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  1. Replies
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    308

    It's not normal as far as I know and they could...

    It's not normal as far as I know and they could have easily avoided it by changing the order of the series components.
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    249

    I prefer the JTM45ri circuit with the extra...

    I prefer the JTM45ri circuit with the extra resistor over your #2 circuit. The #2 circuit reverts to max bias current (-45V) when the wiper loses contact. The JTM45ri circuit reverts to min bias...
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    249

    Edit: I don't like the one above. It's possible...

    Edit: I don't like the one above. It's possible to set the pot to zero bias voltage.

    Try this one.

    55528
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    55491

    55491
  5. I should have posted it but I couldn't find it....

    I should have posted it but I couldn't find it. Here it is.

    55473
  6. Perhaps the PT current ratings are something to...

    Perhaps the PT current ratings are something to do with the 690V PT being intended for a 2 diode full wave rectifier whereas the 350V PT is for a bridge rectifier? Hammond states in their “Design...
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    138

    Assisted by a huge temperature rise (>2000 deg C...

    Assisted by a huge temperature rise (>2000 deg C ?)
  8. I've used the ICL8038 on Vero. Here's a complete...

    I've used the ICL8038 on Vero. Here's a complete kit - link
  9. Replies
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    552

    I've found that wiping both sides of the braid...

    I've found that wiping both sides of the braid with a no-clean flux pen really helps especially if the braid is old and as you said apply a dot of fresh solder to a cleaned tip. Holding a dry tip on...
  10. Thread: Fender 68 prri

    by Dave H
    Replies
    7
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    302

    I've noticed that measuring the high impedance...

    I've noticed that measuring the high impedance grid of an LTP or cathodyne often give a wrong reading. If you measure the cathode voltage it will probably be OK (55V)
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    That sounds backwards to me. If it's heavily...

    That sounds backwards to me. If it's heavily clipping at V1 it needs a tube with less amplification not more. A tube with more amplification will make it clip even harder. Also if it's already...
  12. Replies
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    1,124

    You could use a couple of ordinary diodes (not...

    You could use a couple of ordinary diodes (not LEDs) in series.
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    Here's the list from the man himself. Schematics...

    Here's the list from the man himself. Schematics below.


    "Here is how to make the amp sound/behave like a “proper” AC30."

    1 – R6 and R7 are the plate resistors for V1 (Top Boost and Normal...
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    4,950

    So the circuits are different but their EQ is...

    So the circuits are different but their EQ is similar? :confused:
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    103

    It looks like they were trying to increase gain...

    It looks like they were trying to increase gain (does it need more gain?) Shorting R18 increases the gain of V1B by bypassing its cathode resistor with C26, A job already done by K1A in the position...
  16. Replies
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    29,353

    Sticky: Could you use the online version? - Image2PDF...

    Could you use the online version? - Image2PDF
    I use this one - To PDF
  17. Replies
    141
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    2,367

    The voltages I posted were across the 220k/110k...

    The voltages I posted were across the 220k/110k resistors but I forgot to increase the cap values (it was late), When I calculated the 5D5 output impedance I used huge caps. Doing the same with...
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    141
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    2,367

    I'm not sure. Asymmetrical clipping, increased...

    I'm not sure. Asymmetrical clipping, increased distortion before clipping, reduced output power?
  19. Replies
    141
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    2,367

    47n, 25k build-out 55158

    47n, 25k build-out
    55158
  20. Replies
    141
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    I surely did :)

    I surely did :)
  21. Replies
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    2,367

    220k AC load Left triode 2.62V, Right triode...

    220k AC load
    Left triode 2.62V, Right triode 2.53V

    110k AC load
    Left triode 2.256V, Right triode 2.173V

    Edit:
    220k Left triode, 110k Right triode
    Left triode 2.62V, Right triode 2.248V
  22. Replies
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    Yes, I could do that. Which schematic did you...

    Yes, I could do that. Which schematic did you have in mind?

    I calculated the output impedance of the 5D5 second triode in sim and it is 12k as Zollner stated.
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    I tried it in sim on your circuit and 25k was the...

    I tried it in sim on your circuit and 25k was the optimum value for the build-out resistor.

    25k build-out resistor
    55154

    no build-out resistor
    55155

    Edit:
    The above plots were with 2u2...
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    2,367

    5D3 has the second triode's cathode unbypassed. I...

    5D3 has the second triode's cathode unbypassed. I think that halves open loop gain and doubles output impedance. Would that account for its high output impedance?

    There's also a 56k from the...
  25. Replies
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    I don't think there will be any differential...

    I don't think there will be any differential ripple signal with that cap removed. It removes the second triode's NFB making its output impedance the same as the first triode and the second triode no...
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    To use unmatched tubes?

    To use unmatched tubes?
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    2,367

    You may well be right :)

    You may well be right :)
  28. Replies
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    True, the autoranging fooled me. I just noticed...

    True, the autoranging fooled me. I just noticed the increased phase shift and the differential signal now being larger than the grid to ground signal. There goes another theory. I'm still thinking...
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