be seen in many tables, not only direct-drive

Your Web site speaks about 'speed modulation kills tone' in terms of 80's direct drives, though here in current tense. Do you think today's DD on par with those of 40-50 years ago?

 

[microstrip]

You are completely wrong I am sorry: :https://ieeexplore.ieee.org/document/7551633, you are presenting the facts the way you always prefer, like the continuous need of maintenance for the turntables you mentioned earlier.

Another wrong assumption and misrepresentation of yours is related to the Brinkmann motors which are not BLDC but DC and hall sensors are not only absent but have no use at all.

Sorry you are unable to understand the point being discussed - in fact you seem to ignore how a BLDC motor keeps the speed - pointing IEEE papers will not help. My facts are technology, my opinions are surely subjective and IMHO.

Please read from Brinkman " An electronic circuit drives the coils via two magnetic sensitive
resistors that react to the magnetic fields in a highly constant and slow circular movement.” Anyway Brinkman misrepresent their motors with very romanticized descriptions (many manufacturers do the same BTW) no one knows exactly what they are telling.

 

[morricab]

The point is that speed in not being modulated. See my previous post on metal lacquer cutting.
Remember that Newmann disk cutting lathes used vacuum to couple the lacquer to the platter.

If the speed was being modulated it would be very easily detected - many studies were carried with two tonearms playing simultaneously different tracks, including test tracks, and analyzing them. Turntable, tonearm and cartridge designers and manufacturers of the past spend a lifetime studying such problems. Unfortunately these studies predate digital press and are ignored as google can't find them.

Which turntables and when and in what press? I have seen it with my own eyes...aided by a speednic...I don’t need a 40 year old study. As I said only one TT I have tried this with had an obvious modulation ... I never tried on really affordable TTs though.

 

[Vienna]

Sorry you are unable to understand the point being discussed - in fact you seem to ignore how a BLDC motor keeps the speed - pointing IEEE papers will not help.

Please read from Brinkman " An electronic circuit drives the coils via two magnetic sensitive
resistors that react to the magnetic fields in a highly constant and slow circular movement.” Anyway Brinkman misrepresent their motors with very romanticized descriptions (many manufacturers do the same BTW) no one knows exactly what they are telling.

LOL check again my post that citation was accidental.
I understand your difficult position but smells like sciolism here, I am writing again for you what hall sensors do:

‘....Using Hall sensors is the most basic way to control a BLDC motor; it is unsophisticated, but easy to do. The motor behaves just as a DC motor, with the amplitude of the square waves being switched on/off controlling the speed. Only 2 of the 3 windings are energized at any phase of the rotor and the square wave signal has limited rise time, so they appear more like trapezoids (which is why this is sometimes called trapezoidal commutation). Speed control is poor, unless you use a feedback mechanism. Using Hall Sensors (like SME, Dereneville etc), the controller does block commutation aka square waves. Block commutation also produces torque ripple and vibration...’

what’s the relation or similarity of a transistor with a hall sensor? LOL you will now claim that Brinkmann is using speed feedback LOL