I'm not familiar with the H3000 series, but like the other harmonizers, these are stereo effects so channel 1 would be left and channel 2 would be right. That being said, on my Eclipse you can go into the Levels settings and choose between Stereo and Mono input and output, also in that group of settings you can set the input and output levels to match the levels of the effects loop you are using. If you notice that when you switch you fx loop on (on clean channel) the H3000 sounds "dirty" or distorted, adjust your in/out levels down (you need to match the fx loop of the amp head or what ever device your are looping this with).
