Aion Electronics Quark Maxon OD-880 Manual

Quark Overdrive
Maxon OD-880 Overdrive / Soft Distortion

Overview

Controls & Usage
The OD-880's controls are as simple as they come:
• Sensitivity controls the amount of gain in the op amp stage that is later hard-clipped.
• Level controls the overall output.
Modifications & Experimentation
The Clipping switch mod allows you to set up a second set of diodes to toggle back and forth from stock.
Extra pads have been provided so you can stack two diodes in a row if desired. (The middle two pads are
connected in each diode.) If you use a SPDT center-off switch, the middle position becomes a diode lift mode,
but you can also use a regular SPDT if you don't care about this.
The EQ switch changes the tone stack from stock to modded. The biggest criticism of this circuit is that it cuts
too much bass, so this mod gives more bass and fullness and changes the overall gain structure of the effect.
Note that this mod doesn't have an "off" mode like a clipping switch or a capacitor mod would, so don't use a
center-off switch here. Just use a normal two-position SPDT.
The original uses a few LM741 op amps. These are fine, and the comparatively low fidelity of these op amps
is part of the sound, like in the Distortion+. However, if you want to experiment, you can swap in any single op
amp here such as a TL061/TL071, CA3130EZ/CA3140EZ, or a NE5534.
MAXON OD-880 / QUARK OVERDRIVE
The Quark Overdrive is a clone of the Maxon OD-880 Overdrive
/ Soft Distortion, originally released in 1976. This pedal was huge
in Japan, being the favored overdrive pedal of Char, one of the
country's most popular guitarists, who—like the pedal—never
really got noticed out of Japan. It was reissued a few times,
notably in the mid-90's as well as in the past couple of years.
It's an interesting circuit from a historical perspective, being
sort of a "transitional species" between the Distortion+ and the
Boss OD-1 OverDrive: it added the input and output buffers and
changed the Drive potentiometer to a flat op-amp boost instead
of a gain modifier that also affected the bass tone, like in the
Dist+. The OD-1 is essentially an OD-880 with feedback clipping
diodes instead of diode-to-ground clipping, though this diode
arrangement turned out to be a very big deal and made way for
the Tube Screamer a couple of years later.
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