Pioneer SM-700 - Quite impressive little thing!

Discussion in 'Pioneer Audio' started by QSilver, Aug 12, 2017 at 12:47 PM.

  1. QSilver

    QSilver Super Member

    Messages:
    1,033
    Picked one of these up a while ago just as a curiosity. I got round to re-capping it today seeing as it days from 1970 I figured it would be best.

    Most caps measured 70% over what they should. Only strange thing was how they had used one capacitors terminals to bridge two sections of circuitry together. I replaced this with a small wire bridge.

    Fitted it with some Nichicon PW's and some Panasonics for output capacitors with fairly low leakage, checked the centre point and idle current and hooked it up.

    I thought it best to go to the top and just hooked it into my SPEC-3 and wow...

    For a little old capacitor output amp, it sounds brilliant! Has a great deep sound stage. Eagles are sounding good along with a few others.

    Anyone else come across one of these - I like it for the tiny dimension and now the sound.
     
  2. larryderouin

    larryderouin Do I get Food, Med's, or more gear this Month? Subscriber

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    19,509
    Location:
    Glen Burnie Md.
    I've got a few small cap coupled Sansui's and Fisher S.S. 1st Gen receivers. I get the same response. Deep sound stage, very nice mids, bass is a bit sloppy, like it's hunting for it's sweet spot but never hits the mark, and nice highs. The bass response is pretty much normal for all of them, you can tone it down with the Bass knob and it'll settle down some. Surprisingly my Pioneer stuff isn't cap coupled, not even the SX-434. Guess they got the circuits for OCL straightened out by 1974.
     
  3. QSilver

    QSilver Super Member

    Messages:
    1,033
    Yes, very clear highs a little over bright at the moment and the bass seems to be improving the more its left on.
     
  4. Noodle

    Noodle LISTEN! I smell Hi-Fi. Subscriber

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    532
    Location:
    Heart of Dixie
    Yep, got three of them with matching SC-700 pre-amp and SF-700 crossover, along with CS-A700 speakers which can be run as full range or separated for each amp.
    Did a test run once with a single SM-700 on some CS-88A's and was surprised at how it sounded.
     
  5. MPXNL

    MPXNL New Member

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    34
    Location:
    The Netherlands
    It's actually a SA-700 without the preamplifier etc.
     
  6. QSilver

    QSilver Super Member

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    1,033
    Nice! Figures about the SA-700.

    I'd love to get hold of a SC-700... SF-700 would be interesting too...
     
  7. Oldsansui441

    Oldsansui441 AK Subscriber Subscriber

    Messages:
    1,006
    Location:
    Victoria, Australia
    What a nice little amp, can't be too many around, l just had to look it up as l had no idea they existed, makes sense from what MPXNL said about it being the amp section from a SA-700.
     
  8. MPXNL

    MPXNL New Member

    Messages:
    34
    Location:
    The Netherlands
    There are 2 parallel added output caps.
    Remove them and do a little rewire there.
    Replace the 2 original output caps on the amp board with > 2200/35 Panasonic FC or something like that.
    Put in 4 new rectifier diodes and a bigger smoothing capacitor will do the rest.
     
  9. QSilver

    QSilver Super Member

    Messages:
    1,033
    A closer look at the schematic would have told me that..... I should have checked. I've just replaced them all yesterday. I used 1000uF 35V Panasonics in both places. A 2200uF in one place would have been neater but nevermind. It still sounds very good. Only capacitor I haven't changed yet is the filter cap. Was considering up rating it a little seeing as there is a lot of space for a capacitor there.
     

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