Maxon - OD-9 Pro Plus Overdrive

The Nine Series Overdrive Pro+ takes Maxon’s classic OD-9 circuit and serves it up with two side orders of Whoop-Ass in the form of 9/18 volt operation and a Mid Boost switch.

In 9-volt setting the Pro+ sounds and functions like the standard OD-9 with the added option of a healthy +3 dB of midrange boost at approximately 800 Hz (actual frequency is dependent on Control settings) – great for cutting through a band during solos.

When set to 18-volts the OD-9 Pro+ becomes an 800-pound Gorilla, offering up beefier lows, tighter saturation, improved dynamics and a chunky, aggressive pick attack that will make your amp sound and feel like it just took a Viagra. Switch on the Mid Boost in this mode and let your solos breathe fire.

Don’t just play like the pros – play with the Pro Plus.

Specs:

Overdrive based on classic OD-9

Switchable 9- or 18-volt operation (runs on 9 VDC)

CAUTION: use a dedicated power supply when chained with other effect pedals.

More Gain and Low-End (18-volt setting)

Mid Boost Switch add +3 dB @ 800 Hz

NJM4558 (JRC) Op Amp

True Bypass Switching

The OD-9 Pro+ starts with a jFET buffer which simultaneously offers high input impedance and low impedance into the rest of the pedal – this helps to preserve high-end clarity in the signal.

The first tone stage is the Mid Boost feature: A switchable Op Amp with clipping diodes in the feedback loop. When this stage is not in the signal path the pedal behaves like a standard OD9. With this stage in the path it adds subtle gain and definition to the sound, similar to a cascading gain stage.

From here it’s on to the standard OD-9 circuitry: A clipping Op Amp with diodes in the feedback loop that clip the signal gradually as well as a high pass filter that keep the low frequencies from being distorted as much as high. Next there comes a passive LP filter and then an active tone stage. After the tone stage it’s through the Volume pot, an Op Amp boost stage which bumps the signal 3X and then sends it to the output.

The Pro+ also utilizes an NJM2374A voltage conversion chip that changes the 9V power input into 9V+ and 9V-, increasing the headroom of the Op Amps (9V to 18V swing) and giving a bigger, chunkier sound to the overdrive.

The OD-9 Pro+ features Mechanical True Bypass switching via a Fujisoku 4PDT switch - Input is switched to ground when bypassed.

Thank you, Gearmanndude