Anyone built a STAX adapter (srd7 clone?) before?

Discussion in 'DIY (Do-It-Yourself) Discussions' started by figo, Apr 21, 2008.
  1. Figo
    After searching in vain for some time for an Srd-7 or other pro STAX adapter, I wonder if anyone has DIY their own? I can't imagine its too complicated.

    Anyone know what goes into one?

    Notice, I don't mean a STAX amp like KGSS, only an adapter to connect STAX headphones to a speaker amplifier.

    -Jim
     
  2. spritzer
    Quote:

    Originally Posted by Figo /img/forum/go_quote.gif
    After searching in vain for some time for an Srd-7 or other pro STAX adapter, I wonder if anyone has DIY their own? I can't imagine its too complicated.

    Anyone know what goes into one?

    Notice, I don't mean a STAX amp like KGSS, only an adapter to connect STAX headphones to a speaker amplifier.

    -Jim




    It's certainly not that hard to do. All you need is a bias supply (the SRD-7mk2 one is easily avaialble) and some 1:25 transformers with a center tapped secondary. The ratio isn't terribly important though so basically most output transformers can be used when wired backwards. To find the voltage stepup (or down) find the impedance ratio (6000:8 or what ever) and take a square root of it.
     
  3. ericj
    Yeah, it's a dead simple circuit. I've considered doing it with transformers from a disused koss energizer.
     
  4. AudioCats
    or just watch ebay closely and get one there. A pair of good output trans is not cheap, if pro-bias is what you after, might as well get a normal bias stax box and add the high voltage bias circuitry.
     
  5. Figo
    I found that Andrea Ciuffoli has a design:

    the STAX Transformer

    I may use this but sub Hammond Iron, at least for the power Tranny. May use the Lundalh OPT.

    Only problem is he says it required 13W + output from amp to work.. mine is a 12W tube.

    Thoughts on this one? Looks straightforward enough. Now I need a STAX plug.


    -Jim
     
  6. spritzer
    Quote:

    Originally Posted by ericj /img/forum/go_quote.gif
    Yeah, it's a dead simple circuit. I've considered doing it with transformers from a disused koss energizer.



    I ripped my E/10 apart and the transformers are a no go. The secondary isn't center tapped so Koss was up to their usual tricks.

    Quote:

    Originally Posted by Figo /img/forum/go_quote.gif
    I found that Andrea Ciuffoli has a design:

    the STAX Transformer

    I may use this but sub Hammond Iron, at least for the power Tranny. May use the Lundalh OPT.

    Only problem is he says it required 13W + output from amp to work.. mine is a 12W tube.

    Thoughts on this one? Looks straightforward enough. Now I need a STAX plug.


    -Jim




    You can also just buy electrostatic step up transformers from Home Page and use those. There is no power transformer needed, only a back to back zener for the bias supply. The power draw is so vanishingly small.
     
  7. gz76
    Fitz was selling one of these yesterday... you could PM him or search the For Sale forum to see if it's still available.
     
  8. d-cee
    I'd buy one if someone DIYed it
     
  9. ericj
    Quote:

    Originally Posted by spritzer /img/forum/go_quote.gif
    I ripped my E/10 apart and the transformers are a no go. The secondary isn't center tapped so Koss was up to their usual tricks.



    the e/9 schematic shows a center tap and there are enough leads coming out of the transformers in my worthless 220v e/9 - do you mean that in the e/10 there is no tap, or that the tap is not in the center?
     
  10. spritzer
    Quote:

    Originally Posted by ericj /img/forum/go_quote.gif
    the e/9 schematic shows a center tap and there are enough leads coming out of the transformers in my worthless 220v e/9 - do you mean that in the e/10 there is no tap, or that the tap is not in the center?



    There is no tap visible but it could be hidden since they needed no 0v point. If there is no CT there isn't much use for the trafo unless for driving piezo drivers or SE electrostatics.
     
  11. AudioCats
    Quote:

    Originally Posted by spritzer /img/forum/go_quote.gif
    You can also just buy electrostatic step up transformers from Home Page and use those.




    I am putting a pair of JRM M99B 1:50 trans into an energizer case (finally, had them for 3 month by now). The price, shipped within the states, was $108/pair. The M99b is the smallest in JRM's offering, but still that is a loud speaker trans so the size is like a 30VA power transformer (meanwhile the trans in a SRD-6 is of 5VA size). Outside finish on the M99b is not as "refined" as a commercial transformer, the sound is respectable though. I do not have anything to do direct JRM vs. SRD-6 comparison at this time.
     
  12. spritzer
    Quote:

    Originally Posted by AudioCats /img/forum/go_quote.gif
    I am putting a pair of JRM M99B 1:50 trans into an energizer case (finally, had them for 3 month by now). The price, shipped within the states, was $108/pair. The M99b is the smallest in JRM's offering, but still that is a loud speaker trans so the size is like a 30VA power transformer (meanwhile the trans in a SRD-6 is of 5VA size). Outside finish on the M99b is not as "refined" as a commercial transformer, the sound is respectable though. I do not have anything to do direct JRM vs. SRD-6 comparison at this time.



    That is a very good price compared to the Sowter ESL transformers. There are also some Hammond output trafo's that can be used but the price is roughly the same.
     
  13. zzhetanay
    tell me where to buy JRM M99B?
     

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