Originally Posted by Chimera1970
Audio-Technica AT-LP120USB (hooked up via Pro-Ject Phono Box MM since the Onkyo doesn't have a phono input)
Bose 601s Series III
That turntable has a built-in preamp, no need for phono input.
If you have it bypassed via the switch to use that external preamp, the sound is still being muddied through the USB section of the turntable preamp PCB. There are a view videos that show you how to remove that section and have a true bypass to actually get the full effect of your external preamp.
I guess what I'm trying to say is that your sound is still being screwed with even with the switch set to phono.