After installing the Supaspin I have been listening to my records in the past days and I would like to share with you how happy I am with the now completely silent motor on the Music Hall MMF 2.2. It is “just” a Pro-ject 2-phase motor that was humming a lot but apparently with decent motor control it can be made completely silent.
Likely the original drive electronics fed it a square wave or something other than a sinewave which would definitely cause the motor to hum.
So if I wanted to try this with a VCR video head motor what all parts and pieces would be required.
So if I wanted to try this with a VCR video head motor what all parts and pieces would be required.
I took a look at the waveforms for my low-voltage 2-phase motor driven by the original AC-adapter here, not too square but not too pretty either.
The fact that the waveforms were kind of flat on top might have been enough to cause the vibration.
Correct. Assuming the current is equal in shape as the shown voltage plot, all other frequencies besides the 50Hz ground harmonic in the frequency spectrum do not contribute to the desired mechanical rotation. They do generate forces inside the motor that will introduce the humming noise. What also helped in lowering the remaining humm is that I lowered the amplitude of the driving signal from ~16V to 9V RMS for 33,3RPM.
By the way: the motor was originally ‘controlled’ by a simple circuit using an elco as 90 degrees phase shifter. I have not measured the waveforms but they probably were very non-sinusoidal.
By the way: the motor was originally ‘controlled’ by a simple circuit using an elco as 90 degrees phase shifter. I have not measured the waveforms but they probably were very non-sinusoidal.
Thank you Richard!
Finally I managed to finish rebuild of almost complete TT. Don't thing it is best in the world, but at least in my opinion it is one of the prettiest, at least for me who like understated retro design loaded with contemporary features:
It is still on my work bench. Need to clean and adjust tonearm, and play with preamp again. Also still looking for shaft encoder to properly measure W&F.
Also I envisioned cover, made from commonly available poly-carbonate sheet that I bent with help of steel pipes and heat gun. Cover is still in design phase, but will come in soon...
It is still on my work bench. Need to clean and adjust tonearm, and play with preamp again. Also still looking for shaft encoder to properly measure W&F.
Also I envisioned cover, made from commonly available poly-carbonate sheet that I bent with help of steel pipes and heat gun. Cover is still in design phase, but will come in soon...
I've got a Sansui SR-2050c record player that runs slightly slow with the solution I chose being to convert an audio amplifier to a variable frequency AC supply.
Is there an easy to find motor which will work with this, fit the Sansui and have a pulley on it for a flat belt?
I'll start my own topic once I get a definite plan together.
Is there an easy to find motor which will work with this, fit the Sansui and have a pulley on it for a flat belt?
I'll start my own topic once I get a definite plan together.
Is that for using with permanent split capacitor motors or specific two phase motors?
I'm looking to add this to my Sansui SR-2050C record player and wanted to be sure if that would work as I can likely easily get one of those that has a pulley for a flat belt.
Also are there any examples of AC motors in vintage equipment that might work well for this?
What class of amplifier is preferred to drive a motor with?
The Sansui has two buttons which move a lever to shift the belt between one or the other motor pulleys. Since the button for speed selection is momentary push is there a way to make it to where the speed can be selected by the Sansui's two buttons?
It should be applicable to any motor type which requires the phases aligned as shown. With a trim range of +-30 degrees relative to nominal, this would allow 60-120 degrees in 2-phase mode, and 105-165 in 3-phase mode, so 60-165 degrees overall.
The easiest way to find out is to measure the relative phases of your setup when running, or as has been shown here, measure both phases of the EMF genereated when driving the motor.
Whatever works! We're not seeking high-end performance for the motor drive, there are various examples of class-D, class-B and chipamps being used.
It curently only supports a momentary push-switch for speed change (and start-stop + menu selection).
https://www.electrical4u.com/split-capacitor-motor/
So that type of motor would work.
My thinking was to try one of those AC motors from an early 8 track player given it already has a pulley for a flat belt provided that type of motor won't induce hum into the cartridge. The problem there is generating around 120Vrms to make the motor work.
Cladd D I cannot do as it will interfere with AM reception unless there's a class D amp that produces no RFI.
Since it's a momentary pushbutton I'd need some way to for instance connect a reed switch and magnet so that the reed switch operates when the magnet passes by it as the 33 button is pushed and operates again as the magnet passes back by it as the 45 button is pushed.
For the circuitry I'd likely put it in its own separate box so that I don't have to cut the cabinet of the Sansui, however if I do that then why should I bother with the 33 and 45 buttons working. Plus by not modding that it keeps it more original so that it can be put back stock if so desired at a later date.
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Just thought about it and those early AC 8 track player motors rotate the wrong way to be useful here, but do rotate the right way for a rim drive phono. That said it would be easier to stick with a lower voltage motor as I wouldn't need amplifiers capable of producing a high output voltage.
Just need to hang the motor upside down. It could be an awesome motor pod design.