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Thread: The next Technics project... SP-10

  1. #41
    Join Date: Aug 2012

    Location: Denver, Colorado

    Posts: 458
    I'm Jim.

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    All right. One down, one to go.

    I've been mentioning making another PSU for awhile now, and I finally made some actual progress. Nothing is complete yet, nothing cast in stone, but here is the basic idea -



    This is as good a place as any to explain a few things, although I know many of you will just skip this and look at the other photos...

    The transformer is something I found in the surplus store, it's awfully close to what I would want if ordering something custom, and saves me a long search for a catalog item of similar spec. It's a custom toroid for Grace Audio designs. The windings have more than enough current for the job.

    Motor Supply Looking at the top circuit, you see the motor drive.

    The secondaries will be in series, giving about 50V after the bridge. This will be sent to a big CRC, then to a Pass 'Zen Regulator' from Zen Variations 3 -- www.firstwatt.com/pdf/art_zv3.pdf I'm using the zen reg for a few very important reasons - 1) there is some excess voltage to drop before the LM317 input, 2) this reg will free the LM317 from dealing with most of the line variations, 3) I have wanted to try this for a while and have all the parts on hand. But honestly, It's mainly about dropping the excess voltage.

    After the ZenReg, a bog-standard LM317 circuit will be used with one twist - it will be elevated by 6.9V as it will sit on top of an LM329 precision voltage reference. Why? To give the 317 an easier job of regulation (as the top of the 329 will be rock solid in respects to ground), to help isolate the 317 from any grunge upon ground, as well as keeping the input-output voltage of the 317 lower than it's maximum. (And I have some and want to play with them... )

    More detail can be found in this diagram -


    And an image of the ZenReg, for those interested (Image courtesy of Nelson Pass)


    Cool.

    Logic supply -

    The 10VAC winding of the transformer will be sent to a PCB with bridge, large cap, and LM317. The caps will not be enormous, as it's important for the logic supply to get to voltage faster than the motor supply.

    Strobe supply

    This one is a bit fun, the strobe voltage will be made by connecting a small 12V transformer 'backwards' to the 10VAC winding of the main transformer. That voltage will then be rectified and sent to a Supratex LR8 regulator, which can take a maximum input voltage of 450V ! Neat. Anyway, this circuit is the least critical of all them, as it's job is merely to light the strobe, it literally is connected to one resistor and the Neon lamp. The regulator will be massive overkill, which is always good, and I thank Dave Cawley for the suggestion of that part.

    A few more photos -


    The chassis it will all be placed into.


    Testing the ZenReg.


    The ZenReg. The plan is to use the chassis itself as the heatsink, and the circuit is built on perfboard. Heatshrink has been used to insulate the assembly from the chassis wall as well as cover up the messy wiring job.

    Comments, criticisms, and questions are warmly solicited.
    SP-10Mk2a, Graham 2.2 tonearm. SL-1200, Graham 2.2 tonearm, AT-150mlx, Benz-Scheu Glider. Jim & Ken Super DC PSU, Oil well bearing, Acromat, Isonoes, strobe lamp switched. Pass Labs Pearl 2. Aleph J amplifier. F6 Amplifier. Nelson Pass Burning Amplifier BA-3. Pass BA-PP linestage, miniDSP 4x10, Linkwitz Labs LXmini speakers, Sony SS-M7 speakers.

    DIY In progress - Syclotron Red Light district valve amp, ZenMod "Iron pre" autoformer jfet preamp, SYclotron 'His Master's Noise' valve phonostage. And about 2-3 other projects in various states at any time.

  2. #42
    Join Date: Aug 2012

    Location: Denver, Colorado

    Posts: 458
    I'm Jim.

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    The Chassis has been sent to be refinished, my brother-in-law owns an automotive paint and body shop, he is going to prep and paint it, I merely need to decide on a color. Somebody has suggested Autoair colors 4584, but it would clash with the plinth.

    These photos were made to assist me in the reassembly of the turntable, but I thought you may want to see them as well -


    Switch assembly


    Edge connector




    Motor bottom


    Strobe assembly


    Mechanical brake


    Various stand-offs on chassis bottom


    Parts removed from chassis


    Bare chassis
    Last edited by 6L6; 20-11-2014 at 02:28.
    SP-10Mk2a, Graham 2.2 tonearm. SL-1200, Graham 2.2 tonearm, AT-150mlx, Benz-Scheu Glider. Jim & Ken Super DC PSU, Oil well bearing, Acromat, Isonoes, strobe lamp switched. Pass Labs Pearl 2. Aleph J amplifier. F6 Amplifier. Nelson Pass Burning Amplifier BA-3. Pass BA-PP linestage, miniDSP 4x10, Linkwitz Labs LXmini speakers, Sony SS-M7 speakers.

    DIY In progress - Syclotron Red Light district valve amp, ZenMod "Iron pre" autoformer jfet preamp, SYclotron 'His Master's Noise' valve phonostage. And about 2-3 other projects in various states at any time.

  3. #43
    Join Date: Mar 2009

    Location: Cork, Ireland

    Posts: 652
    I'm Nathan.

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    Love this thread. What about a nice matt black on the chassis.
    DIY is fine and dandy, but just try selling it on!

    Nathan.

  4. #44
    Join Date: Aug 2012

    Location: Denver, Colorado

    Posts: 458
    I'm Jim.

