Doepfer A-171-4 Quad VC Slew Limiter

The Doepfer A-171-4 is a quad slew limiter module designed for polyphonic or multichannel systems, offering four identical slew circuits controlled by a shared set of parameters. Whether you're building polyphonic patches or just need a compact solution for managing multiple slew functions, the A-171-4 delivers smooth performance with analog character.

Each channel applies glide or portamento to incoming CVs, with a global slew time that can be set manually or modulated via CV. Internally, the circuit uses LED-illuminated light-dependent resistors (LDRs), introducing subtle variations between the channels—adding an organic feel ideal for expressive modulation.

Optimised for Doepfer’s polyphonic system, the module features internal pin headers for tidy pre-patching. External jack sockets override internal connections, so it can function just as well in any modular environment.

• Four independent slew limiters with shared controls

• CV-controllable slew time with manual base value

• Slew time range from 5 ms to 10 seconds

• Uses LDRs for analog response and subtle variation between channels

• LED indication for slew amount (dark = longer, bright = shorter)

• Internal polyphonic pre-patching via pin headers

• Compact and ideal for polyphonic or multi-voice systems