Description
The NOISE 1B is a simple digital noise source that produces pure white noise over the whole audio band – out to more than 40Khz, in fact. With filtering, you can derive pink noise and other colours. It only requires a +5V supply to operate. The chip was arranged to be as close a replacement as possible notorious MM5837 digital noise generator which appears in early Korg MonoPolys, the Sequential Prophet 5, and the Oberheim OB-X, amongst others. It can be used to upgrade the noise source in these synths.
Download the Electric Druid Noise Generator Datasheet
The datasheet includes the pinout diagram and application notes, including using the chip to replace the MN5837 in both Rev.2 and Rev.3 Prophet 5’s, early Korg MonoPolys, and the Oberheim OB-X.
You can compare the features of various Electric Druid noise chips on the “Which noise chip do I need?” page.
Unlabelled chips
Please note that due to the problems with microprocessor supplies, we’re currently sending out NOISE 1B chips that are unlabelled. This is because these have been programmed in-house, rather than by Microchip. We’ll get more labelled chips as soon as we can.
Ben (verified owner) –
I built the circuit in the data sheet. I didn’t have the 2u2 cap for the infra part of the circuit so I wired together a couple of 10u smd electrolytic caps in series to get a non-polarized 5u cap and put it in there instead. The result was barely audible as audio but turned out to be a very nice bipolar smooth random source in the fast LFO range (put it through a slew limiter for a slower random source). I guess the 5u cap is cutting more high frequencies than the 2u2 would but it did make me wonder if mostly sub-audio noise is what I would have gotten from the ‘infra-red’ noise output even with the 2u2 cap.
Ben (verified owner) –
Just found the details of the Polyfusion module in the second PDF at the top of this thread
https://modwiggler.com/forum/viewtopic.php?t=133608
I was confused by the term ‘infra-red’ noise because it seems that Polyfusion are the only manufacturers that used it, but it is intended as random CV (not audio) source. It is a really interesting implementation because of the fact that you are deriving lower frequency CV from an audio source through filtering. If you plug one or both of the other noise sources into a low-pass filter and the use the infra-red noise to modulate cutoff and/or resonance you get modulation that is related to audible noise because it is derived from the same source. The relationship between modulation source and audio becomes more pronounced when you lower the cutoff frequency on the LP filter. Great for synthesizing wind sounds. Makes me think more about deriving CV from noisy audio through filtering.