Ultramaster KR-106 – Juno Synth

I’ve been digging through the web and found something truly special for your arsenal today.

We all know the struggle of trying to get that fat, warm 80s analog synth tone in the box. You usually end up scrolling through thin, plastic-sounding presets, or you’re forced to drop thousands of dollars on vintage hardware that constantly breaks down and introduces unwanted hum into your pristine signal chain.

Trying to get your synth basses and pads to actually sit in the mix with that authentic, wide Roland BBD chorus vibe used to be a massive headache. But not anymore.

Why Ultramaster KR-106 is a Game-Changer for Your Mix & Workflow

The crew over at Ultramaster Group has been tweaking this engine for a quarter-century. They started this project back in a Brooklyn loft in 2000, and after decades of refining their DSP methodology, they dropped this completely open-source gem. Here’s why it absolutely slaps:

Authentic Analog Flavor: This isn’t just a basic wavetable. It features 6-voice polyphony with per-voice analog variance, meaning your chords sound massive, organic, and slightly unpredictable—just like the real hardware.
That Classic Chorus Vibe: The iconic BBD chorus has been circuit-simulated and ngspice-verified. It instantly widens your tracks and glues the sound together without phasing issues.
Warm, Gritty Filters: The TPT ladder filter with OTA saturation ensures you can crank the resonance without losing your low-end. It gives you plenty of headroom and musical grit.
Dual-Mode DSP: It’s essentially three synths in one. You get the raw analog behavior of the Juno-6/60, plus the precise firmware emulation of the Juno-106.
Instant Inspiration: Out of the box, you’re blessed with 240 factory presets (112 Juno-60 + 128 Juno-106), so you can immediately find a patch that works instead of endlessly tweaking knobs.

⚡ Pro Producer Tip: Widen Your Bass Without The Mud

When using the KR-106 for synthwave or pop basslines, crank up that built-in BBD chorus for serious stereo width, but slap a mid/side EQ on your channel afterward. Roll off the low-end frequencies (below 100Hz) on the sides only. This keeps your sub frequencies dead-center and punchy, while the analog chorus washes beautifully over the stereo field.

Tech Specs (Keep it Light)

Download Size: A super lightweight 94.7 MB.
Formats: AU, VST3, LV2, CLAP, and Standalone. (Logic Pro users, take note: they included a separate AU variant ‘aumf’ specifically so you can bypass Apple’s SysEx blocks).
Platforms: Windows, macOS (10.15+), and Linux.
Under the Hood: Built with JUCE, features full Juno-106 SysEx support (IPR/APR send and receive), DAW-synced arpeggiator, and buttery-smooth portamento.

guide:
https://kayrockscreenprinting.github.io/ultramaster_kr106/website/guide.html

The Verdict

The Ultramaster KR-106 is an absolute labor of love. It’s incredibly rare to see developers dedicate 25 years to a project just to give it back to the community under a GPL open-source license. The meticulous hardware measurements and firmware analysis really show when you drop this onto a MIDI clip.

Whether you’re making Lo-Fi, Synthwave, House, or modern Pop, this synth delivers that unmistakable vintage thickness. It looks familiar, it runs efficiently on modern rigs, and best of all, it’s a completely free powerhouse.

Visit Developer Site

KR-106.2.5.12 ( 95 MB )

Let me know in the comments how this sits in your latest project! Are you a bigger fan of the gritty Juno-60 tone or the polished Juno-106 vibe? Let’s talk shop below! 👇

VST

We’re audio producers and sound designers with over 20 years of experience in the industry. Our team has lived through the entire evolution of digital audio production.

Our mission? To filter out the junk and bring you only the studio-ready free VSTs that actually compete with paid gear. We do the digging so you can focus on creating.