ALM Busy Circuits Stereo Sum

4-Input Unity-Gain Stereo Summing Mixer

• A unity-gain summing mixer in just 4 HP
• 4 pairs of stereo inputs and 2 pairs of stereo outputs
• Two independent stereo mixers or a single larger mixer, thanks to normalization
• Stereo or mono inputs via normalization
• DC-coupled for mixing both audio and CV
• Ideal for summing MEGA-TANG, Jumble Henge, or multiple MFX returns
• Low power consumption, suitable for skiff cases, made in England

ALM Busy Circuits Stereo Sum is a unity-gain stereo summing mixer with four pairs of stereo inputs, which can be summed in pairs to two independent mix outputs or combined into a single master mix. It’s the utility you need when your system grows and stereo sources multiply: in just 4 HP, you can efficiently combine the outputs of multiple mixers, voices, or effects processors without wasting space in your case.

Unit-gain stereo summing for your Eurorack system

Unit-gain means that signals are summed without amplification or attenuation: what goes in comes out, combined with the rest. A simple and transparent solution for combining the outputs of mixers like the MEGA-TANG and Jumble Henge, or for feeding more stereo returns from the MFX or other effects back into the mix.

Stereo or mono inputs and audio or CV signals

Each input accepts either stereo or mono signals: thanks to normalization, a signal connected to just the left input is sent to both channels. The module is DC-coupled, so you can also use it to sum control voltages—for example, to combine modulations before sending them to a parameter.

Two stereo mixers or a single larger mixer

The outputs of the upper mixer are normalized to the lower section. If you leave the upper output unconnected, the two upper pairs of inputs are summed to the lower output, transforming the Stereo Sum into a single mixer with four stereo inputs. If you connect it, however, you get two independent stereo mixers, each with two inputs. One module, two configurations, no compromises.

Technical Specifications

• Brand: ALM Busy Circuits
• Model: Stereo Sum
• Type: Unit-gain stereo summing mixer for Eurorack
• Inputs: 4 stereo pairs, compatible with mono signals via normalization
• Outputs: 2 stereo pairs
• Configuration: two independent mixers or a single mixer via normalization
• Coupling: DC-coupled, for audio and CV
• Power supply: +12 V 8 mA, -12 V 8 mA
• Dimensions: 4 HP
• Depth: 32 mm, suitable for skiff cases
• Reverse polarity protection
• Made in England