It was good to catch up with you for a few turns at Breckenridge yesterday.
There's a small group of Galibier owners (amongst whom, Dan_ed is a key contributor) who has been experimenting with driving a turntable. To date, we've played onlly with the Mark Kelly controller (both AC and DC).
The group is diverse in their musical tastes and system architecutre (there are representatives of the box speaker, horn, and planar camp). Of course the commonality is the Galibier connection.
In any event, no clear preference has emerged, as far as conveying all types of music the "best". A three phase controller is certainly on the short list - if we can source a motor in current production. The Kelly controller to date has driven two different two phase motors.
One other theme that is just now beginning to emerge is to run the motors much faster than they have been specified for. Heresy you say? Well, it's already being done when you throw a higher frequency at the motors to spin the the platter at 45 rpm.
This higher speed has the effect of shifting residual vibration to a place the Galibier architecture is filtering it out. My guess is that even low mass, sprung designs would benefit from this as well - with their resonant frequency lying in the 4-5Hz range.
While I can of course manufacture any pulley size I care to, the question arises as to how the purchaser of a Hagtech product can do so as well.
Well, taking the LP12 for example, the Primotec motor uses a Europen standard, 3mm motor shaft - something I've been machining for the Maxon DC motors we've been using. The Hurst motor used in the VPI has a .125" shaft, and I've machined pulleys for these as well. When you begin prototyping this, I can send you pulleys to fit most motors, and manufacturing them for you would likely present no problem.
The intent of this thread is of course to consider an appropriate, adaptable architecture - to not close up ones design options prematurely.
I contend that we should not limit our choices of speed to those dictated by motor manufacturers. These motor manufacturers do not design their products for turntables. You'd be amazed at the discussions I've had with the Maxon engineers. More times than not, their recommendations have been 180 degrees opposed to what we've found to sound best.
Similarly, running AC motors out of spec could have its sonic advantages.
Thom @ Galibier