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+4/-10 switch - What do I do?

CHIP ROBERTS

My Presonus ACP88 arrived today. It will reploace the 'ol Behringer Autocom Pro and Multicom Pro that have searved me well for a long time. The Behringer units have started distorting and buzzing a bit, so it was time to get em' out of the rack...
So anyway, I'm going to rack the ACP88 tomorrow but I don't know if I should push in the +4/-10 switches on the back. I've read and searched many threads on this forum as well as some others, but I just didn't find any answers about this particular unit. I have the manual right here in front of me. Even though the manual explains what these switches are for, the manual does not tell me if I should push them in. I gotts ta know...
I don't know if this will help you to answer me, but I'm using a:
Mackie SR 24-4
DBX Driverack PA
TC M300
DBX 1231 (FOH)
2 DBX 231 (monitors)
I don't know if any of you needed to know that, but oh well. Thanks for the help once again!
July 31, 2008 @06:50am
michaelhoddy

If you are using them on channel inserts, set the switch to -10. If you are using them inline on balanced line level outputs like the mains or aux sends, use +4.
July 31, 2008 @12:34pm
yeahforbes

For your specific mixer:
"The nominal insert send and return level is 0dBu, and the insert return clipping point is +22dBu." http://www.mackie.com/pdf/archive/sr24-4_sr32-4_om.pdf (page 28)
Based on this, I'm going to have to respectfully disagree and recommend keeping it at +4 even for your insert connections, and only use -10 for plugging a consumer cd/tape/dvd (etc.) deck directly into the compressor inputs. It's a common misconception that everything unbalanced (such as single-TRS insert jacks) is -10dBV and everything balanced (I'm talking line-level, obviously not mic level) is +4dBu. To the contrary, +4 is common for many "pro" circuits regardless of bal or unbal, and -10 is common for most "consumer" circuits.
Regardless, if you tend to run your channel strip preamps far below clipping, you can likely get away with setting your inserted device to -10 which would run it with less headroom -- potentially desirable if what you're inserting is noisy. The trade-off is that your signal has the possibility of distorting even when your red OL light isn't flickering.
The last paragraph of http://en.wikipedia.org/wiki/Insert_(effects_processing) is also relevant, describing that not all mixers have hot inserts like your Mackie.
August 1, 2008 @04:47am
CHIP ROBERTS

For your specific mixer:
"The nominal insert send and return level is 0dBu, and the insert return clipping point is +22dBu." http://www.mackie.com/pdf/archive/sr24-4_sr32-4_om.pdf (page 28)
Based on this, I'm going to have to respectfully disagree and recommend keeping it at +4 even for your insert connections, and only use -10 for plugging a consumer cd/tape/dvd (etc.) deck directly into the compressor inputs. It's a common misconception that everything unbalanced (such as single-TRS insert jacks) is -10dBV and everything balanced (I'm talking line-level, obviously not mic level) is +4dBu. To the contrary, +4 is common for many "pro" circuits regardless of bal or unbal, and -10 is common for most "consumer" circuits.
Regardless, if you tend to run your channel strip preamps far below clipping, you can likely get away with setting your inserted device to -10 which would run it with less headroom -- potentially desirable if what you're inserting is noisy. The trade-off is that your signal has the possibility of distorting even when your red OL light isn't flickering.
The last paragraph of http://en.wikipedia.org/wiki/Insert_(effects_processing) is also relevant, describing that not all mixers have hot inserts like your Mackie.

Thanks a lot for the easy to understand explaination. Now I get it. Too bad you don't write manuals!
August 1, 2008 @03:05pm