Yes it's very easy. Steps required:
Download a freeware signal generator (there are plenty out there) and generate a file with a sinewave of the required frequency for about 30 minutes or so.
Copy the same signal to a second channel with a delay of 1/4 the period (eg 5ms for a 50Hz signal).
Convert this file to MP3 (again plenty of freeware file converters) and record it on the player.
If you want amplitude control, don't use the volume control on the player (it's logarithmic and therefore far too crude). Either use a pair of linear pots or change the amplitude of the waveform before you convert it to MP3.
Play back though "T" amp or similar. Make sure the output level of the player is high enough to get close to full scale on the T amp (many players are output limited to stop the world's yoof deafening itself.
Attach a pair of toroidal transformers to the output of the T amps, wiring them as step-ups.
Download a freeware signal generator (there are plenty out there) and generate a file with a sinewave of the required frequency for about 30 minutes or so.
Copy the same signal to a second channel with a delay of 1/4 the period (eg 5ms for a 50Hz signal).
Convert this file to MP3 (again plenty of freeware file converters) and record it on the player.
If you want amplitude control, don't use the volume control on the player (it's logarithmic and therefore far too crude). Either use a pair of linear pots or change the amplitude of the waveform before you convert it to MP3.
Play back though "T" amp or similar. Make sure the output level of the player is high enough to get close to full scale on the T amp (many players are output limited to stop the world's yoof deafening itself.
Attach a pair of toroidal transformers to the output of the T amps, wiring them as step-ups.
Ooooh, very interesting! I was gonna post something up about my own iPod TT supply, I'm really excited about it. Where was this original thread, BTW?
Well, among other things, I found that my Rega P3 certainly does turn fast... I am down to 59.33 Hz, partly because I trued up the subplatter pulley, too (which was disgustingly out-of-round, the speed errors clearly visible with strobe discs).
I think that the sound improvement was immense! I am using a 120W subwoofer amp I had sitting around, with an old 25V filament transformer for step-up. It easily runs my CD player, too, with great results! Probably up to 50W continuous is doable.
I used NCH ToneGenerator and Switch software.
Mark, the idea of using two waveforms 90deg out of phase, would that not require removal of the phasing cap on the motor? I am using plain sine waves.
I also tried different frequencies for the CD player generator, settling on 65.41Hz, a low C. (Don't get me started!)
Finally, a use for iPods that even die-hard audiophiles can respect - make it drone out a single frequency for your analog rig!!! I love it, and encourage more folks to try this.
Well, among other things, I found that my Rega P3 certainly does turn fast... I am down to 59.33 Hz, partly because I trued up the subplatter pulley, too (which was disgustingly out-of-round, the speed errors clearly visible with strobe discs).
I think that the sound improvement was immense! I am using a 120W subwoofer amp I had sitting around, with an old 25V filament transformer for step-up. It easily runs my CD player, too, with great results! Probably up to 50W continuous is doable.
I used NCH ToneGenerator and Switch software.
Mark, the idea of using two waveforms 90deg out of phase, would that not require removal of the phasing cap on the motor? I am using plain sine waves.
I also tried different frequencies for the CD player generator, settling on 65.41Hz, a low C. (Don't get me started!)
Finally, a use for iPods that even die-hard audiophiles can respect - make it drone out a single frequency for your analog rig!!! I love it, and encourage more folks to try this.
awedio said:
Yes, definitely. Take out the cap and throw it away.
The only drawback to the ipod technique is that it is quite difficult to tune the phase delay angle. For each motor there is an optimal value of phase delay, unfortunately usually not exactly 90 degrees.
It isn't very hard to steer the phase angle using vector arithmetic (and a couple of op amps). Once you find the optimal angle for your motor you could record your frequencies with the correct phase delay and you'd be cooking with gas.
The vector arithmetic: you have 0 degrees and 90 degrees. Invert the 0 to give 180. Any angle between 0 and 180 can now be found by addition. The simplest op-amp adder inverts but that just means you need to watch the phase sequence.
Well, the capacitor does not know what the optimum phase angle is, either! So, no harm done at least if you just go with straight 90degrees...
What is the after-effect of phase misalignment? Vibration, noise? Will there be a noticeable difference if it's tweaked into perfection? Is there a seat-of-the-pants way to experiment with different phase angles just by recording different samples?
What about going with pure single-phase sine waves, omitting the cap and starting the motor spinning in the right direction with a push on the platter?
I just want the quietest propulsion, if possible (with this POS motor!)
What is the after-effect of phase misalignment? Vibration, noise? Will there be a noticeable difference if it's tweaked into perfection? Is there a seat-of-the-pants way to experiment with different phase angles just by recording different samples?
What about going with pure single-phase sine waves, omitting the cap and starting the motor spinning in the right direction with a push on the platter?
I just want the quietest propulsion, if possible (with this POS motor!)
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