Home Forums GuitarPCB Build Support Bass Overdriver Question

Viewing 3 posts - 1 through 3 (of 3 total)
  • Author
    Posts
  • #13099
    Brooks
    Participant

    Just built this the other day.  When biasing I was unable to get Q3 below 6.4v.  The recommendation in the build guide was to shoot for 5v.  It sounds fine to me but I don’t know what it would sound like at 5v to compare.  I was able to get Q1 and Q2 right at 5v.

    I have a couple dozen 2N5457’s (bought from legitimate sources…here and SB).  I also have a DCA55.  Is there a way I could test what I have against the one I used to try to select one that will bias correctly?  My knowledge of the DCA55 only extends as far as testing Ge transistors for gain and leakage…and double checking pinouts.

    I would prefer to not attempt to desolder the trimpot or add a resistor in series somehow…or randomly plug in the other 2N5457’s trying to get it in the 5v range.

    Any suggestions would be appreciated.

    #13100
    Billy
    Moderator

    It’s not absolutely crucial to bias at 5v all FETs vary wildly even from the same batch

    You can experiment with Q1 and 2 and bias them slightly higher than Q3 to around 6.5v to 6.7v to see if that makes a difference but my personal opinion is if it sounds good leave it

    I biased mine higher than 5v when I built it

    If you really want to try some additional series resistance you could simply tac a resistor on the underside of the board between TR3 lug 1 and Q3 drain obviously removing Q3 first, I’d start at 2K

    #13101
    Brooks
    Participant

    Thanks for the suggestions.  I messed with the bias of 1 and 2 a little bit but didn’t try them both slightly above Q3.  I will start there.

    And, you are right, not too tough to tack that resistor on the bottom of the board…my mind went straight to putting a higher value trimmer in there and was not looking forward to that.  Not of a fan of having to desolder…

Viewing 3 posts - 1 through 3 (of 3 total)
  • You must be logged in to reply to this topic.