Pro-ject Speed Differences

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Marrow
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Pro-ject Speed Differences

Post by Marrow » 28 Aug 2013 11:00

I have a new Debut Carbon & a used Xpression III. They finish a song at almost a 3 second difference from each other. The debut about a second too fast. The Xpression III about a second too long.

Could the age of the belts play into this?
Could the way the motors are secured play into this? The Debut Carbon's motor is screwed down as it said in the manual not to remove the transport screws. However the transport screws are removed from the Xpression III as is intended. I noticed when putting the belt on that the tension would pull the motor inward very slightly in theory slightly limiting the distance the belt has to travel.
Are the belts interchangeable for the Debut Carbon and the Xpression III? Would swapping belts and re-recording be a possibility or are they not compatable?

I couldn't take a screen shot because when I try it takes the files offline in my DAW. Had to use a cheap camera. The orange tracks are left and right channels of the Xpression III. The middle blue wav file was ripped from cd. The bottom red tracks are the left right Debut Carbon's. It's not noticeable when listening but when I zoom in you can see the difference.

I have to decide which of these I want to keep.
http://s8.postimg.org/kp4saxft1/DSCN2121_1920x1440.jpg

http://s17.postimg.org/5d0kgo1y7/DSCN2124_1920x1440.jpg

analogaudio
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Re: Pro-ject Speed Differences

Post by analogaudio » 28 Aug 2013 19:39

wow, you are a thorough guy :-)

assuming a three minute song 3 seconds in 3 minutes is one in sixty, nearly 2%. Have you looked at the speed accuracy specification for each TT? 2% may be within the manufacturing tolerance, especially if these units use AC synchronous motors, which many belt drive models do. For spot on speed you want either crystal oscillator reference drive, also know as "quartz" or, variable speed DC motor drive for a belt motor or variable speed AC motor drive for a belt motor, all are available. My understanding is that these Project models both use AC synchronous motor drive and some speed inaccuracy is usually tolerated.

Looking at the manufacturers specification for the Debut Carbon it gives + and - 0.8% speed drift. Your 3 seconds is a difference between two machines, each may have a .8% error, the two added together become 1.6% which is not so far from your 3 seconds in 3 minutes total difference, if my reasoning is correct this is close to the manufacturing tolerance.

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Re: Pro-ject Speed Differences

Post by Marrow » 29 Aug 2013 00:01

Thanks for your reply analogaudio. Yes and while they vary approximately 3 seconds from each other they vary even less from the source (about one second). I would not have noticed had I not made a video/audio comparison to aid with my decision. When I was chopping up the audio to jump back and forth from the TT's I noticed the discrepancy.

I think I've heard the word "quartz" with regards to the pro-ject line of speed boxes. I failed to mention that each table was connected to a speed box. I'm not sure if this would play into accuracy or not.

I kind of want to take the Xpression III into an autobody shop and have it custom painted as it has a couple spots in the paint... curious as to what the results would look like. What one would you keep? Upgrading beyond these is not currently an option. The TT will be used almost every day. https://www.youtube.com/watch?v=t3vsTQx63cc

I do like the feet and the tonearm on the Xpression III, but I like the impeccable condition and newness of my Debut Carbon. Guitars break up a bit with Ortofon 2M Red. The Red may be pushing the already scooped mids of modern electric guitars in the cut past it's handling capacity.

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Re: Pro-ject Speed Differences

Post by analogaudio » 29 Aug 2013 01:03

I was able to find information online for the Speedbox S model. Does it change things? Your test is the proof. It appears that some Project turntables use AC synchronous motors. These have two sorts of speed drift. When the incoming AC line frequency, 60Hz, drifts (which is does sometimes by very small amounts) the motor follows the mains frequency and drifts also. The second source of speed error is I think something called slip where the motor, although in theory locked to the rate of the mains frequency in fact runs a little slow on load. If I understand the Speedbox S correctly it is an AC generator that uses a stable quartz crystal as its reference for the 60Hz frequency. This eliminates drift due to 60Hz mains frequency drift. However this does nothing for the intrinsic performance limitation of the AC synchronous motor, which has a tendency to slip. I could be wrong, I am not a motor engineer, but I think your experiment proves the Speedbox fixes some but not all speed drift in the Project turntables.

If the belts are the same you could do an experiment and switch them over and see if it makes any difference, I would expect none but I could be wrong.

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Re: Pro-ject Speed Differences

Post by Coffee Phil » 29 Aug 2013 02:11

Hi Marrow,

Welcome to the forum.
To answer your question about the belt. Yes the belt can effect the platter speed. The effect is small but it is there. Ideally the platter speed should be the motor speed divided by the ratio of the pulley diameters. The issue is that the effective pulley diameter includes part of the belt thickness. This effect is very pronounced in turntables with 4 pole motors (1800 RPM on 60 Hz). The motor pulley is very small and the belt effect is significant. I'm pretty sure your motor has more poles and therefore turns slower but the effect is still there.

