my best opinion is no they wont really affect your sound. I own a ROV series 2 combo and in the loop I have a tuner,EQ,chorus,dely and reverb pedal. The tuner being the only true bypass. I cannot tell a bit of difference in tone at all. I would steer clear of any known noisy pedals though. I believe if you use decent pedals from the get go you will be fine. I am sure that there are people out there that can tell the difference but if you are like me with a normal set of ears and not doing any proffesional recordings I believe a decent pedal will do,,,of course though I would purchase from a place I could return the item to if it proves to be noisy. But if you can afford or like a certain pedal that is true bypass I would by all means get that one...good luck