Mackie ProFX22 Owner's Manual - Page 13

8. INSERT These unbalanced 1/4" jacks are for connecting serial ­effects processors such as compressors, equalizers, de-essers, or filters. The insert point is after the gain control [9] and low cut filter [10], but before the channel's EQ [11-15] and level [23]. The channel signal can go out of the insert jack to an external device, be processed and come back in on the same insert jack. This 20 dB of ­attenuation can be very handy when you are i­nserting a hot signal, or when you want to add EQ gain, or both. Without this ­"virtual pad," there is more chance of channel clipping. 10. LOW CUT Switch All mono channels have a low-cut switch (often referred to as a high-pass filter) that cuts bass frequencies below 100 Hz at a rate of 18 dB per octave. To do this requires a standard insert cable that must be wired thusly: ring tip sleeve (TRS plug) SEND to processor "tip" This plug connects to one of the mixer's Channel Insert jacks. "ring" RETURN from processor Tip = send (output to effects device) Ring = return (input from effects device) Sleeve = common ground Insert jacks may be used as channel direct outputs; post-gain, and pre-EQ. See the connector section on page 27 (figure G) showing three ways to use insert cables. "U" like Unity gain Mackie mixers have a "U" symbol on almost every level control. It stands for "unity gain," meaning no change in signal level. The labels on the controls are measured in decibels (dB), so you'll know what you're doing level-wise if you choose to change a control's settings. 9. GAIN If you haven't already, please read the level-setting procedure on page 3. The gain knobs adjust the input sensitivity of the mic and line inputs. This allows signals from the outside world to be adjusted to run through each channel at optimal internal operating levels. If the signal originates through the mic XLR jack, there will be 0 dB of gain with the knob fully down, ramping to 50 dB of gain fully up. Through the 1⁄4" line input of channels 1-8 (ProFX16) and channels 1-14 (ProFX22), there is 20 dB of attenuation fully down and 30 dB of gain fully up, with unity gain "U" at 12:00. Through the 1⁄4" line input of channels 13/14 and 15/16 (ProFX16) and 19/20 and 21/22 (ProFX22), there is 20 dB of a­ ttenuation fully down and 20 dB of gain fully up, with unity gain "U" at 12:00. We recommend that you use low-cut on e­ very microphone application except kick drum, bass guitar, or bassy synth patches. These aside, there isn't much down there that you want to hear, and filtering it out makes the low stuff you do want much more crisp and tasty. Not only that, but low-cut can help reduce the possibility of feedback in live situations, and it helps to conserve amplifier power. Another way to consider low-cut's function is that it actually adds flexibility during live performances. With the ­addition of low-cut, you can safely use low equalization on vocals. Many times, bass shelving EQ can really benefit voices. Trouble is, adding low EQ also boosts stage rumble, mic handling clunks and breath pops from way-down low. Applying low-cut ­removes all those problems, so you can add low EQ without blowing your subwoofers. CHANNEL EQUALIZATION (EQ) All ProFX mono channels have 3-band EQ with shelving hi, peaking mid with adjustable mid frequency and shelving low. The stereo channels have a peaking mid EQ control in addition to the shelving hi and shelving low EQ controls. Shelving means that the circuitry boosts or cuts all frequencies past the specified frequency. For example, the low EQ boosts bass frequencies below 80 Hz and continuing down to the lowest note you never heard. Peaking means that certain frequencies form a "hill" around the center frequency. With too much EQ, you can really upset things. We've designed a lot of boost and cut into each equalizer circuit because we know that everyone will occasionally need that. But if you max the EQ on every channel, you'll get mix mush. Equalize subtly and use the left sides of the knobs (cut), as well as the right (boost). If you find yourself repeatedly using a lot of boost or cut, consider altering the sound source, such as placing a mic differently, trying a different kind of mic, a different vocalist, changing the strings, or gargling. Owner's Manual 13