The Koch 63'OD is a tube-powered guitar preamp pedal: a 12AX7 preamp tube in a stompbox-sized housing, built to put a two-channel amp-style preamp on a pedalboard. Koch describes it as a preamp with "classic vintage overdrive, OD Boost, and maximum functionality," and the Overdrive channel is meant to fill in a clean tone with "thick tube-driven mids and saturation" in the manner of 60s and 70s players1. It sits in the preamp pedal category, with an overdrive character rather than a distortion or fuzz one.
What the 63'OD does
The 63'OD is built around a single 12AX7 preamp tube, the same tube type found in the preamp stages of many guitar amplifiers. Koch specifies a tube operating voltage of 285VDC, a figure that places the tube's working conditions closer to an amp preamp than to a low-voltage pedal circuit1. Because of the tube and that supply, the pedal is larger than a typical compact stompbox: 13.2 cm wide by 20.5 cm deep by 6.4 cm high, weighing 1.2 kg, in an aluminum housing Koch describes as heavy duty yet light weight1.
Koch describes the two sides of the pedal differently: the Clean channel is "focused on clarity and full-frequency response to accurately reproduce your guitar's tone," while the Overdrive channel adds the thick tube-driven mids and saturation of the pedal's vintage-voiced character1.
Controls and connections
The pedal's layout follows a two-channel amp preamp: two independent channels, Clean and Overdrive, share a 3-band EQ section, and a Boost switch is available for higher gain. Koch names a Volume control on the Clean channel1.
| Feature | What it does |
|---|---|
| Clean channel | Independent channel with its own Volume control1 |
| Overdrive channel | Independent channel for the pedal's tube-driven overdrive1 |
| Shared 3-band EQ | One EQ section serving both channels1 |
| Boost switch | Higher gain, described by Koch as taking blues/rock tones to the next level for solos or heavier drive1 |
| Pre-FX Loop | Non-buffered loop placed before the preamp section1 |
On the back panel, the 63'OD carries a balanced XLR DI REC/PA output with speaker emulation, which lets the pedal feed a PA or recording interface directly, and a Monitor Output with three levels: 0 dBV for a power amp, -10 dBV to an FX return, and a re-amp output to the Clean Channel input1. There is also a Remote Control Input for a MIDI switcher or external switching, so the channels can be controlled from switching gear rather than only from the pedal itself1.
Power
The 63'OD needs a 12VAC supply, and Koch includes the adaptor with the pedal1. That is an AC input rather than the 9VDC center-negative standard most pedals use, so it will not run from a typical daisy-chain supply. In the other direction, the pedal has its own 9VDC/200mA power supply output, so it can power other pedals on a board1.
The 63'OD takes 12VAC, not 9VDC. Use the included adaptor or a supply with a matching 12VAC output, and do not connect it to a standard 9VDC pedal supply.
Where it fits in a rig
As a preamp pedal, the 63'OD can act as the front end of a rig, feeding a power amp through its 0 dBV Monitor Output, or going direct through its XLR DI output with speaker emulation1. Its non-buffered Pre-FX Loop sits before the preamp section, so time-based and modulation effects such as delay or chorus can be placed after the tube preamp, in the position they would occupy in a conventional amp rig1. Players comparing overdrive pedals by type can see how a tube preamp differs from standard overdrive pedals such as those in the Boss SD-1 vs Ibanez TS9 comparison.
Videos
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Questions
Does the Koch 63'OD need a special power supply?
Yes. The 63'OD runs from a 12VAC power supply input, and Koch includes the adaptor with the pedal. That is different from most pedals that take 9VDC center negative, so it will not share a standard daisy-chain supply. As a bonus, the pedal also has a 9VDC/200mA power supply output that can power other pedals.
Can the Koch 63'OD be used direct to a PA or recording interface?
Yes. Koch fitted the 63'OD with a balanced XLR DI REC/PA output with speaker emulation, so the pedal can feed a PA or a recording interface without a microphone on an amp. There is also a Monitor Output with separate levels for a power amp, an FX return and re-amping into the Clean channel input.
What voltage does the tube run at in the Koch 63'OD?
Koch specifies a tube operating voltage of 285VDC for the 63'OD's 12AX7 preamp tube. That is a high plate-style voltage for a pedal, which is why the pedal uses its own 12VAC supply rather than a standard 9VDC one.
Can the Koch 63'OD power other pedals?
Yes. Alongside its own 12VAC input, the 63'OD has a 9VDC/200mA power supply output, so it can act as a small power source for other pedals on a board.
Can the Koch 63'OD channels be switched by MIDI?
The 63'OD has a Remote Control Input intended for a MIDI switcher or external switching, so its channels can be controlled remotely through switching gear rather than only from the pedal's own footswitches.
Sources (1)
- Koch 63'OD pre-amp pedal, Koch Amps (www.koch-amps.com), 2025