VPI/Hurst motor vs SOTA BLDC motor (or silience is bliss)

VPI/Hurst motor vs SOTA BLDC motor (or silience is bliss)

Postby edw » Sat Jun 27, 2020 5:02 pm

I really enjoy the performance of the VPI Prime. I think I have dialed it in pretty well if I do say so myself and am more than happy with its big soundstage, retrieval of details, and musical and lively presentation. Kudos VPI. Currently, the front end of my phono is a Lyra Delos cart > VPI Prime with HW40 feet, periphery ring, HRX weight, and Phoenix Eagle/Roadrunner > Hashimoto/Sansui HM7 step-up transformer > Herron VTPH-2A phono stage > Rowland Synergy 2i preamp. I could leave it that way and ride off into the sunset listening to album after album with a big grin on my face.

But (why is there always a but!?), I thought that my setup could be even more quieter than it is. For example, if I max the gain on my preamp, run the Prime's platter without an LP, and put my ear against the grill of my speakers, I can very faintly hear some noise. Also, when I use AnalogMagik to setup my cart's azimuth and anti-skate, I noticed some residual noise in the spectrum analysis. See screenshot below. I can faintly feel some noise when I touch the motor pod as well.

By way of background, with AnalogMagik, you play AM's special LPs with test tones and use an external USB sound card and laptop to take measurements. For setting anti-skate, you play the 3150Hz test tone for several minutes that gradually increases by 20dB and measure in real time averaged THD in both channels as the cart closes in on the spindle. Of course, lower THD numbers and THD numbers that are very close between the channels are what you want. In the screenshot, however, you can also see amplitude peaks in the 50-200Hz range that should not be there.

OLD HURST AS.jpg
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When I investigated further, I learned that this noise was something inherent in Hurst motors, especially the peak at 120Hz. I also learned that some BLDC motors are often quieter. So when I learned that SOTA had an Eclipse package with a BLDC motor and Condor (similar to the Phoenix Eagle) for VPI turntables, I decided to do a comparison of the two motors to see if I could make my setup even quieter.
Last edited by edw on Fri Jul 10, 2020 3:14 pm, edited 7 times in total.
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Re: VPI/Hurst motor vs SOTA BLDC motor (or silience is bliss

Postby edw » Sat Jun 27, 2020 5:02 pm

SOTA's Eclipse package comes with a BLDC motor, the Condor regenerative power supply, and a wall wart. The Condor has a captive 3-prong wire that connects to and powers the BLDC motor. You can have your Prime motor pod machined to fit the BLDC motor (as others like Dorian have done). I elected to keep my Prime motor pod original and ordered a SOTA motor pod. It is a nice bit of kit. See pics below (I added the RFI blocker on the wiring, BTW). The bottom screws out and reveals some empty space. So, I added some fine lead shot to increase the mass from about 2.25lbs to about 4lbs (based on my bathroom scale). Also, because I already had a Phoenix Roadrunner, it hooked up to the Condor just like the Eagle to provide a feedback loop to maintain speeds at 33.3, 45, AND NOW(!) 78 rpm (If you don't have the Roadrunner, it can be purchased from SOTA). So one pulley will work for all 3 speeds. :mrgreen:

The BLDC motor also ramps up from start so no more chirping of the belts. The pulley is adjustable on the motor's shaft and can support 2 OEM VPI belts. The only real gripe I have with the SOTA motor pod, which SOTA is addressing, is that the screws on the top of the motor should be countersunk to provide better clearance between the motor pod and the platter.

In any event, the SOTA motor works very well. With the Hurst motor, I always felt a slight buzzing from the motor at 33.3rpm and a bit more buzzing at 45rpm. With the SOTA BLDC motor, it is dramatically quieter, although you can just about feel a very faint buzz if you really try to feel for it. Do note that the SOTA motor pod gets very hot if the BLDC is running for a few hours (apparently 130 degrees hot). [EDIT: a voltage adjustment with the Condor solved this problem, see thread below] However, this heat did not impact the platter's speed using the Condor/RR with the BLDC motor, as compared to the Eagle/RR with the Hurst motor.

