THE E-MU MODULAR

E-mu Filters

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Eµ MODULE 2100 - VOLTAGE CONTROLLED LOWPASS FILTER

 The Eµ 2100 Voltage Controlled Lowpass Filter is an exponentially controlled lowpass filter with variable Q for electronic music applications. It contains an Eµ 1100 VCF submodule.

The top two signal inputs pass through their respective attenuators and are summed with the full level input to form the total signal input. This signal is then lowpass filtered with a cutoff frequency determined by the sum of the initial cutoff frequency controls and the control inputs. The cutoff slope is 24 dB/octave, and the signal path is DC coupled.

The control inputs are algebraically summed to give a total control input voltage, which will vary the cutoff frequency one octave per volt around the initial cutoff frequency. The keyboard switch allows instant patching of either of two keyboards at precisely one volt per octave. The 1V/octave control input jack is also accurately calibrated.

[PIC]

Although maximum accuracy is maintained over the range of 20Hz - 20KHz, the cutoff frequency may be brought as low as 1Hz for special effects.

The Q control varies the resonance of the filter at the cutoff frequency. At high Q, the pass characteristic looks like this:

[PIC]

As the Q approaches maximum setting, the filter breaks into oscillation, producing a pure sine wave. Lowest distortion occurs with the Q control set barely into the oscillation region.

 

Power Requirements:

±15 V @ 25 mA typical

Firm-wire Patch Connections:

 

Inputs Signal (2)

Control (2)

Outputs One (3 pins)

Power Bus Connected Inputs: Keyboard Voices 1 & 2

Adjustments: Volts/Octave Offset

Eµ MODULE 2110 - VOLTAGE CONTROLLED HIGHPASS FILTER

The Eµ 2100 Voltage Controlled Highpass Filter is an exponentially controlled highpass filter based on an Eµ 1101 submodule.

The top two signal inputs pass through their respective attenuators and are summed with the full level input. The resulting signal is then highpass filtered with a cutoff frequency determined by the settings of the coarse and fine cutoff frequency controls and the control inputs. The cutoff slope is 24 dB/octave.

The control inputs are algebraically summed to give a total control input voltage, which will vary the cutoff frequency one octave per volt about the initial cutoff frequency. The 1V/oct input and the switchable keyboard connection are precisely calibrated at 1V/octave; the attenuable inputs have a maximum sensitivity of approximately 1V/octave.

The filter's operation is best illustrated by a pass characteristic plot (attenuation versus frequency) given on the reverse side of this page.

[PIC]

Although maximum accuracy is maintained over the range of 20Hz - 20KHz, the cutoff frequency may be brought lower for special effects.

Power Requirements:

±15 V @ 20 mA typical

 Firm-wire Patch Connections:

Inputs Signal (2)

Control (2)

Outputs One (3 pins)

Power Bus Connected Inputs: Keyboard Voices 1 & 2

 Adjustments: 1V/octave trim.

Eµ MODULE 2120 - UNIVERSAL ACTIVE FILTER

The Eµ 2120 Universal Active Filter is a fully voltage controlled filter with simultaneous highpass, bandpass, lowpass, and notch outputs. It contains an Eµ 1120 UAF submodule.

Each of the three signal inputs passes through an attenuator, then the signals are summed and pass through the filter to appear at each of the outputs. The highpass signal is filtered 12 dB/octave below the cutoff frequency, the bandpass 6 dB/octave on both sides of cutoff, and the lowpass 12 dB/octave above cutoff. The notch output is unfiltered except for a 40 dB notch near the cutoff frequency. The Notch Frequency control will vary the ratio of the notch center frequency to the cutoff frequency several semitones to either side.

The cutoff frequency is exponentially voltage controlled by the cutoff frequency inputs. The keyboard switch connects either of two keyboards at precisely lV/octave.

