So people have posted different opinions about how the difference between a slack or taut belt might affect platter speed. I wanted to answer this question for myself, and embarked on changing the distance between the pulley and the subplatter, and taking measurements using PlatterSpeed.
On another thread about Michael Lim's mods, there were also questions about how the double pulley diameter might be different than the stock Rega pulley. Please refer to that discussion, where I posted the measurements of the Lim double pulley and the stock P5 diameters, as well as the diameters of the black and white Rega belts. Spoiler: The Lim pulleys have a larger diameter and the white belts have a smaller
Before delving into the additional measurements, please read my caveat here: viewtopic.php?f=32&t=37636&p=340553#p340553
The bottom line is that I am doing this because I have a curiosity, I have the tools, and I am a scientist and this way by training. None of the data below should be viewed as the end-all, be-all, in fact, the data are presented to open up discussion, examine our assumptions, and perhaps to expand our understanding.
However, the BIGGEST caveat of all is that only speed measurements were taken - no listening tests accompanied the speed tests
. If you don't understand how important this last point is, then you may as well stop reading this thread.
And if you have any suggestions about how to make these two threads less unwieldy with cross-referencing and cross-posting, please let me know.
So there were three trials, all using the TT-PSU and maximum mounting distance. "Maximum mounting distance" was determined by the distance achievable without having the motor contact the plinth (I have the Lim motor isolation base, and allowing the motor to contact the plinth would be defeating the purpose of this mod and might introduce another variable):
1. Double white belt.
2. Double white belt with rubber band around subplatter (to increase the outside diameter of the subplatter) - mostly for sh*ts and giggles.
3. Single black Rega belt.
The "control" was the speed taken with double belts and double pulley at initial mounting distance of motor prior to any mods (see my gallery for measurement). Speed measurements for the control have been posted previously in this same thread, and so there is no need to revisit this (however, I did take another measurement of the control prior to the trials, and results were exactly the same). Nothing else with the P5 was changed in any way other than changing belt configurations once the motor mounting distance was changed.
1. This trial did lower platter speed from the control, and had higher precision.
2. The increased subplatter diameter did have a significant effect on the platter speed, but also had the greatest speed variability.
3. Interestingly, this was closer to target speed, and had a better overall speed stability performance than a single white belt. This is counterintuitive, as one would think that the larger diameter black belt would not be seated as far in as a smaller diameter belt, and thus lead to faster platter speeds. This last finding is a good one to think about and discuss, if you have the inclination.
Therefore, in my system, a further mounting distance appears to be preferred over a shorter mounting distance and looser-fitting belts from the standpoint of the two parameters of platter speed and precision.
For the screenshots, only the "Info" screen is presented. If you're interested in the charts, I can link later, however, they are redundant and aren't comparable in any event due to vertical scaling issues.
Trial 1: Double white belt at max distance
Trial 2: Double white belt at max distance with rubber band
Trial 3: Single black belt at max distance
WT Simplex & Audiomods Classic > Aleph Ono, Bel Canto PL1/DAC3 > Pass X1 > X150.5 > DeVore Nines
: Be Ever Wonderful - EW&F :