Blocks, paths and DSP
Why it stops you adding a block when the meter looks half empty — and the handful of changes that actually buy back space.
Presets are made of blocks, laid out on paths
A path is a chain of eight block positions. Path A is the main one; path B is a parallel branch that leaves A at a Split and rejoins it at a Merge. Devices with two paths give you Path 1 and Path 2, each with its own A and B — four rows in total, and two separate DSP chips behind them.
Helix 3.80 Owner's ManualAn HX Stomp has one path and eight positions on it, so the per-path rules below are simply the rules. Everything is about spending eight slots well.
It is almost never “the CPU is full”
There are hard caps on particular kinds of block, and they bite long before the processing meter looks alarming. No amount of free DSP unlocks any of these.
Four in total, and no more than two on either path
Four amps sounds generous until you build a wet/dry/wet rig, at which point you find the two-per-path half of the rule.
Helix 3.80 Owner's ManualFour Single Cabs, two per path — or two Dual Cabs, one per path
An Amp+Cab block spends one of your cab slots without looking like it. If cabs run out before amps do, that is why.
Helix 3.80 Owner's ManualFour 1024-point, two per path — or two 2048-point, one per path — or two Dual IRs, one per path
The longer IR costs you twice as many slots. That is the trade, and it is not explained on the block itself.
Helix 3.80 Owner's ManualOne per path
Feedbacker, Poly Sustain, Poly Detune, Poly Pitch, Poly Wham, Poly Capo and 12 String. Any one of these can eat up to half the DSP for its whole path.
Helix 3.80 Owner's ManualOne per preset
Not one per path — one, full stop. Worth knowing before you plan a two-looper preset.
Helix 3.80 Owner's ManualOne instance of each per preset
Counts whether it appears as a Return block, an FX Loop block, or as an input on a path. Three different-looking things share one budget.
Helix 3.80 Owner's ManualBypassing a block does not give you its processing back. If you are trying to make room, delete it.
Six changes that free up real room
Stereo costs twice as much as mono
The stereo version of an effect uses roughly double the DSP of the mono version, and a Dual Cab roughly double a Single. If a preset is one block short, the cheapest fix is usually to make something mono that did not need to be stereo.
Helix 3.80 Owner's ManualNewer cabs are far cheaper than Legacy cabs
The IR-based Cab and IR blocks introduced in firmware 3.50 use significantly less DSP than the original Legacy Cab blocks. Swapping a Legacy cab for its current equivalent can buy back a whole block.
Helix 3.80 Owner's ManualOne amp plus a Dual Cab beats two amps
If you want two cabinet flavours, use a single Amp block into a Cab > Dual rather than two parallel Amp+Cab blocks. You get most of the variation for a fraction of the cost.
Helix 3.80 Owner's ManualUse snapshots instead of duplicate blocks
Two copies of the same amp with different settings is the expensive way to do it. One block, with a snapshot changing its parameters, is free.
Helix 3.80 Owner's ManualLook for a “Simple” version
Several categories include Simple blocks that do the same job for less DSP. They are not worse — they have fewer parameters.
Helix 3.80 Owner's ManualAmp models are not all priced the same
Some models use noticeably more DSP than others in the same category, and this is most true of amps. If one preset will not fit and a near-identical one will, the amp choice is the usual reason.
Helix 3.80 Owner's Manual