My Tonewood Amp works perfectly on my Gibson acoustic (in fact I can't play without it) but I recently purchased a Journey OF660 carbon fiber guitar and have been unable to stop the feedback. I followed the instructions associated with adjusting the frequency spectrum and that helped a bit but the feedback is still happening - any suggestions?
If I were you, I'd try a different position on the back to see if you can get rid of the feedback.
Feedback is caused by too much input gain, a hot signal, or the effects being picked up by the pickup and sent back through.
Sometimes, it's a combination of all three.
What kind of pickup do you have on that guitar?
That should work fine.
We actually have a video of Kevin Blake Goodwin in the works using an RT660 which has the same pickup.
When you configure it without a preamp on the guitar, you typically will have to lower the master gain a whole lot and use notch filters to balance the signal.
It's a very hot signal from the pickup because it's not being EQ'd by a preamp before the output.
My K&K Trinity and Pure mini transducer pickups are similar to those in some ways.
I set the Master Gain for those anywhere from 5-15% on my guitars... too much gain and the signal starts to repeat as the pickups start to send the effects back through the TWA causing feedback.
I set Notch low between 100-200Hz and Notch high around 700-800Hz. This will most likely be different for you, though.
Another way to approach it is from the lowest master gain setting and work your way up.
Start at 5%, set the Notch filters, then increase the Master Gain and repeat notch filters if necessary.
Can you attach a photo of the TWA attached to your guitar?