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How stable are record decks in terms of tempo/pitch? (Drifting)

Hi all

I used to DJ many years ago, using vinyl. It's something I mean to get back into at some point, but for a variety of reasons I think I'll go down one of the digital routes if/when that happens.

Part of the plan will be to digitise all of my vinyl (around 600-700). But that got me to thinking how stable my decks are in terms of speed / tempo / pitch. When I did mix way back when I used to beat match, and the two records would always drift slightly and need constant tiny adjustments. I never did fully understand whether that was inherently a vinyl thing or just me not being that good at it! One of the attractions with vinyl would be more stability, but if I am playing an unstable recording of a digitised vinyl, then I guess I'd still be in the same boat.

Any thoughts on this would be most helpful.

I should add that my decks are Numark TT-1s (direct drive) and they do have a Quartz button. But would Technics be more stable? Or would a HiFi deck be a better choice? Are there any turntables which are highly regarded for their stability in terms of pitch shift?

Many thanks

Max

Re: How stable are record decks in terms of tempo/pitch? (Drifting)

Reply #1
Basic speed accuracy of a direct drive TT should be around 0.1% of absolute.  Stability should be much better than that.   But then you're using the variable speed thing, which has a range of +/-8% or +/-16%.  To scale that for you, you'd notice noticeable slip in beats that are only 1% off from each other in under 5 seconds.  That means your initial beat matching has to be within under +/- 1% to hold synch for more than a few seconds.   And that's on a control with at least a total range of 16%.
 That's a task for a human.  

I would think the TT is not the problem.

Re: How stable are record decks in terms of tempo/pitch? (Drifting)

Reply #2
If "beat matching" means mixing two different recordings back and forth or from one to the other (like a dj does when he changes a song), the tempo might also depend on the recording. Recordings from before around 1980 didn't (or rarely) use metronomes, so the start of a song might be a completely different tempo than later in the song. I used to make beats for rap music by using samples of old records, mostly from the 70s, and this lack of tempo stability among the musicians was sometimes a problem if I was sampling a longer section.

As dc2bluelight says, if you use the speed adjuster, it has to be done very, very precisely to match two records.

As for turntable stability, the Technics 1210 has a reputation of being very, very stable and accurate, but I don't know if the Numark is better or worse. To compare, CD hater Michael Fremer's Continuum Caliburn , currently priced at $200,000, has more or less the same speed accuracy and stability as the new Technics 1200 (I don't remember the exact difference and which one is more accurate).
My Rega RP3, which I have otherwise been very, very happy with, was 0.2 % fast from the factory, which is a general problem with Regas (faster sounds more "lively", so some say it's completely deliberate). I put on a couple of rounds of adhesive tape to the subplatter and got it down to around 0.02-0.03 % fast, which is almost the same as for the Continuum Caliburn. I do think, however, that my Rega has a bit more fluctuation in the speed than the Technics and the Continuum.
The VPI Classic Direct Drive is, as the name says, also a direct drive (an audiophile table), but runs faster than the Technics - and it costs $30,000!

So, all in all for speed accuracy and stability, I think a Technics 1200/1210 is actually one of the best you can get. Many audiophile tables measure worse. I don't know how the Numark measures though.

EDIT:
See measurements of the Technics here (as well as links to the Continuum):
http://archimago.blogspot.com.es/2014/08/measurements-technics-sl-1200-m3d-wow.html
"What is asserted without evidence can be dismissed without evidence"
- Christopher Hitchens
"It is always more difficult to fight against faith than against knowledge"
- Sam Harris

Re: How stable are record decks in terms of tempo/pitch? (Drifting)

Reply #3
Why not use CD sources instead?  Pitch stability is a nonissue there.

Re: How stable are record decks in terms of tempo/pitch? (Drifting)

Reply #4
Hi all

I used to DJ many years ago, using vinyl. It's something I mean to get back into at some point, but for a variety of reasons I think I'll go down one of the digital routes if/when that happens.

Part of the plan will be to digitise all of my vinyl (around 600-700). But that got me to thinking how stable my decks are in terms of speed / tempo / pitch. When I did mix way back when I used to beat match, and the two records would always drift slightly and need constant tiny adjustments. I never did fully understand whether that was inherently a vinyl thing or just me not being that good at it! One of the attractions with vinyl would be more stability, but if I am playing an unstable recording of a digitised vinyl, then I guess I'd still be in the same boat.

Any thoughts on this would be most helpful.

I should add that my decks are Numark TT-1s (direct drive) and they do have a Quartz button. But would Technics be more stable? Or would a HiFi deck be a better choice? Are there any turntables which are highly regarded for their stability in terms of pitch shift?

I could give a rodent's hinny about reputations among placebophiles and so should you! What really matters is not the gear's reputation, but what it does for you. After all, who is to say that you didn't get a lemon?