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    The colors that I am considering are the original silver (or something close), a glossy black, and matt black.
    SP-10Mk2a, Graham 2.2 tonearm. SL-1200, Graham 2.2 tonearm, AT-150mlx, Benz-Scheu Glider. Jim & Ken Super DC PSU, Oil well bearing, Acromat, Isonoes, strobe lamp switched. Pass Labs Pearl 2. Aleph J amplifier. F6 Amplifier. Nelson Pass Burning Amplifier BA-3. Pass BA-PP linestage, miniDSP 4x10, Linkwitz Labs LXmini speakers, Sony SS-M7 speakers.

    DIY In progress - Syclotron Red Light district valve amp, ZenMod "Iron pre" autoformer jfet preamp, SYclotron 'His Master's Noise' valve phonostage. And about 2-3 other projects in various states at any time.

  5. #45
    Join Date: Aug 2012

    Location: Denver, Colorado

    Posts: 458
    I'm Jim.

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    This thread has seemed to stall out, mainly because I'm stuck waiting for 2 different things that I myself am not doing - namely repainting one of the chassis and a plinth. Both things are in progress, but will obviously taking some time.

    If you are interested in all things SP-10, I would suggest looking at my thread over at diyAudio - it's taken on a life of it's own, as there are currently 4 people in progress of SP-10mk2 restorations/modifications. A good read, I'm sure you will enjoy -- http://www.diyaudio.com/forums/analo...10-thread.html
    SP-10Mk2a, Graham 2.2 tonearm. SL-1200, Graham 2.2 tonearm, AT-150mlx, Benz-Scheu Glider. Jim & Ken Super DC PSU, Oil well bearing, Acromat, Isonoes, strobe lamp switched. Pass Labs Pearl 2. Aleph J amplifier. F6 Amplifier. Nelson Pass Burning Amplifier BA-3. Pass BA-PP linestage, miniDSP 4x10, Linkwitz Labs LXmini speakers, Sony SS-M7 speakers.

    DIY In progress - Syclotron Red Light district valve amp, ZenMod "Iron pre" autoformer jfet preamp, SYclotron 'His Master's Noise' valve phonostage. And about 2-3 other projects in various states at any time.

  6. #46
    Join Date: Aug 2012

    Location: Denver, Colorado

    Posts: 458
    I'm Jim.

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    FINALLY got it!!









    I think it looks grand. Not super duper shiny, exactly what I was hoping for.
    BTW, this is the uglier of the two original chassis. I'm so completely happy with how it looks, it's a million times better than before.
    SP-10Mk2a, Graham 2.2 tonearm. SL-1200, Graham 2.2 tonearm, AT-150mlx, Benz-Scheu Glider. Jim & Ken Super DC PSU, Oil well bearing, Acromat, Isonoes, strobe lamp switched. Pass Labs Pearl 2. Aleph J amplifier. F6 Amplifier. Nelson Pass Burning Amplifier BA-3. Pass BA-PP linestage, miniDSP 4x10, Linkwitz Labs LXmini speakers, Sony SS-M7 speakers.

    DIY In progress - Syclotron Red Light district valve amp, ZenMod "Iron pre" autoformer jfet preamp, SYclotron 'His Master's Noise' valve phonostage. And about 2-3 other projects in various states at any time.

  7. #47
    Join Date: Nov 2008

    Location: North Down /Northern Ireland/ UK

    Posts: 19,484
    I'm Neil.

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    Looking good.


    Regards Neil

  8. #48
    Join Date: Mar 2008

    Location: Halifax, UK

    Posts: 1,399
    I'm Nick.

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    To give the 317 an easier job of regulation (as the top of the 329 will be rock solid in respects to ground), to help isolate the 317 from any grunge upon ground
    Not sure I understand how thats going to work. The 329 will maintain a constant voltage between its pins, so any noise on ground will be exactly copied at the other pin, so the 371 wont see any difference differential noise wise.
    Nick.

  9. #49
    Join Date: Feb 2008

    Location: Down South

    Posts: 2,413
    I'm Neal.

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    I was curious about that as well, the idea behind using a 329 in place of R2 is to lower the dynamic impedance Seen on the adj pin which has a direct bearing on the o/p noise of the LM317...
    Listening in a Foo free Zone...

    Only a Sith deals in absolutes.

  10. #50
    Join Date: Aug 2012

    Location: Denver, Colorado

    Posts: 458
    I'm Jim.

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    Regarding the 329 as voltage reference, that idea didn't work ( well, it worked just fine, but there was no noise advantage... ) and instead have tried something suggested to me, simply making the capacitor that bypasses the adj-gnd resistor much bigger than normal--220uF instead of 10.

    Look here and read for a few posts until you get to the diagram from a magazine:
    http://www.diyaudio.com/forums/analo...ml#post4124664
    SP-10Mk2a, Graham 2.2 tonearm. SL-1200, Graham 2.2 tonearm, AT-150mlx, Benz-Scheu Glider. Jim & Ken Super DC PSU, Oil well bearing, Acromat, Isonoes, strobe lamp switched. Pass Labs Pearl 2. Aleph J amplifier. F6 Amplifier. Nelson Pass Burning Amplifier BA-3. Pass BA-PP linestage, miniDSP 4x10, Linkwitz Labs LXmini speakers, Sony SS-M7 speakers.

    DIY In progress - Syclotron Red Light district valve amp, ZenMod "Iron pre" autoformer jfet preamp, SYclotron 'His Master's Noise' valve phonostage. And about 2-3 other projects in various states at any time.

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