|This module is based on a rather simple signal delaying circuit which is realized with TDA1022 BBD chips.
The input signal can be attenuated by a 'Level' pot and can be mixed to the output signal via the 'Mix to Out' switch.
The delay time is adjusted by the 'Delay' pot and can be 50 ms in maximum. The amount / amplitude of the delayed signal which is fed back to the input is determined by the 'Reverb' pot. The result is a kind of reverb sound, which is not a real reverb, but sounds quite similar depending on the pot levels. If you separate input and output signals on different stereo channels, you get a quite good spatial effect.
If you don't use the 'Reverb' functionality, you can use the module as a 'single echo'. The delayed signal is put on the output without beeing fed back to the input. The amplitude of the delayed signal is determined by the 'Echo' pot. This sounds like a single sound event in a concrete cellar or similar rooms.
The sound of the module is quite metallic, so it should be used for synthetic effects, not for natural reverb sounds.
The circuit / the module does not belong to the Formant synthesizer originally but comes from the german ELRAD magazine of 1982 Nr. 11 and was presented as a stand alone effect box there. I adapted it as a synthesizer module.
Sound example (first half of each example without, second with Delay Module):
Example 1: Single Echo
Example 2: Reverb