If the source code is available, it would not be a major task to port it over to another chip. One can make allowances for obsolescence by making the controller board separate from the PSU and drivers, etc. So one just needs to make a new controller board with the same electrical interfaces.
However, I've been pondering your idea of not reinventing the wheel (expressed in PM). One would have to replicate the main system blocks using currently available components, so the design effort required should be reduced.
However, I've been pondering your idea of not reinventing the wheel (expressed in PM). One would have to replicate the main system blocks using currently available components, so the design effort required should be reduced.
The SP-10's has some very good noise floor. So whatever controller you build will have to be very sophisticated to be as quiet. ramped pulses, feedback loop for stability etc.
The people that would have the most interest in something like this are archivist's that work with odd variety of disc's. The most important thing would be the pitch control. a very large +/- range would be helpful and it should be adjustable in semitones and cents not % which is about useless. Even if it read out in direct RPM would be better.
Variable speed from 10tpm to 100rpm would be desirable. backwards play at any speed. the ability to control start up and stop speeds. etc.
The controllers for these motors, for any of the technics direct drive motors are pretty well thought out. To duplicate one is no easy task! The hardest part is reducing cogging of the DD motor. the 10's had a -93dB noise floor if memory serves correct where as the 1200's and SP-25, SP-15's had something like -78db
best of luck. let us know how it goes!
The people that would have the most interest in something like this are archivist's that work with odd variety of disc's. The most important thing would be the pitch control. a very large +/- range would be helpful and it should be adjustable in semitones and cents not % which is about useless. Even if it read out in direct RPM would be better.
Variable speed from 10tpm to 100rpm would be desirable. backwards play at any speed. the ability to control start up and stop speeds. etc.
The controllers for these motors, for any of the technics direct drive motors are pretty well thought out. To duplicate one is no easy task! The hardest part is reducing cogging of the DD motor. the 10's had a -93dB noise floor if memory serves correct where as the 1200's and SP-25, SP-15's had something like -78db
best of luck. let us know how it goes!
The SP10 motor generates its own 3-phase sine drive signal, so there is no need to worry about waveforms, ramped or otherwise (if this is what you were referring to).
The motor and its original drive PCB act (electrically) just like an ordinary DC motor - increase the DC voltage and it runs faster / increases torque.
'Cogging' - well thats something that we iron out in the feedback compensator
By 'noise' are you refering to 'noise' as an error/randomness in the speed setpoint?
Are yoiu reffering to the different (MKI, MKII and MKIII) diagrams, or the plinth?
As for the plinth, I would personally use Russian Baltic Birch for the "constrained layer" effect, as this has been my wish all along, to seperate the motor into the plinth.
After isolating the motor like this, it would be much easier to have a slab of slate cut for I believe, even a better plinth... more mass, with the "constrained layer" still there.
"Butcher block" syle plinths, isolation platforms etc. have been found from other sites/forums posters to not be a good design..but, I guess there is always experimentation..
Rick
As for the plinth, I would personally use Russian Baltic Birch for the "constrained layer" effect, as this has been my wish all along, to seperate the motor into the plinth.
After isolating the motor like this, it would be much easier to have a slab of slate cut for I believe, even a better plinth... more mass, with the "constrained layer" still there.
"Butcher block" syle plinths, isolation platforms etc. have been found from other sites/forums posters to not be a good design..but, I guess there is always experimentation..
Rick
I'm interested to know: what are your 'problems' or dislikes with the SP10(ii) as it is from the factory?
As I said, I need to create a drive system since I have nought but the motor, and it's simpler & cheaper to create my own rather than clone the original circuit boards from the service manual.
But IF I had originals, I don't think I'd bother changing them.
[BTW. someone somewhere ( I cannot now find where) asked what crystal the SP10(ii) used. If that person is reading this, the crystal is 3.5795MHz, which is more commonly used as the colour phase reference in NTSC (USA/Japan) TV sets and video recorders. VERY commonly available.]
As I said, I need to create a drive system since I have nought but the motor, and it's simpler & cheaper to create my own rather than clone the original circuit boards from the service manual.
But IF I had originals, I don't think I'd bother changing them.
