Maxon Overdrive Pro Plus (OD-9 Pro+)

The Maxon Overdrive Pro Plus (OD-9 Pro+) is an overdrive pedal from Maxon, built on the company's classic OD-9 circuit and expanded with two additions: 9/18-volt operation and a Mid Boost switch. Pedal of the Day described it as taking Maxon's classic OD-9 circuit and serving it up with "two side orders of Whoop-Ass"¹.

For a player, that means the familiar mid-boosted overdrive voice of the OD-9 family, with the option to run at a higher internal voltage for more headroom and a tighter feel, and a switchable midrange push for solos. Pedal of the Day's reviewer found the pedal "sounds simply phenomenal" and that "there's a lot going on with this seemingly simple pedal"¹.

What it does and how it is controlled

The OD-9 Pro+ is a mid-boosted overdrive in the Tube Screamer tradition. Pedal of the Day described it as giving "all that classic tube screamer-ish tone, with some wonderful options to customize it to play well with any rig"¹. The standard OD-9 it builds on carries Overdrive and Output Level controls that adjust the intensity of overdrive and output volume².

The Pro+ adds two controls of its own:

Pedal of the Day's reviewer found the Mid Boost "great for cutting through a band during solos"¹.

Power: 9V or 18V

The Pro+ runs on 9 or 18 volts. The two settings behave differently¹:

• 9-volt setting: sounds and functions like the standard OD-9¹
• 18-volt setting: Pedal of the Day's reviewer found it "becomes an 800-pound Gorilla, offering up beefier lows, tighter saturation, improved dynamics" and a chunky, aggressive pick attack¹

Under the hood, the pedal uses an NJM2374A voltage conversion chip that changes the 9V power input into 9V+ and 9V-, increasing op-amp headroom to an 18V swing¹. The higher-voltage idea has appeared elsewhere in the OD-9 family line: the OD-9+ reviewed by Guitar World in 2007 also boasted high-voltage operation, 18 volts switchable to a more traditional nine volts.

Inside the circuit

Pedal of the Day broke the Pro+'s signal path into stages¹:

1. A JFET buffer at the input, offering high input impedance and low impedance into the rest of the pedal, which the reviewer found preserves high-end clarity¹
2. A first tone stage built as a switchable op-amp with clipping diodes in the feedback loop, which is the Mid Boost feature¹
3. The OD-9 overdrive circuit itself¹

The pedal uses mechanical true bypass switching via a Fujisoku 4PDT switch, with the input switched to ground when bypassed¹. That continues a family trait: early OD-9s used a DPDT switch with "normal" bypass, and Maxon changed to an actual 4PDT true bypass switch around 2004³⁴. Aion FX notes the OD-9 was also revised to use a new op-amp and true-bypass switching via relays⁵.

Where it comes from: the OD-9 family

The OD-9 circuit goes back to 1982, when the design was repackaged as the Maxon OD-9 Overdrive and Ibanez TS9 Tube Screamer⁶. Guitar World's history of the Tube Screamer notes the OD-808 and OD-9 correspond to the two classic Tube Screamers that Maxon produced, the TS808 and TS9⁷. Vintage Guitar described the OD-9 as an Ibanez TS-9-inspired overdrive⁸, and TONEHOME puts it plainly: "the Maxon OD9 is just another Tube Screamer"⁹.

The OD-9 has since spawned a range of variants, each a different take on the same core circuit¹¹⁰¹¹:

Guitar.com's reviewer summed up the standard OD-9's appeal in a way that carries over to the Pro+: "If you like the idea of a clearer and more refined take on this classic overdrive, with the potential added benefit of true bypass switching"¹².

Where to find it

Pedal of the Day noted the OD-9 Pro+ is sold via the Maxon store at Osiamo Music Gear¹.

Videos

Click to load

Click to load

Click to load

Questions