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Stories From the Road

By Allen Rowand

February 20, 2008

02: Copy that channel

While I love big, heavy, power-sucking analog consoles the one thing I prefer about digital boards is being able to copy and paste. Once you get an input tweaked so that you're happy with the sound, or an output assigned to 30 or so matrix outs you hate to change it; restoring all your settings is a hassle. Let's just say that front panel legends for knobs are not always as accurate as we'd like. So what do you do when you have to replace a failing module but want to ensure that the sound will be unchanged? Use SpectraFoo.

We had an input that was starting to go intermittent and had to be replaced, but I wanted to ensure that the replacement was exactly matched. First, I turned off the EQ and high pass filter and ran a 1kHz tone through the input to measure its gain setting with a level meter. Next I put the EQ and HPF back in and took a transfer function of the module with pink noise; now I could see exactly what the EQ and high pass filter were doing. I took a snapshot of the curve, then removed the failing input and replaced it with a fresh one.

I played the 1kHz tone again so that I could match the input gain. Then I turned on the EQ, switched over to the transfer function and loaded the snapshot of the old module. As I ran pink noise through the new module, I could see its transfer function drawn along with the snapshot. I was now able to tune the EQ and HPF to make the two traces identical, and knew that they would sound absolutely the same.

Obsessive? Maybe. But I like know to that the engineer is going to hear the same thing that he did the previous show. This is also a great way to make sure that stereo channels are matched absolutely- you'd be surprised how a little mismatch in EQ or level it takes to make things sound strange.

Until next time,