Audio Routing

Signal Flow

Sonic Eddy provides five channel types in order to provide the user with flexible ways to organize the signal flow. The normal audio channels take any pipewire node as input, and route its signal either to a group, or a master channel, and to any combination of the return channels.

Group and master channels allow processing of the sum of multiple channel signals.

Sonic Eddy provides two layers, layer A and layer B. Each layer provides 8 channels, 4 group channels, and a master channel. The master channels come together in the global master, where the contribution of each layer is selected by a cross-fader. This setup enabled the simultaneous setup of two different signal path mixed together in the global master.

Every channel, except the return channels, provide another tool directed at live performances, a looper, constantly recording and ready to loop the last bar, 0r 4, or 8. A powerful tool to switch presets on a synthesizer, currently still playing the bass line.

Channels

Each channel picks up audio signals from exactly one pipewire playback node. The connection is managed by wireplumber and created by setting the target node on the relevant node of the channel. The signal goes through a trim section, where it can be raised, or lowered depending on the needs of the signal chain.

Next follows the pre-effects looper, and then the optional filter chain. The send section after the filter chain allows routing the signal to one of the four return channels of the layer.

The post-effect looper allows recording and playback of the signal effected by the filter chain. The following volume and pan section allows setting volume and pan, and the audio to routing section finally allows the selection of the channels destination, either the layers master channel, or one of the group channels.

Group Channels

Group channels get their signal fed by normal channels. The signal of every normal channel is summed and then processed, starting with the pre-effects looper. The pre-effects looper is followed by the optional filter chain, the post-effects looper, and the send section.

The following volume and pan section allows mixing the signal into the master channel.

Return Channels

The return channels are fed by the send section of the normal channels and the group channels. Signal they receive is processed by an optional filter chain, and then a volume and pan section, mixing the signal into the layers master channel.

Global Master

The global master channel sums layer A master and layer B master together with a cross-fader. A filter chain can be added after the cross-fader, processing the summed signal.

Channel Signal Flow

Sonic Eddy channels takes inputs from any pipewire playback node, connecting to the first two ports of the node. Virtual inputs can be used, if better control over the respective ports is required.

The inputs are routed through a channel. Channels can have a filter chain or external effect, which applies LV2 plugins to the audio signal. Every channel also has two looper, one before the filter chain, one after. The looper allow to record incoming audio, and play it back perfectly synchronized. This allows, for example, to completely change the settings of a synthesizer while the looper plays the old melody.

Further processing is split after the post effects looper. Four send controls allow passing the signal to one of the four return channels. The main audio stream is processed by a volume and pan section, and then forwarded either directly to the layer master, or to one of the group channels of the layer. The target is selected in the Audio To section.

graph LR
Input --> LPre{{Looper Pre}} --> FC([Filter Chain]) --> LPost{{Looper Post}} --> CV((Volume)) --> A{Audio To} --> Master[Layer Master]
A --> Group --> Master
LPost --> S1((Send 1)) --> R1[Return 1] --> Master
LPost --> S2((Send 2)) --> R2[Return 2] --> Master
LPost --> S3((Send 3)) --> R3[Return 3] --> Master
LPost --> S4((Send 4)) --> R4[Return 4] --> Master

The group and return channels can also contain a filter chain or external effects, providing ample opportunities to shape the audio signal.

Channel Controls

Each channel has very similar controls, only depending on which features the specific channel presents to the user.

Normal Channels

Group Channels

Master Channels

The Two Layers

graph LR
LayerA[Layer A Master] --> GlobalMaster[Global Master]
LayerB[Layer B Master] --> GlobalMaster

The Global Master

The global master channel can be accessed with the main menu at Mixer -> Global Master.