Electro-Harmonix Bi-Filter Reference Manual

User Reference Manual

Manual Notice:

This manual is provided as both a guide
for instruction, as well as a reference to
be kept near by to aid you in everyday
use. In it you will find general informa­tion, regarding the Bi-Filter as well as
instructions for real and suggested oper­ating procedures, setup and use. This
manual is subject to change without
notice. Electro-Harmonix is not liable for
errors, direct, indirect, coincidental, or as
a consequence of material contained
within this manual.

32-33 47th Avenue
Long Island City, New York 11101
ph: 718 937 8300 fx: 718 937 9111
www.ehx.com

TABLE OF CONTENTS

Introduction 3
Precautions For Safe Use 4
Front Panel 5

Drivers 6
Filters 7

Output mixer 9

Rear Panel 11
Block Diagram:

Audio and Control Signal Paths

13

Specifications 14
Sample Settings 15
Blank Program Sheet 17

Thank you for purchasing the Electro­Harmonix Bi-Filter. Please read this
manual–written to be a reference
guide that you can keep close by–in
order to familiarize yourself with this
unique instrument’s layout. The Bi­Filter’s sound is wonderful and can
truly set your music apart, but the
key is your creativity.

Copyright
2003 Electro-Harmonix. All rights reserved. Bi-Filter
and Electro-Harmonix and logo are trademarks of
New Sensor/Electro-Harmonix. Product and company
names used within the manual are trademarks of
their respective companies.

INTRODUCTION

In the complex world of modulation instruments, Electro-Harmonix introduces the Bi-Filter. It’s a totally analog
instrument, drawing upon the filter designs of the past while utilizing a front panel that brings EVERY relevant control,
for every parameter, to the surface. You are given complete interactive access. Exquisite tone was the bottom line in this
design and the “hands-on control” aspect presents the musician or engineer with the ability to make global, real-time
tone changes that can make the difference between a hit and a miss.

The uniqueness of dual filters working with or against each other presents possibilities only limited by the user's
creativity. The sameness of digital filters, by their very “perfect nature” pale in comparison to the “random” fluidness
that analog filters present. Their uniqueness and full-bodied tone are possibly the most emulated aspects of today’s
modern instruments. Emulations are fine, but the real deal is special.

The Electro-Harmonix Bi-Filter combines two versatile “all analog” envelope and LFO controlled filters in a
configuration that enables the most complex and interesting filter sounds ever possible.

The Bi-Filter continues the tradition of the original Mu-Tron, Beigel Sound Lab and Electro-Harmonix Q-tron products
by using opto-electronic “photo-mod” control. The “state-variable filter” architectures produce the clean and unique
sound, with selectable filter curves preferred by top professionals.

The Bi-Filter uses all analog circuitry, for the best dynamic range and signal-to-noise characteristics of any available
filter product. The effect circuit also uses “true bypass” switching to allow pure unmodified instrument throughput
when the effect is switched off.

The Bi-filter is a single-channel processor, though the filter outputs are individually available. The main effect output is
a single channel MIX of Filter 1, Filter 2 and the input signal. An external FX loop between the input and the filter
allows the use of audio processes without distorting the signal input’s envelope waveform, providing simple access to a
new range of sounds that are reactive to the dynamic of the user—whether engineer, musician or DJ. The Bi-Filter has
all of the best aspects of the past with a sound that makes digital instruments and recordings come alive.

3

Front Panel

Back Panel

PRECAUTIONS FOR SAFE USE

Please read the manual carefully, as it was written to help you understand the operation capabilities of your new
instrument. Carefully review the safety precautions as they ensure a long and trouble free life for your Bi-Filter, as well
as your own safety. Keep your manual in an easily accessible place for future reference.

The following instructions, on this page, are WARNINGS that must be followed.

1. Fluids and moisture: Do not operate this—or any electrical instrument—in an area where it could be exposed to

moisture. This is an instrument. Do not place drinks or fluids on top of it.

