buschfsu

turntable psu (24v sine wave)
« on: July 20, 2020, 01:12:36 PM »
hi all,

looking to replace my wall wort on my rega p3 with a diy linear psu.  would a conventional toroidal with caps into a 24v zenner give me better results that the smps it came with?  i hear the 400$ upgrade from rega produces a clean sine wave at 24 v (don't care about the 45 vs 33 rpm switch)

thanks
jason
PRR said...
OHM'S LAW. Not as an abstract thing: you should be able to glance at a small circuit and "instantly" know I and V, the way a soccer player glances at the ball and knows the angle and kick


squarewave

Re: turntable psu (24v sine wave)
« Reply #1 on: July 20, 2020, 01:40:15 PM »
I don't really know turntables but is the motor different? An SMPS makes DC which would suggest that you currently have a DC motor. If this "upgrade" uses 24VAC, then it sounds like that's only for an AC motor.

Re: turntable psu (24v sine wave)
« Reply #2 on: July 20, 2020, 01:44:56 PM »
Hello

I don't really know turntables but is the motor different? An SMPS makes DC which would suggest that you currently have a DC motor. If this "upgrade" uses 24VAC, then it sounds like that's only for an AC motor.

yes... same question, it's confusing, do you need AC or DC to drive the turntable ?
The motor ? Or it's for embedded electronic ? RIAA and line out ?

Best
Zam

cyrano

Re: turntable psu (24v sine wave)
« Reply #3 on: July 20, 2020, 03:32:59 PM »
Some audiophiles believe that powering an AC motor from something like a 20W audio amp with a "clean" sinus will offer better wow and flutter numbers.  ::)

So I'm guessing it's an AC motor.
Why is it people love to believe and hate to know?

moamps

Re: turntable psu (24v sine wave)
« Reply #4 on: July 22, 2020, 05:03:54 PM »
Some audiophiles believe that powering an AC motor from something like a 20W audio amp with a "clean" sinus will offer better wow and flutter numbers.  ::)
Mains THD can be high (up to 10%), so a good oscillator and output amp  will produce obviously cleaner power supply for a synchronous motor.

@jason
Could you provide detailed info about motor your turntables uses right now, and which version of the turntable you are using (P3 or planar3)? There are lot of infos on the web about mods on Rega turntables.   

Gold

Re: turntable psu (24v sine wave)
« Reply #5 on: July 22, 2020, 08:09:55 PM »
It would be a big surprise if it was a synchronous AC motor. Especially if it's not clearly marked. It would have to be specified for either 50Hz or 60Hz operation.

It would also have to be line voltage. It couldn’t be 24VAC unless the line voltage went though an auto former  or transformer which wouldn’t make much sense.
« Last Edit: July 22, 2020, 11:15:04 PM by Gold »

Gold

Re: turntable psu (24v sine wave)
« Reply #6 on: July 22, 2020, 09:57:37 PM »
Does the wall wart have an AC or DC output? If it has an AC output the regulator is in the turntable chassis. There is not much to be done about that short of surgery.

If the wall wart is a cheap SMPS then just replace with something better.

moamps

Re: turntable psu (24v sine wave)
« Reply #7 on: July 23, 2020, 04:13:46 AM »
It would be a big surprise if it was a synchronous AC motor. Especially if it's not clearly marked. It would have to be specified for either 50Hz or 60Hz operation.

Indeed.



Whoops

Re: turntable psu (24v sine wave)
« Reply #8 on: July 23, 2020, 10:31:13 PM »
hi all,

looking to replace my wall wort on my rega p3 with a diy linear psu.  would a conventional toroidal with caps into a 24v zenner give me better results that the smps it came with?  i hear the 400$ upgrade from rega produces a clean sine wave at 24 v (don't care about the 45 vs 33 rpm switch)

thanks
jason

I don't know  if I totally understand your question,
but a full bridge rectified Linear PSU using a 24VDC regulator (LM7824 or LM317), with proper filtering (Capacitance) is really easy to do, not expensive and will provide completely stable and regulated output with Low ripple.

buschfsu

Re: turntable psu (24v sine wave)
« Reply #9 on: July 28, 2020, 12:46:08 AM »
hey guys

sorry wasnt seeing the responses..

the motor is from the vpi prime. so its 300 RPM, 24 pole, AC synchronous motor.  they sell an ADS power supply but was wondering if i could do better or cheaper

thx
PRR said...
OHM'S LAW. Not as an abstract thing: you should be able to glance at a small circuit and "instantly" know I and V, the way a soccer player glances at the ball and knows the angle and kick


squarewave

Re: turntable psu (24v sine wave)
« Reply #10 on: July 28, 2020, 02:25:06 AM »
For an AC motor you don't want capacitors or zeners or anything else. Honestly an over-sized AC wall wart would work about as well as anything.

If you really wanted to get pedantic about it, you could feed wall-wart AC into a choke from a hi-fi or guitar amp in series with the right capacitor(s) to get a resonant 60Hz band-pass filter and make the purest sine wave that fancy motor will ever see. Angels will descend from heaven to listen to it and complement you. But the filter would have to be designed carefully and tested to consider tuning and power requirements.


 

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