"Noise Ensemble" - simple PT2399 abuse!

[anchovie]

Here's a fun little circuit that I put together this morning. After seeing so many attempts to make the PT2399 sound as clean as possible, I decided to use one with an extreme amount of fuzz and lo and behold the external parts count becomes much smaller when you have less filtering to worry about!

The chip's input stage is set up as a comparator with the aid of the Vref pin, so that gives us an ultra-amplified, squared-off waveform straight away. This squared signal is also used to modulate the delay time (controlled by a 22K pot - anything higher than this made the delayed signal fall apart when modulated). The chip's output stage used to mix the initial fuzz signal with the delayed/modulated version at a fixed 50/50 ratio.

I've called the delay control "Shambles" because as you turn the pot clockwise not only does the delay increase but also the amount of pitch wobble. At small settings, some interesting effects can be heard such as flanger-style sweeps on sustained chords and doubling. There are some obvious mods that can be done if you want this circuit to have more controls, such as adding a blend pot or ditching the 10nF cap and having your own tone control after the output stage.

Soundclips to follow, once I get the chance to record something - if you're itching to hear it, it doesn't take long to get it set up on a breadboard!


Schematic:


Layout (currently unverified):

[earthtonesaudio]

Eagerly awaiting clips.

[Taylor]

Ditto, I like this idea. There are a lot of interesting uses for the 2399.

[frequencycentral]

I'm hooked. I wanna hear it. NOW.

[Slade]

I'm hooked. I wanna hear it. NOW.

+1!!

[anchovie]

Recorded in a snatched moment (I was using one eye to make sure that a little girl didn't harass a guinea pig!):

http://www.youtube.com/watch?v=6tAS8-J2SX4

Minor "Shambles", leading into major.

[glops]

Love it! I have a mutation of the little angel chorus on a bboard right now that I have abusing with a Companion.  Gonna try this one out tonight.  Your circuit is exactly what I have been looking for.  Good work!

[Renegadrian]

Nice project! Thank you!!!

[frequencycentral]

That sounds great for NOISE, very much in Clari territory but a super-low parts count. From the short soundclip it sounded preferable to the Clari to me, more controlled and more closely tracked to what the guitar is doing. Very innovative. Very guerilla.

[Evad Nomenclature]

Damn.
That's crazypants.
nice.

[frequencycentral]

Here's a PCB layout. Unverified. Did it real quick so it will need checking by a pair of sharp eyes. The part numbers follow anchovie's stripboard part numbers. I added D1 for polarity protection and C7 for ripple stability. 1590A anyone?

[Labaris]

 

Great!! (My favorite word in english I think)

Innovation is what we need, and less mojo things

Congrats!!
And it seems you found here a fan of PT2399, he will surely help you a lot to improve the design

[nbabmf]

That is awesome.

[glops]

I breadboarded this tonight and I must say that it is AWESOME!  It is so thick and warbling.  I absolutely love it.  Thank you so much for such a great sounding simple circuit.  Perfect.

[linny1982]

got a few pt's layin around. gonna have to give this a go

[anchovie]

Thanks for the good reactions, folks! And extra thanks to Rick for jumping straight in with a PCB layout!

I'm really pleased with how this turned out, I had the idea while doing the washing-up after breakfast but wasn't sure exactly how it would sound. I'm very impressed with the distortion produced when the PT2399's opamp rails clip the signal, I reckon an experiment in the near future will involve trying to make it more dynamic rather than having the splatty fade-out that a comparator gives. Though for this circuit, splatty is perfect. 


On watching the clip again, I've noticed that the small person in the pink top who walks behind me was carrying my solder sucker. I guess that means it's buried somewhere in the garden now.

[earthtonesaudio]

Too bad solder suckers are usually plastic, or you could DIY a metal detector to help you find it.   

Very cool abuse of the PT2399.  One way to tame the comparator while keeping extreme amounts of fuzz is with some very minimal negative feedback.  For instance like the first op-amp section here, where most of the feedback is shunted to ground through the 1uF/100r path before it gets back to the inverting input.

[~arph]

Wow sounds great!  I'll have to give this a try soon.

[slacker]

Nice 

[RickL]

I've spotted a small problem with the pcb layout. C5 is shown connected to pin 15 of the PT2399. It should go to pin 14. Everything else seems okay.

Rick