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Posts posted by waltzingbear

  1. its entirely possible that one channel had more leeway before breaking than the other. Hence one still working. The hum probably came from a combo of the failure (whatever it is) in the L channel from the unregulated (broken) -400 supply.

    I would get the LV 15V supplies working next after you get -400V regulation back.

    I have no idea which transistor maybe bad, but most likely one is. Once you get the supplies working correctly you should measure the voltages on both channels, that may point to the problem.  The observation that it passes audio while turning on or off leads me to think that is happening when it passes thru working bias points. And stabilizes with everything biased off.

    Check your board well for missed solder joints, cold solder or arcs.

    As an aside, you can use almost any correct type of FET to trouble shoot. The 170 is for low noise and distortion, others will work just fine..


    do you have a scope?

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  2. the two things I would change are the input from single ended to balanced. simple mod, discussed elsewhere on head case, google is your friend.

    and add the constant current loads to the circuit. You can find this in Audio Express July, and I forget what year.

    there are also some grounding changes I would (did) make to get rid of some internal ground loops, yes it's our friends at Stax, they get the hard stuff right and the simple stuff wrong.

    Also mwl168's advice is well stated




  3. Is there a current source of earspeaker jax? I am aware of the Ampenol (WDI) parts, but are there any of the custom teflon ones available anywhere? I couldn't find them.


    cheapest source in US https://vacuumtubesinc.com/index.php/sockets-adapters-and-parts/5-and-6-pin-tube-sockets/a5-5285.html


    as a side note, contacted Richard Summer, he is moving his shop and won't be available for a (unspecified) period of time.

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