Home Forums GuitarPCB Build Support Sunn-T Bass Knob

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  • #12931
    Patrick Garland
    Participant

    Built up the Sunn-T for the first time – really like the sounds I’m getting! Though my toggle switch isn’t oriented right as I just found it is an On/Off/On so I need to get that part replaced. Both sound pretty cool though – very nasty but smooth tones as described.

    My only issue is that my Bass pot doesn’t really seem to be doing much on any setting. Even isolated with other EQ flat or boosted it still didn’t change anything to my ear. Any values I need to double check?

    Really dig the lower gain tones, but the high gain stuff really pushes the treble strings out with a crispness that is refreshing!

    #12933
    Billy
    Moderator

    You can check the filtering caps and resistors around the bass pot C10, R11 and the bass pot itself it’s a passive tone control basically 3 low pass RC filters with C9, 10, 11 the pots for each band and R11

    I’d imagine with your switch middle position being ‘off’ it may have some affect

    Wilkie’s the man for this one it’s his baby !

    #12947
    Patrick Garland
    Participant

    Hey Billy thanks for the quick help –

    Looks like you’re right – once I adjusted the switch a bit I got more tone control out of the Bass knob. I definitely need to redo this input/channel configuration as your list of components involved here is obviously crucial with the switch being right.

    I also double checked my voltages on the trimpot/Q1-4 areas and I got one adjusted more within the 4.5-5.5 range. I think each trimmer was set to about 4.8-5.1 ranges.

    Wilkie I gotta admit – this one is really quite amazing!! Possibly one of the most amp-like pedals I’ve ever built up – well done.

    Consider this one fixed 😀 Thanks again, Billy!

    #12948
    wilkie1
    Moderator

    I just helped with the testing and documentation for the switching.  We discovered that there are different switch patterns for DPDT ON-ON-ON switches.  Once you figure that out, you will find that this is one of Barry’s BEST!

    #12950
    Billy
    Moderator

    Stop being so modest Ray you’re the man

    #12954
    wilkie1
    Moderator

    Rubbish!

    #13009
    Patrick Garland
    Participant

    Ok so here’s an update –

    I am getting awesome sounds with it, but I think my switch is still acting funky. Replaced with an On/On/On and I still have a problem.

    Now the only issue I have is the gain knobs are affecting eachother on any setting of the switch. Mainly my Gain B is cutting the entire pedal out on the Normal switch side when maxed out on the B knob. Perhaps I have the trimmers dialed in wrong? I checked voltages on the Trans and they were all good. Maybe I have a bad pot?

    Let me get some build photos + a video of the issue I am having.

    Thanks again for the help guys!!

    Pat

    #13010
    Patrick Garland
    Participant

    Tested switch and it is the correct type for the job as per the build document. I have it correct with the green jumper in the right connection spot.

    Here is the result of my testing early this morning:
    https://www.youtube.com/watch?v=SMWW-5DSuG0

    #13011
    Patrick Garland
    Participant

    Let me also get some build pictures/circuit board/wiring pictures. I could very possibly have an issue with my build.

    Thank you again for all your help guys!

    #13079
    Tom Sibren
    Participant

    Interesting issue. I’d also like to see the wiring.

    I really want to build one myself so I’m keeping an eye on this thread 🙂

    #13082
    wilkie1
    Moderator

    Take a look at the schematic and you will note that there is connection between the two GAIN pots through lug 1 as well as through the signal path.  So there is some normal interaction between the two.  However, when you turn the GAIN B pot fully clockwise and it cuts out the circuit, that sounds like a pot that is grounding out at max rotation.  I suggest you replace that pot and see if that solves the grounding issue.

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