Behringer DD100/DD400 reverb mod

[gcwills]

As has been referred to here in the past, the Behringer DD100/DD400 delay pedals use the Coolaudio V1000 DSP chipset. As the V1000 has 16 internal programs including reverb I was keen to see if a DD100 could be modded to add reverb to the existing delay function.

To keep it simple, I used the output B socket for the reverb output and maintained the output A socket for delay.
Pin 2 of the V1000 selects ext/int program selection and is normally grounded. When pin 2 is lifted from ground, it is pulled high and the internal programs are selected. As the V1000 pins 7 and 8 are grounded and data pins 5 and 6 are pulled high, the Chamber 2 reverb patch (0011) is activated - a very nice 7 sec tail reverb.

Fortunately, the output A socket ring connection normally used for stereo/mono switching is also pulled high and when this ring connection is connected to the lifted pin 2 of the V1000 it grounds pin 2 to activate delay when an output plug is inserted into output A. However when the output plug is inserted into output B, the V1000 pin 2 is pulled high to activate reverb.

To complete the mod it was necessary to bypass the fet switching associated with the dry signal so that it was permanently routed to output B. This was done by shorting the drain and source of T5 (113). A last mod was necessary to reduce the reverb in the mix by removing R59 (22K) and replacing it with a 100K resistor. This resistor value was selected to provide reverb "to taste".

I was pleased with the final result as no additional switching was required apart from sacrificing stereo functionality which I didn't need anyway.

Here is an excerpt from the DD100 schematic to show the three areas of modification.