Doepfer A-138P Performance Mixer Input Eurorack Module

Modules A-138p/o are used to built a simple performance mixer (instead of an external stand-alone mixer). Module A-138p is the 4-fold input module, A-138o is the output module that can be combined with one or more A-138p.

A-138p features:

• 4 channels
• controls and inputs for each channel
• input (3.5 mm mono socket)
• signal LED (as a coarse monitor of the incoming level, the level is measured after the gain control)
• mute switch
• gain (control to adapt different audio levels)
• Level (the main volume control, linear response curve)
• Aux
• Pan
• internal jumper for each channel to choose between Aux pre/post main Level control
• internal connection to the output module and to other A-138p modules
• A-138p requires A-138o (no stand-alone use)

A-138o features:

• level controls for Left, Right and Aux
• output sockets for Left, Right and Aux (3.5 mm mono sockets)
• A-138o requires at least one A-138p (no stand-alone use)
• Application example for Aux Send and Aux Return: looping in another module for effects (e.g. DSP module A-187-1, BBD module A-188-1, Spring Reverb A-199)
• Application example for Aux Send only: pre-listening in combination with the headphone amplifier module A-139-2

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.