Moog MF101 User Manual

Understanding and using your

moogerfooger®

MF-101 Lowpass Filter

Welcome to the world of moogerfooger® Analog Effects Modules! Your Model MF­101 Lowpass Filter is a rugged, professional-quality instrument, designed to be equally
at home on stage or in the studio. Its great sound and classic effects come from the
state-of-the-art all-analog circuitry, designed and built under Bob Moog's personal
direction.

Your MF-101 is a direct descendent of the original modular Moog™ synthesizers. It
contains two complete modular functions: a Voltage-Controlled Lowpass Filter and an
Envelope Follower. All performance parameters are voltage-controllable, which means
that you can use expression pedals, MIDI-to-CV converter, or any other source of
control voltages to 'play' your MF-101.

While you can use it on the floor as a conventional effects box, your MF-101 is much
more versatile and its sound quality is higher than the single fixed function "stomp
boxes" that you're probably accustomed to. You will find that your MF-101 is a deep
musical resource. It will give you an amazing variety of new sounds and will become
your creative companion as you explore its functions.

The following pages will first tell you how to hook up your MF-101 and set the panel
controls for the 'basic' setup. Next, we'll explain how the modular functions in your MF­101 work. After that we'll give you some suggestions on how to use your MF-101 in
specific applications. At the end of this booklet you'll find technical specifications,
service and warranty information.

GETTING STARTED

Here are some simple instructions on how you can quickly plug in and try out your MF-

101.

1. Unpack your MF-101. You can place it on a table or on the floor. We suggest that
you place it on a table while you become familiar with its features.

2. Check that the power adaptor is rated at your country's standard power voltage (120
volts A.C. for the United States and Canada; 100 volts AC for Japan; and 220 volts A.C.
for most other countries). Plug the power adaptor's cord into the MF-101's '+9V' jack.
Then plug the power adaptor itself into a power voltage receptacle.

3. Note that the BYPASS light is on. It will light up either red or green. Red indicates that
the MF-101's filter is off-line (bypassed), while green indicates that the filter is on-line.
Pressing the 'stomp switch' will toggle the BYPASS light between red and green. For now,
leave the BYPASS light on red.

4. Connect an instrument cable from the MF-101 AUDIO OUT jack to a line-level input
of your amp or mixer. Turn the volume control on your amp down but not off.

5. You can feed virtually any instrument-level or line-level signal through your MF-101.
Examples are guitar, bass, keyboard, theremin, drum machine, or Effects Send output
on your mixer. Connect an instrument cable from your signal source to the MF-101
AUDIO IN jack. Play your instrument (or turn on the signal source). Turn the DRIVE control
clockwise until the LEVEL indicator lights up yellow most of the time.

6. The BYPASS light should still be red. Continuing to play your instrument, adjust the
volume control of your monitor amp until the loudness is comfortable. Your instrument
should sound clean and undistorted.

7. Now set the MF-101 panel controls as follows:

MIX 10
CUTOFF 250
RESONANCE 6
AMOUNT 6
Left Switch SMOOTH
Right Switch 4-POLE

Press the stomp switch. The BYPASS light will now turn green. Play your instrument. Your
instrument's signal is now going through the filter. Listen to how the filter affects the
quality of your instrument's tone. Note also that louder tones 'open' the filter more than
softer tones.

8. In the next section we'll explain exactly what the filter and envelope follower do and
how the controls work. For now, get a feel for the controls by experimenting with
different settings

HOW A LOWPASS FILTER WORKS

Let's start with some definitions, so we're all talking the same language.
Sound is a vibration of the air. The speed of vibration is called the frequency. It is
measured in Hertz (Hz). One Hz is one vibration per second. We hear vibrations from 20
Hz to 20,000 Hz.
Musical sounds generally have many frequency components. They're called
harmonics, or overtones, or partials. They are what give the sound its characteristic tone
color, or timbre.

This “spectrum” graph shows the strengths of the harmonics in a sound.

A filter allows some frequencies to pass and cuts off other frequencies. A Lowpass Filter
is a kind of filter that allows all frequencies up to a certain frequency to pass, and cuts
off frequencies above that. That frequency is called the cutoff frequency of the filter.
We'll call it "the cutoff" for short.
A lowpass filter removes the high frequencies from a tone. It makes the tone more
mellow or muted. The lower the cutoff, the more muted the tone sounds. Imagine a
window shade. As it is pulled down, it cuts out the higher light, then the light from the
middle of the window, then finally all the light. A lowpass filter does the same sort of
thing with the sound spectrum.

This “frequency response” graph shows that the gain of a lowpass filter drops off at frequencies above the

cutoff frequency

.

Your MF-101 contains a genuine classic four-pole lowpass filter. This kind of filter was
first patented by Bob Moog in 1968. It is a big part of the 'Moog Sound' of the '60's and
'70's. The effect has been imitated, but never equaled, by many instrument
manufacturers.

Your MF-101 also contains a classic envelope follower. An envelope follower tracks
the loudness contour (envelope) of a sound, and produces a voltage that follows the
dynamics of your playing. Every time you play a note, the envelope voltage goes up
and then down. The harder you play, the higher the envelope voltage goes.

The Envelope signal follows the amplitude (loudness) of the sound which it represents.

The envelope follower output opens and closes the lowpass filter. Think of the
envelope voltage as an invisible hand that turns the CUTOFF knob up and down every
time you play a note. Since the envelope follows the dynamics of your instrument's
signal, you actually 'play' the filter as you play your instrument.

TOURING THE PANEL FEATURES

The Filter Section

Let's look at the Filter section first. The two control knobs are CUTOFF and RESONANCE.
The 2-POLE 4-POLE switch selects the filter’s operating mode. All three of these affect
the sound of the filter.
The CUTOFF knob opens and closes the filter. As we said above, the filter lets through
the low overtones and cuts off the higher overtones. As the filter closes, more and more
of the high overtones are cut off. The CUTOFF knob is calibrated in Hz. (vibrations per
second). The cutoff frequency is about 15 Hz when the knob is counterclockwise, 500
Hz (about an octave above middle C) when the knob is in mid-position, and 12 kHz,
(12,000 vibrations per second) when the knob is clockwise.