Voodu valve problem

[Fossilshark]

A friend is letting me borrow his voodu valve online preamp and it has a squealing pitch whenever i turn the input up past half. I changed the tube and factory reset it and every preset sounds like garbage no matter what i do. Theres little information on the web about this thing having problems, any ideas?

[Enzo]

First, does it do this if you do not plug a guitar into it?  Does it still do it with a guitar plugged in but he guitar volume control at zero?

[Fossilshark]

Its only when the guitar is plugged in and the volume is all the way up. It sounds like there is way too much gain except even on the clean channel after every note i play there is a little squeal that sounds almost like a microphonic tube, but i just put in a brand new one

[Enzo]

Probably is too much gain.  First, all tubes are microphonic to some extent, especially in a high gain input stage.  Yes, some a lot more than others, but newness is no guarantee of zero microphonicity.

meanwhile if the guitar is turned all teh way up for this, stand back as far from the speakers as possible.  Does it lessen?  Also, whatever way you are facing with the guitar, try turning aside, like aim the guitar 90 degrees from what it is now.  I am asking if the direction the guitar faces has any effect on this symptom.

You can have pickups feeding back in high gain circuits even at low loudness.

[Fossilshark]

Thats what i assumed, but the problem is still there when the preamp is set to clean, and the amp is set to clean at low volume. Moving the guitar does not help, the amp without the voodu valve sounds fine when i just have my rangemaster treble booster hooked up. I do not have the treble boost going into the voodu valve.