TC-Helicon VoiceTone C1

does it's job very well and have no complaints about the sound quality and audio features.
Where I DO have a complaint is in the Power section;
1/ It runs from 12VDC so you cant link it to your normal Stomp box supply - you need to use the supplied PSU - just extra stuff on your pedalboard.
2/ It wont run from Phantom PSU - considering this is probably gonna be used in a live environment and connected to a Mixing desk this is an oversight. (Maybe it draws too much power for phantom operation)
However, - its now mounted permanently into my pedal board and does it's job well. (Just check you have the selector switches in the right place cos if you inadvertently change them - you can get some strange sounds :-) )

The C1 VoiceTone should be called as a HumanVoiceTone as it works quite well with vocals but unfortunately it fails with any (monophonic) instrument with rich harmonic partials / overtones. I could heard noise like boiling eggs with the highest notes of an alto sax, in the altissimo range the pith correction sounded even worse. With a tenor sax it was a bit better.

I tested the C1 in the lab with pure sine wave and discovered that the pitch correction becomes unstable and noisy with frequencies above 1000Hz and above 2700Hz there is no correction at all.

Very few singers can reach such high notes but as I aimed to use the C1 for saxophone demos it seems that I may have to get more expensive device.

However there is nothing to complain about the overall (dry) sound and the preamp has a lot of gain with low noise.