Yes it will work fine with the dual motor. The plot on the left is done with the exact motors in your dual motor flywheel turntable. The temp of the PSU topped out at ~120°F, even after running it for more than an hour and a half non-stop.
No complaints with modular. Do you expect that it will be possible to purchase the controller and power output stages separately (as in buying one controller and three output stages)? Will the controller have two 5V outputs, or only one?
Option A (needs two outputs from controller)
Controller output 1 -----------------------------> power output stage 1 (0 degrees)
Controller output 2 --> phase shifter output 1 --> power output stage 2 (120 degrees)
Controller output 2 --> phase shifter output 2 --> power output stage 3 (240 degrees)
Option B (needs only one output from controller)
Controller output 1 --> phase shifter output 1 --> power output stage 1 (0 degrees)
Controller output 1 --> phase shifter output 2 --> power output stage 2 (120 degrees)
Controller output 1 --> phase shifter output 3 --> power output stage 3 (240 degrees)
thanks, jonathan
I'm on the same wavelength as Jonathan. I'd like to create a 3-phase power supply for my old Empire turntables which use a 3-phase Papst motor. I'll be interested if Jonathan will post further details on hisexperimentation. Hope he doesn't burn out too many amps!
In any case I'd like to be on the list for notification when the new version of the higher-power Falcon (The Eagle?) becomes available. Hope all goes well with your commercialization of the test setup. Thanks for sharing!
Hi Comet: My need for a precise and adjustable 3-phase controller is to support a development project that is likely to take enough time to tax the patience of most of the readers here (smile).
In the shorter term, however, I have a slumbering Final Audio Research VTT-1 turntable that I wouldn't mind converting to take a 3-phase DDS controller.
Is your Papst motor of the außenläufer type?
kind regard, jonathan
In the shorter term, however, I have a slumbering Final Audio Research VTT-1 turntable that I wouldn't mind converting to take a 3-phase DDS controller.
Is your Papst motor of the außenläufer type?
kind regard, jonathan
Yes, my Papst motors are both eddy current 3-phase motors.
Mark Kelly has designed and built a few three-phase motor controllers for these motors. I believe he used a high-precision source to generate a quaddrature signal to feed some high-power chip amps. There was one user (grinagog) who wrote up his impressions of the controller on Audio Asylum. Mark has moved on, although his 2-phase controller is still build by the Lenco/Gerrard diyAudio community. Mark Kelly's write-ups have been quite helpful to me. He still knows more about ac motors in turntable applications than any other person I've ever met.
There are some two-phase controllers around, but most do not have the capacity to power the torquey Papst motors. And I really would prefer to have a 3-phase signal generator. How were you planning to generate a split phase for your motor? I would guess that it is far better to do this in the digital domain than in the analog domain for exact control of the phase relationship.
I've been fussing around with the concept on my bench. I can simulate the effect with three (tube) amplifiers each fed an MP3 60hz signal at 120 degrees out of phase connected to the motor windings directly through an industrial three-phase transformer to step up the power. The experiment covered my entire workbench + a spare table. However, the reduction in vibration of the Papst was significant when fed this way, compared to the stock approach using a capacitor to phase shift 120VAC. My turntable has a 15 lb. platter, but I can reduce the voltage after startup, which also does good things for vibration. I did find that having the ability to change the phase angle also had some positive effect on the vibration/noise, but that may be specific to eddy current motors?
Anyway, I'm not certain the audible effect is worth the pain of designing and building a controller myself. My table is belt-driven and the motor is suspended on isolation bushings. But I'm interested enough to go for high-power Falcon if/when it emerges.
Oh, and I love my Delos cartridge!
Best,
Frank
Hi Frank:
The Final Audio Research VTT-1 controller starts with a Wien-bridge oscillator and provides a bi-phase line-level output, to which the user is instructed to connect a two-channel power amplifier in order to drive the motor (which drives the platter via string or belt). It works OK, but is cumbersome and has no platter speed sensing mechanism (also, sound quality is affected by the choice of power amplifiers). Hence my interest in a solution that is more compact and provides more precise control over platter speed.
Prior to knowing about the Phoenix designs I wasn't planning to use a DDS, rather a crystal oscillator, programmable divider, phase comparator and whatnot. For speed sensing I would have silk-screened a large-diameter stroboscope onto the bottom of the platter, then shined an LED at the stroboscope through a slit and picked up the reflections with a photo-transistor.
I'd be happy if Phoenix were to make a three-phase design with line-level outputs, since I would no longer need to worry about any of that (at the most, perhaps the final drive amplifiers).
Even when feeding the Papst motor with three sine waves spaced 120 degrees apart, you found that slight adjustments to the angular spacing reduced motor noise and vibration? I suppose that it makes sense when motor production tolerances are taken into consideration.
We'll have to hope that if and when Phoenix makes a three-phase version of their motor controller, phase angle adjustment will be one of the features (internal trim pots should be sufficient).
