How two gain stages interact

Written By James Hamilton

The Twin is a dual gain-stage pedal built around interaction. There are two independent boost/drive stages, and the point is how they shape each other when you combine them.

Each side can be used on its own, stacked in either direction, or run in parallel.

Two stages, three ways to use them

Series (1 → 2 or 2 → 1)
You can choose which stage hits the other first. That changes both feel and tone:

  • 1 into 2
    A cleaner, higher-headroom boost going into the bias stage. Engaging the second stage lowers the “rails” and introduces clipping, compression, and fuzz-like textures.

  • 2 into 1
    Set up a spluttery, gated sound first using the bias control, then use the second stage to add level, smooth the edges, or bring back some body.

In series, the first stage sets the gain structure. The second stage shapes the final output, volume, clipping, and overall character.

Parallel
Both stages run alongside each other and are blended together.

This is where it opens up:

  • Keep clarity and dynamics from the cleaner stage

  • Blend in texture, compression, or grit from the bias stage

  • Works well for lead tones where you want presence without losing definition

You can treat one side as your core tone and use the other as a layer.

The two stages

Boost 1 = Gain
A more traditional gain control. Works as:

  • Clean lift

  • Low-gain drive

  • Second stage into an already driven amp or pedal

Boost 2 = Bias
Instead of gain, this stage uses a bias control:

  • Bias up → cleaner, more open

  • Bias down → reduced transistor voltage → clipped, gated, spluttery, compressed sounds

This is where most of the character comes from.

Using them together

Individually, each side can be subtle, a lift or a bit of drive.

Combined, they start to do something more interesting:

  • Series gives you saturation, compression, and harmonic density

  • Parallel gives you contrast, clarity alongside grit

A practical example:

  • Set a dynamic, slightly driven tone in series that stays clean when you play lightly and compresses as you dig in

  • Or run parallel with a driven tone on one side and just enough bias texture blended in on the other

Controls for shaping

Attenuate switch
Both sides are boosts by nature. The attenuator pulls the overall level down so you can use the pedal more as a tone shaper rather than a high-headroom boost.

Treble / presence cut
A simple top-end roll-off to tame brightness and round out the sound when needed.

Feel

The Twin is less about max gain and more about response:

  • Light playing stays open and clear

  • Digging in brings compression and drive

  • The interaction between stages changes how it reacts under your hands

HFX Core

Purchasing a Core pedal (Twin or Embers) includes 12 months of HFX Core:

  • 10% off all Hamilton Effects pedals

  • Early access to new releases

  • Design notes and occasional artefacts (sketches, sounds, ideas)

  • Optional involvement in future designs

The Twin is available now at hamiltoneffects.com.

James Hamilton
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