uglyface and its workings...

[vdm]

hey everyone,

in the spirit of the recent 'how does it work' posts - im mid-way through building an uglyface... (couldnt find a 386 at my local store, and still have to buy the pots and make the led/ldr section).... and i was wondering exactly how it works and what the controls do.

i heard the clips and read lots of praise for the thing - im not usually one to believe what everyone says, but people around here generally have similar oppinions about tone as i do (despite it being a bit of a tone-destroyer....).

i am mainly interested in what the sensitivity control does... im guessing it takes the output which is passed to next stage but also drives the led. so as such the led is brighter when the attack occurs and more dull as the decay occurs. so when this alters the ldr - does it cause the sound to have a distinct envelope filter sound to it like a wah - or does it change a different aspect of the sound.

also is the gain set at maximum all the time, or does the threshold alter the amount of distortion.

if anyone has a very general explanation of the circuit that tells a little bit more than on the uglyface schematic from tim's site.

thanks guys

trent

[strungout]

Oy.

I'd like to know too

I recently built one and I found it pretty cool. The frequency pot would be great as an expression pedal. I wired a 1M pot instead of the LDR, which I can't seem to find around here... (and because I still haven't figured out why my led doesn't light up with the signal...)

Ciao.

[Dan N]

The LDR controls the frequency. Set the Freq knob to low and use the sense knob like on any envelope follower. You can get subtle changes, or you can punch the low through the roof to a hissing scare the cat high. Rate it Daffy on the quack factor scale.

The first half of the threshold rotation is pretty much a decay control (to a lovely sputter). Halfway you can dial in exceptionally awful noise. After that it self oscillates.

When self oscillating you can make spaceship bomb dropping noises as the envelope drops back to the set freq.

If you listened to the samples you know the fuzz is a really synthy processed type. No facial expression will make the fuzz sound anything like SRV.

Hard to furl my brow and think about "tone" plugged into the uglyface. Having too much fun anyway...

Good luck!

[Tim Escobedo]

The sensitivity pot is kind of a volume control for the LED in the vactrol. That the pot is 1k seems to provide about about the right amount of load on the 386 to provide enough brightness for the average input. Basically, it's the envelope control.

I like to describe the Uglyface as a really primitive guitar synthesizer. The guitar signal triggers a rectangle wave oscillator. The triggering happens at the frequency of the guitar signal, with a overtone (or undertone) set by the oscillator's frequency. Which can be modulated by the input signal's envelope, kinda emulating the function of a resonant VCF without any filter at all. No volume envelope control is provided at all, however (thus "primitive").

[primalphunk]

The sensitivity pot is kind of a volume control for the LED in the vactrol. That the pot is 1k seems to provide about about the right amount of load on the 386 to provide enough brightness for the average input. Basically, it's the envelope control.

I like to describe the Uglyface as a really primitive guitar synthesizer. The guitar signal triggers a rectangle wave oscillator.

[snip]
The sample at the circuit snippets site and your comments that you actually think of it as a primitive guitar synth have gotten me hyped enough.  I'm building one just as soon as I finish up my neutron filter and a couple of power supplies.  Oh yeah...I'm also gonna have to work a little harder to figure out what parts to use for your project so I can get them ordered from Small Bear and Mouser.  I expect it will be well worth the effort, however.

[petemoore]

Wild and wacky...I built one from stuff I had around, the LDR was a 'regular' bench find.

[primalphunk]

Oh yeah...I'm also gonna have to work a little harder to figure out what parts to use for your project so I can get them ordered from Small Bear and Mouser. I expect it will be well worth the effort, however.

I'll have to work much harder because when it comes to LDRs I'm ridiculously stupid.  I got two old H11f3's that are getting yanked from the neutron.  I bet I can't use those on a uglyface...heck...what do I know?

Guess I need to get back to Mark Hammer's envelope filter pdf so I can learn a little more.

[Eric H]

No facial expression will make the fuzz sound anything like SRV.

Now, that was funny.

-Eric

[snorky]

Are you guys using linear or log pots for the UglyFace?  I was going to use log for the volume and linear for the rest??

TIA,

- Mark

[Noplasticrobots]

I've got mine on the breadboard right now and I'm using the same pot configuration as you snorky with no problems.

[$uperpuma]

Are you guys using linear or log pots for the UglyFace?  I was going to use log for the volume and linear for the rest??

TIA,

- Mark

Per Dan N's suggestion, I used an audio taper for the volume and linear for the rest.... works great.