I am honored!
kind regards, jonathan
The Final Audio Research VTT-1 controller starts with a Wien-bridge oscillator and provides a bi-phase line-level output, to which the user is instructed to connect a two-channel power amplifier in order to drive the motor (which drives the platter via string or belt). It works OK, but is cumbersome and has no platter speed sensing mechanism (also, sound quality is affected by the choice of power amplifiers). Hence my interest in a solution that is more compact and provides more precise control over platter speed.
Prior to knowing about the Phoenix designs I wasn't planning to use a DDS, rather a crystal oscillator, programmable divider, phase comparator and whatnot. For speed sensing I would have silk-screened a large-diameter stroboscope onto the bottom of the platter, then shined an LED at the stroboscope through a slit and picked up the reflections with a photo-transistor.
I'd be happy if Phoenix were to make a three-phase design with line-level outputs, since I would no longer need to worry about any of that (at the most, perhaps the final drive amplifiers).
Even when feeding the Papst motor with three sine waves spaced 120 degrees apart, you found that slight adjustments to the angular spacing reduced motor noise and vibration? I suppose that it makes sense when motor production tolerances are taken into consideration.
We'll have to hope that if and when Phoenix makes a three-phase version of their motor controller, phase angle adjustment will be one of the features (internal trim pots should be sufficient).
I am honored!kind regards, jonathan
Two quick questions if I may:
1- My VPI Scoutmaster II is currently plugged in to a Monster AVS-2000, which attempt sto deliver 120V constantly. Is there any real benefit to the Falcon for me?
2-I've looked for my motors power draw, but all data I find is for the Scoutmaster, rather than the II. Anyone know? Motor on mine LOOKS identical to the original Scoutmaster but ?? I have the metal platter. Purchase the table 6/24/2013.
Thanks !!
1- My VPI Scoutmaster II is currently plugged in to a Monster AVS-2000, which attempt sto deliver 120V constantly. Is there any real benefit to the Falcon for me?
2-I've looked for my motors power draw, but all data I find is for the Scoutmaster, rather than the II. Anyone know? Motor on mine LOOKS identical to the original Scoutmaster but ?? I have the metal platter. Purchase the table 6/24/2013.
Thanks !!
Regarding the AVS-2000 which is only a voltage stabilizer, the frequency will still vary slightly as it does from the power grid. From the reviews I've read on the AVS, it doesn't remove a lot of the noise from the power grid and might even generate some of it's own. The Falcon regenerates the AC signal from DC so the output frequency is extremely stable (xtal controlled) and clean (<0.5% distortion). The Falcon is also a variable frequency drive. Even if the motor is running at a precise frequency (ie 600 RPM) the platter may not be due to belt slippage, position of the belt on the pulley, etc. I see you just ordered the RoadRunner tach on e-Bay; I would be interested in your impression of the Scoutmaster's speed when you install the tach. Try moving the belt on the pulley and see how much the speed changes. Ditto by moving the SAMA closer or farther from the platter; even ¼" makes a huge difference.
Regarding the motor size, it's hard to tell for sure without looking at the label on the motor itself. Remove the 4 black screws around the top of the SAMA and flip the top of the assembly over to see the motor. If it is 300 RPM (33 RPM spindle is ~1.2" dia), it will be 7.5W most likely. Otherwise it could be 5.5W (PN SP3923) or 10W (PN 3201-003). 5.5W is OK for the Falcon. 7.5 or 10W will need the Eagle.
If it has a phase shift cap, it is an AC sync motor and it will depend on the power requirement. Papst also made AC induction motors that were quite high power, but this would appear to be a sync motor.
The Falcon is limited to 5W max, the Eagle will drive motors up to 15W. You would plug the motor's wall adapter into the PSU output. The Falcon is also 115VAC output only. You would need a step up xfmr or a different wall adapter if it is designed for 220VAC. The Eagle is jumper selectable for 115/230VAC output.
Both the Falcon and Eagle have universal input (100-260VAC) power supplies. Both are front panel programmable for 50/60Hz pulley operation.
Thanks. Yes I figured ordering the Tach would really answer the ultimate question, and allow me to either buy the Falcon/Eagle, or if I was in fact seeing platter speed stability I'd at least have a cool box telling me so!
The AVS 2000 does not regenerate or do anything your Falcon/Eagle does-so I am kind of assuming I will see speed anomalies. I'm going to check on the motor later today to know the deal with the power requirements.
Looks like i am 300rpm, 7.5W, so please add me to your list for new when the Eagle is available. Thanks.
The control unit for the Eagle is the same size (same extrusion actually) as the Falcon. The picture shows a Falcon front panel; the front panels for the Eagle are due here next week. It will fit under your Scout, look the same (except for the name), work the same and operate the same way as the Falcon.
The output is on the front panel of the amp unit and is a NEMA 5-15 (3 prong North American) socket. The cable that connects the control unit and amp together is 6ft long, so you can locate the amp remotely and plug the motor's original power cord into the Eagle output. The cable is a 3.5mm stereo Male-Male, and you can substitute other lengths if necessary.
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