Lmst

This time my #soldering was a fail. This is supposed to be a #keyboard controller for playing my #StackSynth but the sample and hold part needs rework. The output voltage keeps rising. At first I noticed that I used a ceramic #capacitor where I should've used a polymer one, but this bodge didn't help. Maybe the #TL074 are out of spec (most likely fake ones but worked fine in the other modules) or the FETs are bad...
The keys will be attached using a stereo 3.5mm audio jack, and will be extendable like my perfboard version.
#diysynth #synthesizer #sampleandhold

the bottom side with all SMD components soldered in.

the top side with the through hole components soldered in.

the attempted fix for the sample and hold error.

One of the final modules for my #StackSynth project: the #noise generator. It outputs white, blue, and pink noise and uses a #3904 and a #TL074 with a lot of resistors and a couple of capacitors.
It is based on Moritz Klein's video: https://youtu.be/0yB_h_wFkh4
I prototyped it on solderless #breadboard and then designed the #PCB in @kicad and let @aislerhq manufacture them again. It turned out quite nice and sounds great.
#soldering #diysynth #synthesizer #KiCad #pcblayout #MoritzKlein

the prototype on solderless breadboard. it's a bit messy and has lots of resistors scattered around.

the finished board from the top. the components are placed in a neat grid and look very orderly.

Finished #soldering another #StackSynth #diysynth module, an important one: the #VCA - together with the ADSR, it makes the output sound much better.
Again, boards were manufactured by @aislerhq and they look nice.
I noticed that I didn't have any 2MΩ 0805 #SMD resistors, but found a couple of larger 1206 2.2MΩ ones in my recycle bin. They don't fit perfectly, but should do until I have the proper ones.
#synthesizer #LM13700 #TL074

bottom of the finished board. the SMD components are visible.

board from the top showing the LM13700 and the TL074.

closeup of the two larger 1206 resistors (R29 and R11). the top one is a bit crooked.

Finished #soldering my #VCO #perfboard. It is calibrated to 1V/Octave and outputs sawtooth, square/pulse, and triangle waveforms.
The heart is a #CD40106, using only one of the inverted Schmitt triggers. I tried adding more, but couldn't fit them properly. Maybe if I left out the triangle wave output, which would remove the upper #TL074.
My power supply board is getting full, I should add a few more sockets.
Demo video: https://makertube.net/w/bxShHoDY5cCP7krbjnFgh8
#diysynth #waveform

the finished VCO from the top, fully populated and labeled. the pin header to the left is the CV input, the pin headers to the right are the three outputs for the different waveforms.
at the bottom there are three potentiometers, for coarse tuning, fine tuning, and the pulse width of the square wave.

the bottom of the board.l, showing the soldering. I'm quite happy with the result, even if I had to redo a part to the right due to an error in the schematics. thankfully there was enough space to fix it.

the dual rail power supply board with all modules used in the demo video plugged in. the dual supply socckets are all used, just two single supply sockets are free.

Finished #soldering the next #perfboard, the #sequencer core with the #CD4017 counter chip and a #TL074 #OpAmp. I have connected the control board and the rest, see a demo here: https://makertube.net/w/mEobXiLn5so6Rpe2zQA16E
After soldering all components, I had the idea of adding a #LED for the gate output. Fortunately it fit very nicely.
Only VCO and LFO are still on solderless breadboards, and I wasted some time searching for a fault turning out being bad connections on the breadboard...
#electronics #diysynth

the finished board from the front. on the left is the TL074 OpAmp, and on the right the CD4017 decade counter. at the bottom is the reset selector and on the top the step outputs. on the upper right are the connectors for power and return path of the control boards. on the left are the clock input, gate and CV output

the back of the board, showing all the wires needed

the board connected to the rest of my synth. only the LFO and the VCO are on breadboards

#finished #soldering the #perfboard. The #TL074 and the #LM13700 are already inserted, too. Will give it a try tomorrow, now is too late.
I forgot to order 120kΩ #resistors, so I used 100kΩ ones and added 20kΩ #SMD resistors on the back side.
While planning the #PCB layout, I sometimes used diagonal traces. At three places they went directly through neighboring solder joints, so I had to insulate them. In future, I'll use them less often.
#diysynth #VCA

#TL074

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