Question on signal chain issue

is it present when you plug striaght in?

Does the hiss still happen when you are running the looper through the front of the amp (between guitar and amp input?)

you're only getting the sound of the preamp, not the whole amp,there's a lot of tone shaping afte the preamp, even in a channel switching gain banger..... I really don't think its designed to be used this way either.... a buffered effects loop is at low studio impedance out and back in whereas your guitar is a high impedance with less than 1 volt peak to peak output, the input to the looper is probably 1mohm designed to take a low voltage signal, definitely not line level... you can do anything you want, but putting it in the loop is probably a big source of noise here as you have an impedance mismatch and gain staging issues. THe buffered FX loop is designed to feed in and out of a studio processor, line level, so lowimpedance in and out with a very hot +4dBu nominal output peak to peak. its also probably in parallel so you will have to have your dry blend on the looper all the way down to get sound on sound. Just, in short, your idea about 'capturing the preamp; isb't all that crazy in theory, but in theory communism works. The boss looper is designed to capture a raw guitar and give it to the front end of the amp. All stomp boxes are set up this way and while maybe you can get away with soemthing like a smart gate or decimator in the loop, the loop is really for interfacing studio modualtion and ambience processors with an amp, processing the high voltage preamp tone and blending and effected signal back in from something like an spx90 before hitting the power amp. If its a non buffered loop, just poweramp in and out at hi Z, then you can pad down the output into the looper and return nurmally, hope for the ebst, although it will change your tone, particularly the treble because it'll be like a dding a solid state buffer stage to the preamp...

everyoneshould really look at schematics and understand this stuff, tube amps are no joke voltage wise and dicking around with them in ways probably not intended by the designers when you don't know what you're doing might just get you shocked. Know your amp

Look, to each their own of course. I am not actually trying to tell you to put it anywhere. My question was to see if the sound issue goes away when in front of the amp. Think of it as curiousity mixed with troubleshooting.

Clipped for space everyoneshould really look at schematics and understand this stuff, tube amps are no joke voltage wise and dicking around with them in ways probably not intended by the designers when you don't know what you're doing might just get you shocked. Know your amp

This is SO important. If there was a like button, I would thumb this up. Knowing your amp (and its quirks) is one of the essential parts of crafting your tone.

I'd say listen to Jim, my short time here I've found dude knows his stuff, and, on a sidenote, as someone who occasionally dabbles in the world of building tube amps (by dabbles I mean I'm planning a Dumble Clone build), he's bang on spot with what he said about the FX Loop.

And again, for posterity: Everyone should really look at schematics and understand this stuff, tube amps are no joke voltage wise and dicking around with them in ways probably not intended by the designers when you don't know what you're doing might just get you shocked. Know your amp.

Remember, amperage kills, and it takes 100-200mA to stop a human heart. Be safe about it, don't faff about with current, it's not a good way to go.