[Gneiss]

Originally Posted by Andy Carlton

Just wondering (in depth) how manufacturers align the speed of their turntables?

You used to be able to buy "test records" which cost a small fortune....

The deck output could then be fed to an audio analyzer which costs even more. The end result being that you discovered what complete shite most decks were

You could also buy "test tapes" which performed a similar task on tape decks and where equally expensive.

If I remember correctly both the records and tapes were made in Germany.

PS. I found this link http://www.tnt-audio.com/accessories/hfnrrdisc_e.html

[Nigel Goodwin]

Originally Posted by Andy Carlton

The only turntables I know of with a parallel tracking arm is the Panasonic/Technics decks on a few of their 1980's midi systems, and I think Phillips did a few models of the same criteria back in their day.

Garrard did a parallel tracking turntable, it used a twin arm that maintained the tracking as it moved across.

Quite a few cheapish systems used parallel tracking systems, the base of the arm was moved along a screw thread by a motor.

[Andy Carlton]

Originally Posted by Gneiss

You used to be able to buy "test records" which cost a small fortune....

The deck output could then be fed to an audio analyzer which costs even more. The end result being that you discovered what complete shite most decks were

You could also buy "test tapes" which performed a similar task on tape decks and where equally expensive.

If I remember correctly both the records and tapes were made in Germany.

PS. I found this link http://www.tnt-audio.com/accessories/hfnrrdisc_e.html

Interesting...as I actually wondered if you could buy a CD with a test tone and a record with exactly the same test tone to synchronize - and the same with tapes to synchronize the tape tone to the CD tone.

Having downloaded two seperate 50Hz strobe discs, they are both slightly different in accuracy, and BOTH extremely different in vinyl and CD synchronization when matching the speed of a record to CD to the point where the record is a key lower or higher than the CD track. (if that makes sense) Playing them back both together (vinyl and CD) sounds dreadful to be honest if they are aligned by strobe discs.

I have since found that just because the strobe dots are perfectly still, doesn't mean that the actual speed is anywhere near accurate. (Interesting to know how these strobe discs are aligned for 'alleged' accuracy?)

With a record collection of almost 1'500 singles/albums and 12" vinyl, and a healthy CD collection, I do have quite a few tracks on both formats with the stated timing of which is the same on both CD and vinyl and having experimented with several tracks from BOTH formats (with exactly the same timing) the only 'near' accuracy I have achieved is by synchronizing the vinyl to the CD timing...and so far...so good because the timing is out (both on 33 & 45) less than a second on most tracks of which is more accurate than a downloadable strobe disc of which has proved to be anything up to 10 (or more) seconds out of synchronization.

As mentioned, you will never get a 'beat-to-beat' synchronized playback with vinyl and CD...but I am more than happy and satisfied with it's accuracy and I think I have done quite well in obtaining a very near accurate speed with only milliseconds difference from each 3-4 minute track.

Some tracks I deliberately tried were from the vinyl copy of 'Fleetwood Mac' (Tango In The Night) where the actual album itself sounds more of less 'off-key' anyway (just to make it more difficult) It does make you wonder when you buy a turntable (or complete system) how accurate the speed is as most are totally incorrect. It would rather concern me though If I spent nearly £400 on a 'Project Xpression' turntable, only to find that the speed was set incorrectly comparing it to the correct speed of a CD.

What I have learned from with this is good 'fine tuning' using your own ears as oppose to relying on factory settings and downloadable speed strobes.

[RobAnt]

I have since found that just because the strobe dots are perfectly still, doesn't mean that the actual speed is anywhere near accurate. (Interesting to know how these strobe discs are aligned for 'alleged' accuracy?)

As I said in previous posts, the stroboscopic effect can only be accurate if used with an independant light source.

Two devices being fed by the same mains frequency (such as a mains powered light and your turntables motor) will be alignable, but that alignment can only be in reference to the frequency of the mains. If the mains frequency deviates - which it does, then the dots will still aligned, but the actual speed will not be the same as the previous reading.

