Belt Tension
For most of the manual budget turntables from Rega or Pro-ject, the speed selection is done manually - just switch the belt from the 33.3rpm pulley slot to 45rpm slot or vice versa. Very simple and of course, cost effective also (without incurring extra cost of a TTPSU).
But is this the most ideal way? In the first place, if the belt tension is optimized for 33.3 rpm slot, the tension would be a bit higher for 45 rpm; conversely if it is optimized for 45 rpm slot, then it would be slightly lower for 33.3 rpm. Moreover, the belt also tends to get stretched over time. The interesting question here is : how to adjust this small variation in belt tension?
For Rega P5 the motor is bolt-mounted through slots. So it's possible to adjust the motor/pulley assembly slightly forward or backward to optimize the belt tension.
What about other Rega models like Planar 2/3 (including RP1, P1, P2, P3, P3-24) where the motor/pulley assemblies are fixed to the plinth using sticky pads (or rubber band)? No, there's no way to adjust the pulley tension manually without some mod....
Probably we may try ......
1. Bolt-mounted the motor ( like P5) to the plinth with suitable insulator and washers.
Mark the positions of the motor mounting holes before removing it from the sticky pad. Drill two holes(one with a slotted hole) on the plinth for the motor mounting bolts. Mount the motor. Now the motor/pulley could be moved forward or backward to optimize the belt tension for both 33.3 or 45.
2. Decouple the motor and mount it on an isolation motor base.
Since the motor/pulley assembly is not fixed to the plinth, it could be moved forward or backward easily to optimized the belt tension besides solving the "wobbling motor" problem of Planar 2/3 and eliminating motor vibrations from the plinth(for motors mounted with stick pads).
3. Use a TTPSU and the belt tension is set to a fixed slot for both 33.3 and 45 playback!
The next question is which slot is better to park the belt when using TTPSU? 33.3 or 45?
For Rega TTPSU, we have no choice as it's set at 33.3.
However, personally I would prefer to park the belt at 45 rpm slot.... (if there is a choice).
Why? You may ask.
With a TTPSU which requires the TT belt to be parked at 45 rpm slot, the motor actually runs much slower compared to when the belt is parked at 33 rpm slot. This is particularly true for 60Hz region like North America (USA and Canada) where the motor runs at a higher speed of 300rpm compared with EU's 250rpm. By getting the motor to run slower, the corresponding motor noise and vibration would be lowered too (logical?). This could be significant to TT needle which is sensitive to micro-vibrations.
Based on the above, do you think parking the belt at 45 rpm slot(with the tension properly adjusted) would be a better option for turntables in general, considering motor noise/vibration is the greatest "enemy" to our turntables?
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