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Got a lead on a Dynaco Dynakit ST-70 Stereo Tube amp

Discussion in 'Shock Brother's DIY Amps' started by peteb, Sep 22, 2019.

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  1. Sep 22, 2019 #1
    peteb

    peteb Friend of Leo's

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    I have first dibs on an amp like this. PCB based 70 W Stereo amp using 4 X EL34 tubes, no controls except for front mounted bias adjust of the 12AX7 pre amp tubes. Yes, the bias adjust ports look like two tube sockets.



    It’s either convert it into a guitar amp or let a teenager in the family who has a keen eye to sell it, sell it.





    I think I’m going to let him try to sell the most likely non working Stereo, there are speakers, a tuner and a turn table. If he can’t sell it, then I will have no choice but to tear into it.




    I should add that it is tube rectified, which makes it more interesting to me as my big amp is SS rectified. And, the amp in question is a dynakit, not the dynaco in the attached picture.





    19B91D6E-C90E-4EDE-8482-6C608B65FA7C.jpeg 87A2B514-EDC6-4757-AE1D-E75D6B815631.jpeg
     
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  2. Sep 22, 2019 #2
    rangercaster

    rangercaster Poster Extraordinaire

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    Nice hifi amp ... I would use it for that purpose ... If you want to flip it, go for it ...
     
  3. Sep 22, 2019 #3
    ponce

    ponce Tele-Holic

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    What would a Tele sound like through it in a current state, just curious?
     
  4. Sep 22, 2019 #4
    Greggorios

    Greggorios Friend of Leo's Silver Supporter

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    Wadda ya, nuts? If it's in half decent shape, let someone who knows what they're doing take a look at it. It may not take much to get it working for what it was designed for...a quality stereo tube amp. You could have yourself a great vintage stereo rig. Even the dyna-kits can go for $800 and up. That thing could be a real gem. :)
     
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  5. Sep 22, 2019 #5
    peteb

    peteb Friend of Leo's

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    I doubt it will ever work as a hi fi amp again. It has not been tested, but I have my doubts. And it’s PCB based, probably not worth working on.




    I’m not going to sell it. I will let the kid do that.
     
  6. Sep 22, 2019 #6
    peteb

    peteb Friend of Leo's

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    I don’t think it works. It has not been tested.
     
  7. Sep 22, 2019 #7
    peteb

    peteb Friend of Leo's

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    Thanks. The pictures are not the unit in question. The unit I could get looks OK but not as nice. I’m just thinking the Transformers have value and The chassis / cover is kind of cool looking.




    You are right. It should probably be made to work as a hi fi amp. It’s PCB based which makes me not want to work on it.
     
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  8. Sep 22, 2019 #8
    David Barnett

    David Barnett Doctor of Teleocity

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    This is a modified amp, the circuit board and the filter cap have been replaced. That's probably good, depending on the quality of the workmanship.

    You'd need a preamp to play your Tele through it. It would probably sound a lot like a small Sunn amp, since Sunn amps used Dynaco power amp sections.
     
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  9. Sep 22, 2019 #9
    Greggorios

    Greggorios Friend of Leo's Silver Supporter

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    Yes, I didn't notice the PCB part in your OP. I'm not familiar enough with the PCB based version on that amp to offer any input.
     
  10. Sep 22, 2019 #10
    David Barnett

    David Barnett Doctor of Teleocity

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    Oh - the pictures aren't the amp in question?

    I wouldn't worry about the circuit board too much. Yes, the old phenolic boards tend to fail if you do much work on them, the traces will lift. But there are tons of replacement boards available for the Stereo-70, using either the original circuit or with new, modified circuits. If the chassis and transformers are good, the amp can be saved.
     
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  11. Sep 22, 2019 #11
    Musekatcher

    Musekatcher Friend of Leo's

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    I'd set it up for LP-album listening. But, Jerry G used tube McIntoshes on stage with D120s, you could emulate that. I used to run a Les Paul thru my hi-fi, and it sounded super clear, almost acoustic. Not sure what that would sound like in a band. Might be awesome. Or not.
     
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  12. Sep 22, 2019 #12
    DougM

    DougM Friend of Leo's

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    There are plenty of ST70 restoration kits out there (including new PC boards, and recap kits), as it's one of the most iconic, best sounding, and affordable vintage tube hi-fi amps in existence. I would restore it and use it in my stereo setup where it will sing like a bird, and bring new life to all your albums, CDs, or digital files. And the bias trim pots are for biasing the output tubes (the EL34s), not the 12AX7s.
    Those amps have some of the most legendary iron ever in them. David Hafler literally wrote the book on great sounding transformers.
     
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  13. Sep 22, 2019 #13
    schmee

    schmee Poster Extraordinaire

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    That's nice gear. I wouldn't mod it.
     
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  14. Sep 22, 2019 #14
    Mhat

    Mhat Tele-Meister

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    I've always been interested in one of those for my turntable. What are you looking to flip it for?

    I have no problem working on amp projects.
     
  15. Sep 22, 2019 #15
    rangercaster

    rangercaster Poster Extraordinaire

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    Nice iron there ... How much are they asking ???
     
  16. Sep 22, 2019 #16
    peteb

    peteb Friend of Leo's

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    Then it makes a lot of sense to keep it at its original purpose.







    Thanks for all the answers. It’s clear it should stay a hi fi amp. I passed the word to let the cousin’s kid do what he wants with it.





    I will find out what it gets put up for. Again, it’s a unit similar to the pictures. Dusty but in somewhat similar conditio. A dynakit not a dynaco.
     
  17. Sep 22, 2019 #17
    SuprHtr

    SuprHtr Tele-Meister

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    The definition of classic. If I had one, I'd re-hab it and use it for my main stereo amp at home.
     
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  18. Sep 22, 2019 #18
    peteb

    peteb Friend of Leo's

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    The circuit board should look something like this. Kind of robust looking.




    138DB52A-6079-4D80-8838-5FFCCE91CA28.jpeg
     
  19. Sep 22, 2019 #19
    peteb

    peteb Friend of Leo's

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    It’s ultra linear








    6B1EEE41-C8AC-4543-99D0-C5D19C26B715.png
     
  20. Sep 22, 2019 #20
    peteb

    peteb Friend of Leo's

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    You’re right. I should listen to records more. For how much I listen to records I get by with my compact stereo set up. I miss the mono tube record player I had as a youth with the Gerard turn table with wood base.





    I could be missing out on a good thing with that dynakit but it seems over whelming.





    EEEAEED5-3CC2-48E6-A6E9-3763C4286F27.jpeg
     
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