Switching preamps in and out

I would definitely make sure power amp is off before making and breaking any connections.

So the power amp has dual level controls. What about just turning down to "0"?
Can I leave the preamps on when switching IC's? I can press the mute button-would that work? They are all tube preamps so constsantly turning off and on is not ideal.

If the interconnections are RCA I don't think it would be a good idea even if the level controls on the power amp are turned all the way down. The problem with RCA connections is that during insertion the signal on the center pin is applied before the ground connection on the shell is made, and during removal the ground connection is removed before the center pin connection is broken. So there will be moments during insertion and removal when the zero volts that should be present on the center pin when no music is being played will not have a defined ground reference, and therefore may be seen as a very large and conceivably damaging voltage.

XLR connectors, on the other hand, make the ground connection first and break it last, so they do not have that issue. I suspect that it would be safe doing what you are proposing with XLRs, provided that you make absolutely certain to turn down the amp's level controls when changing connections. Personally, though, I still wouldn't do it.

Other approaches: If the output impedance of your source component is low enough in relation to the input impedances of the three preamps, you could use splitters or y-adapters to drive all three preamps at once, and a manual switchbox to select which preamp's outputs are routed to the power amp. If the impedance relationships in that situation would be unsatisfactory for good sonics, you could use a second switchbox to select which preamp the output of the source component is routed to.

If you want to consider those possibilities, and want further analysis of the impedance issue, post back with the specific models that are involved, and the preamp input impedances and source component output impedance if you know them.

The DB Systems DBP-2JAU/5 would be a suitable RCA switchbox. Click on the "photo" and "review" links for further info on it.

Regards,
-- Al

Utter nonesense. Amazing...If a power amp has level controls you can turn it down and switch input cables all day, same goes with the preamp.