Good point. Maybe the design could use a make over as it is rather old technology. Is the 8038 function generator still around? Maybe some sort of digital solution instead? How about a 555 running at 100x the output frequency used to clock a 74HC390 and a Maxim MAX7400 SCF as a tracking filter to change the 390's output to a sinewave?
me 2 
Because a group buy makes sense.
There are however other options. A good stereo amp with adjustable gain. As a minimum it should be biased towards class A, be a very good class D/T or be a proper class A (whether tube or SS based). The quality of the amplifier(s) is critical though. Pure class A output with a suitable voltage, which could be tightly regulated or a suitable transformer to get the required voltage step up or down. Although the Airpax/Thompson/Premotec AC motors were intended (originally) using 115 VAC or 220 VAC (depending on where in the world you live) somewhere I recall that the Linn ( the "basic" version) sounds best with something under 80 VAC.
A stereo signal could then be used with a sound file or suitable generated frequency. A means to adjust the phase of each channel independently with respect to the signal frequency (whether recorded or generated) would be useful to reduce motor noise. A means to check the rotational speed is a must and need not be used in a final version, as there will be a time lag. Simply having the means to accurately check speed (preferably while playing an LP) and make a manual adjustments as needed to the frequency.
I have an old STD 305S turntable that needs something like this. I know damuffin could be able to use one, I'm sure.
Because a group buy makes sense.
There are however other options. A good stereo amp with adjustable gain. As a minimum it should be biased towards class A, be a very good class D/T or be a proper class A (whether tube or SS based). The quality of the amplifier(s) is critical though. Pure class A output with a suitable voltage, which could be tightly regulated or a suitable transformer to get the required voltage step up or down. Although the Airpax/Thompson/Premotec AC motors were intended (originally) using 115 VAC or 220 VAC (depending on where in the world you live) somewhere I recall that the Linn ( the "basic" version) sounds best with something under 80 VAC.
A stereo signal could then be used with a sound file or suitable generated frequency. A means to adjust the phase of each channel independently with respect to the signal frequency (whether recorded or generated) would be useful to reduce motor noise. A means to check the rotational speed is a must and need not be used in a final version, as there will be a time lag. Simply having the means to accurately check speed (preferably while playing an LP) and make a manual adjustments as needed to the frequency.
I have an old STD 305S turntable that needs something like this. I know damuffin could be able to use one, I'm sure.
Hello Nanook,
when we can find a PCB with a stable frequency generator with stereo output and phase control it is the central brick for a turntable power supply. To find a amplifier as motor driver is no problem. I think this can be done by any mid-hifi class-d amp.
I need a power supply for a berger-lahr motor out of a thorens td280. It needs only 12V
when we can find a PCB with a stable frequency generator with stereo output and phase control it is the central brick for a turntable power supply. To find a amplifier as motor driver is no problem. I think this can be done by any mid-hifi class-d amp.
I need a power supply for a berger-lahr motor out of a thorens td280. It needs only 12V
You don't need the second sine wave output. An all-pass filter circuit is quite simple:
https://en.wikipedia.org/wiki/All-pass_filter
You of course want to vary the relative phase and amplitudes of the sine waves, as previously mentioned, to reduce mechanical hum in the motor.
Probably the cheapest way to get a solid, fixed-frequency 60Hz sine is to use a quartz crystal oscillator and divide down the output with appropriate CMOS chips (4040 and/or 4024, and appropriate logic to reset when the counter gets to the right count. Divide to 100/120Hz then use a flip flop to get to a 50/60Hz square wave), and do some heavy low-pass filtering of the output.
But as I've said before (apparently in some other thread), the way to get very stable AND variable frequency is with a microcontroller (with a quartz oscillator clock) running a DDS. Any modern 8-bit processor can generate a 50/60Hz pulse-width-modulated sine (and cosine) wave with freqency resolution and accuracy to 1/1000th Hertz or better.
https://en.wikipedia.org/wiki/Direct_digital_synthesizer
DDS chips already loaded to PCBs are extremely affordable on Taobao/Aliexpress. Just do a search for AD9850 dds. It comes with an on-chip 10bit DAC and with a 125MHz clock can be tuned with a resolution around 0.03Hz. Presumably there's no reason it can't run slower to get even smaller step sizes.
in the linked magazine there is a basic circuit but without regulation for the Phase shift. Look at page 30 http://www.basaudio.net/pubs/DIY_2006_1.pdf
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