The h910 is a Harmonizer / delay with a balanced input and two balanced outputs (stereo out how ...).
Something annoying is that the inputs / outputs are XLR but .... Terminal ... cool, must resort the wire stripper! Anyway, I put the XLR at the end like that ca moving!
It was built between 75 and 84.
2U rackmount.

UTILIZATION

Very simple config:
Line button with LED to bypass or not
Input level knob with LED clipping
Feedback knob for delay
3 digit dial very vintage red
pitch knob
knob "anti-feedback": er .... I have not understood a koi ca used .... ...

for the buttons below:
Delay 1 (Exit 1): 4 buttons: 7.5, 15, 30, 30 ms, we can add them
Delay 2 (output 2): 4 buttons: 7.5, 15, 30, 60 ms, you can also add them.
Also a button for use only delay, not the pitch

4 other buttons to specify the source of pitch change: the big knob OR "AF" (I know that sce pa c) or externally with an optional keyboard now found or "CV" externally too, but I know that c is either ...

SOUND QUALITY

So the first thing in the cable, I expected a lot of breath ... and no! not so much out of breath than that, good output!
I who am in love with the Harmonizers, the I as it were the last straw!
It is easy to set up, it sounds great!
I use AC on a lot of stuff, according to records: acoustic guitars, backing vocals (ouaah! Ca does!), Dobro, electric guitars, to magnify, or to make a nice straight alignment has the fourth ua! but also lead voice! ca and the fact a little "Laurent Voulzy"! ca does well on some titles!

OVERALL OPINION

I bought a week ago!
I had already used the H3000, but already it is expensive! And I wanted a harmonizer.
It is found in OCCAZ between 350 and 400 euros.
An effect that the REAL personality that can be very quiet but very useful!