VPI Classic 4 Platterspeed Measurements

Discussion in 'Vinyl Nutjob World: Turntable and Related Gear' started by purr1n, Mar 26, 2016.

  1. purr1n

    purr1n Burned out

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    VPI Classic 4 Platterspeed Measurements

    OK, I'm glad to be back to "science" after all the recent drama.

    I am using the Android version of the app which is slightly different from the iOS one. There is no low-pass as on iOS, only notch-filter, which seems exclusive to the Android verison. (I did a Google search and it seems documentation is sparse on Dr.Feikert's App.) Anyhow, I don't think this is a bad thing. The low-pass seems to give results I've seen on Analog Planet and other sites don't seem to differentiate as much from turntable to turntable. I like measurements that highlight differences, particularly if these differences are audible.

    Another thing I don't like is that the app only provides a "max deviation" figure. I think a standard deviation would have been useful. This is based on what I hear with the ~ 3150Hz tones. It's like jitter, there are different kinds of jitter, some more annoying than others or perhaps some differently annoying than others. Ultimately, I think looking at the graphs gives you more insight than the simple % numbers provided as a summary.

    Below is a comparison of one vs. two belts for the VPI Classic 4. I got rid of the regular pulley and installed the HRX pulley to run multiple belts. The idea behind this is that belts tend to so funky stuff like expand and contract inconsistently at different points, moreso over time as they age. The use of two belts averages this effect, but possibly at the expense of more motor noise transmitted to the platter. So far I'm not hearing more noise. The Classic 4 is insanely massloaded with a huge plinth composite sandwich base that should convert a lot of that motor vibration to heat.


    VPI Classic 4 One Belt + VPI SDS
    Screenshot_2016-03-26-22-45-11.png

    VPI Classic 4 Two Belts + VPI SDS
    Screenshot_2016-03-26-22-45-18.png


    The variances in pitch (see saw effect between low and high pitch) were more subjectively evident compared with running one belt. With two belts, the pitches changes were harder to make out. You can see that on the average, there was just a tiny bit less see-saw effect with running two belts. Not much though. But with a single tone, this was audible. Also note that was a little bit more slip with running one belt.
     
    Last edited: Mar 26, 2016
  2. ohhgourami

    ohhgourami Friend

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    Will this be your heirloom tt?
     
  3. purr1n

    purr1n Burned out

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    Yes. My grandmother (my primary caregiver when I was growing up) died recently, and my son asked who I was going to give my records to when I die. I assured him that it would be him. I had a few days off after the funeral, so I took the time to install the final parts on my personal custom amp, dismantle the OB speakers (my wife hated them), and bring the BLHs back into the house, etc. This purchase was the last piece.

    My son now goes around saying everything sounds bad. Last time he complained was at the Baskin Robbins where the speaker made fart fart sounds for bass.
     
  4. ohhgourami

    ohhgourami Friend

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    *poot poot*

    I think we all complain.
     
  5. mtoc

    mtoc SBAF's Resident Shit-Stirrer

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    Talking about such a heavy topic with your child, Marv, you are brave. I always avoid this subject with my family... Too sad to think about.
     
  6. Dr. Higgs

    Dr. Higgs Boson - Member

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    Here are my best results with 1 & 2 belts (w/ Android app):

    VPI Classic Signature Two Belts + SDS @ 59.25hz

    [​IMG]

    VPI Classic Signature One Belt + SDS @ 59.34hz

    [​IMG]

    Don't have a clue how to best interpret these (other than keeping everything as low and consistent as possible) but I did notice that after I took one of the belts off to get the one belt measurements, I had to adjust the frequency down to 59.22hz to get similar results to my two belt measurement above once I added the additional belt back on in the same position. Seems very sensitive to any shifts on the belts (probably until they settle in again), so once you get it locked in it's best not to mess with it.

    I wonder what 5 belts would look like :D
     
    Last edited: Mar 27, 2016
  7. BioniclePhile

    BioniclePhile The Terminal Man - Friend

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    How loud is the 'jitter' through headphones? I know dad's Technics has a pretty obvious sound when there's silence or quiet parts in a song that I assume is either the motor vibrations or the platter vibrating as it turns. I mean, it is thirty years old and dad got it for $30 or something, so that's totally understandable.
     
