the cheap Dano Octave is just that...cheap. What do you intend to use it
for? I have tried a number of ocatvers on bass (what I play), and, in
short, have found you get what you pay for. The best, again this is for
bass is the EBS Octabass. But, that is a bit pricey. The DOD might be fine
for guitar, but the Boss Oc2 would be better.
Or if you wanna spend a little more, I believe Fulltone has a nice one!
** i don't think that the dod is very good.
the ebs is good, seems to track lower than the boss.
the boss is pretty good and it does both two octaves and one octave down.
to my knowledge, fulltone doesn't make a pedal that does low octave (and i've tried to get him to make one) - - fuller makes a upper octave fuzz.
the new mxr line features a low octave, don't know about how it is.
i'd look at the harmony-central web site effects section for reviews of each pedal.