some effects like, chorus, flanger, delay and reverb sound better through the loop than they do through the front of your amp
Art & Lutherie Acoustic
Epiphone SG
Electro-Harmonix Little Big Muff
Electro-Harmonix Nano Small Stone
Vox AD30VT
I usually use my effects loop for your modulation types of effects.Eg: chorus,delay,flange,etc. Doing it that way you can keep your overdrives,distortions,fuzzes on the front side of the amp. Not sure I answered your question tho.
Tom Anderson Hollow Classic
72 thin line tele

Barber trifecta fuzz
Mi audio Crunch Box
Clyde Wah
Barber Burn Unit
Ocean efx Texas deuce
Boomerang chorus delay
Barber ltd

1971 Pro reverb
Fender acoustasonic
Fender super champ xd
the effects loop puts the effects after the distortion stage of the amp, where some of them sound better.
yeah ive never really understood why either... so does that mean if u plug it in the effects loop.... when is your sound being "effected" by the effect? if that makes sense....
If you have a reverb pedal and put it before before the amp and not in the efffects loop, the amp will distort the reverb and it will sound horrible. An effects loop makes the reverb come after the distortion. That's basically how to think of it.
ahh ok... so its pretty much a good thing to have an FX loop when looking at buying an amp?
what will be the diference of puting multi-effect procesor in fx loop and puting in input of the amp ? my amp haven't got fx loop will procesor sound good in input ?