Project: Avenger Rim drive with BLDC motors & Class AB Amp

Re: Project: Avenger Rim drive with BLDC motors & Class AB A

Postby Guss2 » Sat Jun 13, 2020 9:37 pm

vienna acoustics wrote:I had the chance yesterday, to exchange some emails with the person who was the first to experience the three phase frequency controlled BLDC motor on his SOTA Millennia turntable and had brought together Bill and SOTA.

Among others he wrote me (... I will also say that I’m exceedingly happy with my SOTA Millennia Vacuum turntable with the tachometer controlled three-phase motor from Phoenix Engineering. It made a substantial improvement in sound quality that was somewhat unexpected.... However, in addition to achieving stable speed, the noise floor improved along with better clarity and transparency..... Today, I wouldn’t trade my SOTA Millennia for any other turntable I know of. I think it’s competitive with the very best regardless of price.. )

It seems that we are sharing the same positive experience

How is John Elison anyway? You, he and Bill all seem to have a lot in common.
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Re: Project: Avenger Rim drive with BLDC motors & Class AB A

Postby vienna acoustics » Sun Jun 14, 2020 1:21 am

Guss2 wrote:
vienna acoustics wrote:I had the chance yesterday, to exchange some emails with the person who was the first to experience the three phase frequency controlled BLDC motor on his SOTA Millennia turntable and had brought together Bill and SOTA.

Among others he wrote me (... I will also say that I’m exceedingly happy with my SOTA Millennia Vacuum turntable with the tachometer controlled three-phase motor from Phoenix Engineering. It made a substantial improvement in sound quality that was somewhat unexpected.... However, in addition to achieving stable speed, the noise floor improved along with better clarity and transparency..... Today, I wouldn’t trade my SOTA Millennia for any other turntable I know of. I think it’s competitive with the very best regardless of price.. )

It seems that we are sharing the same positive experience

How is John Elison anyway? You, he and Bill all seem to have a lot in common.


He is fine I guess.
!
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Re: Project: Avenger Rim drive with BLDC motors & Class AB A

Postby edw » Sun Jun 21, 2020 12:47 am

theeng wrote:The chart for the 300 AC 60Hz synchronous motor is characteristic - there is the strong 60 Hz fundamental that you will see for every 60 Hz synchronous motor, and the dBuA at 60 Hz is the motor current draw, but the 2nd fundamental at 120 Hz is very low. The 500 Hz peaks with side bands should be associated with a speed controller - did you take these measurements?


theeng,
This puzzled me for a bit but then I realized. :D To measure TT vibration on AnalogMagik, you use a track on the test LP that has a 60Hz test tone and a 500Hz test tone playing at a 4:1 ratio and then you use the software to measure IMD%. So that accounts for the 60Hz and 500Hz peaks seen in the graph for the RIM Drive Hurst motors. Not sure why I don't see the same 60Hz and 500Hz peaks in the graph for the BLDC BLWR motors in the subsequent post.


vienna acoustics wrote:Dear Edw, please let me know on your experience with your new project when it will be completed. I can give you some hints to improve further the performance. Also if you will send me your AM VTA measurements, I think that I can help you to match your AM with Dr F results


SK,
Thanks for the tip. I was able to adjust my VTA/VTF, so got the crosstalk closer on AM (Left: -26.03db, Right -27.61). My condor shipped so it will take a few days. :mrgreen:
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Re: Project: Avenger Rim drive with BLDC motors & Class AB A

Postby theeng » Mon Jun 22, 2020 10:01 am

edw,

Thanks for the correction - I found an image of the test lp back cover. Yes, it explains the 500 Hz peak, but if you view the video they have for the vibration test the 60 Hz peak (spike) is similar to to the 500 Hz peak-spike. I found the attached image (from https://www.audionet.com.tw/thread-10728-1-1.html) that shows an example of the VTA test that uses 60Hz and 7kHz test tones, and you see the very distinct peaks at 60Hz and 7kHz. You can see similar images here https://hi-fidelity-forum.com/publish/preview/300, but neither of these sites showed the vibration test. I still think the 60Hz broad peak that VA shows is conductive emissions from the Hurst AC motor. However, as you point out, not sure why the sharp 60Hz and 500Hz peaks are missing from the the BLDC motor test.

theeng
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Re: Project: Avenger Rim drive with BLDC motors & Class AB A

Postby Golear » Thu Jun 25, 2020 2:23 am

I don't get what you guys are saying.

