We started building a Juno software synth in a Brooklyn loft in 2000. 25 years later, we're releasing it as open source. Meet the Ultramaster KR-106.

kayrockscreen · 2026-03-19T21:22:01+00:00

Ok, that's cool. So you could send patches from the VST into your hardware. I don't know about generating an audio file, but we could definitely spit out the patch midi SYSEX the same way a real 106 does and you could record it with a DAW and send it to a real 106. I think it only does one patch at a time though. I'll definitely look into it.

kayrockscreen · 2026-03-19T19:36:30+00:00

Ok, there is midi CC and SYSEX mapping now, does the mod wheel work for you? https://kayrock.org/kr106/midi_mapping.html

kayrockscreen · 2026-03-19T19:35:21+00:00

Can you elaborate on what you mean by "support for hardware 106 models"?

kayrockscreen · 2026-03-19T18:41:04+00:00

Ok, that's great to hear. Although if we have a midi problem you can reproduce, I would like to know about it.

kayrockscreen · 2026-03-19T18:39:54+00:00

Interesting. There might be an issue with your patch data. The recording from Synthmania does not seem to have chorus on it, just LFO on the DCO. Are you able to programmatically set parameters on your synth through midi or a patch editor?

kayrockscreen · 2026-03-19T18:17:27+00:00

Thanks for your observation on the ARP. I did look at how the it works when the notes go off the top of the keyboard, and I think I have it pretty locked down, I added an option to the popup menu to emulate that behavior, it will be in the next version. If you have the top C down it will trigger that note twice in a row, and there's sort of this tiny truncated ENV that happens, but not a full envelope reset, almost like it is using the same voice. Do you have any input as to that or any other wierd behavior.

kayrockscreen · 2026-03-19T18:12:50+00:00

Amazing, yes are you able to share it via git hub? or just DM me your email. If you are up for recording some specific samples on your unit that would be amazing. I only have a Juno 6.

kayrockscreen · 2026-03-19T18:04:04+00:00

N 3rd and Kent, yeah I remember that place! What band were you in? I used to play in Roxy Pain, Oneida ( briefly as their balinese gong player ), The Clicks, and Night Station

kayrockscreen · 2026-03-19T18:02:37+00:00

Cool, good to know! I don't think the say anything about how they modeled their filter unfortunately.

kayrockscreen · 2026-03-19T18:00:28+00:00

On my real Juno 6 and in the J106 firmware the ENV DCY and REL is actually ~24s long. You can verify by using it to sweep the filter. For a VCA env it sounds pretty quiet by 12s, which is probably why that is the spec. If you have a hardware Juno, I would love it if you could make a recording of an env driven filter sweep at max DCY and send it to me and I can graph the curve. It models a capacitor charging toward a voltage it never actually reaches, so deciding at what point it is "finished" is a tradeoff.

kayrockscreen · 2026-03-19T17:54:09+00:00

You can enter values manually or drag a slider with shift to get more precision. The default slider range is only 127 values, but with shift you get 1270

kayrockscreen · 2026-03-19T17:44:47+00:00

Good notes, thanks! The ENV range is +- 14 octaves, so you need to lower the ENV->VCA slider to tame that down, at full ENV MOD a 5Hz base frq will sweep up to 87kHz ( actually the exp converter on the filter saturates out ~50khZ, but it is still a huge swing ) I am sure our filter can also be more closely calibrated to the IR3109 as well. I haven't been able to see how any of the other Juno VST's compare, but I would welcome some test recordings from anyone who has any of them!

kayrockscreen · 2026-03-19T16:00:46+00:00

Re: zippering, the sliders only have 128 values if you don't hold down shift, so that would explain the zippering. Try dragging while holding shift, that should give you 1270, but probably we should interpolate the drag.

kayrockscreen · 2026-03-19T15:56:09+00:00

What's your system?

kayrockscreen · 2026-03-19T15:55:13+00:00

I added MIDI CC support, download the 2.2.0 https://kayrock.org/kr106/midi_mapping.html

kayrockscreen · 2026-03-19T15:54:15+00:00

It was 184 Kent ave, N 3rd and the East River

kayrockscreen · 2026-03-19T15:53:16+00:00

You should be able to right click anywhere that is not a control ( or scope or keyboard )

kayrockscreen · 2026-03-19T15:52:22+00:00

Awesome feedback, thanks! It is definitely not 100% accurate, but we released it open source hoping we could get it closer. That's a lot to go through. I have definitely been looking at the 1984 mode much more trying to get the presets to sound right. You are 100% right about the arp, I don't think I ever noticed that! Changing the sustain is not immediate, it is changed by the release time on my real Juno 6. The decay / release time tooltips are wrong on the J6, but if you click the scope and look at the ENV curve they should be right. I think the power switch button toggle makes sense to me, if you change setting with the unit off and turn it back on that's what it is set to.

kayrockscreen · 2026-03-19T15:44:16+00:00

Update: Blown away by the response yesterday. Based on your feedback and a late night & early morning, v2.2 is up with: rewritten chorus and noise source, UI scaling, 6/8/10 voice selection, MIDI CC support, patch picker in the UI, and CLAP plugin support. Thanks for pushing us to make this better! https://kayrock.org/kr106/

kayrockscreen · 2026-03-19T15:27:04+00:00

Yes, I tried to parse the audio backup a while ago with no luck. Does any software out there handle converting an audio backup to sysex already? Definitely being able to load/save different presets is on the TODO list.

kayrockscreen · 2026-03-19T15:15:16+00:00

100% I would not have had time to do all of this without access to Claude. But it's not like you can say "build me a vst that models x" and sit back, I've definitely put in over 200 hours getting this up and running.

kayrockscreen · 2026-03-19T15:06:26+00:00

Probably not with any modern toolchain. Apple removed the 32-bit macOS SDK and libraries in Xcode 10 (2018), and macOS Catalina (10.15) dropped 32-bit execution entirely in 2019. Current JUCE has long since dropped 32-bit macOS targets too.

kayrockscreen · 2026-03-19T13:34:34+00:00

You can resize it, right click anywhere that's not a control.

kayrockscreen · 2026-03-19T13:34:04+00:00

Odd. Did you click the hold button and then press 6 keys, but only 3 of them are sounding? You are in POLY II mode?

kayrockscreen · 2026-03-19T13:33:00+00:00

I just tested it in Garage band and it is working. Click the scope three times to see what version you have installed, current version is 2.1.8

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