I recorded for three days straight (about 10 hours a day) at a recent bluegrass festival and upon beginning to process the four channel recordings I found that my two aud channels contain intermittent audible and visible spikes. Each performance was about 45-50 minutes in length and each set of aud tracks has anywhere from one to half a dozen of these mystery spikes.
The spikes are there all three days and are only missing in a couple of the sets. They show up duiring music and also in between sets.
AND, the spikes seem to be predominant in the right channel, not so much the left.
The two soundboard channels have no issues. I tested the mics at home this past weekend and ran them two hours straight with no issue/no spikes.
The mics are a set of Teac ME-120s, 48v phantom modded. I had the mics mounted on a t-bar on a wooden beam about 12 feet off the ground, running to my Tascam DR-70D thru 50ft long XLR cables. I used the mics with different cables three times previously since they were modded, no spikes/no issues.
I powered the deck using a heavy duty extension cable that was plugged into a power rack at the soundboard.
I've attched a some examples of the spikes in Audacity.
Any thoughts appreciated, it's a real mystery to me at this point.