Je ne me souviens plus comment on fait (trop longtemps que je n'ai plus mon Helix) mais oui c'est possible et la manip est simple.
“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