Mass Spectrometry and the ER-301

So I promised I’d write up what we were up to at the Bluedot Festival this weekend and while I won’t be able to recount everything we did, I hope the following gives you all some idea, this was all done right underneath the amazing Lovell Telescope :slight_smile:

The basic idea is that we hooked up a Mass Spectrometer (MS) to a modular synth and turned physical materials into audio!

If you thought Eurorack power requirements were difficult the MS makes them pale in comparison, I think I remember correctly in that there are 6 different power sources, one for each stage of the process, some of them reaching as much as 4,000V. Believe me when I say I was checking the voltages we were using with a multimeter before they got anywhere near my modular :smiley:

Anyway, it just so happens that the voltages output by the MS that represent the materials analysed are 0-10V. A little bit of hardware hacking and this voltage was exposed via a mini jack socket so it could be taken directly into the modular.

Here’s a brief overview of how it all works it is a single quadrupole LC/MS which stands for Liquid Chromatography Mass Spectrometry. It is used to analyse solutions of molecules using electrospray ionisation

  1. sample must be in solution could be ibuprofen dissolved in methanol
  2. sample goes into a syringe pump that squirts it really slowly into the electrospray probe which starts the ionisation process
  3. electrospray probe consists of a very very small tube inside a small a tube connected to about 4000 Volts
  4. The sample is squirted through the inside tube, nitrogen gas flows through the outer tube so the sample is nebulised from the probe. The droplets produced are charged due to the 4000 Volts
  5. Around the outside of the probe there is another flow of nitrogen gas which is heated, this helps to evaporate the solvent from the droplets
  6. Once all the solvent has evaporated (droplets get smaller) the charge is left on the ibuprofen molecule and turns it into an ion (an ion is a charged molecule or atom)
  7. Ions due to their charge can be moved by electric or magnetic field
  8. The mass spectrometer must operate at very high vacuum almost like being in space, this is generated by turbo molecular pumps which look like small jet engines
  9. Ions are sucked into the mass spectrometer
  10. The ions then fly through the quadrupole mass analyser and hit a detector
  11. in very simple terms when a low voltage is applied to the quadrupole the low mass ions can fly through and hit the detector. when a high voltage is applied to the quadrupole the high mass ions can fly through and hit the detector.
  12. The quadrupole is scanned from low mass to high mass to generate mass spectra
  13. The output from the detactor will also be used to play music and generate visuals

Using the voltages for control signals was the original idea, but as the data tends to form spikes quite a lot of processing was required to bring the signals into a usable range. However, we also realised that we could use the output as a direct audio source in a single cycle waveform oscillator and because each material produces a different waveform, we should get a different timbre for each material.

As you will probably know already, the ER-301 is perfect for this kind of audio manipulation!

Here’s a photo of the output from the MS displayed in the analytical software on a computer:

And the same waveform recorded into the ER-301 (keeping gear clean in a field is challenging!)

Injecting the MS with a solution of Ibuprofen:

Turning it into music:

And here’s the audio, a nice evolving drone accompanied by Beth playing her Melodica:

We are planning to do more events using this technology as the response was absolutely fantastic, so many people came by and couldn’t believe what we were doing. Being able to show both the MS and modular waveforms on an oscilloscope and manipulate the audio in real time in response to the materials being analysed in a meaningful way kinda blew peoples minds :smiley:

Only other thing I would like to say is a huge thank you to the Bluedot festival - a very family friendly and civilised festival with an incredible array of stunning musical performances - Orbital were out of this world!!


Wow, that looks like good fun. And after listening to the track, my headache sees to be gone. :wink:

I won’t pretend to understand it all. Was the sample buffer actually connected live to the output of the MS as it was doing it’s analysis? Am I hearing the aural footprint of Ibuprofen, or am I hearing the aural footprint of the process of breaking down ibuprofen using MS?

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Hehe - very funny!! It would be amazing if it actually worked like that!

Good question, there’s a certain amount of artistic license because the actual output is essentially spikes of noise if listened to in real time. But otherwise yes - the output in essence is the aural footprint of Ibuprofen - or part of it anyway - other materials produce different timbres :slight_smile:

As this was the first time we have really done this it was as much a journey of discovery for us as for anyone else, we believe it is a world first and totally unique! Chatting about it afterwards we realise there is much more that could be done with these signals, Giles (the gentleman who organised this and who’s idea it was in the first place) has the MS from the photos above and a huge bottle of gas at home now so we will be conducting many more experiments and hacking more of the control signals from the MS to use in a wide variety of ways.

What you see and hear here are just the first tentative steps into our journey :slight_smile:


Amazing use of the headamp output well done! great longidudinal waveforms :smiley:

The Waters Quattro Premier LC-MS/MS mass spectrometer does indeed contain quite power supplies and is quite a complex box of tricks including from what I remember… a few low (3.3, 5, +/-15, 24, 36, 56 V) and high voltage power supplies (+/-430 V, +/-1350V, +/- 5 kV, +/- 8 kV, +9 kV) and a variety of Radio Frequency generators (832 kHz and 1.2 MHz) the quadrupole RF generators go up to more than +/- 10 kV peak-to-peak.

Most of the lenses, gas controls and readbacks all operate on 0 to 5 V or 0 to 10 V signals.

The detector on the mass spec when running in positive ion mode uses a conversion dynode to generate electrons from the positive ion beam, the dynode consists of a low work function electrode at -8 kV. Electrons emitted from the dynode are then attracted to a phosphor scintillation disk held at +9 kV, photons are emitted which are detected by a photomultiplier tube (PMT). The PMT works in its own vacuum envelope the photons strikes the first of a series of metal electron multiplier dynodes causing a cascade reaction which releases releases more electrons on each step of amplification. The resulting ‘ion current’ is then finally amplified by the detector head amplifier to give a 0 to 10 V signal corresponding to 0 to 1.38e8 counts of signal intensity used as the y-axis on the resulting mass spectrum.

The mass spectrometer must operate at high vacuum, typically for that instrument about 6e-6 mbar this is to ensure the ions do not collide with any air which would stop the ions from reaching the detector. 1 bar is one atmosphere so the pressure inside is 6 thousand million times less or 0.000000006 bar.

Magic :atom: :scales: :star2:


The Recycling Organisation for Research Opportunities (RORO) charity is actually giving away the mass spectrometer we used for free! We willl be donating it with a Waters Acquity UPLC system to a university in a developing country.

If you know anyone who may be interested please contact for more details.


Awesome - thanks for the additional info @Giles I totally missed all those other power specs - crazy!

I’m really happy you have explained this as anything more than the basics is all a bit beyond me :smiley:

And I thought it was Interesting granualizing my cat! This is insane! Well done!



Actually I totally predicted that someone would eventually throw some ibuprofen into a mass spectrometer that is plugged into an ER-301. No surprise there. But to do it outside in a tent?! Cherry officially popped! Haha.

@anon83620728, is there anything he will not do?


Hehe cheers guys :heart_eyes_cat:

Honestly, the worst part of all this was having my gear inside a tent for three days… but then again, the best thing about all this was having my gear in a tent for three days!

Everyone on the team is still buzzing and looking forward to the next gig :slight_smile: