Alesis Bitrman bit crusher/frequency shifter w/ expression pedal mod, bypass looper

Alesis Bitrman stereo bit reducer, ring modulator digital multi-effect, from their ModFX series, originally aimed at DJ’s. This one was too strange and noise oriented for mass consumption, and they went out of production before they sold many. It does bit crusher, sample rate reducer/decimator, ring mod (AM), frequency mod (FM), and the (unusual) frequency shifter effect. In addition, you can add compression, distortion, and “Dual Phasor”. Oddly, it has many choices for changing the routing order of the 4 effects.

This unit has been modified for expression pedal control of the “Bitr” knob. The Bitr knob is where most of the action is, it sweeps the frequency of the ring modulators, and controls the bit depth on the bit crusher. The neat thing about how they designed that knob is when it is down, the effect is essentially bypassed, and as you turn it up the Bitr effect modulates in. With the expression pedal, you can have the effect bypassed when it is in the heel position, ready to go when you sweep the pedal down. When the expression pedal is connected, the Bitr knob acts as a maximum setting, so you can sweep up to a specific frequency/setting. In addition, the expression pedal has minimum knob, so you can set a minimum Bitr setting if you want to set a specific frequency/setting for the heel back position as well, like if you want to cross fade between two ring modulator frequencies.

To adapt the effect to guitar use, there is a custom true bypass loop pedal with master volume. The Bitrman has an A/D gain control on the back, that, along with the effects can add a ton of gain. The master volume attenuates it back down to normal guitar level.

The last modification adds internal shielding to the audio jacks, to fix the problem with the original unit, of adding whine noise to high impedance sources (guitar, bass). They are pressed up against the processor, and noise would leak in from proximity to the input.

These modifications are documented at DIY Stompboxes, topic 45777, should you want to reverse them. I’m the author there.



The unit is in good condition, note the scratch on the front, and audio-wise it has a little scratchiness when you adjust the gain pot on the rear of the unit, but it doesn’t seem to affect operation/noise level when you aren’t moving it. Other than that it sounds like it should, 24 bit high resolution processing, and with the shielding modification it is pretty low noise, and the Bitr knob and expression pedal operates at high resolution, no steppiness, feels analog. Does neat stereo stuff if you’re running it into a mixer.