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

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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
 
PSU

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...
 
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
 
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
 
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
 

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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/pcaudio/messages/24191.html
 

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Jonners, Yes, forgot that so that particular SKA kit won't do as it's <40mA but the discrete will do if you follow the guidelines given
The transistors speced are TO-92 package good for 100mA and 500mW dissipation. If you need more you can go with TO-220 package transistors for Q3 or Q6, leave the others as is. I try to choose ones with fairly high Hfe and low noise

Now any good suggestions for a high Hfe, low noise TO-220 device?

How much was the Paul Hynes regulator - can't find your pictured one on his site?
 
That PR3 is not enough DIY for my taste. ;) If there are improvements to a lousy LM317, I have to create my own shunt. It will take a while as my time is very limited, but I hope it is worth it. At the other hand I could use that thing for my XOno as it has LM317 Regulators as well. Let me think about that. Will do something with TL431 -> OP Amp -> Power Amp.

regards,
Rene
 
Well, I decided to use a LM317 regulator. Maybe I will play around with shunt reg. later. As some other guys where interested in professional made PCBs, I orderd some.

http://gesounded.files.wordpress.com/2009/06/dd_psu.jpg

They work well for the SL1210, SP10 MK2 and other stuff as well. As I do have some left, just let me know, if you are interested in obtaining some from me. One PCB goes for 3€ + shipping.
 
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The 140 vdc supply for the SP10 powers the strobe circuit. I didn't see much point in regulating it - I replaced the filter cap with a larger one.

The 32 vdc supply i used 3 x LM 329 In series RC filtered instead of the zener and used a 1 ma jfet current source to feed it. I AC bypassed the feedback resistor with a 100 uf cap. I also cascoded the differential pair. Changed resistors to metal film. This makes a lower noise , higher load and line rejection regulator using the existing board in the Power Supply module - one could design better new ones from scratch, but living with the orignal pc board it"s about as far as i could go .

The 5 volt regulator got new caps, metal films, and possibly a LM 336 1.2 or 2.5 volt reference and the feedback resistor changed to match the new reference . The voltage is too low to a use a jfet current source to feed the voltage reference.

I sold the SP 10 so can't recall the exact resistor values unless i
look at the schematic again to refresh my cocount

The driver boards inside the table were redone with 1 percent metal films and new electrolytics ( replce the 1 uf caps with wima or siemens 50 or 63 volt polyesters.
 
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