2020 update : JC Verdier La Platine
A Speed Controller I have had as a loan item and has proved to be improvement over my owned speed controller, is the LDA Quartz Locked model. Additionally all who have encountered it in use, from my period of loan, have all agreed, the use of it has provided noticeable improvements to the SQ. This assessment of the improvements offered has been for a Garrard 401, Lenco Models and Non Synchronised Belt Drive TT's the LDA has been attached to.
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AC motors vs DC. I'm sure some will debate but here is my take - AC motors lock to frequency and any speed errors are self corrected by the fields within the motor. DC motors rely on measurement and feedback to maintain speed, in other words they require speed error to draw more power from the power supply. Also AC motors, when they speed correct, the recovery behaviour is sinusoidal. When DC motors are corrected, the recovery behaviour is trapezoidal. So in my view the speed correction is smoother and more benign with an AC motor. DC motors rose to prominence because DC controllers are simple ( voltage controlled ) and cheap to make. Speed controllers for AC motors are far more complex because you have to control frequency rather than voltage. Now from my experience with a huge range of TT's I have a view that you want a big AC motor. My reference TT uses a regenerated power supply, a preamplifier that generates both a regulated sine wave, and a separate regulated cosine wave to drive the two sides of the motor. The preamplifier feeds the sine and cosine waves into a power amplifier that drives the AC motor. The motor is about the size of a decent sized fist and drives a 26kg platter. Compared to the big Micro Seikis that use DC motors, my reference has far better speed stability and precision. Same when I tried the reference motor on the Verdier - massive improvement. Specifically the bottom end is much cleaner and tighter. I also have a couple of idlers - Garrard 301 & Pioneer/Exclusive broadcast idler. The idlers slaughtered my Platine Verdier again on speed stability and precision, bottom end timing. Though not up to my reference TT they are the closest of any other TT's I have experienced. I omit the Technics SP10mk3 from this comment - it has a very tight bottom end and good timing, but the grey wash and lack of transparency compared to my reference I find not musical. I have come to the conclusion that the key to the idlers is not just the lack of elastic rubber belt, but I think the large AC motors employed contribute to the "idler" sound. Discussions I have had with Win who designed the Saskia suggest we are in agreement. His suggestion for the Verdier was exactly what I proposed - pull a big AC Paps motor out of an Empire - no-one makes AC motors as good as these any more. The AC motor in my Pioneer/Exclusive broadcast idler is about 50% bigger than the Garrard and it is dead quiet, as in dead, unless the idler wheel is engaged you cannot hear a thing. Nobody makes these AC motors today. I note that the new reference from SME, the model 60 has an AC motor.
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@ledoux1238 There is a Thread on this forum that made a reference to the LDA. The use of the device is to have it receiving the Input Power from the Power Cord and the output from the device will connect to the TT's IEC Power Cord Connector, hence supplying the TT with a improved power upply. The first time I ever heard it in use was as a prototype, on a system that has a substantial purchase value, and the Idler Drive and Belt Drive it was used with showed substantial improvements. Later down the line I had a loan of the final design for a few months, and put it to use in other systems and against other Speed Controllers the LDA was the preferred device being made known by all attendees at the arranged demonstrations. On a UK forum there were also reports being made where it was stated attaching this device to CDP's or CDT's ? had a very noticeable effect for the better as well. |
