The Carl Martin Heavy Drive is a high-gain distortion pedal aimed squarely at heavy rock playing. Carl Martin describes it as delivering "massive amounts of gain with a focused, tight, and pronounced bass response specifically designed for guitarist[s]", along with "massive, tight low-end and heavy rock tones while preserving your guitar's natural character and tonal integrity". It sits in the maker's range alongside other drive and gain pedals such as the Carl Martin Plexitone Lo-Gain, the Carl Martin TOD and the Carl Martin Panama OD, and belongs to the wider family of distortion pedals.1
What it does and how it is controlled
Carl Martin describes the Heavy Drive's tone-shaping options as allowing "radical adjustments to the distortion character and voice". The maker points to two sides of that range: an Edge control offering extensive sonic variation, and controls that let you dial in everything from "tight, modern aggression" to "saturated vintage-inspired heavy tones". In practice, that means the pedal is meant to cover both tight modern heavy rhythm sounds and older, more saturated heavy voices, rather than one fixed distortion character.1
Power and bypass
The Heavy Drive can be powered either way most players need:
- A standard 9V battery, which Carl Martin positions for portable use1
- A 9V power supply, described by the maker as suited to dependable studio and stage performance1
The 9V power supply is not included with the pedal, so plan to use a supply you already own or a battery.1
On bypass, Carl Martin states that, like all of its pedals, the Heavy Drive features true bypass switching, which the maker says maintains signal integrity when the pedal is off. For a player, that means the pedal should not load down your signal chain when disengaged.1
The circuit and a DIY layout
For players interested in what is inside, the DIY pedal-building site Guitar FX Layouts published a vero (stripboard) layout for the Heavy Drive in July 2014. Its author, mirosol, notes that "the low noise MC33097 quad opamp may be required for best results, but i see no reason why TL074 or LM324 wouldn't work", and confirms that the LM347 also works because it has the same pinout as the listed op-amps.2
That makes the Heavy Drive one of the Carl Martin circuits a home builder can recreate on stripboard, using either the specified MC33097 or a common quad op-amp substitute.2
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Questions
Is the Carl Martin Heavy Drive true bypass?
Yes. Carl Martin says that, like all of its pedals, the Heavy Drive features true bypass switching, which the maker describes as maintaining signal integrity when the pedal is off. That means your guitar's signal passes through the pedal untouched until you engage it.
Does the Carl Martin Heavy Drive run on a battery?
Yes. According to Carl Martin, the Heavy Drive can be powered by a standard 9V battery for portable use, or by a 9V power supply for dependable studio and stage performance. The power supply is not included with the pedal.
Does the Carl Martin Heavy Drive come with a power supply?
No. Carl Martin's product page lists a 9V power supply as not included, so you will need to provide your own 9V supply or use a standard 9V battery to power the pedal.
What op-amp does the Heavy Drive circuit use?
The Heavy Drive circuit centers on a low-noise MC33097 quad op-amp. On Guitar FX Layouts, mirosol notes the MC33097 may be required for best results, but sees no reason why a TL074 or LM324 would not work, and confirms the LM347 also works because it shares the same pinout.
Can I build a Heavy Drive clone on stripboard?
Yes. Guitar FX Layouts, a DIY pedal-building site, published a vero (stripboard) layout for the Carl Martin Heavy Drive in July 2014, so the circuit can be built at home on stripboard by anyone comfortable with DIY pedal construction.
Sources (2)
- Heavy Drive, Carl Martin, 2026
- Guitar FX Layouts: Carl Martin Heavy Drive, Guitar FX Layouts (tagboardeffects.blogspot.com), 2014-07-11
