Hi EWI enthusiasts. A couple years ago I successfully hacked my EWI4000s to get the direct breath sensor voltage without converting into midi and back. This allows you to control analog synths with super smooth full resolution breath CV. Doing so totally opened up the world of modular synthesis to me and made me love playing the 4000s so much I sold my vintage EWIs. Here’s how I did it.
Step 1: Dissasemble the EWI until you can access the daughter boards for the trim pots and output jacks. You can find step by step instructions for that here. You can skip the steps of taking off the pinky keys.
Step 2: Solder a wire to the leftmost pin of the “Breath Sensitivity” trim pot (red wire). This carries the breath sensor signal. Solder another wire to a ground point (black wire). In my case I used the casing of the pot because the other pins are not wired to ground.
Step 3: On the daughterboard which contains the output jacks, cut traces R313 and R314. I used a small dremel tool but you could use a razor blade too. This disconnects the headphone jack audio so we can repurpose that jack to be a CV output.
Step 4: Run the wires through the length of the EWI and solder your breath signal ( red wire) to the jack contact marked “tip” and the ground wire (black wire) to the contact marked “ring”.
Step 5: Reassemble the EWI
Step 6: Because the breath sensor puts out 3v with no breath and 0v with full breath, the signal needs to be processed in order to be useful with analog synths (which typically use 0-5volts). I built a simple scaling/inverting circuit on protoboard and put it behind a 4hp Eurorack panel. See schematic below.
The “10k preset” are fine adjustment pots. Adjust those until you get true zero with no breath and 5v with full breath.
Don’t mind the extra jacks. With the other unused half of my opamp I built a simple unity mixer.
Controlling the modular with direct breath CV is awesome! No more latency or slewing, or grainy midi signals. Super responsive and the FM tones you can get by growling are amazing. Midi functionality and the internal sound generator are not affected by this mod. I still use a midi to CV convertor for the pitch CV, but having the direct analog breath frees up a channel on my convertor (Mutable Yarns) so I can have an additional pitch CV and make use of the duo phonic hold mode on the EWI4000s.
Hope this helps you!