I have to disagree with Ted on the motor. The speed of a synchronous motor is the angular speed of the AC line divided by the number of pole pairs. That is why we call them synchronous motors. AC induction motors slip but not synchronous motors within their torque limit. I do agree with Ted that some error is tolerated. With an aftermarket belt my Rec-O-Kut (4pole synchronous motor) was ~5% fast. I ground the belt down to the point where I can't see any error with a strobe disc. I understand belts are now available for my machine which will save me that aggravation.

In the US our power line frequency has traditionally been accurate enough to use for clocks with synchronous motors. The is some ugly talk of relaxing that accuracy.
At any rate both of your machines are running on the same line or speed box so that variable is illuminated. If your speed box has provision to vary it's frequency you might use a quartz strobe light and strobe disc to set the speed by tweaking the frequency of the speed box. If that is not an option be sure you are using an OEM belt. If all of this fails, I believe they make a servo controlled variable speed DC motor conversion kit.

Phil

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Re: Pro-ject Speed Differences

Post by Stumpy21 » 29 Aug 2013 12:58

Marrow wrote:Yes and while they vary approximately 3 seconds from each other they vary even less from the source (about one second).
Before you adjust or condemn either of the decks. It is possible that one may be spot on for speed. :idea:

If I am reading your posts correctly your only point of reference, stated in your 1st post, would seem to be a music CD?

You also need to take into account the other variables - the mastering equipment and processes used at the time of transfer to Vinyl and CD.
Even recordings mastered and pressed in different countries can have speed/time variations! :shock:

The best way to answer your questions would be to obtain a quality test record, with a fixed test tone of 3150Hz, used with measuring software.

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Re: Pro-ject Speed Differences

Post by analogaudio » 29 Aug 2013 17:24

Coffee Phil yes I stand corrected regarding motor slip, probably I was confusing synchronous and induction motors.

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Re: Pro-ject Speed Differences

Post by Audirc » 30 Aug 2013 01:41

The speed box s won't make a difference, just stabilize the speed. The speed box se has the ability to adjust pitch. Use this with a strobe disc and you can fix both tables...

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Re: Pro-ject Speed Differences

Post by Marrow » 30 Aug 2013 02:18

I believe Obzen (the song I used is called "Bleed" and it is a beast, difficult for TT's which is why I chose it but it's not in the video I made, that's a different song from a different band) like Koloss was recorded directly into the computer then rendered out. I don't know if any fluctuations occurred during the cd burning process but the guys from Meshuggah don't strike me as the kind of folks that would tolerate such an imperfection as the timing being off. Timing is a big part of progressive technical metal. You can see their recording method in the documentary "Konstrukting the Koloss" here http://www.youtube.com/watch?v=ABIkYU3XsKs&t=5m46s. It is similar to how I record my music. I'm confident if you compared the wav file from the cd to the source files in their DAW they would align perfectly.

As for the vinyl being off that is a possibility however I used the same record, same song, on both TT's. I aligned the tracks myself to ensure they started at precisely the same moment. As they play along you can hear them separate. It sounds really trippy. A weird hall-like reverb that is pulling your brain apart.

I should mention that the Speed Box I used was not the "S" model. It is the previous generation I believe. The Speed Box MK II. I'm going to see if the 1-Xpression III will take the Debut Carbon's belt. If it does I'll re-record it. Then I'll see if I can track down the transport screws and secure that motor down to see if the belt pulling on it floats it towards the center of the TT slightly reducing the distance the belt has to travel.

Oh man AA I would love to have the speed box se. If I were able to work I'd defiantly go that route. One day. In fact one of the reasons I purchased this used TT was because it had the speed box included.

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Re: Pro-ject Speed Differences

Post by Audirc » 30 Aug 2013 03:00

I may end up with one, one day... I need a better amp, then phono pre, then cart,., spending money I don't have in my mind. Why does this hobby have to be so addictive!?!?!

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Re: Pro-ject Speed Differences

Post by cafe latte » 30 Aug 2013 03:34

AA wrote:I may end up with one, one day... I need a better amp, then phono pre, then cart,., spending money I don't have in my mind. Why does this hobby have to be so addictive!?!?!
Its not addictive at all, I am not sure what made me buy 5 turntables and the maybe 10-12 carts I have :D
Regards
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Re: Pro-ject Speed Differences

Post by Marrow » 30 Aug 2013 04:44

I love the ritual. That is why I listen to records. I love the mechanics of it all. The engineering, the design, the way the colors pass through the acrylic platters. The aesthetics. I love that it grounds me to the here and now. It demands my attention. My earliest exposure to music was through records when I was a child. A return to innocents if you will. I like rare things so the limited edition LP's are right up my ally. I love waiting for the mailman to arrive with a new LP. I love the look on his face as he stares at the box experiencing deja vu but not quite sure if what he is holding really is a record. An actual record. It's been decades since I've delivered one of these. They still make these? lol.

