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  1. Replies
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    My Bad - I meant Cathodyne but brain short...

    My Bad - I meant Cathodyne but brain short circuited and typed Paraphase.
    Cheers,
    Ian
  2. Replies
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    That it exactly. CC Gain stage anode load and...

    That it exactly.
    CC Gain stage anode load and bootstrap resistor both 100K in lieu of 250K and 40K in the Wireless World Article.

    In the last SS Amp I did with bootstrapped VAS load I found the...
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    That 12AX7 Gain Stage/Phase Splitter is...

    That 12AX7 Gain Stage/Phase Splitter is interesting.
    The first 12AX7 triode is a gain stage with a bootstrapped anode load resistor.
    The second 12AX7 triode is a Paraphase (Seesaw) Phase splitter. ...
  4. Note that that Application Note I linked above...

    Note that that Application Note I linked above uses the formulae:

    Rshare = 1000/(0.015 x C[uF]) [kOhms]

    That would suggest 303 kOhms MAXIMUM for that 220uF

    This is the same as writing...
  5. The voltage across the series connected...

    The voltage across the series connected capacitors shares according to the capacitors leakage current.
    We therefore size the resistors to conduct 3 to 5 times the expected capacitor leakage current....
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    Very similar to what is done a fair bit in HiFi -...

    Very similar to what is done a fair bit in HiFi - with triode strapped EL84 as the phase splitter and a centre tapped inductor load.
    L:ike this:
    http://turneraudio.com.au/8585-amp-october-2006.html...
  7. I use this a lot....

    I use this a lot.
    http://tdsl.duncanamps.com/tubesearch.php
    Links to datasheets plus summary operating conditions.
    Example:
    http://tdsl.duncanamps.com/show.php?des=EL34

    Cheers,
    Ian
  8. Bed time reading for the terminally bored....

    Bed time reading for the terminally bored.
    https://www.nichicon.co.jp/english/products/pdf/aluminum.pdf

    BUT
    I like this older one from Evox Rifa,, it even has a Valve (Tube) Amp Calculation...
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    The Wiz covers the Cathodyne Phase Splitter...

    The Wiz covers the Cathodyne Phase Splitter pretty well.
    http://www.valvewizard.co.uk/cathodyne.html

    It is Not a good choice for amps where the power amp is going to be overdriven although there...
  10. Electrolytic Cap life is dependent on their...

    Electrolytic Cap life is dependent on their internal temperature which has a drying effect on the paste electrolyte.

    Caps self heat according to Power = current squared x resistance, in this case...
  11. 105 degrees C rating for tube amps and even then...

    105 degrees C rating for tube amps and even then apply a bit of thought to physical placement - where possible place away from heat sources.

    Cheers,
    Ian
  12. Double the ripple current rating infers 1/4 of...

    Double the ripple current rating infers 1/4 of the temperature rise and MUCH longer lifetime.
    I would perhaps use the F&T for repairs to replace F&T purely to keep an amp "original".
    I would use...
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    See the datasheet...

    See the datasheet
    http://www.farnell.com/datasheets/2001459.pdf

    I would be looking at the gain set resistors R11 = 20K and Ri = 1k and that 22uF cap (check for a shorted cap too). Most likely...
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    These Transformers 2 x High Voltage Windings are...

    These Transformers 2 x High Voltage Windings are both intended for voltage doubler power supplies, therefore the current ratings are X2 what you would otherwise expect.
    Cheers,
    Ian
  15. Replies
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    The Paraphase is great in simple /minimalist...

    The Paraphase is great in simple /minimalist circuits - easy to add a 1 knob tone control
    See the GA40 for example of this
    https://music-electronics-forum.com/showthread.php?t=49627

    Cheers,
    Ian
  16. Replies
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    Up to 200W...

    Up to 200W
    http://www.tungsol.com/tungsol/specs/kt150-tung-sol.pdf

    OR
    For 6550 - how can 2 x 42 W = 100W
    Answer is Class B Operation (or Class AB with very low idle currents , that is close to...
  17. I looked at the '68 Custom Deluxe Reverb Service...

    I looked at the '68 Custom Deluxe Reverb Service Manual and it says +415V for B+ whereas the original 1968 Deluxe Reverb said +398V so probably leave it alone.
    If you MUST trim it back a bit, the...
  18. Calcs are good. For V8, 28.7 mA x 425.5V = 12.2...

    Calcs are good.
    For V8, 28.7 mA x 425.5V = 12.2 Watts Anode dissipation in a tube which has a data book rating of 12 Watts anode dissipation.
    So it is a bit hot but not that unusual.

    The...
  19. Good point - I used an uncommited 5V winding,...

    Good point - I used an uncommited 5V winding, that is, ONLY my little supply was on it.

    Cheers,
    Ian
  20. Just for info: If the 5V winding is not used...

    Just for info:

    If the 5V winding is not used or has spare capacity:
    Bridge rectify the 5V winding using Schottky Diodes - 4 off something like 1N5821 (30V @ 3 Amps) into a 10,000uF electrolytic....
  21. Replies
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    Just a bit of a caution - I have never fully got...

    Just a bit of a caution - I have never fully got my head around the 2nd cap bank , the one after the standby switch.

    Stacked caps will share voltage according to their capacitance. The same charge...
  22. Yes - minimise stray inductance is the goal AND...

    Yes - minimise stray inductance is the goal
    AND
    Yes - metal oxide resistors would be better.
    Cheers,
    Ian
  23. The Screen Grid (g2) exhibits gain when a signal...

    The Screen Grid (g2) exhibits gain when a signal is applied to it with respect to the cathode - just like the Control Grid (g1).
    The 1st function of the screen resistor is therefore as a grid stop...
  24. Not applicable according to your post just above ...

    Not applicable according to your post just above

    BUT for future reference:

    Hum or noise being max at mid setting on a volume pot or guitar volume control is a big clue. Actually with a log pot...
  25. Replies
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    The Application Report has details of B+ of 200V...

    The Application Report has details of B+ of 200V operation - that will do.

    Cheers,
    Ian
  26. Replies
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    Also remember that the screen supply is far more...

    Also remember that the screen supply is far more critical than the anode supply so make sure it has additional filtering.
    Cheers,
    Ian
  27. Replies
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    Slightly Off topic or an extension of it: The...

    Slightly Off topic or an extension of it:

    The GROUNDED Faraday Cage thing is why when using isolated input jacks with the cold (cable shield) side tied to 0V at the input tube it is a good idea to...
  28. ECC99 is a good tube but is really "just" a bit...

    ECC99 is a good tube but is really "just" a bit more linear 12AU7 with 3.5W vs 2.75W plate dissipation.

    So for circuits it is just an option (a good one) to use in place of a 12AU7 or 6CG7, it...
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