hey there, I found a nice roland bolt-60 the sound is amazing. tried it at the guy selling me, it was fine. back home, the old 6L6 tubes were dying, really blue-purple lit up ... no sound any more. okay. changed the tubes. the sound is back and sounds really good, BUT there unfortunately is a big hum ... static hum ... more like a buzz. it gets louder when I get close to the amp / speaker magnet with the guitar. but the buzz stays when I turn off the guitar volume, or unplug it. the buzz is there immediately after turning on the standby switch. it doesnt fade or change ... the buzz is less on channel 2, the overdrive, but that's not really an option. somehow I have the feeling that the buzz is becoming less when I turn up the master, to 7-8 ... but maybe then it's just drowned out from the normal tube hum ... don't know. I have a very big suspect. a really strange and badly soldered effect loop switch, and all the stuff connected with this effect loop. maybe the buzz is coming from there. there is settings "pre-eq, post eq, post-volume" the channel is loud and clear in the pre-eq and kind of the post eq-setting, but when switching to the post-volume mode (without anything connected to the effect loop) the channel volume drops, significantly, simply less volume. also tried another 12at7 phase inverter tube ... same thing. the bolt only has the two 6L6 and the 12at7. would it be safe if I just took out anything related to this effect loop from the amp? the switch and the cables ... (of course after the usual safety measuresin tube amps, unloading caps, etc.). if i wouldnt need it. in this thread there is a whole section about this damn shi*** effect loop switch. https://music-electronics-forum.com...ng-repair/39829-roland-bolt-60-reconditioning bye thanks all the best ... sounds like pretty standard ground-buzz, but from the amp, not the guitar. and annoying in a flat-playing setting.