triggered gate

[gammamu]

i searched and couldn't find anything quite like what i need.  what i want is a white noise generator which is gated by a drum trigger.  ever time i hit the drum trigger, white noise is passed out of the circuit.  Preferably, i would also like to be able to use this with low freq. ticks, as well.

here's what i have, which is sort of spliced circuits.



The bottom section is just the power supply/voltage divider.

The 555 section is a monostable ciruit.  Input spike generates an output spike (square wave on).  The duration of the output spike is determined by R3.

The 2N2222 section is the white noise generator.  The positive input voltage is 9V, instead of the 19V listed in the schematic.  [bad scan of an erase mark]

The 741 should be an Op Amp used as a comparator.  This is the part I'm really unsure of.  Will the square wave spike from the 555 circuit just open the gate or will it vary the wave form of the white noise?  Should i use it inverting (like i think it is in the schematic) or non-inverting instead?  Should i switch to a differant Op Amp for white (and later pink) noise, or is the 741 fine?

Thanks in advance for the help!

[gez]

The 2N2222 section is the white noise generator

As wired it’s just a common emitter circuit.  Is it supposed to be a negistor (spelling)?  If so, I can’t help you there 'cause I’ve never messed around with them, but if it is you want some sort of switching to mute the signal coming from it when not triggered (if I‘ve understood you correctly that is).

As shown, the opamp isn’t going to work (unless I've missed the point of what you're trying to do).  There’s no DC bias to the -ve input.  Even if there were (if you got rid of the output cap from the 2n2222), the output of the op-amp would just go high every time the 555 is triggered.

Simple switch (4016) at the output of generator leading to an op-amp buffer might do the trick.  

Normal apologies apply if I’ve got the wrong end of the stick…

[gammamu]

thanks for that.  i posted the schematic at school before i could breadboard everything.  right now i've just done the 555 and the 2222 sections.  the  555 section works right, but the 2222 is worthless.

i had no idea the 4016 existed, but i'll get right on it for this!!  thanks for that!

[gez]

the  555 section works right, but the 2222 is worthless.

i had no idea the 4016 existed, but i'll get right on it for this!!  thanks for that!

There should be some stuff in the archives about negistors (perhaps someone could post a link).  Can't remember how they're wired up, but I'm sure somebody here will put you on the right track.

Check out Andrew (Tone God) and RG's articles on switching to get some hints on how to use the 4016/4066/4053.

[puretube]

the transistor noise generator schems I`ve seen, look different...

[sean k]

http://www.tricountyi.net/~randerse/noisegen.htm
here you'll find a simple transistor wired in avalanche mode to create white noise

[Nasse]

http://www.paia.com/syndrum.htm

There is some drum talk and a schem too, with noise generator for snare

But not much talk about how the hell the noise is gated... maybe the opamp is just pushed to v+ or ground so no AC can pass... but just quessing, in the text says those circuits do more than one thing at the time...

I have one simple gate schem somewhere in my pile of documents, with just 741 and few components controlling a fet used as voltage controlled resistor, and some drum circuits using MC3340 voltage controlled attenuator. SImplest I could imagine mighth be diode switch...

Maybe I can post these tomorrow or some day later

[gammamu]

thanks again everyone.  i'm about to start breadboarding the noise generator now.  when i'm done i'll analyse the drum synth circuit.

[gammamu]

http://www.tricountyi.net/~randerse/noisegen.htm
here you'll find a simple transistor wired in avalanche mode to create white noise

i made this circuit, but i get no output.  i  am running it through a simple 386 amplifier and a 2" 8ohm speaker.

[puretube]

be sure to run it on 12V;
those kind of noise-gen. are reported to refuse to "avalanche" at 9v.

[gammamu]

serves me right.  was running the 386 off of 9V and missed the 12V on the noise gen. schematic.  thanks!


you have all been a HUGE help and i cannot understate my gratitude!!!