Bat Signal is a simplification of Bat Synth to increase replay quality, This requires a 384kHz USB-C DAC, about £15 from Amazon, to replay audio from computer or phone.

Hand soldering of this will be trivial, no need to order a solder stencil - there's only the headphone jack and the LTK5128 module.

The back of the main PCB exposes bare pads for +5V and GND, simply chop the end off a USB charging cable, strip the wires and solder to the PCB, then power from a USB power bank. Audio comes in on a 3.5mm jack.

3D printed frame attaches base plate to main PCB, and is quoted as about £1.50 from Midlands3D in HP MJF, probably the same or slightly less from PCBWay.

IMPORTANT

The circuitry can be minimized if you can source a high gain 5128 module from AliExpress - I have bought some that were assembled with a 100R rather than 100k input resistor. Failing that, just remove the 100k and short it with a solder blob, then short the location shown in the third image -ignore everything blocked out in red, and put solder blobs on the locations marked in yellow.

So with a high gain 5128 amp the only components needed are the LTK5128 module, headphone jack and 4x 100R resistors, and these can be omoitted if you are powering from a phone charger - they are only there to ensure a minimum current draw so that USB power banks do not switch off due to under-current. Even with a bog standard "gain of 2.0" 5128 this minimal component mod works, but your output may be a little quiet unless you crank your phone’s output.