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...?
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.