Wow, I think you are right, it is a cap!!! That is mad. This is a Fuzz War, 3 knob version, from early 2017. Not sure if they are all supposed to be like this, but that cap is very surprising to me.
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Show posts MenuQuote from: Scruffie on September 30, 2018, 08:49:39 AMPin 4 is connected to ground via the Delay pot.
What happens when you ground pin 4? That's always a fun surprise when some of the PT2399 like it grounded and some don't.
Quote from: reddesert on September 16, 2018, 06:05:50 PMQuote from: garfo on September 16, 2018, 03:00:32 AMQuote from: reddesert on September 09, 2018, 11:23:46 PMTo try to make it clear.
It's possible that you set the volume trimmer based on the guitar into the delay, and then when you put another pedal in front you get the volume back, so it seems like a boost. If this is the case (and I'm not sure from the information provided), then a high-impedance buffer at the input might help, but you have to be sure that it's a really high impedance.
I plug a Standard strat straight into the Sea Urchin and I have unity gain when the pedal is engaged. Now, I have a Fulltone Soulbender Clone that I have been playing and also a Fuzzface Clone. With both of them I set the volume pot to match my clean signal in terms of volume. The problem is that, when I have any of the fuzzes engaged and turn on the Delay pedal there is a huge volume boost. Could this be a mismatch of the output impedance of both fuzzes (500k) and the Sea Urchin input impedance(180k)? Also, isn't R1 (1M) setting the input impedance?
R1, the pull-down resistor, doesn't set the input impedance (I guess it's an upper limit to the input impedance). For an inverting op-amp, the + input is held fixed at the reference voltage, which means that the - input is also fixed at the reference voltage of +4.5 V, because op-amps try to equalize their inputs. That means your input is connected by a 180K resistor to the fixed +4.5 V. So the input impedance is 180K. The link I posted above to radio-electronics.com has a pretty good explanation of this and how it differs for a non-inverting op-amp.
The output impedance of a pedal like a Soul Bender or Fuzz Face that has a volume pot on its output is a little complicated, because it depends on where in the pot's rotation you have it set. The 180K input impedance winds up being in parallel with the lower leg of the volume pot, that is it's in parallel with pins 1 and 2 of the volume pot. (There is probably a coupling cap between the volume pot and the Sea Urchin input, but for AC audio the cap passes signal.) This can make the volume drop when you switch the second pedal on, which is not what you are reporting.
What's a little out of the ordinary is that you put in a trimmer to adjust the output level. I am wondering, of course I don't know, if the Sea Urchin's natural state with just a guitar plugged in is to drop the volume, you adjusted the trimmer to take that out, and now when you put the fuzz pedal between the guitar and delay, it's boosting.