hook up enclosure to audio to add 'noise'

[darron]

i'm making a new crappy sound degrading pedal to sound like a small radio or overdriven 0.25w speaker. one thing i was thinking about adding was noise to the signal. with insulated jacks, i was thinking of having the enclosure switch from ground in bypass, to the signal in 'on' mode. this would pick up all of the nearby noise. on my breadboard, i hooked up he bottom plate and it added quite a lot of noise. maybe too much. of course, if you touched the plate with your hands it sounded horrible, like touching the tip of the jack.

another option might just be to disconnect the enclosure from ground when not in bypass so that there would not be anywhere near as much interference.

has anybody played with this sort of idea before?

darron

[chi_boy]

Can't say I have experience, but I'm currently obsesing over a similar project.  Parts are on the way now.

Take a look at this:



You may be able to adapt the noise generating part to your project.  If you do, be sure to post some clips.

[caress]

google search for a simple white noise generator.  use a mix knob to mix in the amount.
use a narrow band pass filter around 1-2khz? for the tinny sound. 
i would add a wee bit of clipping to it... just a bit of grit!

[darron]

ahh. but you see i want the whole thing to be passive. i've built something like this before and they are cool.

from the input, asymmetrically clip only one side of the wave with a schottky diode, then pass it all through a small value ceramic capacitor for high pass, then optinal volume control, then on the other side of the high pass clip it again on the SAME side of the wave with another schottky. sounds really splattered like someone's blown up your amps speaker. literally.... i thought it might be cool to use passive interference noise. your blending idea might be a better idea also. it would sound horrible if someone trying playing it while touching the case though, wouldn't it?

[darron]

what about trailing an arial of insulated wire out of the enclosure and adding a blend pot? (:

[Processaurus]

another option might just be to disconnect the enclosure from ground when not in bypass so that there would not be anywhere near as much interference.

it might not be noisy enough if there are any electronics upstream, as the impedance will be fairly low.  Just like you can get away with using an unshielded speaker cable to run to your amp from a buffered pedal if you aren't ultra picky.

I like your idea, though I wonder if most of the noise will be 60 cycle hum?

[darron]

another option might just be to disconnect the enclosure from ground when not in bypass so that there would not be anywhere near as much interference.

it might not be noisy enough if there are any electronics upstream, as the impedance will be fairly low.  Just like you can get away with using an unshielded speaker cable to run to your amp from a buffered pedal if you aren't ultra picky.

I like your idea, though I wonder if most of the noise will be 60 cycle hum?

i think that you would be right on both accounts. the noise was just about all 50Hz hum and didn't sound very good. maybe it needs to be processed to just get radio noise i'll have a play with some capacitors to at least get out the frequencies below 100hz or so. could be interesting

[birt]

this is an idea i have tested quite a lot in the past. you might find some posts about it.

first i used a switch that connected a ridiculously long wire inside the enclosure from to the signal path. it works but is not great. then i switched the enclosure from ground to signal path to go from shielded circuit to antenna. this works a bit better already. i got the best results using the noise generator from R.G.'s lofi pedal. the metal case of the noise source transisto is connected to the enclosure. a DPDT was used to connect the noise generator to the signal path and to disconnect the enclosure/transistor from ground so it became an antenna.

i wish i could make very theoretical postst like others here but i'm pretty proud that i figured all of this out by myself

[darron]

this is an idea i have tested quite a lot in the past. you might find some posts about it.

first i used a switch that connected a ridiculously long wire inside the enclosure from to the signal path. it works but is not great. then i switched the enclosure from ground to signal path to go from shielded circuit to antenna. this works a bit better already. i got the best results using the noise generator from R.G.'s lofi pedal. the metal case of the noise source transisto is connected to the enclosure. a DPDT was used to connect the noise generator to the signal path and to disconnect the enclosure/transistor from ground so it became an antenna.

i wish i could make very theoretical postst like others here but i'm pretty proud that i figured all of this out by myself

hey birt! from what i found on breadboard using the metal plate it didn't really work out. filtering with caps didn't really work either (dah.. in retrospect). i don't want to move to something active. R.G.'s noise generator certainly does seem like it's the go though. the next theoretical build would be a tiny/cheap speaker and cheap mic in a box

[birt]

that's another part of my pedal :p
a telephone mic and speaker taped together.

[darron]

alright guys... we're going to start needing sound samples to take this discussion any further (: hehe

link here

edit: neodymium pickups in epi SG going onto breadboard into a small 15watt laney amp. picked up on MBS's internal mic. i also stepped on some bubble wrap, that wasn't cool 'noise'. no clipping from the recording, only the passive circuit.