What is an acceptable rpm variation?

S Clark · « **on:** 14 Apr 2016, 11:28 pm »

When comparing a belt drive with an outboard chinese motor to either my Technics SP10-Mk2 or to a JVC QL-F6 with RMP Calculator app there are differences. The direct drives run completely true, albeit .1 rpm fast. The belt drive varies +- about .15 rpm. Is this typical of belt drives?

FullRangeMan · « **Reply #1 on:** 14 Apr 2016, 11:45 pm »

The belt drive may vary according room temperature or belt and groove wear.
The DD x BD difference is too small.

S Clark · « **Reply #2 on:** 15 Apr 2016, 12:32 am »

I understand that there will be variations, and that room conditions can affect that, but my question is what is usual and acceptable? Surely there are lots of VPI guys that can give me some figures.

Letitroll98 · « **Reply #3 on:** 15 Apr 2016, 12:48 am »

My lowly VPI Traveler is spec'd at .02% wow and flutter, .1% speed variation, I haven't measured anything so I don't have any rpm figures. Somebody can do the math I suppose.

S Clark · « **Reply #4 on:** 15 Apr 2016, 12:59 am »

Thanks, that helps. My .15 rpm variation is about .45% variation. I can't hear it, but I was curious what the standards were.

FullRangeMan · « **Reply #5 on:** 15 Apr 2016, 07:21 am »

These values you obtained are fine, today current TT are very precise, in the heyday of small TAS mag they measured rpm and it was not this good.

Wayner · « **Reply #6 on:** 15 Apr 2016, 11:58 am »

The RIAA standards (that I can find) have no speed tolerances indicated in their guide.

'ner

neobop · « **Reply #7 on:** 15 Apr 2016, 12:07 pm »

0.02% wow and flutter for Traveler. Dream on.

Don't assume a spec has any relationship to reality. Most table manufacturers just make this shit up.

What is acceptable speed variation?

There is no acceptable speed variation. What's unacceptable is what you can hear in comparison to your quartz locked DD tables.

neo

Letitroll98 · « **Reply #8 on:** 15 Apr 2016, 05:38 pm »

Yeah, that's why I said "spec'd as". I suppose I should download one of those turntable speed apps, no idea how accurate they might be. But right now I'm redecorating a new listening room so that will have to wait. There's no love for the Traveler either here or at VPI it seems, but it's a really a nice sounding table, much better than the HW 19 Jr I previously owned.

Wayner · « **Reply #9 on:** 15 Apr 2016, 07:06 pm »

A slightly slower or faster running platter is not nearly as bad as a table that has a variable speed (or should I say an inconsistent speed). That would drive me nuts. A guy could get used to a slight off speed table (which I think most belt drives are anyway (by their nature).

But some other DD haters say that they can hear the "coggin'" of DD from speed correction. I have both belt and DD and can't really tell the difference.

I'd say if most people didn't strobe their table, they wouldn't know the difference......

But that is just my opinion......

'ner

neobop · « **Reply #10 on:** 15 Apr 2016, 07:28 pm »

My old LP12 ran about 1% fast. That was pre Valhalla mod. I was used to it, but everything else sounded a bit sluggish. This was no good for me on the job so I replaced it with a Goldmund DD. Correct speed took a little getting used to.

I now use a laser tachometer to check speed. You might need a tripod depending on your situation, but you can probably rig something up.

http://www.amazon.com/CE-Compass-Digital-Tachometer-Contact/dp/B008XCUX0E/ref=sr_1_7?ie=UTF8&qid=1460747700&sr=8-7&keywords=laser+tachometer

neo

ACHiPo · « **Reply #11 on:** 15 Apr 2016, 07:52 pm »

Quote from: Letitroll98 on 15 Apr 2016, 05:38 pm

Yeah, that's why I said "spec'd as". I suppose I should download one of those turntable speed apps, no idea how accurate they might be. But right now I'm redecorating a new listening room so that will have to wait. There's no love for the Traveler either here or at VPI it seems, but it's a really a nice sounding table, much better than the HW 19 Jr I previously owned.

There's an iPhone app (turntabulator) that seems very good and is pretty cheap. The gold standard seems to be Feickert's Adjust+ which uses, as I recall, a record with a 1kHz tone. I have the Adjust+, but after a few sessions with the turntabulator, I was satisfied enough not to bother. As an aside, I started my investigation on RPM because a few of my LPs sounded sluggish. When I measured the RPM, it was 1% slow. Replacing the belt got it to 0.3% fast, which is well within spec.

undertow · « **Reply #12 on:** 15 Apr 2016, 08:12 pm »

Trust me the only real way to do this is put a record on the platter, than this strobe shown in link right on top of it, drop your needle because you have to compensate for "drag" which absolutely changes the speed by as much as 1 rpm in some cases, put your weight in the center if your using one as it also creates a speed change, and proceed to check both 33, and 45 rpm. By the way the KAB strobe card is small enough to allow a couple tracks to be exposed in the beginning so dropping a needle while using it on a standard 12" LP is no problem to test for a few minuets with music playing.

