A-199 is a spring reverb module that electronically replicates the Hall effect using spiral springs.
Spring reverb systems have a characteristic sound behaviour that is based on the (impermissible) mechanical properties of the springs used - such as signal distortion, inherent resonances, restricted frequency range, acoustic resonance behaviour, sensitivity to mechanical influences, such as shocks, etc.
But it is precisely these properties that make the spring reverb system so distinctive.
But it is precisely these characteristics that make the spring reverb sound so distinctive.
In the A-199, a spring system with 3 separate springs is used, making the reverb very "dense" due to the different characteristics of the springs.
The A-199 module also has some special features that are not found in many other spring reverb systems:
The first special feature of the A-199 is that the reverb signal can be fed back to the input, whereby the feedback can lead to the system's own resonance.
The Rückkopplung can be done within the module with the feedback controller, but the rückkoppelte signal can also über external modules (eg. VCA, filter, phaser, frequency shifter, vocoder, distortion/waveshaper, ring modulator etc.).
In this case, the pure reverb signal (Reverb Out) is routed through the external module(s) and fed back to the ext. This socket is designed as a switching socket, i.e. the internal feedback line is disconnected as soon as a plug is inserted into this socket.
Another special feature of the module is an emphasis controller with which medium frequency ranges (centre frequency approx. 2kHz) can be raised additionally.
With a mix control, the ratio between original and reverb signal at the mix output can be adjusted continuously.
Using all these possibilities, very extreme and unusual reverb effects can be achieved with the A-199.