6G15 dry path question

Discussion in 'Shock Brother's DIY Amps' started by Nocd, Sep 24, 2020.

  1. Nocd

    Nocd TDPRI Member

    Posts:
    6
    Joined:
    Jun 29, 2012
    Location:
    Wilmington, NC
    Hello. long time lurker, first time poster... I just recently completed my first build; the monotone GA-5 ki. Now I’m planning on building a 6G15 reverb clone using an old Epiphone valve jr head that I have.

    I have a question related to the dry signal path in the schematic (https://el34world.com/Hoffman/files/Hoffman_6G15.pdf), specifically the value of R17 of 100k. I’m thinking that it would be possible to change values of resistors and caps around V2B and add some “drive/dirt” to the dry path (variable)? I’m not looking to add a ton of distortion but maybe to drive that tube stage a bit harder for use as preamp. What would be the best option? Maybe this is a stupid idea? In that case let me know!

    Thanks!
     
  2. Nocd

    Nocd TDPRI Member

    Posts:
    6
    Joined:
    Jun 29, 2012
    Location:
    Wilmington, NC
    Mojotone GA-5 kit is what I meant.
     
  3. andrewRneumann

    andrewRneumann Tele-Holic

    Posts:
    590
    Joined:
    Mar 22, 2020
    Location:
    Cincinnati, OH, USA
    It looks like you have a cathode follower there. It’s got gobs of headroom and provides less than unity gain. (I.e. signal out is slightly less than signal in.) Nothing comes to mind on how your goal could be accomplished. Sorry no help.
     
    Nocd likes this.
  4. Nocd

    Nocd TDPRI Member

    Posts:
    6
    Joined:
    Jun 29, 2012
    Location:
    Wilmington, NC
    Thanks for the info Andy. I’m really don’t know enough about tubes so I appreciate it.
     
  5. elpico

    elpico Tele-Afflicted

    Posts:
    1,121
    Joined:
    Sep 14, 2011
    Location:
    Vancouver BC
    If the goal is to get more signal coming out of V2-B you can get more out by putting more in. Moving c10's input to the output of V1-A or B would do the trick. The reverb signal won't be increased though so the mix of the two paths will changed, the reverb will seem subjectively much quieter.
     
    Nocd and D'tar like this.
  6. D'tar

    D'tar Friend of Leo's

    Posts:
    3,032
    Joined:
    Jan 11, 2013
    Location:
    WNY
    V1b to maintain phase perhaps
     
    Nocd likes this.
  7. andrewRneumann

    andrewRneumann Tele-Holic

    Posts:
    590
    Joined:
    Mar 22, 2020
    Location:
    Cincinnati, OH, USA
    You could start reducing the value of R15 until you get some grid-current limiting distortion. This wouldn’t be variable though since you’re handling high voltage DC there.
     
    Nocd likes this.
  8. elpico

    elpico Tele-Afflicted

    Posts:
    1,121
    Joined:
    Sep 14, 2011
    Location:
    Vancouver BC
    Probably not an issue thanks to the delayed and reshaped signal out of the tank but yeah I'd agree it's worth checking both to see if either sounds better.
     
  9. Nocd

    Nocd TDPRI Member

    Posts:
    6
    Joined:
    Jun 29, 2012
    Location:
    Wilmington, NC
    Great suggestions everyone! I’m building this from scratch so it will take a few weeks until I have results to share. Another idea - what if v2b wasn’t a cathode follower but set up as v1a with a volume (“dry”) control? I would set up the controls as a dry and wet volume instead of “mix”? Also in this case a tube with a lower amplification would probably be better than the 12ax7. Maybe a 12ay7 instead?
     
  10. Nocd

    Nocd TDPRI Member

    Posts:
    6
    Joined:
    Jun 29, 2012
    Location:
    Wilmington, NC
    But then it may be out of phase... I will try to build it per spec first and then tinker.
     
  11. andrewRneumann

    andrewRneumann Tele-Holic

    Posts:
    590
    Joined:
    Mar 22, 2020
    Location:
    Cincinnati, OH, USA
    Out of curiosity, how do you plan to use the reverb unit?
     
  12. tubegeek

    tubegeek Friend of Leo's

    Age:
    60
    Posts:
    3,735
    Joined:
    Jan 31, 2020
    Location:
    Brooklyn, NY
    You can go back and edit your post - there is an edit function.
     
  13. Nocd

    Nocd TDPRI Member

    Posts:
    6
    Joined:
    Jun 29, 2012
    Location:
    Wilmington, NC
    I was hoping to use it both in front of an amp and as a preamp for recording. Maybe that is asking too much...
     
IMPORTANT: Treat everyone here with respect, no matter how difficult!
No sex, drug, political, religion or hate discussion permitted here.