[ranchero]

Intermittent problem - sometimes it work, but most of the time relay disconnects the speakers, but no error signs, no overload sign, headphones work fine (they connected to the same output, but before relays) Any ideas?

 

[lcaillo]

Guesses based on the info provided would be a bad relay driver or bad relay, bad solder connections on the relay, or a problem in the supply to the relay driver..

 

[aNomad]

Yes, it's the relay. Relays are notorious for being intermittent. Please don't skimp on the contacts, go for the gold!