Uglyface build report..... ? wha???

[aaronkessman]

Just built an uglyface and was wondering if everyone else's sounds as crazy as mine.

The frequency pot when turned up goes into crazy oscillations and the threshold only seems to work for the first 1/4 of its turn. the rest of the time it's just full on (the synth tone).

is this normal?

Aaron

[lightningfingers]

heh heh,

sounds about right to me, exept the part about the threshold pot, what value did you use?

this is one crazy stompbox though, and perfect for all those months of pop music my neighbors blasted through the walls at me :twisted:  :twisted:  :twisted:

[petemoore]

CRAZIE AINIT?//
 the threshold is about like that one mine.
 right at about 1/4 turn the threshold amount is close to input amout.
 when input amount is more that threshold it 'plays, threshold amout greater than input continuous oscillation of some wild type...that's when you tweek on the other two knobs.
 fine dialing the threshold knob just around under where threshold takes over is the 'sweet spot' of the knob....once you exceed threshold a certain amount [which a good amount of the pot's range] it's in oscillation mode, and adjustments there cannot be detected...er I think that is what it does, things so dang WILD !!!!!!!!!!!!!
 Vol pot on the guitar or compressor before can make it behave differently...as far as meeting threshold

[Tim Escobedo]

From your description, it sounds like it may be OK. The threshold pot sets the average voltage of pin 4 of the 7555. When it's above about 1.5V it should freely oscillate. However that level isn't very tightly spec'd so it may vary.

[aaronkessman]

that's messed up.



how does this thing work anyway? where is the fuzz coming from?

i asked because I noticed in the layout on runoffgroove there was no diode after the battery on the +voltage, so i left it out on mine as well. didn't know if that was affecting anything (why would it?). other than that i'm doing the same standard circuit plus the "freek" mod done by moosapotamous. this thing is crazy. its crazier than the tycobrahe octavia. by far.

[aaronkessman]

also, why only 100k for the volume pot. normally these things are at least 250 eh?

[Tim Escobedo]

The fuzz comes from triggering the 7555. The guitar signal is amplified so that it turns on the 7555 oscillator on the positive peaks. The output is actually taken from the oscillator, and is not really the guitar signal at all. The Frequency control makes for a kind of multiple pulse for half the guitar period. The number of pulses can be varied dynamically via the Sensitivity control. Sonically, this kinda sounds like a resonant filter, except without using a filter at all, keeping the waveform a raw rectangle.

I use 100k pots on almost every effect. Good enough for the Uglyface. On op amp circuits you could probably get away with smaller values. Stompbox circuits rarely need larger values for the output.

[Marcos - Munky]

Hey Tim, there's a way to use a common 555 in the place of the 7555? I can't get the 7555 here, only the 555.

[petemoore]

I'm not Tim, but my 555's did come from RS.

[Marcos - Munky]

Yeah, there are some places that you can find cool ICs in the local stores. Here I can't . But maybe with a little mod we can use a 555 in the place of the C.MOS 555.