Help with CLOCK module

Hi. Could someone help me again? :slight_smile:

I’m trying to design my own CLOCK module for my existing Eurorack sequencers.

Looks like an astable 555 timer circuit would work well. Let me know if you don’t think so.

I need some guidance with improving this preliminary circuit.

It needs a Clock Rate knob to change the speed. I’m hoping that POT in the picture will do this. It would also be nice to have a switch to change between ranges x1 or x10 speed.

Clock Rate Knob : 0.1 Hz - 10 Hz (x1)
1 Hz - 100 Hz (x10)
Range Switch : x1 or x10

It would also be great to have a knob to change the gate time (duty cycle), around 10%-90%. Is it as simple as adding another POT to R2?

What would I need to add to this circuit and what are the best values for POT, R1, R2, & C?

The plan is to power this from a Eurorack +12V. Is that ok? How can I improve my pulse output connection to be 0-5V and safe for patching to other synth modules?


Found this circuit. Maybe this is a better starting point. It is suppose to be independent variable frequency and duty cycle.


  • Does anyone have a LTSpice model for the LM393? I would like to try to simulate this latest circuit.

There is also this one which looks similar to the second. I would think one of these should work after swapping some components.

Why not just an LFO module with a square/PWM output?

Hi, Toneburst. Yes that would work. The reason I’m trying to build one myself is so I can have exactly the controls I want.

I found one that has almost everything I need :
Out of production though. If I could mod that VC CLOCK module to have a start, stop, and step buttons, I would be all set.

You know of any other vc clock modules with adjustable duty cycle?

The other idea I was thinking about would be to make from scratch using a micro controller and Mutable Instrument examples.