  8. purr1n

    purr1n Burned out

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    Speed instability manifests itself differently from motor or general vibrations. Both are bad. There are different approaches to handing them. For general vibration, we see mass loading, suspension, combination of both, or something totally off the wall like magnets levitating platters or two platters spinning in different directions. For motor vibration, belt drive has been one way to decouple the platter from the motor, but at the expense of speed control. A heavy platter with more inertia will mitigate the effects of belt drive instabilty. Then there is stuff in between belt drive and direct drive, like a rim drive. In the end, it usually a set of compromises. Direct drive is usually the best at speed control.

    Speed stability is crucial and actually has a similar effect to jitter in digital (except that vinyl NEVER has digititus - vinyl can sound very bright with a bright recording, but never has that nasty digital sheen, hash, haze, rasp, glare, or hardness). More speed stability results in a more focused, precise and clear sound, better defined transients, and increased resolution.

    It's only been relatively recently that affordable (well at least semi-affordable) mass loaded turntables have been available. At least I don't remember a vast selection of stuff in the 1990s. Everyone back then wanted an Linn LP12 and Rega owned the rest it seemed.
     
    Last edited: Mar 28, 2016
  9. Chris1967

    Chris1967 Friend

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    It depends also on the quality of the implementation, my 50+ year old idler (custom Lenco GL75) has better wow&flutter than some modern budget direct drives.

    Idlers are another means of motion between motor and platter, most older broadcast decks (EMT/Garrard etc) utilized this kind of connection.

    Rim drive is similar.
     
  10. Priidik

    Priidik MOT: Estelon

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    Is there a optimum in mass?
    Logically at some point the platter being heavy enough should be immune to vibrations.
     
  11. purr1n

    purr1n Burned out

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    No idea. The needle deflections are so small!
     
  12. Dr. Higgs

    Dr. Higgs Boson - Member

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    Are your measurements w/ the periphery ring Purrin? I'm curious how much of an impact the increased "flywheel effect" has on the measurements.
     
  13. Chris F

    Chris F Boyz 4 Now Fanatic - Friend

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    Here is mine. AP test record, VPI Classic 1 (2014 model with motor in the back), ring/weight. iPhone 6.
    IMG_1660.PNG IMG_1659.PNG
     
  14. bazelio

    bazelio Friend

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    Zombie thread revival.

    Does anyone think the HRX pulley is really needed if you are only running two belts? The Hoffman guys using HRX pulleys on Classics are running three belts (and showing near unmeasurable wow/flutter). I gave dual belting a shot with the stepped pulley today. Had to slow down the platter a bit with the SDS. No biggie there.... And subjectively things seem slightly smoother?

    [​IMG]
     
  15. Chris F

    Chris F Boyz 4 Now Fanatic - Friend

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    I don't think the measurement is going to drastically change so how does it sound? :)

    IMO too much weight is put in the numerical result without being able to correlate it to sound beyond the obvious fast/slow pitch. We naturally want a nice metric that will tell us good -> better -> best in absolute terms but the speed control affects a lot more then absolute pitch (such as transient response etc..) and this is not shown in the measurement.
     
  16. Wfojas

    Wfojas Friend

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    If you can get a Phoenix Engineering Roadrunner to try (the company shut down), you will be surprised at the variations you get, even with an SDS. Also, what ever it is that I measured with a KAB is always invariably wrong, once I applied load (the needle on the groove). For the longest time, I always wondered why my lps sounded better in the last 1/3 of the album. Turns out, with load, thats the portion that runs closest to 33.3 rpm. When i cut over to rim drive all hell broke loose, and it was a really depressing experience. Glad I worked through that (2 belts, Phoenix Roadrunner and Falcon).

    SDS may help, but it can get better. I can't wait to test VPI's modulated ADS (if it ever comes out). The sound of stable rotation is tangible for sure, and it improves everything you play. 180gm or 200gm releases are a crapshoot, and pricey as heck, in comparison.
     

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