The solution is to measure, measure, measure. While we don't know entirely what measurements mean, we know what the difference is between 1% and 0.1% don't we? And actually we do know a thing or two one of which is that the human perception for pitch diffences can be reduced to a number. Pitch accuracy is the same as a turntable that turns the correct speed for the record being played.

So lets go all crazy and see what science says! Here's an example: http://www.phon.ucl.ac.uk/courses/spsci/AUDL4007/Pitch%20perception%202015.pdf

This appears to be a slide set for a university lecture about the perception of pitch.  We don't have to sit through the lecture too line and we happen on slide 9 which contains two factoids:

"Practiced listeners can hear differences of less than 1 Hz for a 200 Hz sinusoid (precision better than 0.5%)"

and

"At 1000 Hz, differences of 2 Hz can be detected (precision of about 0.2%)"

What more do we need? Certainly, if an LP is rotating within 0.1% of the speed it was cut at, then its pitch accuracy is good enough. It's 1/5 of what standard texts say is what the average "Practiced Listener" (whatever that is, but it sounds encouraging!) can hear.

Now how to measure it? Let me introduce the wonderful world of test records. If you want to spend money, then Ortofon has one for you, https://www.amazon.com/Ortofon-024909-Test-Record/dp/B01MY3H95W  and if want to spend less, then the Hi-Fi News and Record Review (or whatever they call it this week) disk  https://www.amazon.com/HiFi-News-Test-Producers-Cut/dp/B00KMCL1PE  is available, and if you want to spend less money you can get one of the audio magazine test records from the days when LPs were all we had.  If you read up on what their track list is, the one you want to buy is one that has a test tone, just about any test tone recorded on it. Good frequencies are 1,000 Hz, and 3,000 Hz or so, or even 400 or 440 Hz. Doesn't matter as long as you know what it is and have some faith in it. Other significant test record links:   https://www.turntablelab.com/products/cbs-laboratories-str100-professional-frequency-test-record     https://www.ebay.com/sch/i.html?_from=R40&_trksid=m570.l1313&_nkw=cbs+str+100+test+record&_sacat=0   https://www.ebay.com/sch/i.html?_odkw=cbs+str+100+test+record&_osacat=0&_from=R40&_trksid=m570.l1313&_nkw=shure+trackabiliity+test+record&_sacat=0

Then you do what you are telling us is your dream, and that is to transcribe tracks from the Test LP to a digital file. Then you find an audio editor like Audacity, and you use it to find out what frequency you actually recorded to digital from off of the disk. 

You can do this by running an analysis called FFT (Pick one with a large sample size as you can) or by measuring the lenght of a complete wave or a number of them that you know. Do the arithmetic or simply read the numbers off the screen, and you know how fast your turntable really is turning. For

For adjusting it, let me introduce you to the Turntable Stroboscope, which is just a piece of paper that you can even download off the web, print out and view under a fluorescent light or equivalent, and set your turntable's speed to stabilize the spinning bars.

And for added fun, you can use an FFT to analyze the spectrum of the wave you transcribe to digital and discern reliable information about flutter, wow, jitter, FM distortion whatever you want to call it.

For example, this is an FFT analysis of a 1 KHz test signal transcribed from a test LP: .    You can find the whole article at https://hometheaterhifi.com/reviews/vinyl/turntable-accessories/shure-m97xe-phono-cartridge-review/

Of primary importance for our discussion is the exact frequency of the big spike a 1 KHz.  Most good FFT analysis programs will let you enlarge the display so you can focus right in on it and get the frequency. For example: http://manual.audacityteam.org/man/plot_spectrum.html  For best results, make the number in the size box they show, as large as possible.. Also read here: http://forum.audacityteam.org/viewtopic.php?f=28&t=55013


Another approach is to measure the length of a chosen number of waves for example https://www.soundintheclassroom.org/uploads/2/5/5/7/25574382/audacity_tutorial.pdf

Re: How stable are record decks in terms of tempo/pitch? (Drifting)

Reply #5
So lets go all crazy and see what science says! Here's an example: http://www.phon.ucl.ac.uk/courses/spsci/AUDL4007/Pitch%20perception%202015.pdf

This appears to be a slide set for a university lecture about the perception of pitch.  We don't have to sit through the lecture too line and we happen on slide 9 which contains two factoids:

"Practiced listeners can hear differences of less than 1 Hz for a 200 Hz sinusoid (precision better than 0.5%)"

and

"At 1000 Hz, differences of 2 Hz can be detected (precision of about 0.2%)"

What more do we need? Certainly, if an LP is rotating within 0.1% of the speed it was cut at, then its pitch accuracy is good enough. It's 1/5 of what standard texts say is what the average "Practiced Listener" (whatever that is, but it sounds encouraging!) can hear.
I assume that those numbers refer to the ability to distinguish two sinoids played back sequentially with a small pause. If the sines are played back simultaneously, we are able to detect minute differences due to beating.

