Hum can indeed be difficult to isolate. hifiman5 has given some very good advice. I would suggest the following:
1) Use a quality multi-outlet strip to plug all of your components AC plugs into
2) That may eradicate your hum issue. If it does not then you should lift the grounds on your power amp with a "cheater adapter (not the pre-amp).
3) If the hum persists then get yourself a set of shielded interconnects for your photo stage.
4) At this point I would suspect that you will have a quiet system, if not then experiment with the TT ground connected/disconnected.
You will solve this but only with all of your components plugged into a multi-outlet strip.
1) Use a quality multi-outlet strip to plug all of your components AC plugs into
2) That may eradicate your hum issue. If it does not then you should lift the grounds on your power amp with a "cheater adapter (not the pre-amp).
3) If the hum persists then get yourself a set of shielded interconnects for your photo stage.
4) At this point I would suspect that you will have a quiet system, if not then experiment with the TT ground connected/disconnected.
You will solve this but only with all of your components plugged into a multi-outlet strip.