Hello guys,I am planning to DIY a turntable and need your help for choosing the right motor.
There are 2 motors I really interested:
1.MOOG Silencer series,BLDC motor,the MOOG company said it is very quiet and reliable.
2.MAXON DCX series,brushed DC motor,the Maxon company said it is extremely quiet and smooth.
I prefer the BLDC motor because it is stronger and more reliable than a brushed motor but somebody has use the Maxon motor on the turntable and it works pretty well.If I use a BLDC motor's Hall sensor with a encoder on the bottom shaft to make a closed loop control circuit,the motor speed will be stable and accurate or not?So,how about your opinion for these 2 motors and if you have better ideas,please tell me,thank you very much.
There are 2 motors I really interested:
1.MOOG Silencer series,BLDC motor,the MOOG company said it is very quiet and reliable.
2.MAXON DCX series,brushed DC motor,the Maxon company said it is extremely quiet and smooth.
I prefer the BLDC motor because it is stronger and more reliable than a brushed motor but somebody has use the Maxon motor on the turntable and it works pretty well.If I use a BLDC motor's Hall sensor with a encoder on the bottom shaft to make a closed loop control circuit,the motor speed will be stable and accurate or not?So,how about your opinion for these 2 motors and if you have better ideas,please tell me,thank you very much.
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Having tried a couple of BLDC motors I have reached the conclusion that the sound just cannot compare to my old Maxon powered from a Salas 1.3. The speed with the Maxon is of course not long term stable but this is just a minor inconvenience compared to a vastly superior sound. All imho.
It should not be hard to get a stable speed from the Maxon using a sensor and a very long timeconstant correction.
It should not be hard to get a stable speed from the Maxon using a sensor and a very long timeconstant correction.
The result will be as good as the closed loop controller.
A good PID algorithm or controller will give good results.
At least one well respected manufacturer seems to do that; have a look at the picture:
Continuum Audio Labs
Kronos Audio also uses Maxon motors, but i'm not shure about the controller...
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Kronos also uses the DCX series of motors, or they do now. They used to use an older model previously.
I am curious about you saying they aren't quiet? I've been intrigued by them for a while but they are exceptionally expensive so I've never pulled the trigger.
Here is the engineering firm that does Kronos controller, there's a bit of info on there site about it. LABB Technologies Inc.
I am curious about you saying they aren't quiet? I've been intrigued by them for a while but they are exceptionally expensive so I've never pulled the trigger.
Here is the engineering firm that does Kronos controller, there's a bit of info on there site about it. LABB Technologies Inc.
I once had a Maxon Remax motor with sleeve-bearings and graphite commutation- it was very quiet but it did not last very long (the bearing failed).
Before I ordered it I talk to an engineer at Maxon and while I told him my intended use (low rpm, belt-drive + sleeve bearing)
the motor came with a sticker “test sample” or so, so that I could not send it back after it failed.
So to play it save I next choose ball bearings for the DCX motor. I talked to Maxon again and I was told that the precious metal brushes are
generally noisier than graphite but the DCX line has some special noise reduction. Precious metal brushes allow for a better speed regulation.
So in the end the DCX is substantially noisier than the Remax but the speed stability is much better.
DC motors are more difficult to achieve speed stability. The speed is sensitive to voltage changes and torque loads. Closed loop feedback with an encoder can cause "hunting" depending on the implementation. At a minimum, the DC controller should have current feedback to compensate for speed changes with torque loads and temperature compensation to prevent unstable operation of the current feedback.
Speed stability of AC synch motors is easier to control as the speed is dependent on drive frequency only, and not affected by torque load, voltage or temp. 2 phase AC synch motors can have more vibration than DC motors, but BLDC motors run as 3 phase AC synch are very quiet.
Speed stability of AC synch motors is easier to control as the speed is dependent on drive frequency only, and not affected by torque load, voltage or temp. 2 phase AC synch motors can have more vibration than DC motors, but BLDC motors run as 3 phase AC synch are very quiet.
Hello,Pyramid.I am reading your topic about the motor these day,they are very nice.I saw lots of turntable use BLDC motor to drive the platter now,many of them have accurate and stable speed.How to do that?Very thanks.
Thank you for this: very surprising, especially the ready made controller. I once had the motor from a Criterion and it was a BLDC. It was a few years old and not only sounded horrible, but was also quite noisy. Very curious to try out a DCX motor.
I use a motor controller with negative output resistance to maintain speed stability.
The negative output resistance of the controller equals the winding resistance of the motor.
With perfectly matched resistances the residual speed variation is determined by the temperature coefficient of the copper resistance (I'm already working on a temperature compensation for this). Metal brushes have a constant (and lower) voltage drop compared to graphite brushes so its better to use them with this kind of controller.
I choose the motor according to Mark Kellys recommendations, to have a low ratio of speed constant/torque constant to maintain best speed stability.
The best motor I coud find so far was the DCX22L 48V 10W
Mark Kelly wrote a lot about this stuff here in the past, really good readings.
He wrote also an excellent article for Bas Hornemans DIY magazine but it seems to be offline...
The negative output resistance of the controller equals the winding resistance of the motor.
With perfectly matched resistances the residual speed variation is determined by the temperature coefficient of the copper resistance (I'm already working on a temperature compensation for this). Metal brushes have a constant (and lower) voltage drop compared to graphite brushes so its better to use them with this kind of controller.
I choose the motor according to Mark Kellys recommendations, to have a low ratio of speed constant/torque constant to maintain best speed stability.
The best motor I coud find so far was the DCX22L 48V 10W
Mark Kelly wrote a lot about this stuff here in the past, really good readings.
He wrote also an excellent article for Bas Hornemans DIY magazine but it seems to be offline...
This site explains the principle:
AB-026 : Sensorless Speed Stabiliser for a DC Motor - Precision Microdrives
AB-026 : Sensorless Speed Stabiliser for a DC Motor - Precision Microdrives
Russc already provided the links in post #2 of this thread. The SG4 is a 3 phase sinewave generator, and the MA3D is a 3 channel amplifier that will drive the Anaheim Automation BLDC motors.
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