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noise color control
MUFF WIGGLER Forum Index -> Music Tech DIY  
Author noise color control
Dimitree
I'd like to add to my minimoog clone a control to filter the white noise before it hits the mixer.
I don't need CV for that, a simple potentiometer is fine. But please, I'd like to use a single gang potentiometer, not a dual gang.
this function is present on the ARP2600 and it's called noise color.
This is how is done on the ARP2600, but I don't understand it fully, so I don't know how to do that on the minimoog.
Any hint?



and this is the schematic for minimoog noise where I'd like to add that control
TheSlowGrowth
The noise colour potentiometer crossfades between the original noise signal and a filtered version of the noise that is generated by A35. You can simply copy the circuit around A35 and insert it into your synth.

On second thought: Do you want to crossfade between the white/pink/red noise that is present in your schematic?
For a crossfade between two signals, make sure you have a low impedance source signal for both (e.g. by a simple unity gain oipamp buffer). Connect the signals to each end of a potentiometer (value is not critical) and voila: you have the crosfaded version on the wiper of the pot. Ideally you would add another opamp buffer that buffers the voltage on the whiper before you send it to the mixer.
For crossfading between three signals: That's not so easy. You might want to make one side of your crossfader switchable between red/pink so you can use a simple two-way crossfader.
Dimitree
many thanks for the reply!
if ARP2600 is crossfading between 2 signals, then I'm fine with 2 and not 3 nanners

I can see that one side of the crossfader is white noise on the 2600, but what is the other side?

so do you think I should crossfade between white and red, since pink is in between so you can get that taste while crossfading, right?

about the opamp follower, you mean a simple buffer with no resistors, like this?
https://upload.wikimedia.org/wikipedia/commons/thumb/f/f7/Op-Amp_Unity -Gain_Buffer.svg/1280px-Op-Amp_Unity-Gain_Buffer.svg.png
Dimitree
also,
I'm wondering if it would be more usefull to crossfade between 2 noise colors, or to just filter the white noise with a 6db/oct LPF that I can simply get using a single gang potentiometer + capacitor..
Silver
I'm not sure what your goal is really, but when I was looking for an adjustable colored noise, the most interesting thing I found, was using the Big Muff tone circuit so that a single pot could filter the noise from pink-ish (low pass) to grey (band pass) to blue-ish (high pass).

This is a great description of the circuit.
http://www.electrosmash.com/big-muff-pi-analysis
Dimitree
thank you, that's a great suggestion!
I will use both methods and decide which one I like the most!
LektroiD
I've been looking to build a variable noise generator circuit that goes from white through pink to brownian noise. I'm not bothered about cloning any particular manufacturer, but I'll certainly be following this thread...
KSS
Dimitree wrote:
many thanks for the reply!
if ARP2600 is crossfading between 2 signals, then I'm fine with 2 and not 3

A center-tapped pot could fade from Wh-Pk, then Pk-Rd (L.F.).
Dimitree wrote:

I can see that one side of the crossfader is white noise on the 2600, but what is the other side?

It's labeled on the schematic. L.F. Noise
Dimitree wrote:

so do you think I should crossfade between white and red, since pink is in between so you can get that taste while crossfading, right?

Yes. Connect the pot between White and Red to emulate the ARP style. Or use all three with a center-tapped pot.
KSS
Dimitree wrote:
many thanks for the reply!
if ARP2600 is crossfading between 2 signals, then I'm fine with 2 and not 3

A center-tapped pot could fade from Wh-Pk, then Pk-Rd (L.F.).
Dimitree wrote:

I can see that one side of the crossfader is white noise on the 2600, but what is the other side?

It's labeled on the schematic. L.F. Noise
Dimitree wrote:

so do you think I should crossfade between white and red, since pink is in between so you can get that taste while crossfading, right?

Yes. Connect the pot between White and Red to emulate the ARP style. Or use all three with a center-tapped pot.
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