Meandering Pitch, Where’s The Problem?

As I’ve mentioned in other posts, I’ve been modifying a Thorens TD 160 MK1. It is and will remain a dedicated mono table. Currently, I’m using the original TP 16 MK1 tonearm with an AT 33 mono cartridge. I will eventually replace the TP 16 with an Origin Live tonearm and EMT mono cartridge. I still however like playing records while in it’s current state. What I’ve experienced with a number of classical records is pitch instability. Primarily when playing piano recordings. There are certain passages that are a problem and I’m not exactly sure the cause. My cartridge is aligned using Baerwald. I understand that with some records, especially very old mono vinyl, that the pressings could be off but if that were the case, then the entire album would be an issue. I do need a new belt but I’ve still had this issue with a brand new Thorens or Origin Live belt. Just wondering what others think and if there’s an antidote? Thanks!


It could be a number of things....

If the spindle hole is off center, that can certainly cause a meandering pitch.

If the motor isn't maintaining a stable speed, that can especially be noticeable on sustained piano notes as the pitch will waiver.

If your belt is stretched/worn, etc that can also contribute to the issue.  Also, make sure that both the motor pulley and the subplatter that the belt goes around are clean.

Best wishes,


If the belt is more than 5 years old that's the first thing I would try.  Cheap and it never hurts to have a new belt ....  

AC synchronized motor deck, I’d look at the belt drive system.

Remove and reinstall the outer platter inverted along with the mat and a record stacked on top to accurately load the TD-160’s suspension. Turn on the platter rotation and view the belt’s action on the drive pulley - I believe you’ll see it hunting along the taper causing the pitch deviation.

Dave @ Vinyl Nirvana knows Thorens belts.

@boothroyd Thanks Dave. You've been helpful the many times I've posted. I can do as you suggest but I fail to understand 'I believe you’ll see it hunting along the taper causing the pitch deviation.' Would you please clarify?

The drive pulley has a large 45 rpm diameter surface that tapers to a smaller 33 rpm diameter surface where the drive belt is meant to ride on. A drive belt with the wrong tension can have difficulty staying on the proper area where it will occasionally move vertically along the drive pulley where it bumps into the taper area which alters speed.

Again, Dave will be familiar with this 👍

On my off-Centre records, the pitch instability seems to get worse as the stylus gets to the innermost groove area. Does yours do the same? If it is an off-centre pressing, you will see the cartridge meander back and forth.

I imagine many of your mono recordings are old - or perhaps they were cut during the stereo era on an old lathe and it had speed problems? That would bake the wow and flutter into the vinyl.

I imagine you have checked the motor, and the condition of the pulley and belts?

@oddiofyl Oh sorry, I mistook you for Dave. So what’s the antidote? If it’s tension then wouldn’t a new belt resolve the issue? I can say that the Origin Live belts are wider than the Thorens belts so I gently widened the metal hook next to the pulley that rises and lowers the belt to 45 and 33 &1/3 but the belt is unobstructed there either way.

@fusian yeah but I have the same problem with a Speakers Corner Glenn Gould Beethoven reissue.

I am primarily a digital guy, and one thing that I have always hated about turntables is pitch instability with Piano music. I had a Rega P5 a few years ago that made Wilhelm Kempff stereo recording of the first movement of the Moonlight Sonata sound like a mellotron. I recently bought a direct drive turntable and problem solved

@goofyfoot , the sources of pitch variation are a bad motor control unit, warped records, slipping motor pulley and bad belts. First and relatively cheap is replace the belt, clean the rim of the drive platter with acetone or brake cleaning fluid and make sure the motor's pulley is tight. Also clean the motor pulley. Do not get finger oils on the belt. Use gloves when you handle it.

One other cause: if the suspension is being activated by footfalls or some other source of vibration, then the platter may move however minutely in the horizontal or vertical plane, while the motor is held stationary because it’s not suspended. This would cause intermittent stretching and compression of the belt, if the belt is compliant. Speed becomes unstable.

The first answer you got from Don is the best one and the first thing he told you bears repeating:  If the spindle hole is off, you will get wow.  That is pitch instability.  Piano is the most sensitive instrument to this problem of any.  Many piano music people tend to prefer CDs for this reason.  The only turntable that was ever developed that properly addressed this problem was the Nakamichi, which centered the record automatically.  Everything else can be perfect, but if the spindle hole is off center, even a small amount, wow is unavoidable.  It should be noted that not every person is equally sensitive to this problem.  Some people are quite tolerant, whereas others can't tolerate even small amounts.  Like so many things in our hobby it is important to know yourself first.  If you hear wow easily and cannot ignore it, and if you are a piano aficianado, then vinyl should probably be considered a secondary source, and digital should be primary for you.  Of course that needs to be tempered with source availability.   

Great advice from everyone. My thoughts regarding the spindle hole is that wow would be present in more than one or two spots if it were the cause, though I admit I don't know this for sure. Now regarding the pulley, there is an upgrade replacement that I should consider. Nevertheless, buying a new belt will be the first thing I do.

Hey everybody, let's get clear about off-centre spindle holes.  Do you have speed instability on EVERY record?  if so, it can't be off-centre records - they can't all be off-centre.  Anyway, you can see an off-centre record when it's in play - the arm swings a little left and right.

So if you have the problem on all or most records; some you will hear more than others - eg piano, as above - then it's your turntable.  Posts above rightly say change the belt, check the motor.  Also take off the platter, flush out the bearing pit , clean the spindle and add new correct oil per maker's instructions.

It's nothing to do with cartridge set-up - if that's wrong, you will hear other faults.