Valves in Guitar Pedals | Boost Guitar Pedals

Duncan MacKinnon, founder of Stompnorth Pedals, knows a thing or two about valves in guitar pedals. Below, he dives into how they work and why we love them...

My introduction to building guitar pedals was a Build Your Own Clone – ESV Fuzz. The ESV stood for Extra Special Vintage on account of its Phillips Ac127/01 germanium transistors. Its sound is amazing and is indeed as old school as its name suggests, but I wanted to take "vintage" even further, so I started looking for valve kits and soon found a booster that used a single 12ax7 valve.

I loved the way it sounded and the response it gave, so I knew that valves were the way I wanted to go with my own projects. As a synth player first and foremost, I was used to manipulating waveforms and textures, but even from this hi-tech perspective I still found vintage hollow-state circuitry [i.e valves] offered more pleasing sounds and possibilities than the more modern solid-state, transistor and op-amp driven circuits - which, of course, are also tremendous.

The sensitivity and flexibility of a valve is, in my opinion, unrivalled in guitar pedal building where subtlety, response, transparency and sound quality (not necessarily fidelity) are the aim. A valve in low voltage "starved plate" mode offers a certain type of response and transparency which is different to the more full-on high voltage valve circuits. You can max-out a 12au7 pedal and still know which guitar you are playing. I also think they have a really pleasing and unique sound all of their own. This is the reason I designed one of my own pedals around a 12au7 running 9 volts.

STOMPNORTH Clipshear Getter Drive front transparent | Boost Guitar Pedals
STOMPNORTH Clipshear Getter Drive front transparent | Boost Guitar Pedals
Stompnorth Clipshear Getter Drive Context | Boost Guitar Pedals
Stompnorth Clipshear Getter Drive Right Context | Boost Guitar Pedals
Stompnorth Clipshear Getter Drive Left Context | Boost Guitar Pedals

STOMPNORTH Clipshear Getter Drive


Stompnorth's flagship pedal combines MOSFET, valve, and silicon and germanium diodes to achieve a multitude of low to mid-gain tones.

View demo video

Duncan MacKinnon designed this pedal to be an integral part of your rig, an 'always on' pedal that enhances your core tone. Based around a 12AU7/ECC82 valve, it can thicken up your tone and layer on harmonically rich gain in a progressive way, enhancing rather than masking your core tone.

The Stompnorth Clipshear Getter Drive provides up to 21dB of boost that can really drive the input of your valve amp, but the analogue character and true valve gain also makes it a brilliant solution for recording.


The Gain control adjusts the amount of pre-amplification applied to the input of the valve circuit, and can be used in conjunction with the Volume control to “goose” the front end of your amp, or Clipshear’s valve circuit.

The Valve control adds gain to the valve signal path, which produces an amazingly responsive and transparent overdrive ranging from subtle boost to sweet overdrive. Used in tandem with the Gain control, you can achieve tons of sustain and a thick overdrive sound.

The Si / Ge / Off toggle switch adds silicon or germanium diode clipping to the signal path. Engaging it with high gain settings turns an overdrive tone into distortion, or at lower settings to a responsive crunch. Si is transparent and precise, Ge is “squidgy” and vintage. Note that engaging either diode results in a considerable volume drop. This is normal.

Use the active Volume control to either trim the output of the Clipshear Getter Drive to parity with the bypassed signal, increase the volume of the signal when the diodes are engaged, or to drive your amp’s input. There's also enough headroom to experiment with rolling back guitar volume to further expand the range of available textures.

The blue power indicator glows when the Clipshear Getter Drive is connected to an appropriate live power supply. When the pedal is activated, an orange indicator light glows from within the pedal.

Handmade in the UK from the highest quality components - just take a look at that beautiful Jupiter capacitor! - the Stompnorth Clipshear Getter Drive is perfect if you're after superb translation of your core tone for low to mid-gain purposes.


  • Gain, Volume, Valve, Si/Ge/Off controls
  • 12au7/ECC82 Valve drive with silicon and germanium diode clipping
  • 21dB of boost
  • Highest quality components
  • Handmade in the UK
  • Power: 9V power adaptor (min 100mA), centre-negative (not included) 

Read the manual

See the demo:

View Details

How a Valve Works

A valve can be thought of as a glass tube, with an anode (plate) at the top, and a cathode at the bottom. Electricity in a valve flows in the opposite direction to the accepted norm of positive to negative, and it does so in a wash of electrons called space charge; this is the bit I love the most! When you turn a valve on, the cathode has to warm up, and then space charge is produced. This flows from the cathode to the plate through a vacuum. Not carried by radio, or wire of any kind, but literally floating through space, a tiny bit of outer space, (with flying saucers and ray guns), right there in your pedal.

Your guitar signal enters through another internal component, the grid, which sits in between the plate and cathode. When a signal with positive potential enters the grid it gets caught up in, amplified by, and carried in the flow of space charge all the way to the plate, then on into your amplifier in an awesome shower of tone-bearing electrons.

Another fascinating thing about valves is their sheer theatre. They are huge in comparison to other components - you can see the internal workings through the glass. Also, each one is slightly different inside. The getter flash (silver cap) is another brilliant factor of valves. The science is fascinating and they look great, but this subject is best saved for another occasion.

Guitar Pedal Buying Guide | Boost Guitar Pedals

Read: What Is A True Bypass Pedal?


In short, I think valves are magnificent, eloquent, and beautiful pieces of engineering that have un-reinventable qualities, which I think is why they are still so commonplace in guitar gear (and high end audio gear) today. They were not replaced by the transistor as we were told they would be - valves are here to stay.

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