Doepfer A-171-4 Quad VC Slew Limiter

The Doepfer A-171-4 provides you with four Slew Limiters that share one set of controls.

It is one simple and small module mainly intended for polyphonic portamento, but it can also be useful in larger systems where several Slew Limiters are required.

The A-171-4 fits perfectly into the polyphonic system Doepfer is offering. Therefore the Slew Limiters inputs and outputs are available at internal pin headers for pre-wiring of polyphonic patches within the Doepfer polyphonic system. This comes in handy because it keeps the front of the module free of cables. As the switching contacts of the sockets are used for the internal pre-patching the internal patch can be overridden by using the sockets on the front panel. But obviously you don’t have to use the module in the context of a Doepfer poly-setup.

Now to the more technical side of things. The common slew time of all four channels can be adjusted manually by an external control voltage. For slewing the input signal, the A-171-4 uses light-sensitive resistors (LDR). Because of that the slew times are not exactly the same for all units due to the tolerances of the LDRs and the LEDs, which are used to illuminate the LDRs. We are looking at truly analog circuits here, so we see these tiny differences as a feature and not a bug!

• manual control of the slew limiter value (base value)
• attenuator for the signal applied to the CV socket
• slew time range is about 5 ms ... 10 s (1:2000)
• visual control of the slew amount (dark = long time, bright = short time)