The Synth - Schematics and Infos

[Schlatte]

Hi all!
Next up - The Synth!

It is a small synth with either manual control or modulation via LFO.

Schematic:
Can be downloaded as PDF from my Google Drive: https://drive.google.com/file/d/1rKjPMnOV5-bsueZgq95SsLs1o5HwA-y3/view?usp=sharing

SPOILER : show

Controls are as follows:
LFO Section
-P106 LFO Frequency
-P101 LFO Wave Shape
-S103 LFO Frequency Range
-S203 LFO or manual sweep selector switch
-P103 Sweep Depth in LFO mode, manual sweep in manual mode

VCO Section
-S101 VCO Frequency Range
-P105 VCO Frequency
-P102 Output Filter (LPF)
-P104 Volume

For P105 you can use other pot values but it is important, that the parallel resistance with R108 stays in the same range (~200k).
Here are some combinations that work well:
P105: 250k, R108: 1M
P105: 500k, R108: 330k
P105: 1M, R108: 270k

Tinkering and improvement ideas:
-) Replace the filter section (P105 and C109) with a tone stack, so you can get LPF and HPF going!
-) Add a 5V LDO and run the whole thing on 5V with an LMV324 and 74HC4046. They are more "modern" and you can get them more easily than the "old" stuff that runs on 9V.


If you have any questions or comments, just ask!

[Dowi]

Just spent lunchtime jamming with The Synth and shot a video of it.
The first part is pure "getting to know" the synth exploring the different waveforms and messing with LFO sweep and filter (with just a bit of delay/reverb here and there); the second part is me messing with a pulsating synth setting and some effects to see what could happen with various combinations. After shooting the videos i've paired it with some dirt pedals too, and it sounded extremely good with a mid-scooped fuzz.

I have basically no experience with drone synths, so i cannot compare it to others. It's pretty aggressive, as you would expect from a single VCO, and I find it very simple and fun, If the modulation rate could go even slower I would appreciate it a lot.
I don't know if I'd prefer a tone control as i like the filter, and it would be even cooler with a resonance knob. Maybe the chance to select it to be a LPF or HPF could be an interesting feature.
Another maybe easy addition could be a momentary switch to easily trigger it manually in a rhythmical way (or maybe a CV in?)

Gonna explore it more in the next few days, some real good work Schlatte!!

[Schlatte]

Glad you dig it!
Thanks for the awesome video and the feedback! Have fun playing some more with it!

[goroth]

I thought it was an expression generator and plugged it into some pedals expression inputs.
It worked.

OTOH I'm glad I didn't fry any pedals.

[Schlatte]

I thought it was an expression generator and plugged it into some pedals expression inputs.
It worked.

OTOH I'm glad I didn't fry any pedals.

THAT IS NOT THE INTENDET USE, SIR!
but if you didn't turn the volume all the way up on the Synth and the pedals you plugged it into have at least some half decent protective circuitry, you should be alright.

[coldbrightsunlight]

I thought it was an expression generator and plugged it into some pedals expression inputs.
It worked.

OTOH I'm glad I didn't fry any pedals.