Hi all -
I was taping The English Beat at a local venue here in Boston, and my setup exhibited some very strange behavior. I set levels at the beginning and all looked fine. About 2/3 of the way through, I went back to check levels, and now the right channel was running significantly lower than the left, like 20db lower. I thought, "Oh crap" and increased the right channel gain on the preamp to being the levels back up to equal to the left channel. When I got home and reviewed the take, I found that after I did that increase in gain adjustment, about 10-15 mins later, the recording level on the right channel began to rise, eventually getting to the point of clipping. Ugh.
So, over a 2hr15min period, my right channel started out ok, then after about 30-40mins lost about 30db of amplification, then after another hour, regained that 30db. Both the fall off and rise in recording level were pretty smooth over at least a 20 min period.
The slow nature of the rise and fall makes me think of some sort of screwiness going on with a capacitor charging and discharging, but I have no idea where in the signal path such activity could have occurred.
The rig:
2x AKG 463's, the caps were bought new from B&H, the bodies bought used (and arrived broken, grr) but sent to AKG / LAND Audio for repair ($200, grrr).
2x 10db barrel attenuators
1x Shure FP24 (rebranded MixPre, transformer-based pre) bought used on Ebay, in great cosmetic condition, told by seller had seen low use
2x 10db barrel attenuators
1x Korg MR1, bought new, set to 0db of gain, line input
Both the Korg and the Shure were powered by a Tekkeon 3400, running 12v to the Shure and 5v to the Korg.
Anyone ever run into a similar problem? Or have any ideas about where in the signal path I'm running into problems? Any ideas welcome!!!
Mike