VPI Classic tweak

VPI does that for enthusiasts like me that don't have SDS,and no control over AC frequency, so we can obtain correct speed by changing belt position on the pulley, to go faster or slower.

The actual diameter of each position is different. It allows enthusiasts without a SDS to dial in the speed as close as possible to 33 or 44. Check it out with the friekert app and test disk. It gets faster in one direction and slower in the other. Just by moving the position of the belt on the pulley. You can't notice it with the naked eye, but it is true.

Don't see how that can be done on classic series pulleys. Every pulley position is a different diameter, to allow for speed adjustment for variable AC frequencies. Multiple belts will each be at a different speed.

interesting to see what speed you will end up with, since the belts will be fighting each other, with my AC frequency and I don't have a SDS I run at the top groove for 33, it is the closest using freickert android app and the test disc.

No different with the SDS, different pulley positions are different diameters and will yield different speeds. You can verify it with the friekert app and test disc. The different pulley positions are for those that don't have the SDS to get as close as they can to 33 or 45 since without the SDS you have no control over AC frequency. With the SDS you don't need all the different pulley diameters since you can control AC frequency and optimize any of then for perfect speed. Adding another belt at different pulley diameter just upsets that balance.

I don't agree. Check it with the friekert app and test disk, each position is a different diameter resulting in a different platter speed. Whether you use a SDS or not, the 2 belts will be spinning at 2 different speeds.

How else could the speed be different? The pulley is machined to a different diameter at each of the pulley positions.

I believe the position on the platter is irrelevant, the platter is machined to the same diameter up and down its sides. I believe the pulley is machined intentionally with a larger diameter on each groove progressively to accommodate those enthusiasts without a SDS. This is the only way they have to compensate for AC frequency differences, which is how speed is determined on an AC motor.

The belts will be binding, one belt will try and turn the platter faster in each rotation than the other. Therefore one will have to slip. The belt with the most torque will probably win. Hard for me to visualize how this could be an improvement in sound.