Improved PSU for Technics SL1210 MK2 and SP 10 MK2 (and others)

[beetle]

Hello,

I'm investigating in building an external PSU for SL 1210 MK2 and SP 10 MK2 players. For that I need a regulated voltage at about 21V DC. The internal regulators of the Technics deck will be bypassed. For a SP 10 MK2 there are 3 voltages (DC). 5V, 32,5V and 140V. Except 140V is easy to generate.

I am using a well known LM317 regulator for doing that. I already did a PCB design.

http://www.abload.de/image.php?img=sl1210psuavsu.png
http://www.abload.de/image.php?img=1210d747.jpeg


Now I have a prototype running. There is sound improvement. Soundstage is more stable, bass is more detailed. So it is woth it to build an external PSU.


Does anybody has an idea how to generate 140V DC? I don't have a glue. Any comments about my PCB Design? Is anybody interested in PCBs from me?


Cheers,
Rene

[Citation16]

I have owned a similar turntable the 1200 MkV.

Now, I did buy a ready made external PSU from KAB

http://www.kabusa.com/ps1200.htm

The power supply did make quite a difference, as you noted.

As for your question, I did take a photo of the inner of the KAB psu, I could send to you, if you are interested. Its basically a transformer & with some electronic parts.

I would also be tempted to connect your PSU to a PS Audio current regenarator so see & hear the effect...

I also modified a number of things on that tecknics, namely, added a lawer of silicone with saran wrap inside the TT (so it does not stick) to better bond with the rest of the turntable underside elements, since the individual parts of the belly of the TT are held only by screws.
Its a fantastic TT & I wonder why I sold it -
but I wanted to add more weight to a TT -
so I modified an Oracle but stck with speed acuracy issues -
not a perfect world...

[jonners]

Hi Rene

I've been using a 21V regulated supply with a 317 in my SL1210, and it is certainly an improvement over the built-in supply. It seems that there is still more improvement to be gained with something better than a 317: I'm presently trying out a low noise, low impedance psu module made by Paul Hynes (UK).

Regarding the 140V supply, the Tubes forum might be the place to search. You can even do it with a 317: The book "Valve Amplifiers" by Morgan Jones shows how.

John

[beetle]

I don't think there is any improvement by replacing the LM317 regulator by a low impedance regulator ie. shunt. The main issue with the original PSU of the SL 1210 MK2 is the noise floor under load. This side explained that very well: http://www.soundhifi.com/sl1200/SL1200 PSU.htm So why did you came to the conclusion that a "betther" regulator will result in an even huger gain of sound quality? If there is an explaination for this, I will go for a shunt regulator.


cheers,
Rene

[jonners]

The regulator I'm using is a Paul Hynes PR3. It's not a shunt reg, though. I have no explanation for the improvement, and I won't say it's 'huge' , but with the PR3 there is some sense of the treble being better integrated and the 'being there' factor seems enhanced.
The photo shows the PR3 installed where the mains transformer used to be.

John

[beetle]

I think there is no schematic available?

[jonners]

I doubt if the schematic is available, but I'm sure there are reg. schematics posted here on diyAudio which could be used.

[jkeny]

The LM317 has reportedly bad PSRR at high frequencies and so allows high freq power supply grunge through. If ther has been a noticeable improvement in moving from the 3 transistor stock regulator on the Technics to the LM317 then I would imagine there is more improvement to be had from a better regulator - how much improvement, I don't know.

A low noise, low impedance regulator should be an improvement over the LM317 types.

Here's a discrete regulator which is reported as sounding good http://www.audioasylum.com/forums/pc...ges/24191.html

[jkeny]

Or for a simple & well performing regulator kit you can't go far wrong with Greg Ball's approach (he knows all about Power Supply distortions) http://www.ska-audio.com/Forum/YaBB.pl?num=1221704470

[jonners]

When choosing a regulator, bear in mind that the SL1200/1210 consumes about 170mA at 21V during steady rotation. There is a brief peak current of around 450mA when the platter starts or stops.