V1 cathode resistors?

Discussion in 'Shock Brother's DIY Amps' started by Uncle Daddy, May 13, 2019.

  1. Uncle Daddy

    Uncle Daddy Tele-Holic

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    Has anyone tried altering the v1 resistor value on a 5e3; how did it change things?

    Thanks
     
  2. Wally

    Wally Telefied Ad Free Member

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    What would be the Goal? A 5751 or a 12AY7 would be two steps of lower gain. IF a person wanted to increase gain, then rebiasing that triode with a smaller value resistor would do that...as would a bypass cap. I have never needed more gain there. Ommv.
     
  3. Paul-T

    Paul-T Tele-Meister

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    Just hopping on the same lick.... I always see cathode caps listed as 25uF, when these days the value most folks offer is 22uF.

    I presume that using 22uF makes no significant difference at all, given that especially older electrolytics were +/- 20% in any case. I see the few people that offer the 25uF value seem to charge a huge premium so to control costs was planning to buy generic 22uF. Does that sound plausible or am i missing something important?
     
  4. Tom Kamphuys

    Tom Kamphuys Tele-Meister

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  5. robrob

    robrob Poster Extraordinaire Ad Free Member

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    If you bias 5E3 V1 warmer you'll add a little gain, cool it and cut some gain. You won't get any asymmetric clipping because the guitar signal isn't strong enough to clip at the first stage.

    V2A is where a bias change could be productive. Putting a 12AX7 in V1 and making V2A a cold clipper could yield some interesting results (I haven't tried this) but it definitely wouldn't be a 5E3 anymore.
     
    muswell_hillbilly likes this.
  6. Tom Kamphuys

    Tom Kamphuys Tele-Meister

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    I did some calculations on the gain of an (unbypassed cathode) gain stage.

    I found this (load 1M, Ra 100k):

    gain.png
     
  7. David Barnett

    David Barnett Doctor of Teleocity

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    But if it's bypassed...
     
  8. Tom Kamphuys

    Tom Kamphuys Tele-Meister

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    it's different.

    Nice homework assignment for tonight...
     
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