Behringer 911A Trigger Delay

911A Trigger Delay

Introduction In August 2020 I bought a set of Behringer System 55 modules, as my first journey into Moog modular. My plan is to recreate the Klaus Schulze Moog IIIP synthesizer and Dual Sequencer setup that Klaus bought on 22nd December 1975, and used successfully for many years.

Rather than rack up a set of Behringer modules and ride away making music, I thought it would be useful to explain how the modules work, how to calibrate them, and how I have set them up and augmented them. I will also check their specifications, to see if they replicate the originals accurately and so I can understand them better.

The 911A Dual Trigger Delay This module is a simple transistor based design that uses a JFET, 10uF capacitor and a 1M log potentiometer to create the time delay. A 100R resistor next to the 1MA potentiometer means the delay cannot go below 1 ms, which means there is always a slight delay. There are two channels which can be used independently or switched in series or parallel. The S-triggers inputs are typically connected to a keyboard or sequencer, and the S-trigger outputs to two 911 Envelope Generators.

The two delays can be varied from 2 ms to 10 seconds from the front panel potentiometers, and the panels are marked accordingly. I measured the Behringer 911A timing delay from 1 ms to 11 seconds. There is an End of Travel (EOT) limitation on the timing pots where the full CCW position has a step into the first position of the taper itself. For example the pot steps from 1ms to 15ms with no  intermediate values. I have replaced the Behringer pots with more expensive Bourns 9mm pots.

To drive the 911A you will need either a V-trigger to S-trigger cable, a S-trigger keyboard (like the Arturia Key Step) or use the 961 module to do the conversion for you. I am building a bigger modular system, so I have used the 961.

Moog 993 Module

Setup There are two trimmers on this module, which adjust the delay time of each section. My module was reasonably well calibrated at 11 seconds maximum, so I left it as is.  Here is the user manual 911A Quick Start Manual, in case you didn’t get one in the box. In the  larger Moog systems a 993 module was used to control 2 trigger sources, the 911A and 3x VCA and 3x ADSR’s.

This is a very useful module as it cuts down the number of patch cables and sets up the first ADSR as direct with no timing delay, and then the 2nd and 3rd ADRS’s with delays from the 911A. Behringer have not manufactured this module as they are using open patching rather than any bus or trunk lines. I have made a 993 module, details are here.

Summary The 911A is a cheap and cheerful module that works as expected, and it is useful in creating complex envelopes. It does introduce a minimum of 1ms delay so you may want to ensure you have some envelope generators available without going through the 911A, to ensure you getting snappy fast attacks.

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