Making acid | 303 techniques

the little silver box is one of the few electronic music devices that not only inspired whole music genres but whose quirks and idiosyncrasies are essential to the sound.

let’s talk about all things 303 and 303 inspired - techniques for making the sound, favourite clones (hardware and software), mods, sequencers to use (anybody making acid with kria or teletype?), complimentary effects etc etc. and check out this thread for inspiration!


There will always be a place in my heart for that sound. I recently got another x0xb0x and been creating really slow sequences while laying in bed before I go to sleep. It has some groovy purple squiggles on it and a “perv” button (not sure if that was a typo or intentional.)

Also sounds amazing with Lyra 8 FX delay and distortion!


if anyone finds any schematics or details to the sound-generating specs out there, would love some links(been trying to translate to max patch for the past year but only found loose descriptions so far).


have you seen this from robin whittle?
also this:

my understanding is that a lot of the sound character is due to how various components interact, which is what makes it more difficult to replicate properly (and that’s not taking the sequencer quirks into account which is what i’m obsessed with currently).


ah cool, ya that’s some helpful info. thank you so much(only other things i’ve found are that the mono-oscillator is a sawtooth which can turn to square and is fed through 24dB 4-pole lo pass) these envelope descriptions make a huge difference, that cumulative accentuation on the filter envelope is especially nice :+1:

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the actual waveforms apparently are not typical square/saw:

i think there was also some debate whether it’s 18dB or 24 but according to roland it is 24:


Huge acid fan here… :slight_smile:

Tim Stinchcombe also has some incredibly cool info on Diode Ladder Filters (VCS3/303 etc.) here:

Lots of info on the 18 vs 24 dB per octave debate too.

All his synth pages are worth a read, really nice guy too. Great doc on Moog Ladder Filters and their derivatives, for example:


When I used to patch 303 style things up on my modular, I’d make sure I had enough multiples and attenuators to mult the Accent from the Mobius sequencer to multiple destinations at once, to get things sounding really wobbly, organic and swinging, VCA, VCF, Res, Decay time etc.

I still kinda have a lust for the sound here, I’ve never owned a real 303, can anyone recommend one that isn’t made by B and isn’t crazy expensive, but nails the sound and feel at least 90%?

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speaking of sequencer quirks, this excellent paper by julian schmidt from sonic potions is a good source of info:

here is my summary:

  • slide signal latches the pitch and accent values, so there needs to be a short pulse even on notes that don’t have slides. if slide is set and spans multiple notes, it gets pulled down to allow pitch and accent to be latched.

  • slide signal lasts the whole step duration and is high during a tie and the following rest steps even if slide is not applied.

  • accent is synchronized to the whole step duration.

  • the gate is not turned off if the next note has slide (and also is set high before slide step?)

  • gate duty cycle is 3 clocks on and 3 clocks off in 4/4 mode (4/4 at 24ppq is 6 pulses per step) but the actual duty cycles vary between ~50-56%

  • gate duty cycle is asymmetrical in 3/3 mode: 5 clocks on, 3 clocks of.

  • there is a varying latency between the clock and the gate signal: mean valud of 2.06ms for the rising edge and 3.51ms for the falling edge. this latency accounts for a slight beating in the note accentuation, especially with higher speeds and slightly different note lengths.

these obviously don’t matter for various midi controlled clones but do matter for something like x0x heart or acidlab 303 which are replicas of the original. in my experiments i did get sound that was closer to the original when replicating some of these quirks with teletype. are there any hardware sequencers that also implement some of these?



for me this is one of the most interesting things about it, you could have the same sequence sound very differently based on accent / env mod / decay / filter parameters, different notes getting accentuated. sometimes it’s almost like it’s an interplay of 2 voices with notes slowly fading in and out, sound texture being equally or more important than the actual note sequence. alessandro cortini’s risveglio album particularly comes to mind.

having a compressor helps, i’m using hexinverter batteryACID module - very handy as you get both distortion and compression.


Yes to this thread!

TB 303 owner here. Definitely more of a square wave guy. I have also always enjoyed the emulation by Anton Savov - . Windows 32 FTW!


Maybe I should send you my x0xheart to play with (for science!) :grin:

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yeah x0x heart is what i’ve got, i’ve been using this system:


but tempted now to expand it, it really needs a delay, another filter and some modulation.


haven’t found the time to put the code online yet but i used “Analysis of the µPD650C-133 CPU timing” for this sequencer and it turned out fun and very playable. editor runs on norns but can also upload the pattern to crow for standalone playback.


Haven’t used one myself but also worth a look:


those waveforms will help perfect :ok_hand:
ya the square never sounded quite like a square to me, seeing the actual waveforms will help(think i might start from trying to get those as close as possible)… thanks again :beers:

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very cool! are you using crow for CV outs?

yeah i added crow support later. in the video its midi to malekko sync w/ cv/gate expander


how do you handle slides? overlapping midi notes?