Doepfer — A-138B

Manual PDF

Doepfer A-138 Mixer Manual PDF

Doepfer A-138 System A-100 Mixer

Type: 4-channel mixer (audio & CV)

Panel Reference

Label	Function	Voltage Range
In 1	Input 1 (also offset generator, see below)	Audio/CV ±10V
In 2	Input 2	Audio/CV ±10V
In 3	Input 3	Audio/CV ±10V
In 4	Input 4	Audio/CV ±10V
Out	Mixed Output	Depends on input

Knobs/Controls

Label	Function
In 1	Level (attenuator) for Input 1
In 2	Level (attenuator) for Input 2
In 3	Level (attenuator) for Input 3
In 4	Level (attenuator) for Input 4
Out	Master output level
lin/exp	Module type:
- A-138a: Linear pots (CV mixing)
- A-138b: Logarithmic pots (Audio mixing)

Internal Jumper (JP4, mid-2004 and later only)

No jumper: Offset disabled
Jumper at edge: Input 1 knob generates +0...+5V offset (if nothing is patched to In 1)
Jumper near panel: Input 1 knob generates 0...-5V offset (if nothing is patched to In 1)

How To Use

Audio Mixing (A-138b recommended)

Patch audio sources to In 1–4
Set individual levels with In 1–4 knobs
Adjust mix output with Out knob
Take final mix from Out jack

CV Mixing (A-138a recommended)

Patch up to 4 CV sources (LFO, ADSR, etc) to In 1–4
Set individual CV levels with In 1–4 knobs
Adjust summed CV mix with Out knob
Output to target CV input (e.g. VCF, VCO)

Use as Offset Generator (Modules built mid-2004 onwards)

Leave In 1 unpatched; configure JP4 for desired offset polarity.
Use In 1 knob to set offset voltage, available at Out jack.

Cheat Sheet Summary

Inputs (4): Accept audio or CV, ±10V typical range.
Outputs (1): Mixed sum, level set by "Out" knob.
Type: Linear (A-138a) for CV, Logarithmic (A-138b) for audio.
Manual Output Level Control: Yes, via Out knob.
Offset Generator: Available for Input 1 via jumper.

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