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jose

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Posts posted by jose

  7. The Headcase Stax thread

    in Headphones

    Posted

    On ‎15‎/‎12‎/‎2017 at 3:27 AM, Blueman2 said:

    I too was worried.  Just bought a brand new pair of SR-007A and was surprised to see the SZ2 serial number.  But they look brand new, still in the box with plastic sealed around the box.  BTW, johnwmclean, I am 230x, so ours were probably born on the same week!!  Or, given the random serial numbers, years apart!?!

    I want to buy some SR-007A but it looks like a lottery.

  23. goldenreference low voltage power supply

    in Do It Yourself

    Posted

    Hi

    I read all thread and I though that all resistors was necesary. :huh:

    I use this GRLV with my Dynalo SS. I didn´t any adjust (I matched all resistors, leds and I adjusted trimpots on 50K before plug in). With the Dynalo SS connected to this, I can measure; -19,993 volt and +20.000 volt and between rails 40,00volt exact. With no load, same measures.... I hadn´t noises or issues.

    I´m using a r-core with 25Vac@1Amp x2 

     

  25. The Multi Amp aka Dynalo Mk2

    in Do It Yourself

    Posted · Edited by jose

    On ‎31‎/‎01‎/‎2015 at 2:03 AM, mwl168 said:

    Sharing my findings with attempts to raise output BJT current as promised.

     

    I am running +/- 16V rails.

     

    Using 255R in R38 and R39, I got around 186mv voltage drop on the output resistors (20R) when the amp is fully warmed up (160mV at cold start). That's around 9mA current. I could barely feel a temprature on the output transistors at this operating condition.

     

    I finally settled on 301R in R38 and R39 which results in 250mV across the output resistors at cold start, rising to and stablize at 320mV after a few minutes. The output BJTs are quite warm to the touch but not hot. I am really liking the sound of the amp at this condition.

     

    For what it's worth, here is a few other values of R38 and R39 I tried and the resulting voltage drop across the output resistors:

     

    R38/R39 = 287R, 230mV cold start, 273mV warmed up

     

    R38/R39 = 317R, 300mV cold start, 360mV warmed up

     

    R38/R39 = 402R, 500mV cold start, did not wait for it to warm up.

     

    This amp really sounds great on both my Senn. HD650 and LCD2. Subjectively the best among the headphone amps I own and heard.

     

    Many thanks Kevin for your ingenuity and help!

    My Dynalo SS lives too.

    My amp runs with 20Vdc rails and 255R Bias resistor and like Pars, I use Jfet (2SK170GR/2SJ74GR) instead That340 (I learned the lessond with my Dynahi). 

    I measured 160mV at cold start and after 20 minutes my amp is stable to 0,205mVolt (around 10mA) with an offset of 0~4 mVolt. Transistors temperature is 35º and 40º.  I read all thread and on speciality this answer. I´m going to change R255 for other value around R280.

     

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