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Gyro SE w/full Orbe upgrade: Speed instability

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Gyro SE w/full Orbe upgrade: Speed instability

Postby richbdd01 » 16 Jul 2018 01:46

Hi all

I bought my turntable around 4 years ago now used. However, much of it was upgraded by me including Orbe platter, double spyder and HR power supply.

The speed stability has never been spot on, ie varying about 0.7 rpm either way. What i mean by this is that if the minimum speed is measured at 33.30 rpm, the maximum speed measures up to 33.37 rpm and it would measure anywhere between these two points. I have never really noticed any audible issue with regards to this.

However, recently, I have noticed some much more significant variation and I am trying to pinpoint the cause. I sat down to listen to a record the other day and noticed it was running fast. It sounded noticeably faster whilst listening and was obviously too fast. I measured the speed and it was about 3 rpm too fast. I then adjusted it back on the HR speed adjustment. Everything was fine for about 3 records and then I noticed it again. It was back up to 35 rpm.

I have been racking my brains as to what is causing this. Could it be my belt? I wouldn’t expect such a noticeable increase in speed if it was the belt though...?

I cleaned the belt with warm soapy water this evening and rinsed, leaving it to dry. I have tested it a few times since cleaning and I think it seems slightly better now. Would a dirty belt cause such a fluctuating speed? I hope it has sorted the issue out but I thought it was okay previously and don’t want to tempt fate if it happens again.

Is there anything else I can do to improve the situation? I am moving house soon and I am thinking of cleaning the bearing and re-oiling. It has been very warm here in the UK and the room temperature has been elevated. However, I wouldn’t have expect it to be sensitive.

I am speed testing it with the iPhone turntabulator app and RPM app.

Anyway, if anyone has any ideas or tips then I would be really grateful.

Thanks

Richard
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Re: Gyro SE w/full Orbe upgrade: Speed instability

Postby ChrisfromRI » 16 Jul 2018 05:14

Yes, belt condition is important. In that it has been 4 years in service, cleaning and re-oiling the main bearing is a reasonable thing to do. Check also if you can lubricate the motor shaft bearings as well.

Someone just complained to me yesterday about that iPhone App not being perfectly accurate. I don't know if it is or isn't. What I know works well and is very inexpensive are those laser tachs coming in from China that come with a strip of reflective tape. You cut a small piece of the reflective tape and stick it to the edge of your platter. You shoot the laser at the reflective tape and in a few revolutions see the speed on the tach's display. I paid around $10 for the laser tach, a few inch long length of reflective tap, and a fabric zip-up case.
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Re: Gyro SE w/full Orbe upgrade: Speed instability

Postby GyroSE » 17 Jul 2018 12:12

richbdd01 wrote:Hi all

I bought my turntable around 4 years ago now used. However, much of it was upgraded by me including Orbe platter, double spyder and HR power supply.

The speed stability has never been spot on, ie varying about 0.7 rpm either way. What i mean by this is that if the minimum speed is measured at 33.30 rpm, the maximum speed measures up to 33.37 rpm and it would measure anywhere between these two points. I have never really noticed any audible issue with regards to this.

However, recently, I have noticed some much more significant variation and I am trying to pinpoint the cause. I sat down to listen to a record the other day and noticed it was running fast. It sounded noticeably faster whilst listening and was obviously too fast. I measured the speed and it was about 3 rpm too fast. I then adjusted it back on the HR speed adjustment. Everything was fine for about 3 records and then I noticed it again. It was back up to 35 rpm.

I have been racking my brains as to what is causing this. Could it be my belt? I wouldn’t expect such a noticeable increase in speed if it was the belt though...?

I cleaned the belt with warm soapy water this evening and rinsed, leaving it to dry. I have tested it a few times since cleaning and I think it seems slightly better now. Would a dirty belt cause such a fluctuating speed? I hope it has sorted the issue out but I thought it was okay previously and don’t want to tempt fate if it happens again.

Is there anything else I can do to improve the situation? I am moving house soon and I am thinking of cleaning the bearing and re-oiling. It has been very warm here in the UK and the room temperature has been elevated. However, I wouldn’t have expect it to be sensitive.

I am speed testing it with the iPhone turntabulator app and RPM app.

Anyway, if anyone has any ideas or tips then I would be really grateful.

Thanks

Richard

May I ask if these speed fluctuations are audible? I'm a little sceptic about the precision in these speed apps- if you really want to know the real speed try to lend a stroboscope and stroboscope disc to really determine the speed. On the HR PSU you can adjust the speed very easy using a small screw driver.

I clean the belt and the motor pulley on a regular basis. This is my work flow; I remove the belt, clean the pulley (both the 33 and the 45 RPM slots) with the motor running with a cotton swab moistened with a couple of drops with isopropanol. Then I boil the belt for a minute to recondition it, rinse it and let it dry before I put it back on the turntable. On my Gyro SE I also clean the belt slots on the side of the platter with cotton swabs/isopropanol and on my Orbe SE I clean the sides on the platter with a damp microfiber cloth.