For reference, a semi-tone (two neighbour keys on a piano) are separated by a factor of 2^(1/12) or 6%, and Hollywood movies played back at 24/25 speed to "fit in" with PAL video frame rates has a shift of 4%. Very few people complained that peoples voices sounded pitch-shifted over here.

I don't know much about DJ-ing, but I assume that having a steady beat synchronous between two sources is handy. If you are playing back song#1 at 120bpm, synching that to another song at 120bpm and letting them free-run for 1 minute before trying to switch back, you might find that small relative inaccuracies in tempo (recorded or played back) will accumulate into audible "tempo-discontinuity" when switching.

-k

-k

Re: How stable are record decks in terms of tempo/pitch? (Drifting)

Reply #6
If you get substantial drift, there's either something wrong with your TT (in case of a direct drive) or - with belt-driven ones - it's usually a sign that your belt is wearing out.

But just assuming the playback speed stays stable for the duration of one side of a record, there's a very simple method to correct the overall speed of the digital recording. At least if your turntable is a manual one.

Just record a few rotations of the runout groove. Take the repeated "pop" sounds as a guide. Maybe average it over a few rotations. For 45 RPM a single rotation should take exactly 11/3 Seconds, for 331/3 RPM it's 1,8 Seconds. Use your audio editor of choice to measure the time passing between two "pops", then multiply it by the target RPM speed, divide it by 60. The resulting number is the factor by which you have to slow down or accelerate the audio to result in the right speed.

It doesn't get easier then that. No real need to worry if your turntable's (overall) speed is slightly off.

Re: How stable are record decks in terms of tempo/pitch? (Drifting)

Reply #7
The new SL1200G is one of the most speed stable machines made today, being within 0.1%. You don't hear that as a pitch change, but in terms of timing due to sampling it could still show up.

There is a very nice speed measuring device made by Sutherland called the Timeline. One thing that is often not taken into account is the effect of stylus drag on speed. This usually affects belt drive more than direct drive. The Timeline casts a number of laser spots on the wall; the trick is to keep them in the same place over the duration of the LP.  Drift can easily be seen especially when the tone arm is initially set down on belt drive machines. With the SL1200 you can play the same LP over and over all day long and the Timeline has the spot in the same place all day long too. So for samples where timing is important (as well as speed) the SL1200 seems to be the best out there.

Of course the SL1200 has its own strobe so the Timeline might be redundant :)

Re: How stable are record decks in terms of tempo/pitch? (Drifting)

Reply #8
Of course, if you have two turntables with differing speed accuracy, you can create your own Steve Reich-style tracks.

 

Re: How stable are record decks in terms of tempo/pitch? (Drifting)

Reply #9
You could also look for an old Dual turntable. I still have mine. They are belt driven, have a 7 1/2 lb. platter, and a speed adjustment with a built in strobe.
Glass half full!

Re: How stable are record decks in terms of tempo/pitch? (Drifting)

Reply #10
You could also look for an old Dual turntable. I still have mine. They are belt driven, have a 7 1/2 lb. platter, and a speed adjustment with a built in strobe.
I was going to say something similar. In the days when I still messed around with vinyl because better things hadn't been invented yet you basically had two types of turn tables. TTs for listening used to have a heavy platter so even if the motor wasn't that good, the inertia of a few hundred grams of spinning metal would prevent audible fluctuations. They also came with a thick rubbery mat so the vinyl wouldn't move in relation to the platter.

TTs for DJ-ing on the other used to have ultra light platters made of aluminium. This allowed them to reach or change target speed extremely quickly, useful for beat matching etc. They also often came with a slipmat made specifically to have very low friction for easy scratching and pitching.

Needless to say, if you want to record the vinyl true to its intended sound (and don't want to spend money on digital versions) you would want to invest in one of the first types of turntables and stay away from the DJ types.
Every night with my star friends / We eat caviar and drink champagne
Sniffing in the VIP area / We talk about Frank Sinatra
Do you know Frank Sinatra? / He's dead

Re: How stable are record decks in terms of tempo/pitch? (Drifting)

Reply #11
You could also look for an old Dual turntable. I still have mine. They are belt driven, have a 7 1/2 lb. platter, and a speed adjustment with a built in strobe.
TTs for DJ-ing on the other used to have ultra light platters made of aluminium. This allowed them to reach or change target speed extremely quickly, useful for beat matching etc. They also often came with a slipmat made specifically to have very low friction for easy scratching and pitching.

Needless to say, if you want to record the vinyl true to its intended sound (and don't want to spend money on digital versions) you would want to invest in one of the first types of turntables and stay away from the DJ types.

The old SL1200 did not have an ultra-light platter and yet is very popular with  DJs. It had a fairly robust drive and so was able to get up to speed quite quickly (the new one can do it in 1/10th of a second). If you are on a budget, the older SL1200s are a pretty good deal for LP playback- DJ or no.

 
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