The trouble with using an independant lamp is that you will have to align the motor frequency every time you have a listening session - and if it is an extended period - say 2 or 3 albums, then you'll need to do it again at some stage.

Things like locals turning on kettles during a popular TV programme WILL have an effect on the local mains frequency and voltage.

To fully enjoy your records it is best to suspend your desire for an absolute speed match with other devices which are digitally speed controlled - such as a CD player. A CD play will always be as accurate as possible, because it uses a computer clock, which is referenced to an excited crystal.

Also, when these disks print out, are they identical sizes? If not, then your printer may not have printed the image at the corrrect size. Easy to do, when it's a graphic. You'd probably be better off buying a plastic pre-printed one.

[bobcar]

Originally Posted by RobAnt

Also, when these disks print out, are they identical sizes? If not, then your printer may not have printed the image at the corrrect size. Easy to do, when it's a graphic. You'd probably be better off buying a plastic pre-printed one.

What is the problem if the print size is different?

Originally Posted by Andy Carlton

I have since found that just because the strobe dots are perfectly still, doesn't mean that the actual speed is anywhere near accurate. (Interesting to know how these strobe discs are aligned for 'alleged' accuracy?)

It's difficult to see how they can be inaccurate if they are still as if the dots (or whatever is on them) were not accurately spaced you would get jitter. Where did you "find this out"?

[Andy Carlton]

Originally Posted by bobcar

What is the problem if the print size is different?


It's difficult to see how they can be inaccurate if they are still as if the dots (or whatever is on them) were not accurately spaced you would get jitter. Where did you "find this out"?

By downloading two seperate strobe discs from two seperate web sites. If I align one up and place the other one on in it's place, there is slight variation on both, also with playing back vinyl at the same time as a CD, there is a huge difference not only in timing, but as mentioned in my other post - the track sounds out of key too.

I bet I could go out and buy a specialised rubber strobe disc and that would probably give a different reading again to the downloadable ones.

Here are the sites I used: http://www.vinylengine.com/ (This is a pdf file so you will need adobe reader/or similar)

http://www.extremephono.com/free_tur...trobe_disk.htm (mentioned in earlier posts)

Give them both a whirl, then use the same vinyl track as CD on another source and you will hear the huge difference in the vinyl track being out of key.

[bobcar]

Originally Posted by Andy Carlton

By downloading two seperate strobe discs from two seperate web sites. If I align one up and place the other one on in it's place, there is slight variation on both, also with playing back vinyl at the same time as a CD, there is a huge difference not only in timing, but as mentioned in my other post - the track sounds out of key too.

It doesn't matter if there is a variation between them. All that matters is that there is uniform sequence of dots or other shapes around the circumference of a circle properly distanced (in angle not linear distance) such that at the strobe frequency the dot will have moved the correct amount. You can halve or double the size of the disc and it will make no difference.

Absolute accuracy in the disc does not matter as long as there are the correct number of dots or sectors, at worst if they are inaccurate you will get jitter. If the speed of the platter is off then the disc will appear to rotate whatever.

What you are doing with using one of these discs is tuning for a beat frequency of 0, this is a technique very much used to tune electronic oscillators to the correct frequency. What matters in terms of accuracy is the reference ie the strobe not the disc.

[gemma-the-husky]

i am sure the angular effect of a pivoting turntable arm is negligible. you are more likely to get jitter from mains variations than that i would think.

a decent turntable cartridge tracks at a very modest weight 6-8 gms maybe, to avoid damaging the vinyl - i forget which way - its probably centripetal force on the outside of the groove - but a tonearm naturally puts pressure on one side a groove - hence arms come with a weight counterbalance to offset this.

finally, i am sure the isolation of a motor system to parallel track an arm, would be harder to achieve than that with a rotating pivot arm - or Linn/Michell etc would all have done it years ago.

