Electro-Harmonix Mainframe Installation manual

1

WARNING: Your Mainframe comes equipped with an Electro-Harmonix 9.6DC-200BI
power supply. The Mainframe requires 90mA at 9VDC with a center negative plug. Use
of the wrong adapter or a plug with the wrong polarity may damage your Mainframe and
void the warranty. Do not exceed 10.5VDC on the power plug. Power supplies rated for
less than 90mA will cause the Mainframe to act unreliably.

Congratulations on your purchase of the MAINFRAME, a powerful but easy-to-use
sample rate reducer and bit crusher. Introducing old-school digital audio sounds
into your music has never been easier. A broad range of controls help you fine­tune the digital artifacts, and the innovative Sample Rate Tuning Mode makes it
easy to match the sample reduction to a pitch, even on the fly. Access the
MAINFRAME and immerse your tone in the sounds of the arcades, consoles, and
terminals of yesteryear.

- FEATURES -

 Sample Rate Reduction ranging from 48kHz to 110Hz
 Bit Depth Reduction ranging from 24-bit to 1-bit
 Selectable High/Low/Band-Pass filter to shape the artifacts of the bit crushing

and sample rate reduction

 Sample Rate Tuning Mode allows you to set the sample rate to match the key

of a song, or continually adjust the sample rate based on what you play on
your instrument

 Programmable preset or expression pedal setting allows you to save your

sound or control any combination of the Mainframe’s knobs with an external
expression pedal

 Secondary knob parameters allow you to fine-tune the Mainframe’s effect
 High quality buffered bypass and silent switching

- SPECIFICATIONS -

 Audio input impedance: 2M
 Audio output impedance the OUTPUT jack: 500
 Current draw: 90mA
 Maximum input signal level: 6.25 dBu (4.5V peak-to-peak)

2

CONTROLS AND CONNECTIONS

1. VOL Knob This knob sets the master output level of the Mainframe.

2. BLEND Knob This knob blends between the dry guitar signal and the

effect signal. As the knob is turned clockwise, the output ranges from
completely dry guitar to a fully effected signal with the filter applied.

3. BIT DEPTH Knob As this knob is turned clockwise, the bit depth of
the signal is

4. SAMPLE RATE Knob As this knob is turned clockwise, the sample
rate of the signal is

5. FILTER HPF/BPF/LPF Switch This toggle switch controls the
direction of the Mainframe’s filter:

HPF: High-Pass Filter
BPF: Band-Pass Filter
LPF: Low-Pass Filter

reduced

, producing a distorted, noisy tone.

reduced

, producing a ringing or glitchy tone.

3

6. FILTER FREQ This knob controls the frequency of the Mainframe’s
filter. As the knob is turned up, the frequency increases. The frequencies
cut/passed by the filter vary by the filter type:

HPF: Frequencies above the FREQ knob setting are passed,
frequencies below are cut.
BPF: The FREQ knob controls the center frequency of a pass band.
Frequencies above and below this center frequency are cut.
LPF: Frequencies below the FREQ knob setting are passed,
frequencies above are cut.

Tip: For a tone with no filtering, set the FREQ knob to maximum and set
the toggle switch to LPF.

7. FILTER PEAK This knob controls the resonance of the Mainframe’s
filter. Turning this knob clockwise increases the resonance, producing a
sharper, more cutting tone.

8. EXP / PRESET Button and Green LED This button turns expression
mode or a saved preset on and off. When the Green LED is lit, expression
control is enabled, or the preset is enabled. See pages 6-9 for details on
how to save expression settings or a preset.

9. Footswitch and Red LED Press and release the footswitch to toggle
between bypass and effect modes. When the red LED is lit, the Mainframe
is in effect mode. Double tap the footswitch to enter Sample Rate Tuning
Mode, and tap it once again to exit Sample Rate Tuning Mode and save
the tuned sample rate.

10. INPUT Jack This 1/4" phone jack is the audio input of the
Mainframe. The input impedance is 2M.

11. OUTPUT Jack This 1/4" phone jack is the main audio output of the
Mainframe. The output impedance is 500.

12. EXP Jack Connect an expression pedal or control voltage jack to
allow for external control over every knob on the Mainframe. See pages
6-9 for a description on how to set up and control the Mainframe with an
external expression pedal.

13. 9V Power Jack Plug the output of the Mainframe’s supplied
EHX9.6DC 200mA AC adapter to the 9V power jack located at the top of
the pedal. The Mainframe requires 90mA at 9VDC with a center-negative

plug. Do not exceed 10.5VDC on the power jack.

4

SAMPLE RATE TUNING MODE

In Sample Rate Tuning Mode, the Mainframe analyzes your input signal in
real-time, and sets the sample rate to match the pitch of your signal, or a
set interval above your signal. You can use this mode to lock the sample
rate to a certain pitch for a song, or you can keep it constantly tuning
along with every note you play.

HOW TO TUNE THE SAMPLE RATE

1. Double-tap the footswitch to enter Sample Rate Tuning Mode. The

Red LED will begin blinking in a slow pattern to indicate that the
Mainframe is actively tuning the signal.

Note: You can leave the Mainframe in tuning mode indefinitely and it
will continually tune to your signal.

2. While in Sample Rate Tuning Mode, turn the SAMPLE RATE knob to

select the interval above the guitar pitch at which the sample rate will
be set. See the diagram below for the available interval ranges. The
default interval is two octaves.

3. While in Sample Rate Tuning Mode, tap the footswitch again to lock

the sample rate to whatever note you’re currently playing. You must
be playing a note while pressing this footswitch for the Mainframe to
save the note/interval combination.

INTERVAL RANGES IN SAMPLE RATE TUNING MODE

While in Sample Rate Tuning Mode,
the Mainframe reads the input
signal, then multiplies it by the
interval selected with the SAMPLE
RATE knob (see diagram) to produce
the tuned sample rate of your
choice.
Example: If the interval is set to 2
octaves and the guitar plays an A2
(110Hz), the sample rate will be set
to A4 (440Hz).

Tip: When the interval is set to Unison or Octave, you may hear little to
no sound while in Sample Rate Tuning mode, because the Mainframe is
sampling the signal in the same place every cycle.