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Consistent with Dorian's prior summary of the Eclipse package ( http://www.vpiforum.com/viewtopic.php?f=7&t=14253 ), the BLDC motor provides more details, textures, and nuance in the softer passages. Also, the music seems more effortless at all volume levels. I never thought a motor change like this would make such a difference. I stand pleasantly corrected based on this experience. I am very impressed with these improvements in sound and listening enjoyment.
Last edited by edw on Thu Jul 02, 2020 5:31 pm, edited 14 times in total.
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Re: VPI/Hurst motor vs SOTA BLDC motor (or silience is bliss

Postby edw » Sat Jun 27, 2020 5:03 pm

To see if my listening impressions correlate to test measurements, I went back to the AnalogMagik anti-skate test to run comparisons between the VPI/Hurst motor and the SOTA BLDC motor to see if there was (or wasn't) noise in the 50-200Hz range. While the anti-skate test is not designed to measure motors, it does provide a spectrum analysis in the range I am concerned about. My preamp was set an unity gain, the preamp output fed into an external USB sound card, and that was fed into a laptop running the AM anti-skate test with a 3150Hz test tone. Tests were run for exactly 30 averaged frames, which amounts to several minutes.

Here is the screenshot of the VPI/Hurst motor test...

HURST AS.jpg
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Comparing with my first post above, the same peaks are there as before (@ 55, 60, 90, 120, and 180Hz), although lower in amplitude. This is likely due to the fact that this test was run early on a Saturday morning when all lights, AC, dimmers, etc., were off in the house. While these peaks are about -85dB down, they are still there.

And here is the screenshot of the SOTA BLDC motor test...

BLDC AS.jpg
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As you can see, the 50-200Hz range is a lot quieter, although there is a negligible peak at 90Hz and a small peak at 180Hz. So it demonstrates a significant improvement in this area, presumably because of the BLDC motor. This test was measured a few minutes before the one for the Hurst motor.

A check between the two screenshots shows that the L&R levels and RMS mV are almost the same, which they should be if test conditions are similar. So the spectrum analysis does seem to correlate to a more quieter background and what I am hearing. Some will note that the anti-skate readings are a little better with the BLDC motor, and while true, that improvement is negligible IMHO.

So, it looks like the Hurst motor is a bit noisy given the peaks at 60Hz and 120Hz, as expected. The peaks 90 and 180Hz mean I have some more work to do to try to make it more silent, although these peaks are very small relatively in amplitude.
Last edited by edw on Sat Jun 27, 2020 11:40 pm, edited 16 times in total.
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Re: VPI/Hurst motor vs SOTA BLDC motor (or silience is bliss

Postby edw » Sat Jun 27, 2020 5:03 pm

Also, AnalogMagik has a test for table vibration, so I ran this with both motors. Apparently, there are several ways to measure vibration. One cheap and easy way is to use 2 test tones consisting of a large amplitude low-frequency tone linearly mixed with a high-frequency tone at ¼ the amplitude of the low frequency tone, and then measure IMD and products produced by these two test tones - that is, beat frequencies. In AM's case, it uses a 60Hz and 500Hz test tone in a 4:1 ratio and measures real time and averaged IMD in both channels.

Here is the screenshot of the VPI/Hurst motor test...

HURST VIBR.jpg
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And here is the screenshot of the SOTA BLDC motor test...

BLDC VIBR.jpg
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As before, a check between the two screenshots shows that the L&R levels and RMS mV are almost the same, which they should be if test conditions are similar. Also, the IMD measurements are pretty much the same for both motors, although slightly better with the BLDC motor. It should also be noted that prior vibration tests resulted in quieter IMD measurements on the order of 1.8 to 2.4% depending on the time of day the test was performed (see http://www.vpiforum.com/viewtopic.php?f=7&t=13920&start=80 ). So I do not believe the IMD measurements are conclusive or correlate well with differences in motor vibrations in this particular case. Or my setup had too much background vibration at the time of these tests.

However, if you look and the number of beat frequencies between the 60Hz and 500Hz test tones, there are more beat frequencies for the Hurst motor (I count 6) than for the BLDC motor (I count 2, maybe 3), which suggests that there is more vibration with the Hurst motor that is interacting with the test tones to generate these beat frequencies. This does seem to correlate with the other test above. So all in all, it seems that the tests available through AM (while somewhat limiting as to measuring table vibration directly) do correlate to there being lower vibration with the BLDC motor. Confirmed also with my ear next to the grill of the speakers and listening to LPs too.

