DI Boxes For Live Use: Questions...

[RAK]

Is that universally true? I was under the impression that on higher end consoles they were actually two seperate signal paths. I could well be wrong though...

It depends on the channel strip. Not that I have block diagrams in front of me, but I'm trying to think back to some of the console's I've used. Something like on the SSL 4056 I believe does have two seperate signal paths, so the mic/line switch actually "enables" the input. Meaning if you're running something into the mic in, but you have it in "line" mode, you don't get anything. It's been a while since I've used an SSL though, so I could be confused.

On the other hand, something like an A&H GL3800, the mic and line inputs are on the same signal path, so in that case, it is just a pad switch.

 

[xstatic]

On many budget consoles the mic/line button doubles as a pad, but only for signal present at the XLR connection. It also is used as a switch to switch the signal source from the xlr connector to the 1/4" jack. On most desks you can have signal running to both the 1/4" line input and the xlr input. By defualt the xlr typically takes the signal selection. However, depressing the mic/line button will not pad the xlr signal in this case, but will actually switch which connector that channel derives it's signal from.

Any way I look at it, a direct box is always preferable to just running 1/4" in to a console with an instrument.

 

[RAK]

So here's the block diagram for the A&H GL3800 series.
As you can see for the mic/mono inputs the mic and line inputs meet at the "Line/Pad (-20dB)" switch

This is actually the analog desk I have the most time on, and while it's been a while since I've used it regularly (that's what day jobs will do) I seem to remember the button is just labeled as -20 dB Pad, and it Pads both the XLR or 1/4" input.

http://www.glseries.com/Downloads/gl3800_blockdiagram.pdf