Scale + Flip + Shift + Combine
The 321 includes the most useful functions we always need in every patch, to edit and combine dynamically the signals in use.
It is composed of three identical sections, the red, yellow and green, where each of those is capable of scaling any signal, from 0 up to 2 times (+6dB), flip its phase, and apply a DC offset, allowing to shift your audio or CV up or down.
In case no signals are connected to the section input, the offset may act as a CV source too.
The three sections are then summed together into two independent summing stages: the top right jack outputs the sum of all three sections, while the top left outputs the sum of the unconnected sections only (semi-normalled).
The 321 is entirely DC coupled, allowing the process of control voltages as well as audio signals.
In case CVs or audio signals are particularly hot, the two 6dB attenuators, one per each summing section might be helpful to reduce exactly by the 50% the incoming signals.
Audio and CV Attenuation/Amplification
The 321 features a DC-Coupled amplifier that can attenuate or amplify audio and CV. It can add up to 6dB (or double a signal level).
Phase and Polarity Inversion
A switch flips the phase of an audio source or inverts the values of a control voltage. The combination of switch and attenuator instead of an attenuverter allows you to precisely reach the 0 and completely mute a channel.
Positive and Negative Offset
The Offset section allows to add or subtract a DC offset to the incoming signal. It is excellent to make unipolar signals bipolar or vice-versa. A switch can disable the offset completely to guarantee a more transparent audio treatment.
When no signal is patched to a section, its Offset control allows you to output a steady voltage. It can be either positive or negative, according to the Offset knob position.
Three Independent Sections
The 321 has three independent circuits, each of which can scale, flip, and shift an audio or CV signal.
Two Ways of Summing
Two outputs at the top provide two different sums. The right one outputs all the three sections, including potential offsets, while the left one outputs just the sections that aren’t using their local outputs. You can use a dummy cable patched to a section’s output to remove it from the Unpatched output sum.
-6dB Sum Attenuation
Both sum outputs feature a -6dB switch that can halve the output amplitude whenever the sum is too hot.
Info from Frap Tools