AeManual / KeuerslagerkurtQuadBoost

Kurt’s Quad Boost

Kurt’s Quad Boost is a module consisting of four transistor amplifier circuits, inspired by the old-school ‘LPB-1’ guitar pedal. Each amplifier circuit has its own dedicated ‘Boost’ knob that controls the input volume. The amplification has a distinct ‘transistor sound’. Due to the non-linear nature of this simple component, it is by no means a clean boost at all. Depending on the input volume, you will get everything in between crispy high end accents and deep low-end fatness.

This module is designed and distributed by Keuerslager Kurt and you can purchase the module here:


There are four separate inputs that each lead to their own amplification circuit.


The outputs of the four amplification circuits.


Each of the four boosts has its own dedicated input volume knob. It should be noted that this knob does not act as an attenuator, it does not completely silence the incoming signal when turned fully left. Rather, it gives you a control for the amount of ‘drive’ or ‘clipping’ that the circuit gives.

Patch Suggestions

The most straight-forward use of the Quad Boost is to boost signals that are lower in volume, like the triangle or saw wave from the 2Osc module. You will notice that you can get some fairly clean amplification of these waves, but also some more ‘colored’ sound depending on the amount of ‘Boost’ you set. If you input already ‘loud’ waves, like the square waves, the effect will be less noticeable, as these are already at the maximal ‘internal’ volume of the AE system (i.e. 0-5V).

A more interesting approach to exploit the transistor sound is by controlling your incoming waves with a VCA module. Depending on the input volume, the timbre or tone of the output can drastically change. So setting a slow LFO to modulate the incoming volume via the VCA, will create an interesting shift in tone and make your patch come alive. More drastic volume changes, for example using the 2Env for short notes, can also give really musical results.

A sound demo patching different volumes of the same triangle wave in the Quad Boost:

It is also worth noting that the circuit might behave differently depending on the module you patch behind it. Don’t be afraid, you can’t break anything! But if you use ‘unbuffered’ modules right after the Quad Boost output, you might notice some volume drops. This is due to the simplicity of this circuit (for the electronic geeks: it has a rather moderate output impedance ranging from 5k to 50k depending on the specific resistor values you use). I myself have noted no problems yet, but I mostly feed it straight into the mixer. Just wanted to give a quick heads up!

Page last modified on March 26, 2021, at 08:52 PM
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