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Synthesis Technology
E440 Discrete OTA VC Lowpass Filter - 14HP

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Item: N13-3584

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E440 Discrete OTA VC Lowpass Filter - 14HP


The Synthesis Technology E440 is a lowpass voltage-controlled filter with 3 simultaneous outputs. The input is any audio source, (which can be from line level to synth level) and the output is via the different slopes of the filter: 2pole (-12dB/oct), 3pole (-18dB/oct) and 4pole (-24dB/oct). There are 3 CV inputs to control the cutoff frequency plus a separate CV input for the resonance. The E440 will self-oscillate at high resonance and can be used for a sine VCO (each output is phase shifted 45 degrees from the prior one) with 1V/Oct tracking (trimmable) over a 4-octave range. This response is also temperature-compensated. An external audio mixer module can be used to blend the 3 outputs into “in-between” slopes and by inverting them relative to another, different frequency responses.


  • Resonance: amount of filter resonance. This knob setting is added to whatever CV is plugged into the Res CV jack. The filter will self-resonate (with no external applied CVs) at the ~9 tick mark.
  • FM1: filter frequency modulation standard attenuator for whatever is applied to the FM1 jack.
  • FM2: filter frequency modulation reversing attenuator for the CV plugged into the FM2 jack.The 12:00 (straight up) position is maximum attenuation: rotating CCW will add the inverted signal to the FREQUENCY control while rotating CW will add the applied CV.
  • Frequency: the cutoff (or self-oscillation initial frequency). The VCF will internally add all 4 CV inputs together to determine the filter’s cutoff frequency. The range is 20Hz to ~ 18KHz.
  • Drive: this is a combination attenuator for the AUDIO IN and a booster amplifier (~2X gain). The filter can be over-driven to clipping (with a large voltage output swing, ~14V pk-pk). You can use this control to boost line-level signals as well. The unity gain setting is ~ ‘4th' tick.
  • CV inputs. The range of each input is -5V to +5V. FM1 and FM2 are on attenuators, while 1V/Oct and RES CV are not.
  • AUDIO IN can be any level up to 14V pk-pk. The 3 outputs are the lowpass responses. All 3 outputs share the resonance and cutoff CVs. You will note that the relative levels of the 3 responses are slightly different, which is resonance dependent. This is just the nature of the electronics. The 4 OTA stages are not gain-matched and the filter caps are +-5%. This will cause each stage to vary slightly in gain relative to the others. Consider this part of the E440’s charm.

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  • +12V @ 23mA ; -12V @ 23mA
  • 14 HP

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