Home GuitarPCB Forum GuitarPCB Build Support Sunn T V3 Fizzy Decay (Solved)

Viewing 11 posts - 1 through 11 (of 11 total)
  • Author
  • #32742

    Hello all,

    I just completed a build of the Sunn T V3 and I’m noticing a lot of fizz on the note decay regardless of setting. Is this something anyone else has experienced? I have everything everything biased to 4.5 and tried several j201s with the same result.

    If this is not what’s expected, I’ll post some pics of the PCB/build after.

    Also, this is a was kit purchased from pedal, parts & kits (link)


    The term “fizzy” is too subjective and used in various contexts, making it difficult for me to provide a useful suggestion based solely on that.


    I have a very clear video of me playing the circuit to help you decide.

    If you are not getting a similar sound then either post a video showing off your specific issue or provide clear photos showing the color bands of all resistors.

    Also please note any substitutions.


    I can’t record today, but will try tomorrow. I did not make any substitutions and followed the build doc Attached are a couple pics of the pcb. I’d also like not note that the treble pot was properly soldered after this pic was taken.


    I would also like to know if you are hearing something different in your build than what you heard in my posted video.

    I checked all of the resistor values which are fine.

    I am assuming that the yellow capacitors are all ceramic, and none of them are tantalum.

    Since I cannot verify capacitor values I would double check all of them as they are important to remove high end noise.

    Also I notice the power wire laying directly on a JFET which could cause amplified electrical noise. Route it away from anything in the audio path. I would also suggest to make sure all JFETs are firmly seated in the sockets.

    You could also try a different JFET such as J113 which would be the same orientation. You would have to re-bias.


    I would say it generally sounds the same as the video you posted, but I have a sizzle/fizz on the decay on. I tried recording some audio but it doesn’t appear to be coming through on the recording.

    I’ll check the caps and will follow up once complete and will also try the j113


    Alright checked the labels on the small caps and here us how they’re labeled

    C1 = 221

    C2 = 471

    C3 =220uf

    C4 = 223j100

    C5 = 223j100

    C6 = 221

    C7 = 220uf

    C8 = 22uf

    C9 = 271

    C10 = 223J100

    C11 = 223J100

    C12 = 271

    C13 = 100uf


    Will follow up once I try different jfets


    And here is a sound file.  You can hear the fizz closer to around 10 seconds



    The audio file is very helpful.

    That is absolutely not normal at all, does not sound like a JFET issue, or even a circuit issue, except for the possibility of something clipping.

    The first thing I would make sure of is that I use only (2) 100% known good cables, the Sunn-T, (1) known good power supply, Guitar, Amp, and absolutely nothing else in between. No multi power adapters. Just a single good 9v power supply hooked up to a single pedal.

    Make sure that your red power wire is nowhere near your circuit board, particularly the JFETs.

    Since this is a multi stage JFET circuit it could easily be taking line noise and amplifying it multiple times to be audible.

    If after doing all of that and nothing improves I would look into the possibility of something clipping. Then you can try switching out the JFETs to another type and re-bias.

    Another thought could be to check your In and Out jacks as well as making sure the off-board wiring is solid. A re-flow may be in order for everything. In that case be patient. It only takes about 5 minutes to touch and reheat the solder joints over the entire project. Take care in that you do not burn any components or wires.


    Ty for taking a look and providing guidance!  I’ll give everything a reflow and will follow up once complete


    Hello Barry

    Wanted to follow up and say a was able to resolve issue.  Looks like it was a tube issue with my amp. I went back and compared the pedal to my friends model FET that did not have the same issue. Once I plugged it in to compare, the fizz was there too!

    I just finished swapping and doing some biasing and the fizz is gone!

    I appreciate your help and guidance through this wild goose chase




    I agree that it did not sound like circuit noise to me.

    Glad you sorted it out. Don’t forget to post a show off thread.

Viewing 11 posts - 1 through 11 (of 11 total)
  • You must be logged in to reply to this topic.