Decks that had parallel tracking were just gimmicks imo

[gemma-the-husky]

Originally Posted by bobcar

Why would the belt stretching slow it down? I can imagine it slipping but that would cause other problems, if the tension is uneven because of stretching I can also imagine it causing wow and flutter but not a steady slowing down.

i think the poster meant that the belt stretched over time, leading to a change in the gearing between the capstan and the drive wheel (or whatever they are called) not that it affected playback of a single track.

i know there were some electronic devices on some turntables (goldring?) that tried to adjust the speed electronically by some feedback loop.

you get the same arguments about CD transports as well. - so meridian can justify charging fortunes for stuff - maybe it makes a difference.

Instructions on my rega planar said "dont stop the turntable" once its going - if you need to change a record, just lift it off the moving turntable

indeed at the time i bought it, it was a surprise that you changed form 33 to 45rpm by lifting off the platter, and changing the belt - before that my cheaper turntable had a frindly little lever - its all to do with isolation I am sure.

[gianni]

It is probably more important that the rotation is stable and consistent than it is accurate (within reason). Unless you have perfect picth you might not notice a variation of 1% if it were constant but a variation of +/- 0.5% would be obvious to most people - called wow and flutter.

Also, don't be convinced that the CD is playing at the right speed! Some devious mixes have sped up tracks to sound sharper and more exciting, not to mention boosting base, etc.

In the world of esoteric turntables (£500 to £100,000+) you will find multiple motors, variable belt tensioning, computer controlled speed correction devices, turntables made of solid concrete weighting 75kilos, etc. You will also find parallel tracking arms running on air-bearings and an incredible range of styluses (stylii?) and step-up devices.

The thing about esoteric turntables is more really is more. They can sound incredibly life-like and pure compared to a CD. What they are doing is making the basic function of a turntable/arm/stylus - to measure the shape of the groove - very, very accurate and consistent.

Read up on some of the engineering principles and practices and apply them to any turntable and you should get better sound. Place it on something solid and level, use a good record cleaner, make sure the leads are clean and correctly fitted, make sure the arm can move freely, make sure the rotation speed is accurate and consistent, etc.

I really hope you enjoy what old-fashioned vinyl can do because there are millions of old records out there in charity shops at 50p a go!

[gianni]

Supplemental responding to gemma-the-husky....

Meridian CD players do digitally in software what I just described for turntables. I have one of their better CD players, its great but my turntable still trounces it for sound quality.

BTW, don't let your Rega (or whatever) run forever. The bearing wears out or dries up and knackers the turntable.

Speed change on the Rega was about maximising sound quality for a price. Most people listen to 33rpm most of the time so why charge another £20/£30 for a few people to play 45s instantly? My Roksan uses an electronic control unit to change speed at the touch of a button - at a price.

Guilty admission here - I am a vinyl junkie

[bobcar]

Originally Posted by gianni

It is probably more important that the rotation is stable and consistent than it is accurate (within reason). Unless you have perfect picth you might not notice a variation of 1% if it were constant but a variation of +/- 0.5% would be obvious to most people - called wow and flutter.
!

Indeed most people don't notice the 4% speed up when playing a DVD, those with perfect pitch of course do but I'm not a member of that exclusive club.

[RobAnt]

a decent turntable cartridge tracks at a very modest weight 6-8 gms maybe, to avoid damaging the vinyl - i forget which way - its probably centripetal force on the outside of the groove - but a tonearm naturally puts pressure on one side a groove - hence arms come with a weight counterbalance to offset this.

I set mine for 1.5-2gms, but no matter how much the weight of a cartridge and tonearm is offset by it's counterbalance, because it is in such a very tiny area, the combined mass being supported is often equal to the weight of an elephant standing on one leg.

A good point about the strobe disk was raised by someone. Well spotted.

[gemma-the-husky]

Originally Posted by gianni

Supplemental responding to gemma-the-husky....

Meridian CD players do digitally in software what I just described for turntables. I have one of their better CD players, its great but my turntable still trounces it for sound quality.

BTW, don't let your Rega (or whatever) run forever. The bearing wears out or dries up and knackers the turntable.

