Effects routing: series or parallel
From Axe-Fx II Wiki
Series/parallel routing basics
- You can put effect blocks in series (in a single row) or parallel.
- Axe-Fx II and AX8: extensive routing possibilities, using the 4x12 grid.
- FX8: a single row and the possibility to place an effect in parallel with another effect. You can adjust the placement of effect blocks in the preset configuration (Config page). Examples are provided in the FX8 manual. The first PRE and first POST effect are always series.
- Parallel routing is a common method in traditional analog rigs to avoid loss of tone. However, there's no need to use parallel routing to prevent loss of tone quality when using Fractal Audio gear.
- Parallel routing makes it possibe to have, i.e., independent delay and reverb paths. Or you can use it to put effects after a specific effect only, not affecting the main signal. Also, on the Axe-Fx II and AX8 it allows you to put more than 12 effects in a preset, overcoming the limit of 12 columns.
- You don’t want to place "100% wet” effects in a parallel path, such as Tremolo or Compressor, because dry signal will still be going through the main path and affect the effect.
- More information: thread, thread, thread.
Series/parallel routing and Effects Mix / Level / Input Gain / Bypass Mode
- When running an effect in series, using its Mix parameter (if available) may affect the level of the dry level too. This is not the case with effects in a parallel row, when Mix is set to 100% (fully "wet") and using Level or Input Gain to dial in the desired effects level. So: when using effects in parallel, always set Mix at 100%, and use Level to dial in the desired amount of effect. With effects featuring an Input Gain parameter, keep Level at 0 dB and use Input Gain to dial in the desired amount of effect. Also, setting Mix at 100% avoids creating "double" direct signal paths, which result in undesirable increase of volume.
- If an effect is placed in parallel, bypassing that effect may pass "direct" signal, which, when merged with the main signal, may increase the overall signal level. To prevent this, select a suitable Bypass Mode: Mute Out or Mute In. Do not use Mix 0% / Thru Mute FX In / Mute FX Out.
- The FX8 automates all this, using "smart" controls. Mix, Level and Bypass are automatically adjusted when moving an effect from series to parallel, and vice versa. The Axe-Fx II doesn't have smart controls (yet).
- FWIW, 25% Mix and Level 0 dB in a series effect are equivalent to 100% Mix and Level at -12 dB in a parallel effect.
- Bakerman: "Decibels use a logarithmic scale. You need to double the voltage (paths of identical signal) to see a ~6 dB increase. 1 to 2 is doubling. 2 to 4 is doubling. 2 to 3 (voltage gain of 1.5) is only a ~3.5 dB increase." source
- "Don't think in terms of dB. Assume you are putting 1V in (for convenience). If you add two rows you get 2V out. That's a 6 dB increase. If you add three rows you get 3V out. That's a 9.5 dB increase. If you add four rows you get 4V. That's 12 dB." source
- Forum member GM Arts: "Here's a bit of trivia to cover the comments we often see along the lines of: when I combine two blocks in parallel into a single block, it gets louder... The two signals sum, so it's necessary to reduce the output levels of the two blocks so they combine without volume boost. For an equal mix, each block must be set to -6dB. What's not so apparent is what levels to use for unequal mixes, so here they are. This applies to combining two blocks that each have the same level into a single block without volume change." source