Actually it`s a switched stereo jack Miro, to be honest i think the best place to be asking questions about this build are on Harald`s site. This is a VERY complex build and as a flanger enthusiast it`s one i considered...... for about 10 seconds. I`ve built over 200 working circuits and the one of the biggest mistakes i made early on was thinking masses of enthusiasm could overcome lack of experience.... it can`t. By experience i don`t just mean building, i mean debugging too. The thought of spending a couple of days building this and it not working straight off (very, very likely), and even thinking of debugging virtually guarantees this would`ve ended up in a drawer. Anyway, my quest for a diy flanger ended with the 9v electric mistress pcb from tonepad (madbean`s current lover is similar).Anyhoo, Best of luck with it.
If it wasn't for this website I would definitely have a life.