If the work flow doesn't Help then get a new belt and if the problems still are there then get in touch with Michell Engineering and ask for advice what to do.

If you're going to move house then change the bearing oil- then you know you're good for the upcoming 3-4 years.
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Re: Gyro SE w/full Orbe upgrade: Speed instability

Postby Steve_Nine » 29 Jul 2018 03:05

You are entirely right to be sceptical about the phone apps. I am currently putting the finishing touches on a high precision turntable power supply and have spent the last couple of weeks testing and adjusting an automatic calibration routine.

The controller has been designed to give a consistent pitch accuracy of less than one musical cent (1/100 of a semitone relative to Concert A-440 Hz). This figure was chosen because it gives pitch accuracy at or below that which can be audibly discerned by a concert trained lead violinist in an orchestral setting. The initial target was to achieve a consistent, stable pitch at 33.333 rpm.

After trying a series of trial filtering algorithms in an attempt to minimise "hunting" behaviour, the device is now rock solid stable at 33.3333 rpm. The lab where these measurements were performed uses a Caesium Clock reference signal and the measuring device used was worth close to $30,000 so the four decimal place accuracy is beyond doubt.

After we'd finished patting ourselves on the back, we decided to try both the Apple and Android speed apps to see how they stacked up. Neither were remotely accurate, results varied from phone to phone and from app to app.

Given the symptoms you've described, I would suspect something is amiss with the Quartz crystal clock. Pretty much all of the turntable controllers currently on the market use a bog standard 100 ppm / 1°C clock chip. So depending on the sophistication of the hardware and firmware, the frequency of your reference clock can vary with temperature. I chose to use a 2.5 ppm temperature stabilised clock module to eliminate this problem.

A simple test: next time the turntable sounds as if it's running fast, disconnect the speed controller, shove it in a plastic bag and pop it in the freezer for 20 min. Check the turntable with a strobe before and after chilling the circuitry and if there is any variation it would suggest thermal problems. Not completely conclusive but it might provide a useful starting point for the technicians and save you a few bucks.
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Re: Gyro SE w/full Orbe upgrade: Speed instability

Postby Alec124c41 » 29 Jul 2018 14:05

To check the average speed of your platter, put a bit of masking tape on the edge of the platter, and time 100 revolutions. The ideal is 3 minutes flat,
Older turntables with electronic speed controls can develop speed irregularities from the tarnish that occurs on control surfaces. Contact/control cleaner and a few swipes of the control will usually cure this.

Cheers,
Alec
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Re: Gyro SE w/full Orbe upgrade: Speed instability

Postby PAR » 30 Jul 2018 11:54

richbdd01 wrote:Hi all

I bought my turntable around 4 years ago now used. However, much of it was upgraded by me including Orbe platter, double spyder and HR power supply.

The speed stability has never been spot on, ie varying about 0.7 rpm either way. What i mean by this is that if the minimum speed is measured at 33.30 rpm, the maximum speed measures up to 33.37 rpm and it would measure anywhere between these two points. I have never really noticed any audible issue with regards to this.

However, recently, I have noticed some much more significant variation and I am trying to pinpoint the cause. I sat down to listen to a record the other day and noticed it was running fast. It sounded noticeably faster whilst listening and was obviously too fast. I measured the speed and it was about 3 rpm too fast. I then adjusted it back on the HR speed adjustment. Everything was fine for about 3 records and then I noticed it again. It was back up to 35 rpm.

I have been racking my brains as to what is causing this. Could it be my belt? I wouldn’t expect such a noticeable increase in speed if it was the belt though...?



Richard


If you are using an HR PS I would explain that this is not the one that a full Orbe uses. The Orbe has its own supply with the " Never Connected" feature. It does not have an easily adjustable speed trim although it is possible to do this by removing the cover and adjusting the two blue trim pots, one is for 33.3rpm and one for 45 rpm.

We need to distinguish between incorrect average speed and speed deviations which can occur over short periods yet, even though clearly audible as "wow", may still provide a correct average speed of 33.3rpm.

You can forget using phone apps that measure speed by placing the phone of the platter. That is just a gimmick and will , at the very least, mean that the platter is no longer properly balanced. If you want an app that does work then download PlatterSpeed fro Dr. Feickert ( it's in App Store) but you do need a test disc with a 3150Hz tone to make it work. It will not only show the average speed but also those small deviations which can be audible. At least buy a strobe disc - they do work using ordinary tungsten lighting.

I have to say that unfortunately achieving a low figure for speed deviation with Michell turntables is difficult due to the comparatively poor quality of the drive belts that they now supply.

I have not experienced significant fluctuations in average speed over an extended period however and I think that your measurement apps may be the the cause of misleading data. Of course the weather has now cooled down somewhat so if it was a result of the heatwave you can now check again.
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