Author Topic: Record Speed/Pitch  (Read 391 times)

dlmckain

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Record Speed/Pitch
« on: November 03, 2021, 09:01:04 AM »
I notice that track breaks (imported from Discogs) seem to be ahead of the actual breaks in my recordings. Understandably, a lot depends on how long after you start recording the first side (which produces an offset for all tracks), how long you wait before needle up on first side and before the actual beginning of the first track of the second side. These I understand. However, that the breaks get further and further (in time) from the actual breaks as you go through a side is concerning.

I worry that my pitch control on my turntable is not accurate even though the strobe is spot-on. I'd assume the crystal (older turntable) that controls the strobe would be relatively accurate.

Also, whether the Discogs track lengths are a) accurate of b) include silence between tracks is a bit of a crap shoot.

Any thoughts on how to check whether it's an equipment issue?

Really love using Vinyl Engine to digitize/clean-up/archive my vinyl collection.

Dave


Paul Sanders (AlpineSoft)

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Re: Record Speed/Pitch
« Reply #1 on: November 03, 2021, 10:09:13 AM »
Hi,

I'm not sure I'd rely on Discogs track timings to that extent.  Most of them are pulled from CDs, not vinyl, so the gaps between tracks will almost certainly be different.  There are definitely more reliable ways to check the speed of your turntable.  You used to be able to strobe from mains lighting, but I'm not sure that modern bulbs 'flicker' in the way that filament lamps do.

One little trick that you might find useful in VinylStudio is to hold down the Alt key while dragging the first track break for the album or album side.  The track break markers then all move as a group (everyone seems to miss that one)

And, um, Vinyl Engine is an enthusiasts' website (and a very good one) ...

Steve Crook

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Re: Record Speed/Pitch
« Reply #2 on: November 05, 2021, 09:26:44 AM »
As a rule the strobe should be good enough, particularly if it's one that relies on mains frequency to report on speed. You don't mention the TT type. If you need help with electronics or mechanicals then DIY Audio have an analogue source forum where there's discussion on a wide variety of things including Technics, Thorens and others, refurbishing them and making repairs or upgrading.

For example there's this recent thread: https://www.diyaudio.com/forums/analogue-source/378446-technics-sl-1301-running-1-fast.html but there are loads of others...

dlmckain

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Re: Record Speed/Pitch
« Reply #3 on: November 05, 2021, 10:02:28 AM »
As a rule the strobe should be good enough, particularly if it's one that relies on mains frequency to report on speed. You don't mention the TT type. If you need help with electronics or mechanicals then DIY Audio have an analogue source forum where there's discussion on a wide variety of things including Technics, Thorens and others, refurbishing them and making repairs or upgrading.

For example there's this recent thread: https://www.diyaudio.com/forums/analogue-source/378446-technics-sl-1301-running-1-fast.html but there are loads of others...

It is a Technics SL-D3. I'm not sure but, from what I can tell of the schematic, the strobe operates from mains frequency. I'll look into it further.

I have a digital strobe but not sure of it's precision and would have to pick a multiple of the frequency (556 or 5556 or 55556 Hz, 100 * 1/3 / 60 * 10^x) and see what I see.

I also have an SL-Q3 and some other tables (SL-1900, SL-2000, Realistic Lab-400, etc.) that I can check against.

Would be interesting to be able to use my old "test" record and see if a 440 Hz "A" is played as 440 Hz.

Science!

Paul Sanders (AlpineSoft)

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Re: Record Speed/Pitch
« Reply #4 on: November 05, 2021, 10:04:05 AM »
> Would be interesting to be able to use my old "test" record and see if a 440 Hz "A" is played as 440 Hz.

Why can't you?  Do you no longer have it?

Steve Crook

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Re: Record Speed/Pitch
« Reply #5 on: November 05, 2021, 11:54:14 AM »
Seems to be a highly regarded TT, thought to have accurate speed control. Apparently it doesn't use an XTAL for speed control but something referred to as 'pulse detection circuitry' which sounds like an early PWM controller. https://vintage-turntable.com/technics-sl-d3.html. Plenty of people have dragged one out of the cellar and found it to be perfect.

The test record would be a good idea IMO. You'll also see how speed stable it is. I have to say though, for your track positioning to be a long way off it would have to be running some distance away from 33.3 and I can't help thinking it'd probably be audible. If you've got two decks, connect one and actually time the track. Then try the other one, see how the times compare. Do a whole side and even 10 seconds difference is a small percentage error on 20-30 minutes.
« Last Edit: November 05, 2021, 05:31:06 PM by Steve Crook »

dlmckain

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Re: Record Speed/Pitch
« Reply #6 on: November 08, 2021, 01:53:51 PM »
Okay, sorry for the delay, disco party over. At 555.6 Hz and the table strobe locked (stationary) the speed seems correct (no motion on 60Hz indicators).

Just so happens I just recorded Yes - Tales from Topographic Oceans (yes, progressive overload) but handy as it is one track per side.

I compared the track lengths (after I split) to the track lengths listed on Discogs and was right about 4 seconds longer on each track/side as the listing. If you include lead-in/out and the like the cascading effect over the record is that the difference between the recorded and indicated (by discogs) breaks/splits get further and further from each other which is understandable. My lead in on track 1 is 14 seconds before the music starts (your results may vary). This would be dependent on how the table is set up (for automatics) and where you decide to drop the stylus (manual cueing). Add the 20 seconds at the end for the software to stop recording and the difference is going to keep getting bigger as you add sides.

Add to this the differences on Discogs and whether anyone bothered to put in the actual track length and it all becomes somewhat of a crap shoot and the software can't guess.

However, the "scan for track breaks" functionality, which I don't use very often, might help matters depending on whether there are actually breaks.

Using the Beta version and the behavior between sides has improved. It used to separate end and start breaks and, if the music tailed off, it would jump to the next side without being able to listen to what was happening. Now it puts in a break that makes it easier to do audible differentiation.

So I believe that the problem isn't with the software or hardware but just the way track lengths are defined.

At least my turntable isn't screwed up eh?

Now to sort out normalization on my end. Gain controls on A/D converter are overly sensitive and the L/R channel conundrum (as the stylus tracks across the record) comes into play.


dlmckain

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Re: Record Speed/Pitch
« Reply #7 on: November 08, 2021, 01:56:15 PM »
As for the circuitry - I looked at the schematic to try and figure out how the strobe got it's signal to no avail. Will look at the topic Steve linked in his post.

Steve Crook

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Re: Record Speed/Pitch
« Reply #8 on: November 08, 2021, 02:15:45 PM »
Glad the timing issue isn't an issue...

DIY Audio is a mine of information some of it useful some not :-) There are also some really interesting amplifier designs to build and modify.

I'm partway through building a motor speed controller for my Heybrook TT2, designed and distributed by a guy on DIYA, the design has since been purchased by a company and is available as a complete unit. I also built an excellent valve phono stage designed on DIYA.

People are helpful, polite and very knowledgeable. If DIY build or repair interests you I highly recommend it.