White noise hats

Oh and also @Dud have you tried driving the inputs on this harder? At 11v or so it gets a nice hard percussion at the start, very different even at 8v which is softer

1 Like

I think the Beatstep Pro send 12V gate out

1 Like

Ah! That’s a spicy output :fire:

1 Like

I would use an op amp configured as a comparator with a diode on the output, and the reference voltage set to something like 1V.

(sorry for the rubbish photo)

A comparator works by taking a reference voltage and an input voltage. If the input voltage is larger than the reference voltage, the op amp will swing its output as far as it can* to its positive rail. If the input voltage is less than the reference voltage, the op amp will swing its output negative.

(which on a TL07x with bipolar 12V supply is something like 10.5V)

This means it should work with any input level. The trimmer is used to adjust the threshold at which the output swings high.


That’s much better! Definitely gonna go that route instead, I’ll draw it up hopefully tomorrow thanks!

The weird and wibbly world of op-amps


I made a cheatsheet:

though the one conspicuous ommision just so happens to be the comparator.


Funnily I find transistors mich harder to understand! XD you need to somehow bias them and then there are also different combinations and there are npn and pnp and also mosfets… confusing stuff!


Oh, me too. Op amp behavior is simple — well, the basics of it, there’s subtle (sometimes not so subtle) details way beyond me. Transistors, I dunno man. And I haven’t found a good general writeup about designing with transistors that isn’t mainly about logic circuits and MOSFETs.


Moritz Klein did a livestream about (analogue uses of) transistors that you can watch back if you join his Patreon.


Can i suggest the bipolar transistor cookbook?

I had transistor circuits in school when i was studying to be an aircraft technician but i like to use this as a reference for diy stuff :slight_smile:


I feel that bjt transistors have been this constant in my life, always there and part of so many things, but I find the more I learn about them, the less I understand. Mosfets however I use a lot, but generally I’m just switching motors with them.

It is a nice thing to release thinking you know something sometimes and admit that there are hidden complexities that will continue to become apparent as you go for your entire life.

1 Like

Exactly, it’s always those edge use cases that put you in a spin with transistors

Just tested this comparitor to boost the gate voltage up to the hottest the op-amp can do (something like 10.something V) and it works super well

I’ll chuck it onto a stripboard now and put it in with the percussive noise voice for that punchy crunch I crave now.

EDIT: an earlier version here I’d flipped the TL072, fixed now, onto to update the stripboard


And here this mess is in all its glory:

Made to adapt an already built module, or maybe you have something odd that just doesn’t do well with the standard eurorack level gates, and needs something spicier to make them pop.

Another addition is the unity gain buffered outputs as some older/simpler designs don’t always have them.

This is to fix that I built a stripboard without fully testing it (only a cursory “does it work?” test) and needed to up the input to get the percussive hit that the design was intended to give (not a problem for those with BeatStep Pros that output 12V gates/triggers).

EDIT: updated the stripboard layout that carried across an earlier flipped TL072 in the schematic


Multiply the 220 and 1K by at least 10, even up to 100… OpAmps only need a few uAmps…


Excellent thanks, I had no reference as to what it’d be happy with so I’ll update it

1 Like

maybe you can amplify the output with an inverting opamp like this ?..
(gain x10)