How can i sync more than 3 pocket operators? and what can i do with the HISS noise when i conect them?

i want to record some jam sesions with my pocket operators (i have 7 of them: 12, 14, 16, 20, 24, 28 & 33) and i can’t sync them in a chain, also when i don’t use any sync option they have a HISS really annoying. Does anybody can help me with this things please? Thanks