Mixbus : Ardour + Harrison DSP for OS X

Harrison, the manufacturer of world-class analog and digital consoles, along with Paul Davis, lead developer of Ardour are proud to announce Mixbus®, a customized version of Ardour for OS X.

Mixbus enhances Ardour by providing critical mixing functions in a knob-per-function interface called "True Analog Mixing"(tm). True Analog Mixing is based on Harrison's renowned 32-Series and MR-Series console designs, combined with Harrison's proprietary digital mixing technology. Mixbus enables the user to record, edit, and mix a musical performance "in the box" while achieving a sound that harkens back to the golden age of album recordings.

Features include:

  • Straightforward “knob per function” mixer layout based on Harrison's renowned 32-series and MR-series music consoles.
  • Precision DSP algorithms for EQ, Filter, Compression, Analog Tape Saturation, and Summing based on Harrison's world-renowned large format analog and digital mixing consoles.
  • Unlimited stereo or mono input channels (based on available CPU power) featuring High-pass Filter, EQ, Compression, and 4 Mix Bus sends on every channel.
  • 4 Stereo Mix Buses (can be used for groups or auxes) featuring Tone controls, Compression, Sidechaining, and Analog Tape Saturation.
  • Stereo Master Bus that features Tone controls, Analog Tape Saturation, K-meter, and Limiting to help you make polished mixes.
  • Plugin delay compensation to support effects such as parallel compression.
  • Comprehensive "at-a-glance" metering with peak, peak hold, and compressor gain reduction visible on every track and bus.
  • Extensive DAW features via the Ardour Digital Audio Workstation.
  • Supports AudioUnit plugins and any CoreAudio interface.

According to Harrison product director Ben Loftis, "Harrison didn't want to launch a "me too" workstation in an already crowded market. Instead, we used the Ardour open-source workstation as the Mixbus recording/editing/playback engine. Because Ardour has been around for nearly 10 years, and has thousands of users, it is a stable platform that doesn't further add to the fragmentation of the workstation market." Harrison has had an ongoing collaboration with Paul Davis since 2004, when they used Ardour as the basis for the Xdubber product

The original idea behind Mixbus was a simple Harrison "channel strip" plugin. But after some experimentation, it became obvious that simple plugins don't interact correctly to recreate console functionality, and freeform DAW summing architecture does not lend itself to analog production styles. So during an extensive testing and experimentation phase, the design morphed into a combination of Ardour and Harrison features in the channel strip.

For those who are familiar with Ardour's existing design, Mixbus was implemented using a single closed source LADSPA plugin to provide Harrison's channel strip DSP, along with a set of extensive but non-intrusive changes to Ardour's core. The source code for everything except the plugin is available as usual via the svn repository at ardour.org. Harrison has been a long-time supporter of Ardour, and they will continue development of the Ardour open-source platform. Some of the proceeds from Mixbus are being directed towards Ardour developers and increased development efforts.

Special thanks to Thomas Vecchione (Seablade) and Malte Rogake for design reviews and testing during the development of Mixbus.

For more details or to purchase Mixbus, go to http://mixbus.harrisonconsoles.com

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is really good work! Thnks for everything.


A while ago someone asked about Mixbus based on A3, and the answer was something like… totally hypothetical and depended on how well is 2.X received by the world…

Now i’ve seen a few “very good” LV2 plugins that leaves me very little to nothing to envy to pro plugins on other platforms (ozone for example for windows or mac)… so now it seems with A3a3 that low-cost / high flexibility and performance / home recording is getting very close to be true in GNU/Linux… to that you add a great low-cost project like Mixbus…

so my question is: does Mixbus based on A3 keeps being absolutely hypothetical or would that change? a Mixbus addition to A3 would be a great improvement over an already greatly improved DAW.

@fernesto: I think its extremely important that you understand two things clearly. Ardour 3 is still at the alpha stages, and Mixbus is still undergoing its own development based on the Ardour 2 codebase. Even with all the will in the world to eventually release a version of Mixbus based on Ardour 3, Harrison still could not feasibly do this in any near-term time range. They know that there are audio related features in Ardour 3 that will be a good complement to Mixbus’ own features. That doesn’t mean that it makes any sense for them to start working on an Ardour 3 version when Ardour 3 has not even reached a beta release. I think its rather likely that in the long term some version of Mixbus will be released that uses Ardour 3 as the starting point. But its not likely to happen for quite some time. For myself, I consider the Ardour 2 codebase to be more or less a dead end, so I will certainly welcome it whenever Harrison decide to switch. But Ardour 2 is also far better tested and known, and therefore I would not attempt to hurry Harrison into that decision.

