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Electron Brothers


The Brass Knuckle uses an all-tube signal path to create the harmonically rich overdrive tones only tubes can.


Although based on the much-revered British amps from the late 60s to early 80s, the circuit has been modified to create everything from classic-styled crunch to searing saturated lead tones, all dripping with pleasing harmonics. This pedal does not “clean up” in the traditional sense, rather it is “driven” from the get go and responds beautifully to the player’s touch on low to mid gain settings whilst retaining harmonic content. You could say it’s always just a little angry, but can be tamed by anyone willing to explore different guitar volume settings. Of course, it’s always ready to explode back to life as soon as pick attack and/or guitar volume is increased.


The signal overdrive is created purely by tubes being pushed beyond their operating limits like the gods of Rock ‘n’ Roll intended. An internal voltage multiplier provides 290 VDC allowing the tubes to be biased as they would in a typical guitar preamp section. In fact, apart from special circuit design aimed at making the output suitable for pedal boards, that’s precisely what the Brass Knuckle is – an all-tube preamp.


Being a real tube amp front end, it loves being slammed by your favourite boost or drive pedal!

It’s friendly to others, though, with an output section designed to work well with most pedals. The Brass Knuckle makes a great addition to any ampless rig as well, so there’s no need to sacrifice any of that wonderful tube amp feel just because you’re going direct.

As with any situation, wherever long cable runs are involved we advocate for the use of a good buffer to ensure all the carefully crafted tone makes it from your board to your amp.


Let’s start with the Tone Stack.

Based on a typical guitar Treble-Middle-Bass (TMB) tone stack, but optimised for pedal outputs, the tone controls have some of the usual quirks present in their amp counterparts.

High: This control has quite a powerful effect on the overall tone of the pedal. It’s helpful to think of it a mix control combining treble frequencies with the bass and mid frequencies from those controls before sending it all to the output. The higher this control is set, the less influence changes to the Mid and Bass controls will have, whereas they can tend to overpower the top end when the treble is set low.

Mid: This control has two functions. The first is obvious – it controls the mid frequencies. It also has an effect on the perceived overall loudness of the pedal. Falling into the mix? Don’t be scared to wind this control up until you pop out like you deserve to!

Low: This control is deliberately more subtle in this circuit than it might be in a complete amp circuit. More a trimmer for low frequencies than a fully-fledged Bass control. Higher gain settings will accentuate the bass control’s influence, so be careful that the nice, fat tones don’t turn boomy!

Loud Knobs

Gain: This control adjusts how much signal is pushed from the input gain stage to the subsequent gain stages. You will find good levels of harmonically rich overdrive available at low settings, with saturation increasing as you turn the knob to the right.

Turning the gain knob down to lower settings won’t cause the tone to become brittle like it can in some of the amps to which it pays tribute, which is great for gain stacking with other drives…or just wind it up and go it alone – either way you won’t be disappointed.

At higher gain settings there is more overall bass content available, so it is advisable to use the “Fat” and “Response” switches to tailor the sound to your liking.

Level: The Level control is reasonably self-explanatory. It adjusts the overall signal at the output (post-gain and post-tonestack). Due to output filtering necessary to work with pedals, this control will cause some darkening of the tone as it is turned down. If the darkening effect is undesirable, just flick the bright switch on and the high-end content will return.

Toggle Switches

Fat switch: This switch progressively increases the bandwidth of boosted frequencies in the first two gain stages. Centre position is the tightest setting and is in the ball park of a hot-rodded plexi type sound. The next two positions add slightly more mid content in each position.

Response switch: This switch changes the response of the tone stack. In effect, it governs the proportion of signal reaching the bass and mid controls. The centre position attenuates bass and mid frequencies and lessens the influence of those controls in comparison to the treble control. Each of the other positions gives the bass and mid controls more influence over the output. This can be useful at lower gain settings, whilst higher gain settings can have quite a lot of low end content if this switch is in position 3 (fully to the left).

Bright switch: This switch allows some upper frequency content to bypass the level control at lower output volume settings if required. If you’re familiar with the bright switch on some vintage American amps or the bright cap in many British stack amps, it does the same thing.The higher the level control setting, the less effect this switch will have. When level is at 100% this switch has no effect on the sound.

Note: Level, tone controls, Response, and Bright switch are all post-gain. Adjusting these will shape the signal which comes out of the gain stage. Gain control and fat switch are within the gain structure and changing them changes the gain structure accordingly.

!!! Safety Notice !!!

Do not open the case unless power has been disconnected for > 45 seconds. The Brass Knuckle contains internal voltages in excess of 250 Volts DC, which can cause serious injury or worse. Only qualified technicians should open the case when necessary. For more information contact

Weight 1.8 kg
Dimensions 22 × 16 × 10 cm
Pedal Dimensions

11.5 x 11.5 x 6 cm

Circuit Type

All Tube

Power Supply Voltage

12 Volts DC, Centre Negative

Current Draw