Zero Distortion: Tango Time

[microstrip]

Which TTs use this technique?

TechDas AF0, not sure if the AS2000 uses it, one of our members owns a Bauer Audio dps turntable using three phase drive, I have seen such controllers in audiocirc.com and I developed a simple one to be used with a three phase motor in an old Oracle long ago ...

 

[Folsom]

Interesting - are you are considering that stylus drag reacts with the servo action? Although one of the processes is magnetic and the other electromechanical the only thing that distinguishes them in terms of mechanical interaction is vinyl friction.

Tape is considered an analog reference by most audiophiles as it is at the origin of the LP - unless we consider direct cut LPs.

Well and tape can have a pulling action that’s somewhat constant. It’s also much slower.

One of the most stable speed TT’s is TD124, and it uses a constant brake to do it.

 

[ddk]

There is a lot in common - both media move a physical support at a speed that should be as regular as possible - any deviation will modulate the signal. If servos systematically introduce "nasty" variations in speed they would easily show and be listenable in tape.

Curiously tape drive has been fully studied in great depth by professionals and scientists that published and released valuable information, but vinyl is still in the phase where knowledge is mostly empirical or manufacturer property.

A conveyer belt is also servo controlled so what? Tape is a different medium and a tape head functions totally different from a cartridge retrieving information from the crevices of a record spinning on a platter, every variable has an effect on the sound, nothing even close to it with tape. The negative influence of servo controllers and feedback loops in vinyl playback is already a known fact and discussed at nauseam for years.

David

 

[Folsom]

Tape also has an advantage that it doesn’t vary in speed from being “out of round” which causes the best TT’s speed to be off when nothing is perfectly centered unless it’s on a Nakamichi 1000 thing.

 

[microstrip]

A conveyer belt is also servo controlled so what? Tape is a different medium and a tape head functions totally different from a cartridge retrieving information from the crevices of a record spinning on a platter, every variable has an effect on the sound, nothing even close to it with tape. The negative influence of servo controllers and feedback loops in vinyl playback is already a known fact and discussed at nauseam for years.

David

In the known cases where there was a negative effect people have analyzed it and found the technical reasons why - manufacturers published reports on them.

IMHO Ad nauseam discussions of "known facts" never brought any truth to the high-end, just propagated old myths.

As you know the Airforce One does not have any servo - I have no horse in the servo race.

 

[microstrip]

i guess the real question is whether reality is the reference? or the source? do the drives on platters for cutting heads on lathe's have speed controls? my (admittedly minimal) understanding is that they are all direct drive. with servo's.

so if the master recorders, and the lathe's, are both servo controlled, how does a tt not using a servo somehow stay pure? does it fix the problem? or is there not a problem?

and.....maybe......it's all execution.

just say'n.

i got no answers.

IMHO there is no absolute reference in stereo sound reproduction. Each of us has its own reference - even our perception of reality is very different, reality can be a very misleading and variable reference. However sometimes groups of people share similar references - as we see in WBF.

IMHO if servos had interaction with the vinyl rotating system lathes would suffer a lot more from it - the drag forces involved in cutting are orders of magnitude higher than in playback.

 

[ddk]

IMHO there is no absolute reference in stereo sound reproduction. Each of us has its own reference - even our perception of reality is very different, reality can be a very misleading and variable reference. However sometimes groups of people share similar references - as we see in WBF.

IMHO if servos had interaction with the vinyl rotating system lathes would suffer a lot more from it - the drag forces involved in cutting are orders of magnitude higher than in playback.

How do you know how much we're suffering Francisco, do you have a way of measuring or comparing anything in that world? Any basis for your conclusion? We know the type of amplification makes a difference with cutting heads but according to your logic why should it, after all a groove is a groove. There are so many bad LPs around do you know for a fact that a servo controlled lathe didn't have anything to do with the poor results?

david

 

[ddk]

In the known cases where there was a negative effect people have analyzed it and found the technical reasons why - manufacturers published reports on them.

IMHO Ad nauseam discussions of "known facts" never brought any truth to the high-end, just propagated old myths.

As you know the Airforce One does not have any servo - I have no horse in the servo race.

You're right about most high end discussions but not this one, the effects of governors are well known by design engineers and if you read the claims of manufacturers using them they all claim to have overcome their negative effects with some new scheme that they've come up with to counter it, of course there's always a v2, v3, v4, v5, etc., etc., etc. to fix what they claimed to have already fixed, give me a break Francisco.

None of my comments were aimed at any particular turntable at any point in this thread including the AF1 which has a governor and a feedback loop.

