|
Audio Asylum Thread Printer Get a view of an entire thread on one page |
For Sale Ads |
203.214.90.154
Thanks to the sterling efforts of Ray-o-stat and Mosin I got the motor and the rest of the parts for this project today.I thought it would be worth posting that I've now tested the motor and can confirm that it is a true three phase hysteresis motor, seemingly identical to the one out of the Empire.
I need to test the T amps for maximal output and required drive then we should be off and running. A benchtop version of my digitally controlled analogue oscillator has been built and tested but we may decide to upgrade to a software controlled direct digital synthesis (DDS) engine, depending on timing. The DDS guarantees generator speed stability matching the system clock (1 part per billion with the OCXOs we already have).
Follow Ups:
Hi Mark,I've been extremely impressed by your work and posts both here and at Clarisonus. My question for you regards the EAD motor on my newly acquired Rek O Kut T12 table. Its a synchronis hysterisis motor with a cap. Would this be a candidate for your new controller, even if its not the Pabst? From reading your piece on turntable motors, it appears to be of the same type.
Thanks,
Without seeing the motor I can't be sure.If you have access to a three channel scope it's very easy to check for yourself. Remove the cap so the three supply wires are separate. Attach a resistor to each wire, attach the other ends of the resistors to each other. Value is not critical, 1k is convenient.
Connect the three wires to three channels of the scope with the common point as ground. Run the motor (by hand will do) and check the trace. You should get three evenly spaced sinewaves which form a braided pattern.
If you don't have access to a multichannel scope you can check out each pair of wires in turn on the XY trace of a single channel scope. All three possible pairings should give you the same phase difference which should be 60 degrees (you are checking in delta format so it isn't 120 any longer). This is harder to judge unless you are used to phase angle estimations.
Could you send an e-mail to:mike (at) protedyne (dot) com
I'd like to ask you a few questions about your motor controller off board.
TIA
I should have said that the internal construction of the ROK and the Emptire motors appears identical.They have different housings and different shafts - the ROK shaft has a single pulley machined into it, the Empire shaft has a pulley machined into it at the top plus a two step pulley pressed onto the shaft below that.
Some Rek-O-Kuts have arrangements like the Empire. The one that Ray sent was from a N-33H, but there are at least two other variations.Mark,
This is going to be a masterpiece. You know that, don't you? ;)
Be sure and keep us up-to-date with developments; your REK-O-KUT is a rim-idler like the Garrard 301/401, or a belt drive? Believe R.O.K made both types....
Ours are belt driven, but when we finish, they will be string driven. Rek-O-Kut made a variety of idler drives, and at least one of them uses the Papst motor, but most do not.
I lost some prat to the idler tables I have built....But holy main bearings Mosin, the sound is so sublime! It has a three dimensional image to the music that I have only heard from top flight Basis and other 25k and up turntables.
Now I need to take thread tying lessons ;-) I had too much Bourbon to tie a knot last night. It would play for a side and then work itself loose!
Thanks for the upholstery thread idea....
.
Idlers are superb PRAT turntables...details are realistically projected like you are there in a recording studio. I would characterize the sound as tight and direct. It is awesome for Rock and Roll.Belt drives like my Thorens and Linn had nearly inky black bacgrounds and had an introspective feel like being half way back in the hall.
The thread drive on this N-33H is simply sublime. It has the same inky black background as my Thorens project table but with greater bass and slam. It sounds more like being right there in the pit of the orchestra than my idlers sound.
Moreover the 3 D soundstage is the most lifelike you could imagine.
There is enough space between instruments and depth to the soundfield that you could easily take a stroll on the stage and move around between the players. This is an experience I generally only get on extremely well recorded LP's with my best cartridge and tonearm.
I heard this on all my LP's last night and with the clunky stock Rek O Cut model 120 stereo arm with about 20 tons of effective mass. Plus no antiskate, so my channel balance was off as well.
I cannot wait to hear this with my fav arm and cartridges.
The thread drive is night and day different from the belt...I played both back and forth (not easy with thread by the way) and the thread just allowed the music to roll over me like a big ocean wave. In contrast the belt drive sounded like the sound was pushing and pulling.
The belt drive was fine, the thread drive was unbelieveably awesome. I can see now why Ray O Stat commented that a three phase motor and thread drive turned his perspective of turntable playback upside down. It did exactly the same for my non optimized platform.
I will keep an idler for rock and keep the thread drive for jazz and classical--and maybe Pink Floyd too! I cannot wait to listen to it on some marginal albums tonight just to see how the sound stage will sound on non optimal recordings.
The thread drive is simply sublime. I will give up a little prat any day of the year to hear a soundstage this convincingly real. And I am not even done tweaking anything yet! Mosin warned me about this. I just did not understand what he was saying until I experienced the sound for myself.
My speed control is off, so I need to do some mods to get the speed properly adjusted. And I need to learn to tie a better knot (probably easier without a bunch of Bourbon!)
The tables belong to Mosin and Ray-O-Stat, I'm making the drives for them. I believe they are using thread drive, the motors themselves were made to run belts (they have a small crowned pulley machined into the motor shaft)
I believe it is a tight fit pressed on piece. I would not think that Pabst would make different motors for the same purpose. They would just press on the fittings they need to do the work.Actually this might have been a Rek O Kut piece pressed onto the motor shaft.
Just for grins, can you inspect your Empire Pabst motor to see if it uses the exact same pulley?
I was hoping to have my brother in law machine a pulley for a thread drive that would provide more positive thread alignment.
Yes I have inspected it and yes it is certainly all one piece.I do think Papst made motors to OEM specification, that is, after all, their business. The same holds today - Maxon will make any motor configuration you want as long as you want 10,000 of them.
Yes, and we will most likely press new pulleys over the machined part. My thoughts are to make a simple nylon collar that presses over the shaft with the pulley extended beyond where it is currently located. This would make for a longer shaft that is more like the Empire's, but suitable for string.
Otherwise it would be my design and it might or might not be successful ;-)
but IIRC correctly, the ROK motor has its own external housing and is larger and heavier than the Empire (pictured)The spindle is pressed onto the motor shaft as one piece on both motors; the Empire has 331/3 /45/78 steps
I'm 99% sure these wouldn't interchange from one T/T to the other, tho' these are from the same era and maker so indeed, v. similar designs
Grins
No. The ones that we are using are identical, except for the shaft. The color and the top plate are different, but we are indeed talking about the same motor. The Rek-O-Kut and Empire are strikingly similar in mechanical features. This makes the more ugly Rek-O-Kut ideal for a ground-up DIY.
This post is made possible by the generous support of people like you and our sponsors: