The Electro-Harmonix Bi-Filter is an analog, dual envelope follower utilizing multimode filters and myriad of state-of-the-art features. Its tone is virtually unmatched by anything else on the market.

The outputs of each filter are available separately as well as mixed with the input signal in the main output. An effects loop allows insertion of the external effects before the filters, after the envelope detection circuitry.

The front panel allows direct access to all parameters for realtime tweaking. The envelope of the input signal controls the filters, with an oscillator provided along with controls for the rate and waveform shape. The 2 filters and their controls are identical, with control of the envelope attack/decay characteristics, filter type, frequency, and Q, and envelope and oscillator filter sweep. The output controls each of the filter outputs and the dry input, with inversion controls for each filter input and the ability to arrange the 2 filters in series or parallel. Switches also let you bypass the unit completely, and disengage the effects loop on the fly.

Rear panel connections include input, effects send and return, outputs for the 2 filters and the main output, CV outputs for the 2 envelope detector units, a pair of CV inputs for manipulating the filters from external devices, and a bypass footswitch jack.