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Grok: The Papst 24V AC motor, often referred to as the "Aussenlaufer" (outer rotor) motor, was used by several turntable manufacturers, particularly in high-end models during the late 20th century. Based on available information, the following manufacturers are known to have incorporated this motor in their turntables:
Michell Engineering: The Michell Gyrodec, especially early models from the 1980s, used the Papst 24V AC motor. This is well-documented in discussions about the Gyrodec’s design and upgrades, with specific mentions of the motor’s 24VAC requirement and its use in models like the Gyrodec serial number 111 from 1982.
Thorens: Early Thorens TD-124 models are noted to have used the Papst Aussenlaufer motor, particularly the 3-phase, delta-wired version. This motor was a key component in some of Thorens’ classic turntables, valued for its hysteresis synchronous design.
Rek-O-Kut: Models like the Rondine 2 and N-33H featured the Papst Aussenlaufer motor. These turntables often utilized the motor’s 3-phase configuration, sometimes adapted to single-phase power with a phase-shift capacitor.
Empire: The Empire 208 turntable is cited as using the Papst Aussenlaufer motor, appreciated for its robust design in classic belt-drive systems.
Fairchild: The Fairchild 412 turntable employed the Papst motor, with its 3-phase setup integrated into a tube-driven electronic motor controller, highlighting the motor’s versatility for variable speed applications.
Goldmund: Early Goldmund Studio turntables used a Papst direct-drive motor, though some sources describe it less favorably compared to belt-drive applications.
SOTA Industries: SOTA turntables, particularly some of their older models, are mentioned as using Papst motors, with the company still offering rebuild services for these motors.
Notes:
The Papst motor was highly regarded for its low vibration and high torque characteristics, making it a favorite for belt-drive turntables with heavy platters. However, it was discontinued around 1999, leading manufacturers like Michell to seek replacements, which impacted its availability and earned it the reputation of being "unobtainium."
The motor’s 24V AC specification often required specific power supplies, sometimes with phase-shift capacitors or advanced controllers to optimize performance and minimize hum.
While the Papst motor was predominantly used in high-end or professional-grade turntables, its application varied, with some models requiring custom power supplies or modifications for optimal operation.
Due to the motor’s discontinuation and specialized nature, sourcing it today is challenging, often requiring repairs or aftermarket solutions like those from Origin Live or custom controllers. If you’re looking for a specific model or need further details on compatibility, please provide more context, and I can narrow it down further.
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A slight correction to the above:
Papst motors were used in later samples of the Thorens 124/II, when supplies of the original E50 motor became exhausted.
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Well it's doing something, bless it.
Even with the amp on lowest volume I am getting about 80Vpp. Don't want more than 68Vpp for 24V RMS.
Frequency stability is fine.
Time for a think. There's no load on the amp output and no phase cap yet.
https://uploads.tapatalk-cdn.com/202...05957cdbca.jpg
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This thread is on hold. Grok didn't consider the impedance of the Pabst when coming up with the design and now reckons a 150 Watt power amp is needed, not the 50 Watt one.
Don't try and build the above, obviously.
I will continue it only when I have something that is proven to work.
Update: Grok went on a bender and now doesn't think a 150 Watt amp is necessary. Giving it more info on the Pabst stopped it freaking out. No more posts until something works, though.
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Its like Grok aint the most reliable source Justin?
Not adverse to AI by the way, use it in Adobe graphic design all the time.
Anything Elon Musk related... well.
ChatGPT might be at least worth a try?
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I assumed Grok knew the spec of a Pabst motor. It seemed all confident about it especially with the early Michell Gyrodec reference I gave it, plus the TNT Audio link
When I fed it some better information about the Pabst, everything changed.
Just by using Google, it appears the Pabst needs 3 Watts. Not the 50W of the class D jobbie it went through a phase of thinking was not enough.
I have been getting some weird gradually rising voltages out of the class D amp I have used. Tried everything including a 4Ohm load plus a cap on the output and various probe / earth configs and even though I have no clue about hardware, it seems like a total lemon.
So I have ordered various other bits e.g. a 15 Watt class D amp for £4.99, a 12V SMPS for £5.89 and another 50 W class D power amp for £12.99.
Cost no object, this project.
Basic philosophy is - try all sorts until I see an output on the scope that makes some logical, reasonable sense.
It's going to happen. Maybe;):)
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Gotta smile. This Dollatek TPA3166A 50W class D produced an output that made sense, at least.
Photo shows one AD9833 output feeding both input channels of the Dollatek to produced about 10V RMS at 50Hz.
Trouble is, it can't produce more than that for long with the volume on full as the chip overheats and protection kicks in shutting down the output very quickly.
It can't even maintain 10V for long without stress.
So I might try a TPA3255 amp - good for 315W at about £20 with a 36 or maybe 48V SMPS also at about £20.
These boards don't have volume pots. But the AD9833 board I am using actually has an inbuilt amp that can be used to bang up the default 600mV output to trim the power amp output. If I can get that to work, I'll try the 315W route.
BTW you must feed both channels of this class D amp otherwise the output is a strange shaped sine wave indeed.
https://uploads.tapatalk-cdn.com/202...c884ba6e53.jpg
https://uploads.tapatalk-cdn.com/202...282149dd73.jpg
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1 Attachment(s)
If you look at the AD9833 above you will see a PGA / GND pair. This PGA is a programmable gain amplifier.
I've managed to program it to provide 2Vp-p in the screenshot below, but it will go as high as 3.6Vp-p. It's basically controlled by an 8 bit unsigned value so 255 possible volume levels.
That's great news. That means we can trim a TPA3255 to give the desired 19V-24V output. That sine wave now looks lovely and smooth.
Grok reckons the TPA3255 is best with a 48V rather than 36V SMPS as it will run more efficiently and cooler.
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Two AD9833s are a no-no. I asked Grok to do some some phase shift calculations and the results surprised me given the 25MHz crystal in each board. Grok says:
Implications for Your Application
For your Pabst turntable motor requiring a 90° phase difference for 4 hours:
Dual AD9833s: Even with optimistic assumptions (0.09°/s), the phase drift (1,296° over 4 hours) causes multiple 360° cycles, disrupting the motor’s rotation. Periodic re-synchronization (every 100 s) mitigates this but introduces complexity and potential glitches.
Single AD9833 + Capacitor: As you proposed, this eliminates drift entirely, ensuring a stable 90° phase shift via a passive component. It’s simpler, more reliable, and better suited for your phase-critical, long-duration application.
Do I Agree with Your Capacitor Proposal?
Yes, I strongly agree that using a single AD9833 with a capacitor is the better approach, especially given the confirmed significance of phase drift. The dual-AD9833 setup’s drift, even at a reduced rate (e.g., 0.09°/s), is problematic for a 4-hour, phase-critical application. The capacitor method:
Guarantees a fixed 90° phase shift.
Simplifies wiring and software.
Reduces power consumption.
Aligns with traditional turntable motor designs.
Ordered some quality parts. Getting more confident.
https://www.audiophonics.fr/en/smps-...c-p-18106.html
https://www.audiophonics.fr/en/ampli...w-p-17252.html
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That 3e board is a nice, seriously heavy thing mounted on a huge metal plate. 48V SMPS also quality. This should last a good few years.
Need a bigger case should be here by Saturday then actually getting it going should be relatively easy all research having been done using cheap shite.https://uploads.tapatalk-cdn.com/202...e7b9229fd1.jpghttps://uploads.tapatalk-cdn.com/202...25a80322ea.jpg
