Surge Synth Team OB-Xf is a modernisation and continuation of the open-source, FREE OB-Xd Synthesizer plugin inspired by the Oberheim OB-X.
Good news from the Surge Synth Team. The new OB-Xf is now available in public beta and can be downloaded for free from GitHub.
There are still a few missing features in the beta version, such as the MIDI learn UI/UX, and the patch browser still lacks patches or banks. I’m pretty sure the community will create numerous patches during the beta phase.
The developers hope to release a 1.0 version well before Halloween. Here is what EvilDragon, one of the developers, added:
Giving the synth a test and sharing bug reports on GitHub or our Discord server is the crucial last step to get there. When reporting bugs, please use the Copy Info to Clipboard function on About page, which you can get to by clicking the OB-Xf logo in top left corner!
Happy testing and huge thanks, Surge Synth Team, for this work.
Article from September 15, 2025
There are hundreds of free synthesizer plugins, but only a few stand out from the crowd. One is undoubtedly the open-source, free OB-Xd project from 2DaT, which is an emulation of, or heavily inspired by, the Oberheim OB-X.
A few years ago, the project was taken over by discoDSP, which created two versions from it: an open-source version that is updated less frequently, and a 99€ premium version with new features and emulation. A decision that was not received so favorably by many.
Good news: the original project is back with the help of the Surge Synth Team under the name OB-Xf.
Surge Synth Team OB-Xf
The new OB-Xf is currently in full development, with the latest updates and improvements emerging almost daily. Please refrain from using the plugin in important projects, as it is still fully in development, in an alpha/pre-beta stage.
Unlike the current ongoing OB-Xa project, the Surge Synth Team OB-Xf is a 100% open-source and free Synthesizer plugin and a fork of the 2DaT OB-Xa project. There will be no premium version, so all the new features are free of charge.
Like the original project, OB-Xf features two oscillators with PWM, sync, and cross mod, a mixer with noise, a multimode filter, two envelopes, and two LFOs. Also onboard are the voice variations, pitch control, and more.
The Surge Synth team has not only continued the OB-Xa project, but the version will also offer many new features and improvements. This already starts with a new, lovely UI by SatYatunes that brings almost all hidden, useful parameters to the front.
New Features & Improvements
Then, the engine now correctly produces 440 Hz when playing the middle octave, and it now has up to 64 voices due to the way they intend to implement the unison voices parameters.
In the mixer, you can find a ring modulator and a new multimode noise color, including white, ping, and red. There are also new, separate pitch bend ranges in the control section, along with a new unison voices parameter.
The filter received a significant upgrade with the introduction of a new 4-pole mode, enabling a smooth morphing from 4-pole to 1-pole. On top of that, it hosts all Oberheim Xpander filters, including HP2+LP1, HP3+LP1, and many more.
On the modulation side, the filter envelope now also has an inverted option at secondary targets (ENV to pitch and ENV to PW). A second LFO, identical to the first, provides additional options for animating parameters like the newly added volume knob.
LFO Waveform buttons became knobs, which act as a panner between sine/triangle, pulse/saw, and S&H/S&G. Additionally, the LFO pulse and sawtooth waveforms now have a pulsewidth parameter.
According to the developers, no multi-FX will be added because they want to keep the project as authentic as it was.
Presets Compatibility?
Other improvements include updated ranges for the crossmod (2x) and of the ENV to pitch parameter, so it properly matches a full 3-octave modulation range.
Surge Synth Team has also added a new preset browser to the OB-Xf with various patch infos (number, name), and functions like previous, next, or randomize. The latter is not yet implemented.
There are also direct access buttons that allow you to select between 16 patches sorted across 16 groups.
A downer, however, is that the patches and banks created by OB-Xd are not compatible with OB-Xf due to the changes they made in the engine. Currently, the plugin includes no presets.
Surge Synth Team OB-Xf First Impression
The OB-Xd has long been one of my favorite free synthesizer plugins. Since the introduction of the two versions, I’ve used the plugin less and recommended it less.
I’m happy that the fantastic Surge Synth Team has now taken over the original project, and I’m curious to see how much community input there will be, especially regarding the patches and future new features.
Surge Synth Team OB-Xf is available now as a free download in an alpha/beta version with nightly updates. Please refrain from using the plugin in important projects, as it is still fully in development.
It runs as a standalone app and VST3, AU, LV2, and CLAP plugin on macOS (native Apple Silicon + Intel), Linux, and Windows. For the alpha/beta, you need to follow the steps on GitHub to activate the theme.
More information here: Surge Synth Team (GitHub)
We always welcome the warm coverage we get from synthanatomy of our work but I do want to flag that we are still in an alpha/early beta stage with this project. Just don’t want your readers to think what we have here is as rock solid as surge yet.
That said your coverage has inspired us to close those gaps!
as written in the end of the article: Please refrain from using the plugin in important projects, as it is still fully in development.
Great yes thanks! And thanks for the coverage of course!
Now back to closing those gaps. LOL.
Hey, Ob Xd was my go-to synth even having all Arturia Products, You don’t know how grateful I am that you are taking it to bring it to the next level.
I would love to give you feedback and all if you need it. Because this will be my go-to now.
Cheers from Barcelona!
hell yeah, 2dat taking it back and pushin it!
2dat is not part of it. Surge Synth Team is working on it
Oh. Hell yeah, Surge Synth Team takin’ it and pushin’ it!
sounds phenomenal, can’t wait till it supports mpe, if it ever comes to that!
Hey just a note here
After your coverage, we sort of went into a deep sprint mode and closed the bugs and feature gaps for our 1.0 beta release. We still have a couple of big swaths (MPE, Clap poly-mod, and a patch browser) which are outside our first stable release but we are in a stable beta now, enrolling testers, and looking for patches.
Thanks for the coverage. It lit a fire under us to make your article true. Chuckle.
Hey baconpaul, any chance that this could be released on iOS?
Great synth and free! Well done to everyone involved.
Go, BaconPaul & co.! Thanks so much for everything you’re doing.
Viva Surge ~ !