Jonathan's Skeletal DIY "RP8 Plinth" TT ....

Take a look at this DIY Turntable of skeletal plinth design by Jonathan of Cheltenham, Australia. For more adventurous turntable enthusiasts, this would definitely interest you! Why not start a new project too!!

Hi Michael,

Now I have some time off work, I’ve almost finished my turntable. 

Please see new pictures. 

The skeletal plinth now has a modesty skirt (which is not connected mechanically, just sits around it to please the wife) and the speed controller and phono preamp are boxed up and in the boxes below the TT on the shelf. 

I tried a electronic speed controller for the motor, which attempts to compensate load current with increasing voltage motor. 

Although this works and would be ideal for a small electric drill, for a TT its pointless as there is not enough precision, it is of course feed forward not feed back. To do it properly the motor must have an encoder or tacho and this motor does not have that facility. 

So now I just have a simple voltage regulator, made with an LED as a reference and opamp... the LM317T adjustable reg would be just as good if not better! 4.56V at 7mA, that’s 30mW!! Would run for almost ever on a PP3 battery. 

Some feedback and pictures:

The pulley works well, but is compromised in my installation because the maxon motor shaft is quite short, particularly after it has passed through my isolation system which uses a 3mm sticky pad. 

As a result the motor shaft is only around half to 2/3 way through your pulley and the concentricity suffers. I do not claim to be able to hear the wow, it just doesn’t look too good. I have shimmed the motor shaft with cooking foil. 

This is around 0.018mm thick and I have a whole turn of it in there (with no overlap) so I think your pulley is probably around 0.336mm, which is tad large given the maxon shaft spec at 3mm -0.005 to -.010mm. But hey, the pulley is designed for the Reaga motor, so I can’t complain! 

The turntable is a skeletal design based loosely on the RP8, but using marine grade 12mm plywood, with strategic bracing. The main bearing is stand with the addition of a ceramic ball. Arm is SME3009 with Shure V15 III with the SAS stylus. 

Your platter is very well made, excellent. The mid range seems rather brighter too, which is surprising, but good because it was a little recessive before. I need to try the different mats and pick the best. 

Some photos attached for you, this is the new suspended sub chassis made of marine ply rather than Corian, which appears to work better. 

I'll let you know more after I have had a better listen. 

I'm tempted to change the sub platter to one of your aluminium ones, but I have to say the standard one is very good in terms of the run out and the bearing. Much better than I was expecting, maybe Rega have tightened up the tolerances. 

Best regards

Thanks Jonathan!


stew nelless said...

Some have suggested that a cheap and cheerful DIY mod to the factory sub-platter is to fill it with a non-hardening clay type product (such as Bostik Blu-tack, electrician's duct seal, etc). I am not suggesting this is in anyway as good as Michael's metal sub-platter.

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