[BTW. someone somewhere ( I cannot now find where) asked what crystal the SP10(ii) used. If that person is reading this, the crystal is 3.5795MHz, which is more commonly used as the colour phase reference in NTSC (USA/Japan) TV sets and video recorders. VERY commonly available.]
This is the basic system / configuration I've decided upon. I'm working on a breadboard version of parts of it. The actual electronics will use no esoteric or unusual ICs - except for the microprocessor part, but since its only function - other than control logic - will be to generate the quartz-derived timing signal, it could be substituted with a discrete logic divider.
Attachments
I believe that circuit will give performance comparable with the old voltage servos which were used before the FG servo circuit was developed. This is a distinct retrograde step.
The problem lies in the available accuracy and precision of the frequency to voltage conversion being nowhere close to the accuracy and precision available by staying in the frequency domain and using the PLL to generate the lead / lag signal.
The problem lies in the available accuracy and precision of the frequency to voltage conversion being nowhere close to the accuracy and precision available by staying in the frequency domain and using the PLL to generate the lead / lag signal.
Feeding the split magnitude and phase components of the tacho frequency signal back into an error amplifer via an active filter network is how they do it until today (SL-12x0MK5)...
The 'vintage servos' were implemented without a tacho frequency coil signal at all. I have both an SL-2000 (servo control) and an SL-1200 (MK2, servo control with quartz referenced PLL using the tacho speed in a multi-loop) and the difference is like night and day.
Cheers,
Sebastian.
The 'vintage servos' were implemented without a tacho frequency coil signal at all. I have both an SL-2000 (servo control) and an SL-1200 (MK2, servo control with quartz referenced PLL using the tacho speed in a multi-loop) and the difference is like night and day.
Cheers,
Sebastian.
With the regular speed control via position detector coil feedback and servo control, speed regulation is slower and less damped. I attribute this to slower rise time and overshoot in the control loop.
This control scheme works best with heavy platters (flywheel effect) and is susceptible to speed slowdown through stylus drag (or any stronger force).
With the PLL and a stronger motor (like in the Technics MK2 players) higher forces can be applied, which enables the implementation of quicker regulation in the control loop. Speed is stable very quickly, and it behaves well damped with only slight overshoot (if any). Startup and full stop take place in less than a second, respectively, with just one (barely visible) ringing period under heavy load (like added weight or manual slowing).
This control scheme works best with light platters (reduced inertia) and is not susceptible to even tight clamping pressure at the spindle using thumb and index finger (or anything less forceful, like stylus drag).
Criticism of this "high speed, high torque" direct drive scheme (as it's advertised) adresses the noise and muddiness the quick corrections might presumably introduce into the pickup sound. Imagine the stylus dragging inside the groove, and the control loop in turn constantly accelerating and deccelerating the platter...
My personal opinion? I can hear only the improvements and never recognized any audible negative effects. They might exist, but this Technics direct drive scheme is reported to fare very well in comparison to good and very good record players in the sub-1500$ class.
Cheers,
Sebastian.
PS: I cannot provide you with figures and numbers, as I don't have test records available. My experience is based on visible (strobe) and audible (music) effects.
This control scheme works best with heavy platters (flywheel effect) and is susceptible to speed slowdown through stylus drag (or any stronger force).
With the PLL and a stronger motor (like in the Technics MK2 players) higher forces can be applied, which enables the implementation of quicker regulation in the control loop. Speed is stable very quickly, and it behaves well damped with only slight overshoot (if any). Startup and full stop take place in less than a second, respectively, with just one (barely visible) ringing period under heavy load (like added weight or manual slowing).
This control scheme works best with light platters (reduced inertia) and is not susceptible to even tight clamping pressure at the spindle using thumb and index finger (or anything less forceful, like stylus drag).
Criticism of this "high speed, high torque" direct drive scheme (as it's advertised) adresses the noise and muddiness the quick corrections might presumably introduce into the pickup sound. Imagine the stylus dragging inside the groove, and the control loop in turn constantly accelerating and deccelerating the platter...
My personal opinion? I can hear only the improvements and never recognized any audible negative effects. They might exist, but this Technics direct drive scheme is reported to fare very well in comparison to good and very good record players in the sub-1500$ class.
Cheers,
Sebastian.
PS: I cannot provide you with figures and numbers, as I don't have test records available. My experience is based on visible (strobe) and audible (music) effects.