I do not believe the routing in the H90 will satisfactorily allow you to do what you’d like to do, so my recommendation is to merge the two Tonex Ones before the H90 with a parallel pedal (e.g. Sonicake Portal is cheap and effective, GFI Duophony is amazing but costs more, EHX TriParallel is also good and mixes three channels – one thing to note is that all allow for phase correction, level control and dry blend).
If you didn’t need this specific requirement, “So can my H90 sum those two signals beforehand for me and then add its amazing stereo effects after it?”, there are two H90-only options worth trying, though neither does exactly that:
Both of these require parallel routing:
1. Post‑A/Post‑B: place both inserts as mono into Post‑A and Post‑B positions, with two pre-Tonex effects on Presets A/B (e.g. Phaser into Tonex OD on one side, Polyphony into the other Tonex on the other). All the stereo imaging hitting the Tonex Ones gets summed to mono at the insert points, generating two mono chains, which are then summed to dual mono for output — this actually blends the two Tonex signals, closest to what you’re after. Still, there’s no room left for stereo FX afterwards. You’d be relying on the delay and reverbs in the Tonex One unless you have something post-H90.
2. Pre‑A/Pre‑B: place both Tonex inserts as mono into Pre‑A and Pre‑B positions instead. Each Tonex feeds its own separate Preset (e.g. Reverb on one, Delay on the other), so the two amps never actually blend into one signal — but each gets its own full stereo effect, and the two independently-processed stereo paths are blended at the final output. Not a true “sum then FX,” but a genuinely nice way to run two differently-flavoured amp/FX combos in parallel.
Ensure you’re using mono (TS) cabling for the insert loops 3 In/Out and 4 In/Out.
Manual refs
3.2. Two Mono Inserts: Example of connections
6.2.1. Insert Routing: specifically the note “The H90 will automatically adjust to process audio in mono or stereo depending on the physical input and output connections. Insert routing will sum or mult the signal accordingly.”
