Midilab Offers FREE JC-303 Bass Synth VST Plugin


Midilab released JC-303, a freeware bass synth VST plugin for Windows, Mac, and Linux.

Dust off your rave gear because Midilab released the JC-303 bass synth plugin, which you can pick up for your favorite DAW on any major OS.

The JC-303 bass synthesizer is designed to be an authentic clone of the Roland TB-303 Bass Line, a hardware bass synthesizer manufactured from 1981 to 1984.

The Roland TB-303 was intended to mimic the sound of a bass guitar, but it spectacularly failed at that and bombed commercially as a result. However, throughout the ‘80s and ‘90s, the synth became a staple of acid house and techno, and was featured on hits such as Daft Punk’s “Da Funk”.

The TB-303 has since become highly sought after on the second-hand market, with units selling for as much as £1,000.

However, you don’t need to worry about saving your pennies to get your hands on it, as the free JC-303 does a pretty damn good job at recreating the sound.

Midilab, an open-source DIY initiative, stated that the plugin is a “JUCE port of Robin Schmidt’s Open303 DSP engine, with a mission to make Open303 accessible across different platforms and plugin formats.”

The developers said that the project aims to deliver “faithful clone emulation of the TB-303 step sequencer” and that “We understand that the TB-303 isn’t just about its distinctive sound; it’s about the entire gear and the iconic sequencer that defines its unique character.”

True to the mission statement, the majority of the controls on the JC-303 are identical to the original Roland unit. The following controls are copied over – Volume, Tuning, Cut Off Freq, Resonance, Env Mod, Decay, and Accent.

The original TB-303 featured a Waveform switch on the back panel. Interestingly, Midilab has implemented this differently by providing a Waveform pot instead, which enables a broader range of tonal choices from this parameter.

The Roland TB-303 features a dedicated sequencer, which takes up half the control scheme. At this point, the Midilab JC-303 does not feature this and just provides the controls listed earlier in the article.

However, Midilab does plan to implement this, stating that they have a roadmap for implementing a “faithful step sequencer, capturing the essence of the original TB-303 experience.”

The Midilab JC-303 is available in VST3, LV2, and AU formats for Windows, MacOS, and Linux.

Download: JC-303 (FREE)


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Steve is a musician and journalist who hails from Melbourne, Australia. He learned everything he knows about production from Google and used that vast knowledge to create a series of records you definitely haven’t heard of.


      • No, of course not. But what is a free emulation good for if it does not sound like the hardware it wants to emulate…?

        “The JC-303 bass synthesizer is designed to be an authentic clone of the Roland TB-303 Bass Line […]”.

        The filter sounds completele different (I know most of the other emulations and also the real TB-303 and the TD-3).

        • The actual quote from the website is: “Additionally, the JC303 project aspires to deliver a faithful clone emulation of the TB-303 step sequencer”.

    • Unlike Audio Realism ABL 3 ($95) and d16 Phoscyon 2 ($119) the Midilab JC-303 costs $0. If you’re unsatisfied with it, why not just delete the synth from your VST folder and move along?

      Life’s too short to get hung up on whether or not a free plugin sounds as good as hundred dollar commercial software.

  1. I don’t know if it’s just me, but the decay knob doesn’t really do much (vst3 version). Apart from that, I had a blast tweaking around and running it through various distortion FX. Another user commented that it doesn’t sound like a 303. Having owned a real one and now a X0XB0X, I’ll say it does, but careful placement, length of notes and velocities in your sequencer is key to get it more authentic. (Hopefully the sequencer they are working on solves this) Accented full velocity notes sound particularly good and an overdrive/distortion/overdriven channel strip plugin gets it very gnarly.
    Great for a freebie!

  2. Could not use it on Mac M1. This is the message I get when the daw opens: “JC303.vst3” can’t be opened because Apple cannot check it for malicious software. This software needs to be updated. Contact the developer for more information.”

    • That is interesting, I thought Apple Mac platform was immune to viruses and malicious software ?

      I get the same message on Windows 10, but I just chose to ignore it, and plugs install fine.

    • A common Mac issue with anything freeware/opensource stuff from tiny devs who refuse to pay the fee to Apple to sign the binaries. The solution is to open a Terminal and:

      sudo xattr -rd com.apple.quarantine

      You’ll then be asked for your admin password. Should work. Should. What do I know, The only MacIntosh I ever had was a Spectre GCR emulator for the Atari ST… :D

  3. I never understood why the 303 sound is so hard to emulate. I tried it with many synths using different filters, but it never really works. For a while I even used it as a test for synths (and distortion plugins). Many failed (all if you’re remotely a purist). Even Icarus which lists two specific 303 filter emulations, or Synthmaster that has “Acid” mode on some filters sound nothing like it. The free Odin 2 synth came close, especially its distortion/saturation. ANA wasn’t bad either, I remember. Yet none really nailed it (not counting specialized synths like Phoscyon, of course). There is something truly magical about the filters used in the 303.

    • In my view, it’s not that it’s hard, it’s that for years nobody did the work. Or used bad knowledge.
      A long rumour was that the filter was 3-pole (18 dB/oct) but that’s a bad interpretation of the circuitry.
      Another ‘problem’ is that the square oscillator is in fact the sawtooth being transformed by magic (i forgot how exactly, so I’ll pretend it’s magic… ^_^).
      The glide/slide is another issue, because being a sequencer-based instrument the way it behaves cannot be accurately transposed into a pure MIDI instrument. That’s the best emulations (hard- or soft-ware) take care into reproducing the sequancer (sometimes to a fault, the insane way to enter the notes is optional…)
      The accent being another quirk, because it affects the VCA in a very particular manner.
      The TB-303 is a very bad, cheap design, and that’s why it’s harder than a clean analogue synth using quality components and good design. That’s both what makes it wonderful, but a pain to re-create.
      Imperfections, chaos, are indeed harder to simulate simple predictable things. This goes for everything, audio, 3D CGI, AI, etc…

      • Thanks for that great explanation. I also still believed it had an 18dB/oct filter, even though I usually got closest results simply using some 24dB filter. You’re making me curious about the transformed sawtooth now too. I do remember seeing wavetables with 303 waves that looked like malformed squares/saws, maybe analyzing clean original 303 samples is the best way to go at emulating first. It’s also good to realize that the inability to emulate the 303 is no real indication of a synth’s quality, as at some point I did believe.

  4. A faithful emulation? I don’t know, and I don’t care really. I don’t understand people arguing this is not like hardware 303, it doesn’t matter. It’s free after all, you’re not being ripped off or something. After spendindg some time with it, I can say it is good indeed for acid. WIth a proper sequence, distortion and then delay it sounds very credible and iconic.

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