This silence seems to have added to the improvements in sound that I noticed with just a motor change. Didn't seem possible, but there it is. So silence is indeed bliss.
Last edited by edw on Sat Jun 27, 2020 11:44 pm, edited 12 times in total.
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Re: VPI/Hurst motor vs SOTA BLDC motor (or silience is bliss

Postby Dorian » Sat Jun 27, 2020 5:52 pm

Nice write up thanks Edw. Glad to hear that you’re satisfied with the upgrade. I’m still very happy with mine and agree with your observations. My only comment is that the hot motor pod is somewhat concerning. I’m not experiencing that with the condor motor in the stock VPI motor housing.
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Re: VPI/Hurst motor vs SOTA BLDC motor (or silience is bliss

Postby edw » Sat Jun 27, 2020 7:00 pm

Dorian wrote:Nice write up thanks Edw. Glad to hear that you’re satisfied with the upgrade. I’m still very happy with mine and agree with your observations. My only comment is that the hot motor pod is somewhat concerning. I’m not experiencing that with the condor motor in the stock VPI motor housing.


Thanks Dorian. Yes, I am very pleased with the upgrade. I agree that the hot motor is somewhat concerning. It gets hot after about 3-4 hours of constant spinning. I checked with SOTA and they said it was normal and what they also experienced. My thought was that the hot motor could cause heat-up/cool-down cycles with the belt as it traveled around the hot motor and around the colder platter. So far, I do not notice any ill effects as to speed. The Condor/RR corrects and adjusts speed no different and not any more frequently than the Eagle/RR.

I will continue to monitor to see if it affects belt life (perhaps one additional reason to find EPDM replacement belts).

BTW, if your motor pod is not heating up, that is good. I wonder - what model BLDC is in your pod and whether they are the same or different?
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Re: VPI/Hurst motor vs SOTA BLDC motor (or silience is bliss

Postby madrac » Sun Jun 28, 2020 5:50 am

Nice write-up, edw.

I would suspect the belt isn't in the "hot motor zone" long enough to pick up alot of heat to thermal cycle as it spins the platter. Plus elastomers typically don't transfer heat and have high service temps (depending on the material, >100-120 C).

As to the motor pod, from your picture it looks like the Eclipse one is smaller than the stock Prime housing. Wonder if part of the cause is smaller surface area for the Eclipse pod for air cooling? Also, may be different materials with different heat transfer properties?
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Re: VPI/Hurst motor vs SOTA BLDC motor (or silience is bliss

Postby edw » Sun Jun 28, 2020 11:12 am

madrac wrote:Nice write-up, edw.

I would suspect the belt isn't in the "hot motor zone" long enough to pick up alot of heat to thermal cycle as it spins the platter. Plus elastomers typically don't transfer heat and have high service temps (depending on the material, >100-120 C).

As to the motor pod, from your picture it looks like the Eclipse one is smaller than the stock Prime housing. Wonder if part of the cause is smaller surface area for the Eclipse pod for air cooling? Also, may be different materials with different heat transfer properties?


madrac,
I hope that is the case with the belts. I will keep any eye on the belts, just in case.

I agree with you about the motor pods. It is likely that the thickness and surface area of the VPI motor pod is able to dissipate more heat, if modded to accept the BLDC motor, than the BLDC motor pod. If things get too hot, I may look at attaching some heatsinking.
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Re: VPI/Hurst motor vs SOTA BLDC motor (or silience is bliss

Postby Mr_Putty » Sun Jun 28, 2020 11:50 am

Just a SIDE comment for those that do not have advanced software as described, but want a way to listen to RELATIVE noise in their system for evaluation and reduction. No disrespect for the thread or its content intended. This method is for low-level noise observation (via normal playback, not motor specific noise as is being described in the thread). I record to a laptop using Audacity software. This method requires recording between tracks of a record or recording silent grooves from different sources. I used my normal recording level for the record being used. Then I use Audacity to amplify the level of the track as much as possible. When played back I can easily hear residual noise from my amp (power grid hum?) and surface noise from the stylus (generally hiss with some rumble and typical noise). This is a good way to document low-level changes that may occur when changing or evaluating isolation or other components. This IS safer than tapping around on things with the volume turned up for obvious reasons. The recording will reveal TT setup (base level of noise), but does not include room acoustics or music induced unwanted vibrations (distortion). It should also reveal the cleanliness of your source or its pressing limitations.
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Re: VPI/Hurst motor vs SOTA BLDC motor (or silience is bliss

Postby edw » Sun Jun 28, 2020 11:58 am

Mr. Putty, agreed. You can use Audacity or similar software and a good test LP, like the CBS, HFN or AP, to check many parameters.
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