Okay here are the results. I must say I was wrong. I thought putting the screws into the motor, pulling it back exactly into place slightly, would increase the speed of rotation. I stand corrected. Derp.
http://s10.postimg.org/6lenyaga1/1_Xpre ... _Motor.jpg
http://s8.postimg.org/mzqhj4dlx/1_Xpres ... est_02.jpg

I'm going to put the Debut Carbon belt back on now and run it with the motor screws out. I suspect that will get it even closer. I'll post the results in bit.

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Re: Pro-ject Speed Differences

Post by Marrow » 30 Aug 2013 06:52

I was wrong again... er I was right the first time? I think the belt that came on the Xpression has lost some of it's elasticity and is throwing me off. Putting the screws in apparently did draw it back and increase the speed. I'm lost. My guy at the automotive spray shop asked me if it was a plastic plinth. The specs on the website say "Plinth out of MDF with high gloss anthracite surface."

Here are the results (I ended up deleting the right channel tracks so they'd fit):
Look at the difference between belts. The Debut Carbon's belt gets closer no matter what. Motor screwed in or not. I was sure to run it a few times letting the belt settle fully into position before recording each track.
http://s17.postimg.org/58qo6b7wv/Test_R ... Carbon.jpg

Here you can see how I have the beginning of the tracks lined up (zoomed in). I look for the first real pointy wave form peak then I scrub the time line over to it. Then I line the other tracks up.
http://s8.postimg.org/po3tsxnfp/Begining_Zoomed_In.jpg

Zoomed way, way in. You can see how accurate you can get it with those vertices. I don't know if people in the music field call them vertices but in Autodesk Maya they are called vertices so... for now they are vertices. The right channels are in there too so jump over every second one.
http://s23.postimg.org/t827dwr9n/Vertices.jpg

Zoomed out. I didn't get the beginning of the tracks in that shot but you can see there isn't that much of a discrepancy. The Debut Carbon getting the closest and actually finishing a little fast. The Xpression with the Carbon Belt and the Motor screwed in coming in second. Looks like it's time for a new belt soon. If you are in autocad designing TT's you might want allow for the belt pulling the motor in closer if it's going to be floating like that. Note to self should I ever be healthy enough to manufacture a $500 quality TT here in the States. Because that needs to happen.
http://s12.postimg.org/ig9bz9yot/Zoomed_Out.jpg

I like the look of the feet better on the Xpression. I like the little handle on the tone arm. It has a heavier counter weight should I need it. The Denon DL-110 is a fine cartridge. But I may just sell the Xpression, buy a 2M blue for the Carbon and be happy. You can see in the photo the scratch marks by were you'd grab the tonearm. From a ring perhaps? The ebay auction said pristine. I'd say shy of pristine. But as you probably gathered I look for flaws in everything. Any TT just has to last until I can get back out into the world. But that could be years. Then I'd like that VPI Scout but with an acrylic platter. You sexy devil you.
http://s22.postimg.org/lnr7cavs1/Xpression_IIIObzen.jpg
If you want to buy either of these from me so that I don't have to make a decision let me know. But one has to go.

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Re: Pro-ject Speed Differences

Post by Bob_in_OKC » 07 Sep 2013 15:36

Coffee Phil wrote:...snip...

In the US our power line frequency has traditionally been accurate enough to use for clocks with synchronous motors. The is some ugly talk of relaxing that accuracy.
At any rate both of your machines are running on the same line or speed box so that variable is illuminated. If your speed box has provision to vary it's frequency you might use a quartz strobe light and strobe disc to set the speed by tweaking the frequency of the speed box. If that is not an option be sure you are using an OEM belt. If all of this fails, I believe they make a servo controlled variable speed DC motor conversion kit.

Phil
The accuracy of the power frequency as it pertains to a clock is long-term, such as over the course of a day, a week, or a year. The accuracy of the frequency for a turntable is important only in the moment. When the power frequency has been inaccurate for a while, running it inaccurately in the opposite direction of error corrects AC clocks. However, that practice adds more error in the moment to correct long-term clock movement. The practice the power producers are planning on relaxing is that of introducing error in the moment to correct this long-term clock movement. Abandoning that practice would cause no negative effect on turntables.

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