But I was inspired by this recent SOS magazine podcast – on just this very topic – to build some super simple passive attenuators.
They are literally a 250k dual-gang log pot wired in a box. Segway – I hate hand wiring cables and connectors – but it’s a useful skill. Kudos to the amazing fuzz box builders out there!!

Anyway, the idea is to use these directly on the hot outputs of synths and drum machines.
Really simple, and a quick custom enclosure and print job (well why not!?) makes for a useful studio tool…

My aim is to build light-weight acoustic panels to cover a couple of walls. Something along the lines of this custom one I have in my workshop…

This was printed and made by ATS Acoustics (no affiliate links)

Acoustic panels will absorb different frequencies at different rates, dependent on the material and thickness of the material – and any air space to the wall. What I am building here are modest absorbers, that will make the room sound much better overall (I’ve done this before!) but won’t act as well on the lower bass frequencies – the panels would need to be much thicker… But I can handle that tradeoff…

So where to begin!? As luck would have it, we found a set of four large square canvas prints in a budget store and decided to kickstart the build with those.
My wife also had some plain framed canvases (she is an artist!), which she painted to work with the budget prints.

For an absorber, I used 1″ thick Owens Corning 703 rigid fiberglass board. I got a box of 12 1″ panels at 24″ x 48″ for about $130, delivered.
These have to be cut to fit the back of the prints. Wear gloves, mask and long sleeves to avoid irritation from the fibers. I used a long metal ruler, and cuts easily with a couple of passes with a box cutter.
Use a generous coasting of 3M Super 77 on the canvas and board to fix in place. (I hate this glue – it seems to get everywhere, so keep covered up!)

You could stop here and have functional absorbers, but I have DIY tools, and will use them!

First, I built a wooden frame around the canvases, using coated MDF door trim. Easy to work with and smooth finish for painting… These were epoxied and pin-nailed in place, then painted.

Finally, I cut ¼” plywood back panels, again using epoxy and pin nails to assemble, before finally adding a couple of hooks to hang.

Some comments on other options… First, my panels ended up being about 1 1/4″ deep. There’s nothing stopping you using similar 1″ canvas prints, and building a deeper frame, and filling that with thicker fiberboard, for more bass absorption. Also, you can use something called mass loaded vinyl as well as the ply. It’s meant for construction, but heh…
And finally, you can buy Z hooks to mount these more cleanly to walls, rather than the low cost hooks I used.
And having a wife who is an artist might help!

Here’s the main wall, with the modified and home made panels – the studio is starting to come together

Developed as a fast and reliable way to add an ON-ON stomp switch to a guitar or synth module build for true bypass and LED switching – or whatever else can make use of the 3PDT functionality!

A huge value for rapid prototyping, the 9-way (0.1″ pitch) 2″ long flexible cable brings out each of the three switches in grouped ways. The wiring is uncommitted, but I chose to make pin 4 (on the middle switch) a ground connection, which connects to a solid, uninterrupted ground plane on the upper side of the board. This is done for two reasons – it’s typical to use the middle switch for LED switching, so pin 4 can be utilized for the ground return for the LED. Clearly, also having a ground plane above all audio signals helps prevent electrical interference / return paths also.

Here’s the schematic –

This ground plane also has two 1mm holes for additional ground connections or test points.

The switch posts and cable ways are clearly labeled on the screen silk. The cable itself has a color coded strip indicating a pin 1.

Made with only quality parts, the kit comprises an Alpha 3PDT switch, a 2-layer PCB, and a 2″ 9-way 0.1″ pitch flexible ribbon cable. (The 2″ dimension is just less than the length of the plastic carrier – as shown in the pics.)

The flexible cable enables a short connection to your own PCB or Veroboard, which can sit at a different level than the footswitch PCB. It is very flexible – but note it is not intended for moving applications!

Fundamentally, what I ‘m building is a guitar cord with a decent size coupling capacitor to probe and listen to circuits on the bench. I have a number of test amps, but I like to use this tiny cute Orange Crush mini amp whenever I hook up anything new, or I’m unsure of what I will get (dodgy!) – and it’s perfect for using this probe.

For the test cable, I decided to use a 10′ Fender Pro Tweed cable (Fender look away now!) and cut it in half to make two 5′ test cables. Spares, right? Or as the marines say – one is none and two is one!?
The cable has a nice white braid, so instantly recognizable on the bench. I cleaned up the end with heat shrink to seal the cable braid.

For the ground clips, I decided to hack parts from these cheap probe kits – so the ground can be connected to a banana or croc clip.
These were soldered on, and sealed with more heat shrink. I like how the heat shrink makes the probe-to-be more substantial. But there are more layers to go!

For the probe itself, I chose a 1uF big voltage cap – to allow a lot of frequencies through, but not mess with DC – and more cheap banana probes from Amazon. The idea is the banana plugs will enable connection to different probes in the clips kit. These are nice quality, and solder well.

Now it’s just a case of making the capacitor to cable connection stand up to my use – so, more heat shrink!

It was important to me to form a robust rigid “handle” for the probe out of the cap and banana plug, and I’m very happy how it turned out.
The probe tips are interchangeable and small enough for SM pins and test points on breadboards.

The cable works great – it is robust, has flexible connections and looks great!
Here’s a pic showing the probe in context – with the dev boards I just made. Oh, and my effects setup has an A/B box on the input to the development board. One input is for a guitar, but the other comes from a Re-amp box from a DAW, so I can play a guitar riff or loop into the unit to test and tweak. Way easier with just two hands!

Quick update – fixing the RFI demons
Well, I thought these were finished, but using them one day to fix a dodgy connection (bad solder joint…) in a pedal, I was getting some crazy hum and RF pickup – and it was clearly present in even just the probe, especially with the longer probe tips. Turned out, I had built some good antennas!!

So, I reworked the probes to place a copper film shield / layer over the cap – basically extending the cable shield over the cap to the probe tip… This is connected to the ground / cable shield electrically. The copper tape is adhesive and conductive through the tape.
More heat shrink, and we were back in business…

This indeed made the difference, and so far, no more RF interference!