Home Forums GuitarPCB Build Support Blues Power tone control issue

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  • #10238
    UBK
    Participant

    Hello,

    I built my ‘Blues Power’ overdrive some years ago and been using it for recordings and tours since then.

    One thing I still  have a problem with, is that the tone control is audible only on the first 3rd turn of the knob from dark to bright and then the rest of the way (from 4 to 10) there’s no audible change. After a while of playing like that I have opened the box again, replaced the 100k linear pot and double checked  C4 value. It still behaves the same, which makes the tone control a bit too sensitive to operate.

    Pease advise..

    Thanks,

    Uri.

    #10239
    Cybercow
    Moderator

    Uri – it sounds like the Tone control’s “taper” is somehow ‘off’ on your build. Can you double-check the values of R8 & R9 as well? Short of that, have you considered trying an A100K (audio taper) or a C100K (reverse audio taper) pot for the Tone control? It might make the difference.

    Also, some good clear photos of both sides of the finished PCB might prove helpful.

    Oh, and this is the “Guides” section. Hopefully Barry will catch this and this thread to the appropriate “Build Support” section.

    #10241
    Barry
    Keymaster

    I moved the topic to the Support section.

    +1 Pictures would be helpful so we can see if there is an issue.

    #10373
    UBK
    Participant

    #10377
    Cybercow
    Moderator

    We can’t see where the wires fro the PCB go. In the photo above, that black wire on the “OUT” section suggests it is going to ground. If you move that black a bit an look at the PCB, you’ll see a “T” silkscreened on the PCB – that “T” means it represents the “Tip’ (goes to the signal) or output. The other solder point in the “OUT” solder points is the ground. Check your wiring with this new info.

     

    #10378
    wilkie1
    Moderator

    Since you have signal passing through the circuit, I suggest changing the Tone pot to a A100K.  That taper should give you more noticeable change as you turn it from 4 to 10.

    #10402
    UBK
    Participant

    The wires on the pcb are all going to their correct destinations and the pedal works and sound great. the only issue is the volume knob behavior. I will try to replace the pot. do you have any experience with this specific build ? a pedal to check for reference ?

    Thanks,

    Uri.

     

     

    #10403
    UBK
    Participant

    Is there a way to reverse the behavior of the potentiometer so the last third of the turn will have the most significant influence  on the tone ?

    From what I remember that’s the way a linear taper should behave and not vice versa, so maybe it’s just a matter of wiring after all.

    #10410
    Cybercow
    Moderator

    UBK – perhaps the article in this link will help you understand potentiometer tapers better and to use\manipulate them.

    The Secret Life Of Pots

    #10483
    UBK
    Participant

    I learned how to restore old pots from this article long while ago – It is a very useful page indeed.

    Still I’d like to know if that’s the way this specific circuit should behave with the B100k tone pot that was recommended on the build document.

    I’ve gone through so many overdrive pedals through the years and this one really sounds perfect for me, so it worth the effort of getting a proper tone control.

     

     

     

    #10484
    Barry
    Keymaster

    This version uses a very simple passive filter.

    A B50k would be enough for most people. The higher the resistance here more high-end gets rolled off so you can see why it is limited especially when using a B100k pot.

    Anyway maybe what you might consider is bypassing the tone control altogether since there is not much more you can do with it anyway and insert a Tone TwEQ 3 Band Active EQ which would give you full tonal control.

    #10485
    UBK
    Participant

    I just expect the volume control to sound linear and not get the whole high end in within a 3rd of a turn.

    I saw a video of you demonstrating this pedal – can you please let me know how your tone control pot behaves ?

    Part of that, I already have the tone twEQ3 in another pedal box (which I use for another aplication), but I really like to keep my ‘live’ rig simple and small, so I prefer not to add more knobs or pedals.

    Thanks,

    Uri.

     

    #10489
    Barry
    Keymaster

    I no longer have that pedal anymore to tell you. It would have been the same as yours (+ or – 20% tolerance) as I am fairly certain I would have used the same component values as you did.

    What I was suggesting before to be clear is when there is a circuit you love and it is worth having a proper active tone control to shape “that circuit” exclusively is to insert the Tone TwEQ into the same enclosure. Here is an example of the Plexi Plus and it was able to fit in a 125B although larger is easier.

     

    I completely understand if you do not want to do that. It was just a thought based on the pedal above.

    That said there are two other suggestions already made above that will make the simple passive tone control feel better and less sensitive since you said “It goes from Dark to Bright and not much after that” I was not quite clear on what the Volume Control deal is that you mention half way down. Anyway by changing the Taper as suggested above you can have the whole “Dark to Bright” thing within the full sweep of the Pot.

    I hope that helps.

     

     

    #10490
    wilkie1
    Moderator

    I assume we are talking about the tone control and not the volume control?

    The specified pot is a B100K.  The “B” means linear. So, the resistance is changing at a constant rate as the wiper is rotated.

    As the above excellent article explains, the resistance of an “A” pot increases as the wiper is rotated CW.  If you wish to have a more noticeable change in the action as the pot is rotated in the 5-10 range, try a A100K pot.

    #10542
    UBK
    Participant

    Apologies for my stupid mistake/mistype  – I wrote volume instead of tone in two of my previous replies.

    It is only to tone control that I have a problem with and I will try to replace the pot with a logarithmic one.

    Thanks.

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