Inazone
02-21-2007, 09:23 AM
Last fall, I finished putting together a rack rig for recording. Took it to the studio where we were tracking drums to lay down some scratch guitars. Everything seemed to be working great until I tried using my tuner (see below) to switch between my two preamps. There was a very audible buzz, and one of my preamps would intermittently cut out. Here is the rig:
- Sabine RT-7100 two-channel rack tuner (dedicated left and right ins/outs) with A/B switching
- ART DST-4 solid state preamp > ART Tube Channel EQ > left channel of Carvin Tube 100 power amp
- Peavey Rock Master tube preamp > Rockton Multi-Valve > right channel of Carvin Tube 100 power amp
At first I thought there might be an issue with the Sabine tuner feeding a single guitar signal to both preamps, so I unplugged everything from the tuner and ran through a simple A/B footswitch. Same problem. I unplugged my EQ and effects processors and tried again. Same problem. The only cure seemed to be unplugging one of the two preamps, at which point the buzz went away, and the preamp that was cutting out no longer did so.
I would be fine with unplugging whichever preamp I'm not using on a particular track, but it sure would have been slick being able to switch "sides" at the push of a button. Only the Peavey preamp has a ground lift switch, and I have since added some other units (Rocktron Hush IICX and BBE Sonic Maximizer) that have independent left and right channels to allow the preamps to share them, meaning that every device in the rack is connected to every other device to some degree. If it was a ground loop, would unplugging the cable between the A/B switch and one of the two preamps be enough to eliminate the buzz (as seems to be the case) even though they are still in the same rack and plugged into the same power amp and effects? As long as my guitar signal is only going to one preamp and the other is unplugged, everything works fine. I know that there are a couple of isolation products that supposedly will help prevent ground loops in racks, but I might be way off base about the nature of the problem.
Am I making things too complicated by trying to "share" so many pieces of equipment in my effort to have simple A/B switching? It's not my live rig, so if I can't switch on the fly, it's not the end of the world, but it would have been really convenient.
- Sabine RT-7100 two-channel rack tuner (dedicated left and right ins/outs) with A/B switching
- ART DST-4 solid state preamp > ART Tube Channel EQ > left channel of Carvin Tube 100 power amp
- Peavey Rock Master tube preamp > Rockton Multi-Valve > right channel of Carvin Tube 100 power amp
At first I thought there might be an issue with the Sabine tuner feeding a single guitar signal to both preamps, so I unplugged everything from the tuner and ran through a simple A/B footswitch. Same problem. I unplugged my EQ and effects processors and tried again. Same problem. The only cure seemed to be unplugging one of the two preamps, at which point the buzz went away, and the preamp that was cutting out no longer did so.
I would be fine with unplugging whichever preamp I'm not using on a particular track, but it sure would have been slick being able to switch "sides" at the push of a button. Only the Peavey preamp has a ground lift switch, and I have since added some other units (Rocktron Hush IICX and BBE Sonic Maximizer) that have independent left and right channels to allow the preamps to share them, meaning that every device in the rack is connected to every other device to some degree. If it was a ground loop, would unplugging the cable between the A/B switch and one of the two preamps be enough to eliminate the buzz (as seems to be the case) even though they are still in the same rack and plugged into the same power amp and effects? As long as my guitar signal is only going to one preamp and the other is unplugged, everything works fine. I know that there are a couple of isolation products that supposedly will help prevent ground loops in racks, but I might be way off base about the nature of the problem.
Am I making things too complicated by trying to "share" so many pieces of equipment in my effort to have simple A/B switching? It's not my live rig, so if I can't switch on the fly, it's not the end of the world, but it would have been really convenient.