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!

128x128goofyfoot

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.