Hi all..newbie here...Im a session musician who happens to love my 680 & 690 ive owned since the 90's...However they do sound different and have a few different features...Ive always wondered if one was valued more than the other, or their pros and cons?... for me anyways; i miss the bal. control that the 680 has-(great for working out guitar parts/channel splitting)...680 has more low end,but 690 is crisper on the high end,but lacks some low end.......I like em both, and keep getting them serviced, but whada ya all know of these two boomers?.......(im enjoying reading all the posts!)