The Q of this filter is exponentially voltage controlled over a range from 1/2 to 512, at one volt per factor of two change. The Q is numerically equal to the gain of the filter at the cutoff frequency. As Q is increased, the filter becomes extremely resonant at Fc. Up to 54 dB of gain can be achieved. The notch output is ineffective at high Q.

With such high gains, it is very easy to cause the filter to distort. At high Q, the signal input attenuators should be set for low levels.

The pass characteristics of the various outputs are as follows:

 

With sufficiently high Q, fast signal transients such as pulse and sawtooth waveforms will cause the filter to "ring" at the cutoff frequency. The keyboard percussion switch patches a keyboard's gate and trigger signals into the filter to use this effect. On depression of a key, the trigger signal causes the filter to ring with a decay set by the Q control. When the key is released, the filter Q control instead becomes active, allowing a damping effect if desired. The final Q control has no effect with the keyboard percussion switch off.

 

Power Requirements:

±15 V @ 50 mA typical

 Firm-wire Patch Connections:

Inputs Signal (3)

Frequency Control (2)

Q Control (2)

 Outputs Highpass (3 pins)

Bandpass (3 pins)

Lowpass (3 pins)

Notch (3 pins)

 

Power Bus Connected Inputs:

Keyboard 1 & 2 Voice, Gate and Trigger

 

Adjustments

V/octave

Highpass Offset

Bandpass Offset

Q Rejection

2 slightly different UAF sub modules
Back side showing one is encapsulated and has pins attached.
The larger boards that the submodules attach to
Back side of a UAF

Eµ MODULE 2140 - RESONANT FILTER

The Eµ 2140 Resonant Filter is an audio filter with an output mixer capable of producing virtually any two pole pass characteristic. It contains an Eµ 1140 Audio UAF submodule.

The setting of the frequency control determines the filter center frequency, which can be varied from 20 Hz to 20KHz. A resonant peak may be added to the response by the Q control. The height of this peak is variable from zero to ˜ +40 dB.

The output mixer sums the simultaneous filter functions to produce a single output. An incredibly wide variety of responses can be produced, a few of which are shown below.

Several 2140's can be cascaded in series/ parallel combinations to produce interesting complex resonant formants. Lower input levels should be used at high Q's to prevent clipping.

  

Power Requirements:

±15 V @ 20 mA typical

 

Firm-wire Patch Connections:

Signal Input

Output (3 pins)

1V/octave control input

Power Bus Connected Inputs: None

Adjustments:

V/octave

Highpass Offset

Bandpass Offset

Q Rejection

Eµ MODULE 2145 - FILTER CONTROLLER

The Eµ 2145 Filter Controller allows voltage control of the frequency of two banks of Eµ 2140 Resonant Filters. Each bank of filters may contain from one to four 2140 units connected in any series or parallel combination. The bank center frequency will be determined by the 2145 controller while the formant shape will remain unchanged.

The "A" section initial frequency control alters the frequency of the "A" filter bank by +5 octaves. The "A" section "+" control input will shift the frequency of the "A" bank with a maximum sensitivity of 1 volt/octave, depending on the setting of the adjacent attenuator. The "-" control input will similarly shift the "A" bank, but will respond to a positive voltage with a negative frequency shift.

The "B" filter bank is similarly controlled by the "B" section initial frequency control and the "+" control input.

When no external patch is made to the "-" control input in the "A" section, this is pre-patched to the control output for the "B" section. Hence, with the attenuator turned up, rotation of the "B" section initial frequency control, or applying a voltage to the "B" section "+" control input will shift the "B" bank up in frequency while shifting the "A" bank down, an interesting stereo musical effect.

 

Power Requirements:

±15 V @ 10 mA typical

Firm-wire Patch Connections:

Inputs +A Control

+B Control

Q Control (2)

Outputs A (4 pins to 2140 control inputs)

B (4 pins to 2140 control inputs)

Power Bus Connected Inputs: None

Adjustments: None

 
 
 
 
 

 

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