The necessity for absolute tt speed control

[Lagonda]

The Condor PSU will not drive your Studer motor. It is designed to work only with the BLWS-172 series BLDC motors which are rated at 12W. The PSU runs the motor at ~12W at start up, then reduces the power to ~9W for lower vibration. If you connect the output of the Condor to any other load, it will most likely destroy the output amps.

The other problem with doing this: The Condor starts the motor at 2Hz and ramps up to 20Hz for 33 RPM at the platter; the BLWS has 4 poles and RPM=60*freq/pole pairs =600 RPM. Neither of these frequencies will produce the desired result through a step up xfmr.

The Condor/Eclipse package should be more than capable of driving your platter. If you want to use the Studer motor, look at the SG4 DIY kit:
https://www.diyaudio.com/forums/analogue-source/298018-diy-4-phase-sinewave-generator-turntable-motor-drive.html

I believe DIY member ralphfcooke has done a 3 phase version to drive a Papst motor using step ups and conventional class D amps.

Thank you for the clarification Bill. But why not simply use the motor in two phase, like the system you designed for DDK’s AS2000 ? David contacted me last night and unceremoniously said “ would you want to try the boards i have for the AS2000 ?” WTF ! First i thought i had fallen asleep and was dreaming, after pinching myself i looked at the calendar just to make sure it was not the first of April. And David added
“ you have build your own box for it”
And just like that my little Diy project had taken on a whole new dimension.
Thank you again David !
And thanks to you Bill for creating it !

 

[Phoenix Engineering]

Phoenix, my rim drive could be a candidate for the Condor it's been suggested. What considerations are uppermost?

The Condor can be user programmed for CW/CCW rotation, so it can be used in a rim drive application. A couple of considerations, all having to do with motor speed/platter diameter/pulley ratio. If the existing pulley will fit the Condor motor shaft (¼"), then we need to know what is the platter diameter and the motor speed for 33 RPM. If a new pulley needs to be fitted, you will have more flexibility as the pulley diameter can be adjusted to the other parameters (motor speed/platter diameter). The platter diameter appears to be considerably larger than 12", so the motor speed needs to be higher (would require a custom version of the Condor) or the drive pulley needs to be larger.

 

[Lagonda]

The Condor can be user programmed for CW/CCW rotation, so it can be used in a rim drive application. A couple of considerations, all having to do with motor speed/platter diameter/pulley ratio. If the existing pulley will fit the Condor motor shaft (¼"), then we need to know what is the platter diameter and the motor speed for 33 RPM. If a new pulley needs to be fitted, you will have more flexibility as the pulley diameter can be adjusted to the other parameters (motor speed/platter diameter). The platter diameter appears to be considerably larger than 12", so the motor speed needs to be higher (would require a custom version of the Condor) or the drive pulley needs to be larger.

Bill i use my Falcon with a off size pulley, as i modified it by machining it down to fit a larger flat belt, in stead of the round belt it originally came with. The Roadrunner has no problem adjusting the frequency to fit the off size pullley.

 

[Lagonda]

The Condor PSU will not drive your Studer motor. It is designed to work only with the BLWS-172 series BLDC motors which are rated at 12W. The PSU runs the motor at ~12W at start up, then reduces the power to ~9W for lower vibration. If you connect the output of the Condor to any other load, it will most likely destroy the output amps.

The other problem with doing this: The Condor starts the motor at 2Hz and ramps up to 20Hz for 33 RPM at the platter; the BLWS has 4 poles and RPM=60*freq/pole pairs =600 RPM. Neither of these frequencies will produce the desired result through a step up xfmr.

The Condor/Eclipse package should be more than capable of driving your platter. If you want to use the Studer motor, look at the SG4 DIY kit:
https://www.diyaudio.com/forums/analogue-source/298018-diy-4-phase-sinewave-generator-turntable-motor-drive.html

I believe DIY member ralphfcooke has done a 3 phase version to drive a Papst motor using step ups and conventional class D amps.

Wow i just read your post on the DIY motor controller, very impressive !

 

[Phoenix Engineering]

Bill i use my Falcon with a off size pulley, as i modified it by machining it down to fit a larger flat belt, in stead of the round belt it originally came with. The Roadrunner has no problem adjusting the frequency to fit the off size pullley.

Yes, the Falcon can compensate for a fair amount of variance, but it has its limits. In order for the Falcon to correct, for 33.3 RPM, the speed reported by the RR must be between 30.000 and 39.999 RPM; for 45 RPM, the reported speed must be between 40.000 and 49.999 RPM. Outside those numbers, the Falcon will ignore the reading and assume the wrong pulley is being used etc., and does not try to correct.

 

[Lagonda]

Yes, the Falcon can compensate for a fair amount of variance, but it has its limits. In order for the Falcon to correct, for 33.3 RPM, the speed reported by the RR must be between 30.000 and 39.999 RPM; for 45 RPM, the reported speed must be between 40.000 and 49.999 RPM. Outside those numbers, the Falcon will ignore the reading and assume the wrong pulley is being used etc., and does not try to correct.

