VPI TNT Turntables

phoenixengr,

I am going to interpret that as an agreement to what I said.  All of my examples are increasing the mass and the inertia, right?  So the vpi flywheel would be more stable, due to its increased mass?  The more massive flywheel in motion would be more likely to stay in motion, compared to just a simple motor.  We are talking about the speed stability of the motor/drive system here.  You seem to be agreeing, but believe that the two belt implementation is faulty?

I agree that flywheels are a benefit, provided they are constructed properly for the task at hand.  Usually, the flywheel is larger in both diameter and mass than the object it is trying to stabilize.   Increasing mass does help, increasing radius helps much more.   In the case of the VPI flywheel, it is both smaller and lighter than the platter.  I would guess 20% increase of inertia improves stability by 20% as well, all other things being equal. If that explains the improvement in SQ, then mystery solved. If 20% improvement is acceptable for the added cost, then it's a worthwhile investment.

I agree that anything that improves the speed stability of the platter is a good thing. I don't know that adding another pulley (flywheel) and another belt is "faulty", but it bears investigation. All belt drive systems suffer from belt creep which affects speed accuracy and stability. In theory, having two belt drives in series would make belt creep worse (vs 2 belts in parallel around 1 pulley and 1 platter which should make things better), but I haven't measured it.

>FYI, a properly designed speed controller will provide excellent instantaneous
>speed stability, but long term speed accuracy is improved with feedback.

Can you perhaps recommend one? =)

I assume your of the Phoenix speed controller fame due to your feedback comment?