GGG Shin-Ei FY-2 Clone: leave off the filter at the end?

[juncomatt]

Hi.

I just built the Shin-ei FY-2 clone from General Guitar Gadgets and it sounds INSANE, really screwed up pedal. I want to tweak it a bit and I've read that "leaving off the filter at the end" makes it sound better. Does anyone know what this means or how I can do this mod? I'm very curious. Thanks!

-Matt

[RickL]

The filter is R5, R6, C6 and C7. To leave them out connect R8 directly to R7. This can be done by using a jumper in place of C6 and leaving R5, R6 and C7 off the board.

[Mark Hammer]

Those four components between the fuzz and volume pots provide a passive mid-scoop.  That mid-scoop, in turn, bleeds a fair amount of mid-range signal to ground in order to produce that apparent huge bottom and sizzling top.  Rick is absolutely correct in what he suggests, but if you simply insert a 10k to 25k pot between the .1uf cap and ground you can variably cancel the mid-scoop to get more variation in tone.  Since you are bleeding less signal to ground the output volume is increased noticeably.  This schem ( http://hammer.ampage.org/files/modded_fy-2.gif ) shows how.  The schem indicates a 50k pot, because that's what I first installed.  In reality, just about everything after the first 12-15k provides negligible difference, so 10k should probably make most people happy.  You can hear the difference here: http://hammer.ampage.org/files/FY-2.mp3  The "unscooped" FY-2 is a more aggressive and throatier sounding circuit.  Some may even prefer it.

[tcobretti]

If memory serves, my Shinei version of the Superfuzz has that same filter, but it is switchable.  I much prefer it without the scoop, but I am not a fan of the scooped guitar tone in any capacity.

I would certainly recommend trying it out without the scoop, whether you use a switch or a pot.

[juncomatt]

Thanks all! This helps me a lot.

Mark, to insert the pot between the .1uf cap and the ground, will I just ground it against the ac jack? Sorry, I'm not that technically proficient (trying though) and the schematic kinda confuses me. Still learning all this stuff. Thanks again!

[tcobretti]

You ground it to ground, so anywhere on the circuit where there is a ground you can solder it there.  Ground is marked on the schem as the downward pointing triangle, so the emitter of the transistors and the grounds on the input and output jacks should all connect to the same place, which is probly the sleeve of your ac jack.

[Mark Hammer]

Though all you need are two of the 3 lugs on the pot, best practice recommends using all 3.  So, one outside lug goes to the .1uf cap, and the other goes to ground.  The wiper gets connected to either one of the outside lugs in this case, depending on whether you want the control to introduce more mids...or more scoop...as you go clockwise.  If the intent is to introduce more mids/meat as you go clockwise, then resistance should increase as you go clockwise.

Why is use of all 3 lugs a good practice?  Simple.  The wiper is a movable contact.  In the land of electrons, even ridiculously tiny gaps in contact between the resistive strip and wiper are like the Grand Canyon.  If the two outside lugs are always connected, then the jump in resistance, should there be any momentary discontinuity with the wiper, will never be any higher than the value of the pot.  If all you use are two of the 3 lugs, then tiny discontinuities in contact can go up to infinite resistance (open circuit).  That will show up as objectionable noise.

Like all "best practices", it is not something that is absolutely necessary or applies in every single instance.  It's just insurance against worst case scenarios.  If, like me, you have a bunch of pots hanging around where one of the outside lugs has fractured and broken off, 2-lug installations are a nice way to make productive use of them.  You won't get the added insurance against noise, but then if you don't abuse the pot, or intend to twiddle it on stage while the effect is on, it shouldn't matter.