A-138b Mixer logarithm.

Doepfer A-138b Mixer – Logarithmic 4-channel audio mixer for Eurorack

The Doepfer A-138b is a 4-channel mixer featuring a logarithmic response, ideal for audio mixing in Eurorack modular synthesizer setups. Unlike linear mixers, the logarithmic taper aligns with the way human hearing perceives loudness, offering smoother and more intuitive level balancing for audio signals.

Each input channel has its own dedicated level control, and all signals are summed to a single output. This makes the A-138b an excellent choice for combining oscillators, noise generators, drum voices, or external audio sources into one clean mix.

Key features:

• 4 audio inputs with logarithmic volume control

• Designed specifically for audio signals (not CV)

• Natural-sounding mix behavior

• Clean, uncolored signal summing

• Compact 8 HP width

Whether you're shaping a complex drone, layering voices, or preparing a final stereo feed, the A-138b delivers clarity and musical dynamics with minimal effort.