A number of input modules can be cascaded to form a mixer with more inputs, growing with your needs. Modules A-138p and A-138o are used to built a simple performance mixer (instead of an external stand-alone mixer).

The module A-138p is the 4-fold input module while A-138o is the output module that can be combined with one or more A-138p's, resulting in a mixer with four, eight, twelve or even more inputs.

The following document shows the internal wiring of A-138o and A-138p as well as the positions and functions of the jumpers and trimming potentiometers of module A-138p: A138p_3_trimming_potentiometers_and_jumpers.pdf

Note: Black versions of the small grey knobs used in this module are available as spare parts. If some of the grey knobs (e.g. Pan or Aux) should be replaced by black ones they can be swapped easily by the customer. If applicable pay attention to order the knobs with 11.5mm diameter (A-100KSB in the price list / section spare parts). Vice versa also the small grey knobs are available as spare parts in case that black knobs of the vintage version should be replaced by grey ones.

The voltage controlled version of the performance mixer is the module series A-135-4.

Technical note: Version 2 of the A-138p is equipped with the additional 10 pin connector JP1. It can be used to establish an internal connection to the quad envelope follower A-135-4C. Version 2 can be identified by means of the pc board labelling (A-138p PERFORMANCE MIXER VERSION 2) and the additional pin header JP1. The marker point near JP1 denotes the red wire of the 10 pin ribbon cable that can be used to establish the internal connection between A-138p and A-135-4C. Version 2 of A-138p is manufactured since about June 2017.

The A-138p Performance Mixer Input features four identical input channels. On top is the input socket with a peak LED, the input gain control for adapting to different signal levels is located at the bottom for practical reasons, just besides the mute switch. Beneath the input there's a potentiometer setting the aux send level. Per channel you can determine whether the aux control is pre or post. The next potentiometer sets the panorama position for the according channel and below we can find a bigger potentiometer responsible for the channel's output level which is then sent to the output module.