Are you guys saying that Bill is back to posting (potentially) erroneous screenshots, via his good (but clueless) buddy Vienna Acoustics? In order to steer business to SOTA?

I'm wondering why we don't see torque ripple in the graphs for BLDC motors. Especially since the figures are supposed to be accurate to three significant numbers... Three significant numbers!

Besides, what's the connection between IM distortion figures and vibration? It seems like a leap. Surely we need actual vibration figures, displacement in 3 dimensions.... And given the level of vibrations (3 significant numbers) we should get the 3D vibration via a wireless measuring system (e.g. laser - like in my high school project) because even the stiffness of the wires are going to make a difference when you're reading to 3 decimal places...

Am I being a "Donald Downer" on this?
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Re: Project: Avenger Rim drive with BLDC motors & Class AB A

Postby edw » Thu Jun 25, 2020 9:21 am

Golear wrote:Are you guys saying that Bill is back to posting (potentially) erroneous screenshots, via his good (but clueless) buddy Vienna Acoustics? In order to steer business to SOTA?


No and no. But additional confirming measurements would help. I should have mine eventually. Right now, I am listening and I do notice a difference and like what I am hearing in comparing the VPI motor pod with Phoenix Eagle/RR versus the SOTA motor pod with Condor/RR. At the very least there is significantly less (almost none) vibration of the motor pod at 33 and 45 with the SOTA motor pod by just using my hand on the motors.


Golear wrote:Besides, what's the connection between IM distortion figures and vibration? It seems like a leap.


There are many ways to measure vibration and for many reasons. IMD is one of them. It is not the end-all-be-all of vibration measurements, but an accessible way to measure vibration by the masses. For example, Analog Productions - The Ultimate Analogue Test LP also uses it to reduce vibrations to set VTA.

See AES's definition of IMD (specifically SMPTE IMD)...
http://www.aes.org/par/i/

Additional info...
https://www.nti-audio.com/en/support/kn ... distortion


Golear wrote:Am I being a "Donald Downer" on this?


I think you answered your own question. :)
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Re: Project: Avenger Rim drive with BLDC motors & Class AB A

Postby Golear » Thu Jun 25, 2020 1:41 pm

You're right! I was sad about not appearing to be open to new ideas (yada yada yada). VA's emotional reactions affected me, I do admit. But that's wrong. And condescending - my apologies to VA for that. The stuff I've posted will come up in any concept review. It happens in all fields of research and engineering -- even in creative writing. And VA deserves the best from all of us. We all deserve the best from all of us. I feel so much better.

"An accessible way to measure vibration for the masses".... but then reading test values to 3 significant figures? And no doubt making adjustments until the RoadRunner reads 33,333, not 33,332 or 33,334. That looks like a disconnect?

And I didn't find anything in the two links that says one can specifically measure vibration via IMD. I'd think that you want to measure vibration as directly as possible. One could rest a phono cartridge on the motor block or a non-spinning LP, and send the output from the preamp (via TAPE OUT) to an oscilloscope. Capture the data, do Fast Fourier Transform, then measure the frequencies and amplitudes... Calibrate the whole thing by capturing values when the motor is off, then do readings with the motor on.

So about the measurement that VA posted. An expected effect was visible in the screen shot for the VPI motor (Exhibit A). There was no such effect in the screen shot for the BLDC motor (Exhibit B). The expected effect was there in screen shots for that measurement, posted by other users in other forums (Exhibit C). That is pretty convincing. At best, it was a mixup and VA will post the correct shot. At worst....

What if VA says there's no mix-up, and edw's measurement looks like Exhibit B? Then we'd need an explanation for the effect's absence. So then the measurement mystery deepens. And we can't use the measurement.

People are comparing a VPI motor to another motor, by ear, and preferring one over the other. That's fine. In fact, it would be strange if a change in motor didn't change the sound. But all this stuff about measurements smacks of an appeal to authority - which is a fallacy.

(In VA's case, not only did he change the motor, he added 27 lbs or more of lead. That changes the shelf and stand that the turntable (and other equipment?) sits on, too.)
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