If the duo of your TK preamp and H90 is within an amp’s effects loop, I would say the H90’s operating levels should be line level, but it depends what kind of input the TK is expecting. The main thing we should be concerned about is that there is no significant drop in level when the H90 is bypassed. To set things up properly, I recommend setting the bypass mode to Relay and then using an INIT Program on the H90 which consists of two THRU utility algorithms. Bypassing and activating the H90 should render no change in your signal volume. If it does, adjust the I/O operating levels until everything sounds balanced. Then you can change the bypass mode back to DSP if you want spillover/tails.