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Any chance that the Mixbus plugin will be released (as binary) for Linux as well, or would this be a problem because of incompatibilities between distributions?

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@the CLA: that is precisely the problem. I want to fix this problem for “regular” Ardour too, and when we do, there will be a Linux Mixbus release as well.

Linux! Linux! Linux! Will buy it! Will buy it! Will buy it!

What prevents us from using the interface (which is built on ardour) together with ladspa effects to have the same level of ITB functionality for standard ardour?

I would also buy it if available for Linux… amd64 please.

Would it continue in 3.0?

Awesome! Will buy if there’s a Linux version!

Hi Paul and the Ardour team.

Have Mixbus running on my PPC Mac.
Wow ! What a sound from my speakers. Amazing filters and dynamics, and the option for parallel compression is superb
for mastering.


qharley: theoretically, nothing. in practice, the DSP in Mixbus represents 30 years of development at Harrison. These weren’t newly written “plugins”, the DSP is the same code used in Harrison’s own consoles. The GUI part may inspire some kind of conceptually similar integration of plugins into the GUI in 3.X (something that has been planned in a very simplistic way for a while), but part of the reason this works so well is that there is one plugin and one GUI controlling it for each strip, not one for the EQ, one for the compression, etc. etc.

In terms of a Mixbus based on 3.0 … thats totally hypothetical at this point, and will depend a great deal on how the release based on 2.X is received by the world.

hey guys,

Some time ago, I had (during a dream) installed OSX86 on my old (dreamlike) intel based Dell laptop and could run Ardour OSX-X11 on it (still during the dream).

So (the theoretical question) is the MIxbus plugin compatible with IntelMac platforms or is it PPC only ?

(before I awakened from this dream) I scraped my osx86 partition since I couldn’t use it for anything (yeah, it’s a dream, remember) but I can retry (to dream the same dream) if you Paul tell me that it is also supported on intel platforms.

This is of course for educational purposes and remains a “theoretical” idea or wishful thinking. Do not install OSX86 on non certified platforms :slight_smile:

30 years of development… That could be good.
There are already some kind of interest from some of my buddies on The Womb. :wink:

There are quite a few linux ardour users that would love this setup. The way I see it, is that the GUI could essentially stay the same, and that the user can choose to use an ardour defined cluster of ladspa plugs, or the Harrison module for linux (which you could buy from Harrison)

It is not that we don’t have good quality plugins for ardour, the problem is mostly that they are a bit tricky to control, and it takes time to mix. I currently use the DSP’s on my digital mixing console to do all the things Mixbus would do, because doing it in ardour just takes too long comparatively.

Another thing to chew on, is that there are quite a few capable DSP programmers out there that could write similar plugins for Linux, if the interface were known. There could, for instance, be a LinuxDSP module for linux that does the same as the Harrison one, just with different code (and different core sound of course) - and it could generate an income for that DSP programmer should he decide to sell it.

Just spit balling here, but I truly believe that this will drastically change the way ardour is perceived as a user friendly DAW interface.

Pricing looks quite reasonable at the moment. Unless the non introductory pricing is significantly higher you can pencil me in for a linux version should it be released

So (the theoretical question) is the MIxbus plugin compatible with IntelMac platforms or is it PPC only ?

IntelMac is what I tested it on for the past several months. That being said in your dream world I can’t comment on it on a OSx86 machine obviously;)


Ciao Seablade, if I (dream that I) install OSX86 on my (dreamlike) PC, should I (dream that I) buy a copy of Mixbus or can it be tested for free ?

At the moment there is no demo I know of, sorry.

This looks very exciting. I have not been mixing much stuff recently, but will keep an eye out for a version OS X 10.6 compatible as I am about to upgrade my os. I hope this continues to run parallel to Ardour development as these DSP options mixed with the features which Ardour3.0 is going to have under the hood would make a pretty rocking combination.

Thanks for the work.

Are there significant changes to the rest of the interface or would one feel at home switching between Ardour and Mixbus? Or do one really not gave to swicth between them to reach each versions advantages as they are and are working the same (except for the mixer)?

Are the onboard eq controls, bass and treble sweepable shelving filters plus a semiparametric mid?


The Editor page is identical in both products. You won’t have any trouble going back and forth (except that the Mixbus elements are missing in Ardour, of course)

The track EQ’s are Lo Shelf, Mid Peaking, and High Shelf, all with sweepable frequencies. The buses are similar but with fixed frequencies.