Elektrosluch - Listen to EMI
MAKE recently featured a very cool project that I had to build: the
Elektrosluch! What’s an Elektrosluch? It’s basically a microphone of
sorts that allows you to listen to electromagnetic interference (EMI)
which is found all around us in our personal electronics, homes,
automobiles, and many other places. The Elektrosluch includes a built-in
amp, so listening can be done with headphones, or it can be connected to a
recording device for sampling. The tutorial was written by Jonas
Gruska, who designed the circuit. It was a lot of fun to build, and
overall not too hard. I took my time and checked everything multiple times
and it worked the first time I tried it.
I didn’t really follow the tutorial, but I read it and the schematics
and set out to design mine based on that information. So my circuit is
basically the same but the layout is different. The most notable things I
did with my build are:
- I used the Radioshack 276-150 PCB instead of a perfboard. This was
inspired by the Tangentsoft
cMoy tutorial, which uses the same board. I’ve previously
built a cMoy based on that tutorial and I like the layout used
with the PCB. It works nicely since the middle tracks can be used as the
- I used a Serpac H-65 case to house the circuit, also inspired by the
same cMoy tutorial.
- I used an OPA2132 OpAmp instead of the OPA2134. I still had some
leftover from cMoy builds, and the Tangentsoft tutorial indicates
they basically sound the same.
- I included some additional capacitors which are found in the pre-built
Elektrosluch units. Specifically, 2 47pF capacitors in series with the
390k ohm resistors. When I inquired about them on the MAKE tutorial
page, Gruska responded that “They offer high-frequency filtering to
protect from RFI frequencies. However, in effort to make the design
easier, I decided to not include them.” Including them was a
challenge, but I got them in. I’m not sure how much difference it makes,
but it probably would have been fine to leave them out and save a lot of
hassle. I couldn’t resist trying it though.
- I added an Alps 10k ohm pot with built-in switch for volume and power
control. Actually, it may be the same one used in the Elektrosluch
Mini DIY Kit. I had some leftover from building cMoy headphone
Here is my Elektrosluch in action, before I added a volume pot and cased
Many thanks to Jonas Gruska for sharing his design and writing the
tutorial, and to MAKE for featuring it!
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Originally posted April 20, 2016 on my old site; posted here April 6,
2018 with minor revisions.