Audio Note TT2 Power Supply/Speed

Do a call out to Mark Kelly..

he certainly has the knowledge and know-how :)

It does seem that Audio Note use typical Airpax/Premotec AC synchronous style motors. As far as I understand it, the creation of a power supply requires a good amplifier (usually class A---no notch distortion) and a reference signal. In the UK the basic power is 50Hz, if I remember correctly. create a 67.5 Hz. reference signal and you have 45 rpm. (50 Hz*100/3 *1.35=67.5). Many of these Ac motors require much less voltage (I think someplace I read that the Linns like 72 Volts) to spin the motor. The up side to this is reduced mechanical motor noise.

The current usually required by these types of motors is usually quite small (I think the Premotec asks for 18 mA of current and a total of 1.8 watts at 220 VAC). Feeding it a reference signal through an amplifier requires quite a small one (amp). I am not sure if a T-amp would be suitable. I do know that Mr. Kelly has suggested not using class AB amplifiers.

BTW, in North America, where 60 Hz line frequency is the norm, 81 Hz is the frequency required to generate so that a 60Hz motor will turn at 45 RPM.

If someone in North America gets a European table requiring a 50 Hz voltage, it is the frequency that is important. So the same thing can be used. Create a 50Hz signal, then amplify it and feed it to the turntable. If 45 is required do as above, feed it a 67.5 Hz signal. The beauty with this idea (particularly if you use an MP3 player with a display on it to record signals to) is that you can have quite good control of the speed, regardless of the pulley sizes involved.

Mr. Kelly's designs are more elegant and proper. My solution allows for some experimenting.
 

studeb

Member
2008-02-14 10:39 pm
San Diego
i think the AN TTs are based on the Systemdek decks.
As far as commercial units go, there is the VPI SDS and VPI PLC.
I think Linn had an external box that would work. i think the Valhalla does not have a 33/45 switch, but there are aftermarket mods that can do this.
And there might be a Project box that would work.