2 Placement and ventilation: The Bi-Filter is a rack-mount instrument and thus may be placed in a 2-space rack

location. It may also be placed on a support or table that is designed to handle weight. Placement must be balanced
and even, while still leaving an unobstructed space for proper ventilation. Proper ventilation ensures long life and puts
far less stress on the instrument. Again, keep all fluids away from the storage location. All bracket mountings must be
able to bear the weight of the Bi-Filter.

3. Cleaning: Extreme care must be taken when cleaning the exterior of the Bi-Filter. The exterior may be wiped down

with a damp sponge and an extremely mild detergent. Damp means slightly moist and not wet or saturated.
UNPLUG THE INSTUMENT before any cleaning.

4. Heat: The unit should be situated away from heat sources, or other equipment that produces significant heat. When

the unit is rack mounted, be sure it has proper ventilation.

5. Power Sources: When the unit will be unused for extended periods, disconnect the power supply from the outlet.

Be careful that the power cord is out of the way and specifically away from traveled areas. When connecting or
disconnecting the cable, grasp the plug firmly and push or pull. Do not pull from the cable. Make sure that your
hands are dry.

6. Service Situations: Situations that must be immediately addressed if encountered.

a. Damage to the power cord or to the power supply.

Immediately shutdown and disconnect the power cable.
b. Water, or any other fluid, that has fallen into the interior of the Bi-Filter.
c. Exposure to natural elements such as rain or lightening.
d. Sudden impact of the instrument, such as dropping or a hard external impact.
e. Sudden and noticeable differences in performance and consistency.
f. Functional change where a marked difference in operation is noticed.

Note: All electrical failures must be handled by an authorized service technician.

Do not attempt user service.
A qualified technician will handle it swiftly, accurately and correctly.

For your safety and proper repair, call:

Electro-Harmonix: 718-937-8300. Ask to speak with a service representative and you will be instructed on
how to proceed. You must call in order to receive service.

4

FRONT PANEL

Main Features in the Front Panel

The front panel is organized into the following main sections:

Filter and FX Loop switches: Panel control to bypass the
filters (entire unit) and external FX loop effects

Drivers: Provide the control signal sources to sweep the filters

Filter 1: State-variable voltage controlled filter

Filter 2: State-variable voltage controlled filter,

identical to Filter 1

Output Mixer: Allows mixing of both filter

outputs with the input signal as well as
switchable options for the filters

5

Drivers

Envelope Drive

ENV DRIVE Slider: Controls the envelope follower sensitivity to the input signal. Generally set it so the red OVER
LED blinks on the loudest notes, but all settings produce interesting effects. This is not an all or nothing fader. Different
locations on the slider produce different results.

LOG/LIN Switch: Provides different dynamic response to the input signal.

• The LOG position produces consistent envelope tracking
no matter how soft or aggressive your input signal is.

• The LIN position produces an envelope that follows the
full dynamic range of the input signal.

OVER LED: Lights when the envelope follower is saturated (100%) by the input audio signal

AUDIO BOOST Switch: In the DOWN (OFF) position, the audio signal into the filters is set at unity gain. In the UP

(ON) position, the audio signal into the filters is amplified according to the setting of the ENV DRIVE slider.

Sweep Oscillator

RATE Slider: Controls the Low-Frequency sweep oscillator (LFO) rate.

SHAPE Slider: Changes the LFO waveform duty cycle from 50% in the center position to 10% or 90% at the top or

bottom positions. The Shape Slider can be used to change the shape of a triangle wave to a rising sawtooth wave (in the
top position) or falling sawtooth wave (in the bottom position). When in square wave mode, the Shape Slider controls
the length of the pulse width, from short (in the top position) to long (in the bottom position).

SHAPE Switch: Switches the LFO waveform from Triangle wave in the top position, to Square wave in the bottom
position, to completely Off in the middle position.