Build a set of walky-talky eurorack modules which accept modular level signals trough their electret microphone inputs. To accomplish this I assembled a line level signal to microphone input adapter (following this guide: 20 dB PAD for line to electret microphone input) and included a 47k resistor before the 10uf capacitor. The walky-talky speaker output is routed to a tl071 based line level to eurorack level amplifier (I followed the TrAniModule line1-lineout design). The push-to-talk button is routed to a switch which is mounted on the panel. At first I powered the walky-talkies using 7805 chips (build heat sinks from salvaged aluminum) but they run quite hot so I replaced them with LM2596 buck converters. This also dropped the consumption from 200mA to around 80mA (~2mA on the negative rail) but this is dependent on the amount of signal amplification the units uses (which seems to be a automated process, based on some kind of feedback between the devices). The power supplies have reverse-polarity protection. I got the idea for building them from a youtube video.

The sound is interesting, like in megaphones but they are still unstable. One feature of the unstable behavior is that in some tests, some frequencies of sine waves would cause the unit to glitch and go silent. Once a different frequency is transmitted the connection is re-established. Very high frequencies cause a morphing glitchy interference space. The units distort sounds in interesting ways, almost like wave folders and I can also pass clock signals trough. Bass drum tones get removed but low frequency clicks pass. I think the glitches are a power-supply issue (my bench power-supply is very noisy), also there are a lot of loose wires and dodgy connections. I’ll rework the connections and set the rattling wires with hot glue, after I receive on-off-(on) switches (I’ll use them for the push-to-talk button). Also had the idea of adding voltage to control the push-to-talk button but it wouldn’t work as the devices make a loud beeb every time they establish a connection. When nothing is inserted to the input the microphone can be used.

The walky-talkies are Exibel FX-27’s, which we got from Kiasma and used with the xxx_group back in 2009. They have been collecting dust for 11 years! They have 8 channels and I’m currently using 446.00625MHz (the same as baby monitors, which I can now use as inputs for my modular!). I’ll have to wait until the libraries open to laser cut pretty faceplates for them and I also want to mount their antennas properly. Currently the PCBs are attached on a dodgy plywood sheets and the antennas are located in the back. They look like bombs. Sending wireless signals has been a longtime fascination. The last time I’ve worked with wireless audio of this type was in 2006 when we established Storijapan with Kristian (a layout of the our wireless setup is still on our server homepage). Transmitting signals from and in a eurorack system feels like a dream I had a long time ago.

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