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Moritz Klein

@moritzklein0

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synthesizer circuit design
berlin
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Most reverbs use either springs, plates, or code. This one is purely analog and solid-state: two bucket brigade chips bouncing the signal around a feedback matrix until it turns into a room.

The first prototype just arrived, and it sounds better than I expected. On the breadboard, clock noise kept bleeding into the output. Once we transferred everything to a PCB, it came out completely clean.

The full story of how this went from breadboard to module is up on my Patreon. Link in bio.

#synthdiy #analogsynth #eurorack #reverb #electricalengineer taken in Berlin, Germany by @moritzklein0

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3 days ago

Every time I post about my BJT-based VCO design, someone tells me it can’t work: “BJTs are current-controlled, so you can’t control them with a voltage“. Yet the design works just fine.

That’s because it’s not an either/or. A BJT’s base is a diode, so it gradually opens up as the voltage across it increases. And because it does so exponentially, BJTs are perfect for building VCOs that track volt/octave.

You can try this yourself with our DIY VCO kit. Available now in the Erica Synths web shop.

Link in my bio.
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#diysynth #synthdiy #electricalengineering #vco #analogsynth taken in Berlin, Germany by @moritzklein0

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a month ago

I was up to my neck in reverb research when I hit a weird detour: turns out synth people and reverb people mean completely different things by the term „all-pass filter.“ The synth version was useless for my reverb – but perfect for building a phaser.

So I built one. But instead of JFETs or Vactrols, I found a way to make it work using plain NPN transistors. Cheaper, easier to source, and they sound great.

Full schematic and longer demo up on my Patreon.

Link in my bio. . . #diysynth #synthdiy #electricalengineering #phaser #analogsynth taken in Berlin, Germany by @moritzklein0

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a month ago

A low pass filter usually needs a capacitor. Here’s another option: take a plain inverting amplifier and add a single tiny resistor between the op amp’s inverting input and ground. On paper that resistor does nothing – practically no current flows through it. Yet it somehow rounds the corners off every signal you put through the amp.

Took me a couple days to work out what’s going on. The full write-up is now up on my Patreon: why it happens, how it impacts the functionality of 909-style VCAs, and how you can design around it (if you’d rather avoid this behavior).

Link in my bio. . . #diysynth #synthdiy #electricalengineering #opamp taken in Berlin, Germany by @moritzklein0

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2 months ago

Reverb usually needs a spring, a plate, or a lot of code. Here’s another option: two bucket-brigade delay chips feeding back into each other and into themselves, until two echoes turn into hundreds.

Took me four full months to get it working, but the prototype schematic is now up on my Patreon – including a section-by-section walkthrough, a complete BOM, and calibration instructions, so you can build it yourself.

Link in my bio.
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#diysynth #synthdiy #electricalengineering #reverb taken in Berlin, Germany by @moritzklein0

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2 months ago

Normally, every step in a sequencer needs its own knob. This one works with just one button.

Each button tap inserts a bit into a shift register. That bit travels through the chip, passing four differently sized resistors that all connect at the other end. This way, the bit’s position determines the output voltage. Send it to an oscillator, and we get a melody.

My new book teaches shift-register sequencer design from scratch – starting with the bare-bones single-button version, then adding accents, variable pattern lengths, half-time mode, and the melodic output you see here.

Out now in the Erica Synths web shop – link in my bio.
. . #synthdiy #diysynth #electronics #synthesizer #circuitdesign taken in Berlin, Germany by @moritzklein0

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3 months ago

I wrote a book that teaches you how to design a shift register-based drum sequencer circuit from scratch.

Starting from a simple single-button tap looper, you gradually build up the full circuit – adding a clear button, an accent CV output, variable sequence length, and even a pitch CV output along the way.

Each chapter includes a breadboard layout and a QR-linked simulator, so you can actually try every step yourself.

This is the second circuit design guide in the series – the first covers an analog kick drum. Both are available now in the Erica Synths web shop. Link in bio.
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#synthdiy #eurorack #modularsynthesis #electricalengineering taken in Berlin, Germany by @moritzklein0

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3 months ago

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4 months ago

Did you know you can build a resonant voltage-controlled filter from just seven basic parts? This circuit uses fully saturated NPN transistors as makeshift voltage controlled resistors in a simple two stage RC lowpass setup.

By feeding the output back into the first stage’s capacitor, the filter becomes resonant – without any extra parts.

To make it compatible with Eurorack-level signals, add a 100k/330Ω voltage divider at the input, then restore the output signal with a non-inverting op amp amplifier using a 100k/680Ω voltage divider in the feedback path.

I built and tested this on LABOR – a prototyping station I designed with Erica Synths. If you want to try this yourself: it’s available now, link in my bio.
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#synthdiy #diysynth #electronics #analogcircuits #electricalengineer taken in Berlin, Germany by @moritzklein0

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5 months ago

Did you know you can turn a 606-style kick into a voltage-controlled instrument with just one transistor? Instead of being locked to one pitch, it can now be sequenced, bent, and pushed into sharper, more aggressive tones.

My new Kick Drum Circuit Design Guide covers this and many more techniques for designing analog percussion circuits from scratch. Now available in the Erica Synths web shop.
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#synthdiy #diysynth #electricalengineering #synthesizers #electronics taken in Berlin, Germany by @moritzklein0

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6 months ago

KONSTRUKT-8 is here!

The Erica Synths & MKI DIY Modular Drum Machine is in stock at Thonk and shipping NOW.

Go to thonk.co.uk or check the link in the Thonk bio.

This post is intentionally silent. Go to the product page for demo videos. by @moritzklein0

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6 months ago

I wrote a book that teaches you how to design an analog kick drum circuit from scratch.

Starting from a simple oscillator, you gradually build up the full circuit – adding variable decay, pitch modulation, distortion, and CV control along the way.

Each chapter includes a breadboard layout and a QR-linked simulator, so you can actually try every step yourself.

Available now in the Erica Synths web shop – link in bio.
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#synthdiy #electricalengineering #circuitdesign #electronics taken in Berlin, Germany by @moritzklein0

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6 months ago