doepfer/a-121d
A-121d Dual Multimode Filter
Dual multimode filter with two independent VCF channels; one provides highpass and bandpass outputs, the other provides lowpass and bandpass outputs. Includes a common frequency control, a frequency spread (Delta) control, individual resonance and CV attenuators, and a simple mixer unit. Can be used as parallel or serial dual filter, stereo filter, or cascaded with additional modules.497
Capabilities 2
Jacks 12 (8 in / 4 out)
| Name | Signal | Voltage | Description |
|---|---|---|---|
| Inputs (8) | |||
| DCV | cv | — | CV input for frequency spread (Delta); sensitivity adjustable via internal trimming potentiometer.497 |
| FCV | cv | — | Common frequency CV input for both filters; approximately 1V/octave sensitivity.497 |
| FCV1 | cv | — | Individual frequency CV input for Filter 1; processed through the FCV1 attenuator knob. FCV2 socket is normalled to FCV1.497 |
| FCV2 | cv | — | Individual frequency CV input for Filter 2; processed through the FCV2 attenuator knob. Normalled to FCV1 socket when unpatched.497 |
| In1 | audio | — | Audio input for Filter 1. Also normalled to In2 when In2 is unpatched.497 |
| In2 | audio | — | Audio input for Filter 2; normalled to In1 so that the same signal feeds both filters when In2 is unpatched.497 |
| Mx1 | audio | — | Audio input 1 of the mixer; normalled to Bandpass 1 (B1) when unpatched.497 |
| Mx2 | audio | — | Audio input 2 of the mixer; normalled to Bandpass 2 (B2) when unpatched.497 |
| Outputs (4) | |||
| B2 | audio | — | Bandpass output of Filter 2; normalled to mixer input Mx2 when Mx2 is unpatched.497 |
| H1 | audio | — | Highpass output of Filter 1.497 |
| L2 | audio | — | Lowpass output of Filter 2.497 |
| MxO | audio | — | Audio output of the internal mixer unit. When multiple modules are cascaded, only the master module's MxO is active.497 |
Parameters 8
| Name | Type | Range | Behavior |
|---|---|---|---|
| Delta | knob | — | Controls the frequency spread (difference) between Filter 1 and Filter 2. At center position, both filter frequencies are approximately equal.497 |
| FCV1 | knob | — | Attenuator for the individual frequency CV input FCV1, controlling the sensitivity of external CV for Filter 1's cutoff frequency.497 |
| FCV2 | knob | — | Attenuator for the individual frequency CV input FCV2, controlling the sensitivity of external CV for Filter 2's cutoff frequency.497 |
| Frequ. | knob | — | Master frequency control shared by both filters; sets the common cutoff frequency for both Filter 1 and Filter 2.497 |
| In1 | knob | — | Attenuator/level control for the audio input of Filter 1.497 |
| In2 | knob | — | Attenuator/level control for the audio input of Filter 2.497 |
| Q1 | knob | — | Resonance control for Filter 1. Ex factory does not reach self-oscillation; can be adjusted via trimming potentiometer to allow self-oscillation.497 |
| Q2 | knob | — | Resonance control for Filter 2. Ex factory does not reach self-oscillation; can be adjusted via trimming potentiometer to allow self-oscillation.497 |
Firmware history 0 versions
No firmware history recorded.
References 1
-
[497]
Doepfer A-121d Dual Multimode Filter product pageproduct_page● verified 2026-05-17