Deux ABY box comme dit lamakina ou une seule et un sommateur (mono) genre le JHS summing (https://www.jhspedals.info/summing-amp).
Sinon une Boss LS-2 permet aussi d'avoir deux lignes d'effets en parallèle.
“The type of cap is not as important as the value of the cap, for guitar. In an Amp, your cap type is much more important, as the signal is being passed through the cap all the time. In a guitar, you’re not hearing the cap itself, you’re hearing what the cap is impeding”. Lindy Fralin