My chances of good result with the AS2000 controller should be fairly high i hope, it would keep all the wonderful features in the Phoenix system, with added power output at 50W max

 

[Lagonda]

I was woken up by the postman and scrambled out in my underwear, as he does definitely not ring twice ! The shear size and weight of this Studer A80 special edition motor blew me away, close to 5 kg with 2 kg probably in the extra flywheel alone. Bearing seems in perfect order, not a sound when turned manually, with smooth rotation. Now i will make a temporary box for it and get my TT up higher, as this thing is just much larger than i imagined . My metalworks guy is on vacation so wood will have to do for now. Will confer with Micro, David and Bill for right choice of capacitor. This is definitely getting interesting

 

[bonzo75]

Why would anyone sleep in their underwear

 

[Lagonda]

Why would anyone sleep in their underwear

I don’t want to scare the shit out of the postman, naked is out . Pj’s are just to British for me, you probably wear the whole gettup with little hat and everything Ked

 

[Folsom]

The Falcon IIRC is also just a single read device, meaning you could have half speed and double speed for half a rotation and it would come out as correct.

 

[Lagonda]

The Falcon IIRC is also just a single read device, meaning you could have half speed and double speed for half a rotation and it would come out as correct.

With no drift( +/- 0,001) at idle i doubt a deviation on one rotation is audible, i expect the variation to be higher with the larger motor, but hope the added power will translate into musical differences.

 

[Folsom]

With no drift( +/- 0,001) at idle i doubt a divination on one rotation is audible, i expect the variation to be higher with the larger motor, but hope the added power will translate into musical differences.

I'll stick with frequency specific driving

 

[Lagonda]

I'll stick with frequency specific driving

That’s what i normally do,
I also prefer my TT without the RR constant feedback, it’s good for setting the speed, but i prefer the sound set with needle down halfway through the LP after warmup. Album will start 0.003 rpm to slow and end with 0,003 rpm to fast because of needle drag(less deviation on LT arm)
On idle without needle i have deviation of 0,001 up and down without feedback, it is actually larger with feedback. I just love heavy platters with air bearings

 

[microstrip]

(...)
I was woken up by the postman and scrambled out in my underwear, as he does definitely not ring twice ! The shear size and weight of this Studer A80 special edition motor blew me away, close to 5 kg with 2 kg probably in the extra flywheel alone. Bearing seems in perfect order, not a sound when turned manually, with smooth rotation. Now i will make a temporary box for it and get my TT up higher, as this thing is just much larger than i imagined . My metalworks guy is on vacation so wood will have to do for now. Will confer with Micro, David and Bill for right choice of capacitor. This is definitely getting interesting

Congratulations, the hard work is starting!

The capacitor will depend on the rotation speed - 8 microfarad (4.7 parallel 3.3) is a good starting point, although it will depend on how you are going to implement the controller.

The critical point now is the pulley - it will determine the motor rotational speed - they are used usually around 500 rpm.

 

[Folsom]

Congratulations, the hard work is starting!

The capacitor will depend on the rotation speed - 8 microfarad (4.7 parallel 3.3) is a good starting point, although it will depend on how you are going to implement the controller.

The critical point now is the pulley - it will determine the motor rotational speed - they are used usually around 500 rpm.

Wait, are you sure that motor uses a capacitor? (not all do, and I'm not sure if this one does or doesn't)

The Phoenix controller and some others on DIYaudio skip the capacitors all together and just use two channel output for better speed control if the motor has two windings.

 

[microstrip]

Wait, are you sure that motor uses a capacitor? (not all do, and I'm not sure if this one does or doesn't)

The Phoenix controller and some others on DIYaudio skip the capacitors all together and just use two channel output for better speed control if the motor has two windings.

If we want to use it with a single phase AC supply, yes. The capacitor is not used with double or triple phase controllers.

 

[Lagonda]

This is what my current Hurst motor uses on the Falcons controller.

 

[Phoenix Engineering]

The Falcon IIRC is also just a single read device, meaning you could have half speed and double speed for half a rotation and it would come out as correct.

This is a logical fallacy. In theory, it would be true, but the chances of something causing a slow down in speed , then another increase in speed of exactly the same amount to offset the reduction, within exactly one revolution is just about nil.

People have used the RR tach to diagnose problems with the bearing, lubrication, misaligned or contaminated belts; and that's just using it to measure the speed without feedback to control and maintain speed.

On idle without needle i have deviation of 0,001 up and down without feedback, it is actually larger with feedback. I just love heavy platters with air bearings

That's not uncommon with heavier platters. Unless the motor has a correspondingly larger amount of torque to make the correction within the same time frame, the system will be underdamped and you will see more overshoot.

 

[Phoenix Engineering]

Will confer with Micro, David and Bill for right choice of capacitor. This is definitely getting interesting

The capacitor is a function of the winding impedance and frequency used to drive the motor. Note that in most cases, it is not possible to get the desired phase shift via a single capacitor; the value is usually arrived at empirically and is a trade off between lower vibration and ability of the motor to start. Using only one cap at different frequencies will also affect the performance (Rega switches in different caps between 33/45 on some of their tables). The best way to drive a 3 phase motor is with a 3 phase supply, but doing so at these voltages and without transformers is not trivial.

I had an e-mail conversation with one of the engineers at Hurst to determine if there was a spread sheet or other formulas/equations that I could use to determine the optimum value for the phase shift cap on one of their motors; his response in its entirety was "No."

 

[ddk]

The Falcon IIRC is also just a single read device, meaning you could have half speed and double speed for half a rotation and it would come out as correct.

I can't speak about other similar devices but the Road Runner is extremely accurate. I've checked the readings against a digital tach and it's spot on and with more resolution. They're in daily use with all the AS tables.

david