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  1. Replies
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    589

    This power stage cannot be pushed into overdrive,...

    This power stage cannot be pushed into overdrive, at least into actual configuration. It is a pretty clean amp. As time did not benefit by a hefty driver is hard to believe the grids can be pushed...
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    589

    And still 12bh7 at 600v, 33k plates/100k load,...

    And still 12bh7 at 600v, 33k plates/100k load, great swing, much better

    57302

    It will take only 5-6 volts aroud on input to get power tubes full drive
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    589

    C'mon... with 15V over 1.5k R cathode meant 10mA...

    C'mon... with 15V over 1.5k R cathode meant 10mA / 2=5mA/ tubeŚ47k=235v + 310on plate=545 V.. I think...almost 600:)...not quiet but close
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    589

    UL yes, like mine. Voltages in the chart attached...

    UL yes, like mine. Voltages in the chart attached for 200w57300
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    589

    I just looking what Marshall did in their 200w...

    I just looking what Marshall did in their 200w heads. 12AU7 driver supplied at 620V with 310V on plates at iddling,biased at 15v around
    57296

    57297
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    589

    Is not 600v on the plate. It will be supplied at...

    Is not 600v on the plate. It will be supplied at 600v , almost same as screens for max excursion. The plates will stay at 240v around at idling and max excursion negative peak will be 500V for 0 mA...
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    589

    Thinking more like this. 57289 Supplied at...

    Thinking more like this.
    57289

    Supplied at 600v seems within the limit. With 33 k on the plates got 240v iddling and max 500v max negative swing for 0 mA current to 100 k load. 100k grid...
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    589

    It seems unsafe with those big value resistors....

    It seems unsafe with those big value resistors. 12ax7 seems weak to can push the power tubes into grid current territory. For the moment it not work properly as it is, have to do a fresh recap. but...
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    Simms watts 200 question

    Hello. Got a Simms watts 200 to restore, 4xkt88 in UL mode supplied at ca. 650V arround. What is wondering is its poor 12ax7 driver into big 220k grid leaks. Thinking more to add a pair of...
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    1,015

    Always I try to look and understand who have to...

    Always I try to look and understand who have to gain something from this
  11. Someone consider a hundred volts as a safe limit....

    Someone consider a hundred volts as a safe limit. For this reason a diode or neon bulb will work. As time the voltage drop below 90v it will be blocked so in fact is out of circuit.
  12. Isolation between grid and cathode is supposed to...

    Isolation between grid and cathode is supposed to be passed through. When cold we have whole HT voltage on the grid whilst cathode stay at 0 potential. ( cold heaters meant no current flow, no...
  13. Can You post a picture how you tone stack is...

    Can You post a picture how you tone stack is wired ?
  14. Actually there are two separate secondaries in...

    Actually there are two separate secondaries in parallel think they did it for interleaving reasons .
  15. Eminent is not a guitar amp. Get full...

    Eminent is not a guitar amp. Get full documentation here, from Mr.Peter Andersen effort. Many Thanks!
    http://www.peel.dk/Dynacord/

    Almost forgot: Get first check to bias trimmers. This is very...
  16. ...Let see the donor...TG9375, right ? 56886...

    ...Let see the donor...TG9375, right ?


    56886

    Have some scope screenshots by my tests. You can get 120w at 480V with a quad of EL34.
    This trannies runs pretty hot I remember. Don't worry to...
  17. Think it was. I don't remember precisely. I...

    Think it was. I don't remember precisely. I recovered a bunch of good Partridges from SC scrap but had care to carefully notice its specs. What I remember precisely after I did some tests it was this...
  18. These are the specs of my tranny: 4 ohm -...

    These are the specs of my tranny:

    4 ohm - green
    8 ohm - brown
    16 ohm - yellow
    100V - blue
    Common - black
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    Hi, Yes, is ringing also without nfb connected,...

    Hi,
    Yes, is ringing also without nfb connected, same manifestation. Time to look for a Zobel alternative. Thanks for support.
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    834

    Similar arrangements into a Grommes amp, not...

    Similar arrangements into a Grommes amp, not quite same paraphase aplication.

    56606
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    834

    So what are substantial diferences between those...

    So what are substantial diferences between those two variants pls?
    Why classical arrangement with the shunt resistor in the bottom is preferred?
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    834

    56604 The original circuit was modified to...

    56604

    The original circuit was modified to allow the whole bias over nfb resistor
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    Thanks for You answers..The circuit comes from an...

    Thanks for You answers..The circuit comes from an old schematic relative to applying nfb into a paraphase inverter, I remember. In any nfb circuits some bias is developed over nfb resistor, I just...
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    Well, I have to keep those 1.5k resistor as bias...

    Well, I have to keep those 1.5k resistor as bias resistor for cathode. I will play with the value of shunt resistor till desired nfb amount. Thanks
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    Hey, thanks for input. The bias for first stage...

    Hey, thanks for input.
    The bias for first stage is made over 1,5k resistor which is relative to ground through secondary winding. The feedback ratio is determined by 1,5k / 47ohm resistor which is...
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    NFB network compensation help pls.

    Hello,
    I trying to implement some (6db arround) nfb into my project. For some reason testing at 1 kcps with square wave is ringing a little bit too much. I tried to compensate with a capacitor...
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    Those MV is not "transparent" and think no one...

    Those MV is not "transparent" and think no one will be. But is great useful tool even for bedroom levels. Put it into max position and restore the amp in factory condition. I installed tens in...
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    Thank You

    Thank You
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