ISD1820 Audio processing thingy

DIY STUFF
1

TLDR: ISD1820, great sounds out of it, cheap and easy.

ISD1820 thingy
ISD1820 thingy1144Ă—668 66.8 KB

First of all, the chip is used in feedthrough mode and therefore we are not using its looping abilities at all. Secondly, there is no pitch CV input (from OMSynth project 3) as I build this to be used as a guitar/synth pedal. Finally, all this stuff deserves a personal page, this is a special discovery.

Here is the list it can do with different input signal levels:

  • No input: Bandpassed noise
  • Low input: Chip will amplify signal, applies sampler colour, filter not yet working
  • Medium input: Filtering starts working, occasional crap sounds
  • Hot input: Velcro fuzz, rhytmic crap, most useful stuff
  • Precise hot input: Subharmonics :scream: can be created by adjusting the cutoff knob. Black magic happens.
  • Very hot input: Aggressive digital clipping

I will try to make some sounds demos soon.

Some background on this idea:

7 Likes
2

Woah, weird. I built a module out of the Lonershy looping design, had no idea this was possible. Would love hear it.

1 Like
3

Subharmonic demo :DDD

4 Likes
4

And here it is again, this time with some shimmery REVERB :DDDDD

7 Likes
5

The “audio processing thingy” just got better! I checked the datasheets and juiced up this little chip.

ISD1820 Filteroid
ISD1820 Filteroid854Ă—727 74.5 KB

About the new switches:

  • The AGC is either connected correctly or to output. When connected to output the gain increases a lot in a strange way.
  • Differential switch connects input reference to speaker - and gives some bubbly resonance. Also changes AGC behaviour.
  • Digital ground when connected to analog ground makes the chip more stable.

Even more juicy ideas:

  • A resonance pot from output to input. 50k seems okay.
  • Differential switch with a potentiometer to adjust the sound.
  • The AGC pin could be connected to pot that goes from 0V to 5V as that determines the gain of the chip according to 1800 family datasheet.
4 Likes
6

I add this ISD1820 related post :wink:

3 Likes