 

[Lagonda]

For me the ideal feedback loop is once every 10 min
I connect the “Roadrunner “ in the middle of the record after warmup,
if speed is not correct, and leave it disconnected when i play music.
And yes Francisco i can hear a difference, leaving the feedback system running
constantly makes the treble sound a little digital

 

[Tango]

For me the ideal feedback loop is once every 10 min

Lagonda man. My feedback loop is so instantaneous.

 

[Lagonda]

Lagonda man. My feedback loop is so instantaneous.

And sometimes i’m totally out of the loop

 

[the sound of Tao]

And yes Francisco i can hear a difference, leaving the feedback system running
constantly makes the treble sound a little digital

My proctologist has a little digital.

 

[Lagonda]

Good for you ! But does it get the job
done ?

 

[microstrip]

You're right about most high end discussions but not this one, the effects of governors are well known by design engineers and if you read the claims of manufacturers using them they all claim to have overcome their negative effects with some new scheme that they've come up with to counter it, of course there's always a v2, v3, v4, v5, etc., etc., etc. to fix what they claimed to have already fixed, give me a break Francisco.

None of my comments were aimed at any particular turntable at any point in this thread including the AF1 which has a governor and a feedback loop.

Well, it seems we read from different people. And it is not only manufacturers, we also to consider the many happy users who prefer such turntables with ultra accurate speed.

As far as I know the AF1 has a governor and feedback loop during startup to reach the correct speed, after locking the speed it is not operational any more. Do you hear it during playback?

 

[microstrip]

For me the ideal feedback loop is once every 10 min
I connect the “Roadrunner “ in the middle of the record after warmup,
if speed is not correct, and leave it disconnected when i play music.
And yes Francisco i can hear a difference, leaving the feedback system running
constantly makes the treble sound a little digital

Well my turntable exceeds your rate - once every 25 minutes, when I change side or LP ...

Each case is a different case and I do not have any information on your turntable, but IMHO you should listen to proper digital - treble sounds really great, it is not a problem since very long!

 

[Lagonda]

Well my turntable exceeds your rate - once every 25 minutes, when I change side or LP ...

Each case is a different case and I do not have any information on your turntable, but IMHO you should listen to proper digital - treble sounds really great, it is not a problem since very long!

I’m messing with you Francisco, heard a top of the line Lampi recently, and was
impressed

 

[bonzo75]

I’m messing with you Francisco, heard a top of the line Lampi recently, and was
impressed

There is very well set up analog, then Lampi, then analog, then digital.

 

[Lagonda]

I heard the Lampi in a full SMT room, not in a familiar setting, but still prefer
my TT at home.

 

[ddk]

Well, it seems we read from different people. And it is not only manufacturers, we also to consider the many happy users who prefer such turntables with ultra accurate speed.

As far as I know the AF1 has a governor and feedback loop during startup to reach the correct speed, after locking the speed it is not operational any more. Do you hear it during playback?

People can use and like what they want it doesn't change the fact that a governor will degrade the sound of a turntable! It wouldn't be there if the turntable was accurate enough by itself !

Try an external motor with your AF1 and you'll see that it doesn't turn off.

david

 

[microstrip]

People can use and like what they want it doesn't change the fact that a governor will degrade the sound of a turntable! It wouldn't be there if the turntable was accurate enough by itself !

Try an external motor with your AF1 and you'll see that it doesn't turn off.

david

Well David, your suggested experiment does not prove anything - a different motor will probably sound different, as expected by anyone. I am not carrying experiments with the Airforce, it is good enough in standard form for me , but did a lot with the damned Forsell Aribearing motor in the past, even using synchronous motors driven by Studer cards to drive it - a trick I learned from the Brakemeier original Apolyt Turntable

Anyway I now checked the drive of my Airforce One with an analyzer and I can assure you that both phases of the synchronous motor are steady in frequency and amplitude when playing - only a strong disturbance such as my hand could change it.

Looking around I found a clear explanation for non technical people in the TAS review:

The two phases of the asynchronous motor are each driven by a 50-watt Class A amplifier. Once the speed is selected—33.33 and 45 rpm are available—a “torque switching circuit” is engaged to bring the very heavy platter up to speed, which takes a few to several seconds. When the platter reaches speed, the circuit reduces torque to the minimum necessary to maintain speed and the servo is completely disengaged and out of the system. Speed thereafter is controlled only by the motor and the inertia of the exceptionally heavy platter.

Do you have a similar system in the AS2000? Perhaps we can have a separate thread on motor drive systems, just technical, free from our preference debates!