http://www.elusivedisc.com/KAB-SpeedStrobe-Turntable-Speed-Tester/productinfo/KABSPEED/

You will learn the truth on how off your table is. Belt, nor direct drive matters because no matter what you need a manually adjustable speed controller. Voltage variations, and environmental conditions, bearing lubrication etc... all play into synching it in optimally. This all only works with real conditions, mechanical / physical drag, and a pure accurate strobe setup period. No apps, or any other methods can account for the real performance of your motor under stress, and being used in real time conditions, sorry. It's like plugging your Ferrari into a computer to see what the horsepower readout is at 450hp, but not having the physical tires rotate on an independent machine compensating for true physical loss of output which would show its only getting about 418hp to the ground.

Believe me I have heard tables with no compensation, and they cannot match what you can do with a true speed controller that is adjustable for both speeds independent. It is shocking to see so many manufacturers selling 2500 to 25,000 dollar tables without a strobe light, and adjustable speed controller! Their tables would sound 10 times better if you can customize to your conditions at home adjusting it properly. But marketing is the game. 'Origin live' makes really nice kits for true speed control. I have modded many tables using these methods, but you may have to replace your motor if its not a 12 volt dc, AC motors normally suck honestly... And they all sound by far better, because it's every single recording that benefits from being dead on speed, not necessarily the table.

Letitroll98 · « **Reply #13 on:** 15 Apr 2016, 10:41 pm »

Well I downloaded an Android app and it claims my VPI is running at 32.6 rpm, again, don't know how accurate that is. Which I think calculates to .13% slow, three hundreds of a percent off the spec. of .1%. The app only goes to tenths so there's no way to check the wow and flutter beyond that it never wavered off that 32.6 number, but I won't know about the claimed .02% figure with this app.

I like neo's laser rpm meter. Looks like you have to buy reflective tape as well, still cheap by half.

ACHiPo · « **Reply #14 on:** 15 Apr 2016, 10:57 pm »

Quote from: undertow on 15 Apr 2016, 08:12 pm

Trust me the only real way to do this is put a record on the platter, than this strobe shown in link right on top of it, drop your needle because you have to compensate for "drag" which absolutely changes the speed by as much as 1 rpm in some cases, put your weight in the center if your using one as it also creates a speed change, and proceed to check both 33, and 45 rpm.

My WTT has a screw-on record clamp with a flat top. I was able to measure RPM using the Turntabulator with and without stylus drag. I could detect stylus drag, but it was pretty small--Turntabulator measurement precision was ~+/- 0.02 RPM and the effect of stylus drag was about 0.02 RPM. I also measured RPM without the weight by placing my iPhone directly on the record and there was no discernable difference in RPM between with and without the weight. I'm sure results vary by turntable, so these results may not be representative.

If I had a strobe disc or a laser I would have used them. I had an iPhone with pretty sensitive transducers inside, and it turned out to work pretty well.

ACHiPo · « **Reply #15 on:** 15 Apr 2016, 11:02 pm »

Quote from: Letitroll98 on 15 Apr 2016, 10:41 pm

Well I downloaded an Android app and it claims my VPI is running at 32.6 rpm, again, don't know how accurate that is. Which I think calculates to .13% slow, three hundreds of a percent off the spec. of .1%. The app only goes to tenths so there's no way to check the wow and flutter beyond that it never wavered off that 32.6 number, but I won't know about the claimed .02% figure with this app.

Not sure which app you have, but the Turntabulator (iPhone) had two measurements: a fast measurement that took about 20 seconds and only displayed tenths, and a precise measurement that took about a minute and displayed hundredths. I like the strobe technique as well, but the smart phone transducers are pretty sophisticated, precise, and accurate.

orientalexpress · « **Reply #16 on:** 16 Apr 2016, 12:06 am »

The Teres turntable have a strobe light and strobe plate under the plater ,it automatic adjust the speed itself.

SteveRB · « **Reply #17 on:** 18 Apr 2016, 07:17 pm »

I use turntabulator. I can hear some records as 'slow' at 33.1. I think acceptable variation comes down to preference (and how much you spent on your turntable).

undertow · « **Reply #18 on:** 18 Apr 2016, 07:20 pm »

Quote from: SteveRB on 18 Apr 2016, 07:17 pm

I use turntabulator. I can hear some records as 'slow' at 33.1. I think acceptable variation comes down to preference (and how much you spent on your turntable).

Definitely 33.1 is slow... 33.3 RPM can easily make a big difference with a High res enough system under full load conditions on the arm, and motor.

ACHiPo · « **Reply #19 on:** 18 Apr 2016, 08:22 pm »

Quote from: SteveRB on 18 Apr 2016, 07:17 pm

I use turntabulator. I can hear some records as 'slow' at 33.1. I think acceptable variation comes down to preference (and how much you spent on your turntable).

My RPM was 32.95 - 33.03 prior to the new belt, and a few of my records definitely sounded sluggish. I'm at 33.40 now and things sound as they should.