You might consider NOT putting the full power on a device you are constructing before you know it is working correctly. I always slowly turn up the voltage while keeping an eye on an ampere meter, so that I discover any excessive load early and before the supply voltage can do any harm.
In most audio processing modules the LEDs are the ones that consume the most current, maybe about 10mA each. Without leds any audio processing module that is not a power amp (or contains some hefty dsp/microprocessor) should only use a few tens of milli ampere at most.
Itās hard to bootstrap a system, I have little to test it with, Iām using a function generator on an old phone as a sound source, and a lot more alligator clips than sensible.
This is Matt Skalaās / North Coast Synthesis MSK 006 VCA, it uses a bunch of transistors rather than an IC (for sport). Itād be hard to make docs more beginner-friendly than he does, almost every mistake you could make during the build is anticipated.
Just a test module, so I donāt care about aesthetics, but I hoped to mount the PCB properly with a little holder on the back, unfortunately thermal expansion was higher than anticipated.
I still have 4 PCBs (one channel per) for a cleaner version one day. For now Iām gonna need the finest cardboard and duct tape I have in the house to make a proper test case.
Sounds like my first synth case; I did buy a pair of TipTop rails, but the rest was Coroplast (repurposed political campaign signs), black sticky vinyl, and black duct tape. Served me well for over a year until I filled it up and built something bigger.
It is a LMN-3 (project home). i have two pcbs on sale in the BST thread. It is a cool but expansive project. Mine uses a pi4 8gb and boots up in ~30 seconds. i hope it gains traction and the software gets improved. there is a lot of potential in it. video review (yt)
Iām not really sure how anything made a noise and didnāt pop on previous steps, as I had the breadboard round the wrong way, in an effort to align it with the diagrams. All would have been fine if Iād also turned the power header round too, so I was sending -ve into +veā¦
I have forgotten pretty much everything I learned last winter.
Edit: It also looks like Iāve blown at least the TL074, so have replaced both chips just to be sure.
Yes, see the photo immediately above. Iām now wondering if Iāve knackered either the breadboard or the power header somehow. Iāve changed all the components, twice, and the none of the CD40106 will oscillateĀ¹. All I get is a heavy ground hum when the POT is turned round to the bit where it should oscillate, nothing anywhere else. Pondering on wither something is not grounded properly when I think it is. The voltmeter thinks everything is hunky dory thoughā¦
Might strip the other breadboard, build the Kosmo Mini power header I have and try again.
Ā¹ At least as far as I can tell, when prior to the frying incident, there was a distinct high pitched oscillation.
Definitely 50Hz? Iāve been (regularly) fooled by VCO not connected to CV, thought it was mains hum but it thought it was music. Maybe check that your control voltage is actually changing with a meter?
I am wondering: are you daisy-chaining the power cables, daisy-chaining the distributor boards or are there more outlets in the panel to connect multiple boards?
I ran out of distributor boards and now started to daisy-chain module with the power cableā¦
What? The day after election day you go out and grab some signs and stick them in the garage. The next time you have a project that could use Coroplast, youāre set.
Thereās a single PSU connecting to a nearby barrier strip, and for now a single bus board also connected to the barrier strip.
Assuming I donāt fill the case with 40 cm modules (I canāt, anyway, itās about 70 cm wide) Iāll need to add a second bus board later, and itāll connect to the same barrier strip in parallel with the first. The PSU can supply 1.5 A on each rail, so it should be able to comfortably handle the whole case.
(The panel mounted to the rails is just a power display, nothing behind it but a PCB with a power connector, two resistors, two LEDs, and three test points.)
And my 2nd Kosmo module (mostly) done! Thereās still an issue to sort out, the final build oscillates much slower than it should, likely a wiring issue a multimeter will reveal, too tired to do it today.
I repurposed circuits I already used in my CMOS synth. No need to tell me there are much better LFO plans available, I just wanted to try out making a somewhat original module duct taping existing circuits. Iām not expecting those early modules to be more than stepping stones and learning exercises.
A bit of hot glue will be applied to protect the ugliest part of the build ā stripboard is unforgiving of mistakes. And since my layout had mistakes, and my circuit was just made for learning, I wonāt share the flawed layout, but hereās the circuit if you wanna comment on it - not that anyone should use it:
now i have some questions 
