Hi Peter,
An AC synchro motor requires a 90* phase shifted signal to run, usually derived from a cap. But the lowest vibration that the motor can exhibit will often come at a different phase shift, usually within 10* of 90, and will vary with different motors. Either burn a disc with a number of different phase shifts, and testing the motor for vibration, or using your soundcard output and varying the phase for minimum vibration, then burning a disc from those settings.
My Gyro motor is only 20V, so I could probably run it directly from a small amp I already have, 1 channel per phase. Might hit the stores today and see if I can pick up a cheap CDP, and burn a couple of CDs (no soundcard). I'd prefer to do this all solidstate, but I do like to irony of a CDP being the mere controller of my TTs motor, and it's also cheap and easy to implement. Later I will use the DC motors and a tape drive I'm getting through Bernhard.
Of course my SP10's don't need any such frippery.
Cheers
Brett
An AC synchro motor requires a 90* phase shifted signal to run, usually derived from a cap. But the lowest vibration that the motor can exhibit will often come at a different phase shift, usually within 10* of 90, and will vary with different motors. Either burn a disc with a number of different phase shifts, and testing the motor for vibration, or using your soundcard output and varying the phase for minimum vibration, then burning a disc from those settings.
My Gyro motor is only 20V, so I could probably run it directly from a small amp I already have, 1 channel per phase. Might hit the stores today and see if I can pick up a cheap CDP, and burn a couple of CDs (no soundcard). I'd prefer to do this all solidstate, but I do like to irony of a CDP being the mere controller of my TTs motor, and it's also cheap and easy to implement. Later I will use the DC motors and a tape drive I'm getting through Bernhard.
Of course my SP10's don't need any such frippery.
Cheers
Brett
Brett
You seem to like your SP10. I still keep my L07D too but only because shipping it to a willing buyer will be more expensive than anyone sane will pay (35kg). Writing two phase shifted sines to a CD never crossed my mind, have to admit it's a brilliant idea, but adjusting the phase shift is of course a bitch. From what i understand the optimal shift is specific to every motor. I built a simple 90s8015 based oscillator for my synchronous TTs which outputs two shifted sines at two of its ports with any preset shift. It uses a lookup table to generate the sines and using 100 points per cycle and a DAC0800 followed by 12db/oct filter at output i get about 0.01% distortion, similar to the Wien bridge.
May every cd player end up driving a TT one day.
peter
You seem to like your SP10. I still keep my L07D too but only because shipping it to a willing buyer will be more expensive than anyone sane will pay (35kg). Writing two phase shifted sines to a CD never crossed my mind, have to admit it's a brilliant idea, but adjusting the phase shift is of course a bitch. From what i understand the optimal shift is specific to every motor. I built a simple 90s8015 based oscillator for my synchronous TTs which outputs two shifted sines at two of its ports with any preset shift. It uses a lookup table to generate the sines and using 100 points per cycle and a DAC0800 followed by 12db/oct filter at output i get about 0.01% distortion, similar to the Wien bridge.
May every cd player end up driving a TT one day.
peter
Typical synchronous motors only need about 3W, which is less than 20mA rms per winding at 90V. This is easy to achieve from a simple chip amp and pair of step up transformers.
Step up is the safest way to do this, 90V rms is already a hazardous voltage. You don't want a driver amplifier running off +/- 150 Vdc rails.
Step up is the safest way to do this, 90V rms is already a hazardous voltage. You don't want a driver amplifier running off +/- 150 Vdc rails.
Gilid,
You can build this supply I did this for my Thorens TD124 and Garrard 301 and 401 turntables, 50 hz Wien oscillator and poweramp .
It is amazing how much better the sound is from the turntable I did also some measurements between the mains supply and the dedicated supply concerning distorsion ,
see picture from the supply
Volken
Attachments
This looks interesting.. Do you have plans to publish the design or can we nicely request you post the schematics?
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