Home Forums GuitarPCB Build Support After Blaster R4 (answered)

This topic contains 7 replies, has 2 voices, and was last updated by  MattyJ 6 months, 2 weeks ago.

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  • #4083

    MattyJ
    Participant

    I’m adding the After Blaster to a build, and I would like to use the 2N5457 for added grit. In the build doc, it states that R4 will need adjustment for this. If using a J113, it has 2k4 as a starting point for R4. I’m wondering if I should go up from that R4 value for the 2N5457 and if so, what is a good starting point? I’m wiring the Red special with a Tone TwEQ and the After Blaster in a 125-B, and R4 is mounted on the underside of the foot switch. With so many wires and connections, I’m just trying to minimize the times I need to flip the foot switch over and replace that resistor.

    #4084

    MattyJ
    Participant

    In hindsight, of course, I should have probably mounted the sockets for R4, R1 and Q1 facing up on the PCB with the switch mounted.

    #4085

    Billy
    Moderator

    You can bias your fet prior to connecting the after blaster to the other circuits

     

    Simply connect your dc jack power and ground  to it then change your resistor till you get 5v on your drain

     

    I used a J201 with 20K to get 5v on the drain so I’d say start at around 10K

    #4086

    MattyJ
    Participant

    Hey thanks Billy. That really helps me out.

    #4087

    Billy
    Moderator

    You can also bridge the after blaster I and O pads to have a listen to it once it’s biased

     

    I used a breadboard jumper wire for a nice solderless connection, if you don’t have any a bit of solid core should do the job no problem

    #4088

    MattyJ
    Participant

    So, bridging the I and O pads and connecting the input/output jacks, it will basically act as “stand alone”?

    #4089

    Billy
    Moderator

    More or less

     

    If you look at the schematic you can see

     

    Looking at it your IN jack tip goes to I (input of main circuit) through the circuit to O (output of main circuit) then to the DIP or DPDT switch where you can switch to either position 1 after blaster active or position 2 bypassed / off , so you could theoretically use it as a stand alone by jumpering I and O and doing away with the DIP switches

     

    I like the idea of it as an add on to liven up an anaemic circuit and being able to boost it add more gain etc as required

    #4090

    MattyJ
    Participant

    Got it. I like the idea of being able to sound test it before running it to the other circuits. Thanks for the input Billy.

     

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