My five-year-in-the-making Eurorack gift is coming to a close!

[alexanderbrevig]

Five years ago, I decided to build my dad a modular Eurorack synth for his 60th birthday, and I finally placed the order!

I've done mostly digital designs and embedded programming (fix it in software), so this has been a steep learning curve.

After countless hours of simulation, breadboarding, and test PCBs, here are the modules I've designed — built on topologies and ideas gathered from the synth community:

• ADSR: Listed as EG (Envelope Generator) on the panel. Looping mode doubles as an LFO
• ATT: Simple attenuator
• DIST: Diode clipping distortion
• FIL: Voltage Controlled Filter with a diode ladder design
• MIX: Four-channel mixer; the fourth channel adds DC offset when no jack is plugged in
• NOISE: Generates white and bright noise (-3dB at 1.5kHz). Integrated slew limiter for portamento
• OUT: Dual channel mix and pan with line and headphone outputs
• SUB: Logic divider producing square wave outputs at 0, -1, and -2 octaves
• VCA: Dual voltage-controlled amplifier with pot or CV control
• VCO: Sawtooth output with FM; pulse width output with CV-adjustable width
• MULT: 8 jacks. Either 1 to 7 or two sets of 1 to 3

I've let out smoke, broken LEDs, and made opamps oscillate when they shouldn't; it's been worth it. I'm much less scared to prototype audio circuits, and much more thankful for my oscilloscope and triple power supply  .

It's been a while since I've posted, and a wall of text about analog synth design is probably random from me, but I had to share with people who might appreciate it (my wife don't, hehe). Thanks for reading!

PS: The panels are white since my brothers and I will paint and lacquer them. We discovered black silk screen doesn't show through paint, but they are handy when picking up a panel to paint and label.

[Simmed]

nice ! 

[alexanderbrevig]

It lives! NB: I'm a total noob at eurorack so just having fun to the best of my ability as of now :p

[tom66]

Very cool.

[ebastler]

Five years ago, I decided to build my dad a modular Eurorack synth for his 60th birthday, and I finally placed the order!

Nice! So, how old was your dad when you came up with the idea? Are you still on schedule? 

[alexanderbrevig]

Thanks!
He just had his 54th birthday when I came up with the idea and I knew I could not make the 55th (as I had no analog experience then) so it became a 60th goal.

I think I'm on schedule We celebrate his birthday in one month, and I just need to wire up some more of the modules and mount to the case.

[Analog Kid]

It lives! NB: I'm a total noob at eurorack so just having fun to the best of my ability as of now :p

Sorry, but that sample or whatever it is is horrible (musically speaking, not electronically). Very weird loping rhythm.
I'm curious, though: what waveform(s) is/are that? Sounds kind of sawtooth-y to me. (Which is the basis of the sound of a violin.)

Project is very kewl.

[alexanderbrevig]

Sorry, but that sample or whatever it is is horrible (musically speaking, not electronically).

Haha! The VCO was not tuned (this was literally first take, press some keys on the keyboard in arpeggio and go. I listen to and play technical progressive death metal, and microtonal death metal so I'm less sensitive to polyrythms and challenging the diatonics  Sorry for the chaos!

My next sample will be with a tuned VCO and some normal melodic choices 

Very weird loping rhythm.

It's a 3/4 65% shuffle loop, and the wobbles happens when I flip my ADSR to loop mode and I just quickly made it rougly in time.

I'm curious, though: what waveform(s) is/are that? Sounds kind of sawtooth-y to me. (Which is the basis of the sound of a violin.)

You are spot on! The top voice is a Saw, and the two octaves below are square. They are mixed, filtered and some distortion added (more towards the end).

Project is very kewl.

Thank you so much! I'm excited to gift it and free up some time for my next projects. Though I do like the Eurorack format and probably will make a few more modules, but for myself this time 

[tszaboo]

Five years ago, I decided to build my dad a modular Eurorack synth for his 60th birthday, and I finally placed the order!

Good for you, very nice gift. I designed him a weather station with an ESP32, because that was his interest.
I encourage others to do the same for someone else, it's the best gift you can give. Time and shared passion.

Nice job as well. I looked at Eurorack in the past, seems like a well thought out system to build on. This also looks well made, good job.

[alexanderbrevig]

First powerup and play!

[ebastler]

First powerup and play!

Judging by the broad grin at the end, it seems to work well enough! 

[nctnico]

Five years ago, I decided to build my dad a modular Eurorack synth for his 60th birthday, and I finally placed the order!

Good for you, very nice gift. I designed him a weather station with an ESP32, because that was his interest.
I encourage others to do the same for someone else, it's the best gift you can give. Time and shared passion.

Still, it is better to spend time with a person rather than for a person.