Speed change on the Rega was about maximising sound quality for a price. Most people listen to 33rpm most of the time so why charge another £20/£30 for a few people to play 45s instantly? My Roksan uses an electronic control unit to change speed at the touch of a button - at a price.

Guilty admission here - I am a vinyl junkie

i didnt mean let it run forever - i just meant they said in a single listening session dont keep stopping/starting

i rarely listen to vinyl now - but i can certainly hear more depth to the sound - eg tremendous bass guirar on Jam The Gift probably my best example

[Gneiss]

Originally Posted by Andy Carlton

Interesting...as I actually wondered if you could buy a CD with a test tone and a record with exactly the same test tone to synchronize - and the same with tapes to synchronize the tape tone to the CD tone.

Having downloaded two seperate 50Hz strobe discs, they are both slightly different in accuracy, and BOTH extremely different in vinyl and CD synchronization when matching the speed of a record to CD to the point where the record is a key lower or higher than the CD track. (if that makes sense) Playing them back both together (vinyl and CD) sounds dreadful to be honest if they are aligned by strobe discs.

I have since found that just because the strobe dots are perfectly still, doesn't mean that the actual speed is anywhere near accurate. (Interesting to know how these strobe discs are aligned for 'alleged' accuracy?)

With a record collection of almost 1'500 singles/albums and 12" vinyl, and a healthy CD collection, I do have quite a few tracks on both formats with the stated timing of which is the same on both CD and vinyl and having experimented with several tracks from BOTH formats (with exactly the same timing) the only 'near' accuracy I have achieved is by synchronizing the vinyl to the CD timing...and so far...so good because the timing is out (both on 33 & 45) less than a second on most tracks of which is more accurate than a downloadable strobe disc of which has proved to be anything up to 10 (or more) seconds out of synchronization.

As mentioned, you will never get a 'beat-to-beat' synchronized playback with vinyl and CD...but I am more than happy and satisfied with it's accuracy and I think I have done quite well in obtaining a very near accurate speed with only milliseconds difference from each 3-4 minute track.

Some tracks I deliberately tried were from the vinyl copy of 'Fleetwood Mac' (Tango In The Night) where the actual album itself sounds more of less 'off-key' anyway (just to make it more difficult) It does make you wonder when you buy a turntable (or complete system) how accurate the speed is as most are totally incorrect. It would rather concern me though If I spent nearly £400 on a 'Project Xpression' turntable, only to find that the speed was set incorrectly comparing it to the correct speed of a CD.

What I have learned from with this is good 'fine tuning' using your own ears as oppose to relying on factory settings and downloadable speed strobes.

As you may already know CD recordings and playback are by no means of guaranteed accuracy either, but so few people notice they don't tend to worry...

For years people have been watching film converted for British TV without noticing that every piece of music was slightly off key by the ratio 24:25. The trick being that they simply ran the film faster to match the 25 frames/sec required!

The mains frequency mentioned earlier is hopelessly inaccurate... the only thing the generating companies are obliged to guarantee is that the frequency will average 50Hz over a 24hr period - this is why clocks that still rely on this manage to maintain long term accuracy.

[Gneiss]

Hit reply by mistake before I finished! With regard to factory testing..

At completely the opposite end of the scale as I mentioned good audio test equipment required for true accuracy is very expensive... A quick search for the Audio Precision System One that I used to use reveals that they still appear to sell for around £2,500 if you can get anyone to give you a price that is - then there is regular calibration and on top of that you require a PC to drive the thing. http://www.ietlabs.com/SystemOneCopy.html

That is the sort of equipment the manufacturers will be using to ensure quality, although I expect a lot of it will be automated these days particularly at the lower end of the market.

If only you could get hold of a 440Hz (generally regarded as middle A) tone and borrow one of those electronic instrument tuners then bingo - an easy fast solution.

[bobcar]

Originally Posted by Gneiss

As you may already know CD recordings and playback are by no means of guaranteed accuracy either, but so few people notice they don't tend to worry...

CD playback speed is extremely accurate. Of course there's no guarantee about the recording especially if it's an old one.