MACKIE ONYX 1640I - Manual (Page 11)

Owner's Manual 11
5. LINE INPUTS
These 1/4" jacks share circuitry (but not phantom
power) with the mic preamps, and can be driven by
balanced or unbalanced sources.
To connect balanced lines to these inputs, use a 1⁄4"
Tip-Ring-Sleeve (TRS) plug, wired as follows:
Tip = Positive (+ or hot)
Ring = Negative (– or cold)
Sleeve = Shield or ground
To connect unbalanced lines to these inputs, use a
1⁄4" mono (TS) phone plug, wired as follows:
Tip = Positive (+ or hot)
Sleeve = Shield or ground
These line-level inputs can also accept instrument-
level signals if the hi-z switches [25] are pressed in.
This allows you to connect guitars directly to channels 1
and 2, without the need for a DI box. The input
impedance is optimized for direct connection, and
high-frequency fi delity is assured.
6. INSERT
These unbalanced 1/4" jacks are for connecting serial
effects processors such as compressors, equalizers,
de-essers, or fi lters. The insert point is after the gain
control [26] and low cut fi lter [23], but before the
channel’s EQ [29-34] and level [38]. 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.
To do this requires a standard insert cable that must be
wired thusly:
Tip = send (output to effects device)
Ring = return (input from effects device)
Sleeve = common ground
Insert jacks can be used as channel direct outputs;
post-gain, and pre-EQ. See the connector section on
page 30 (fi gure G) showing three ways to use insert
cables.
4. MIC INPUTS
This is a female XLR connector, that accepts a
balanced microphone input from almost any type of
microphone. The microphone preamps feature our Onyx
design, with higher fi delity and headroom rivaling any
standalone mic preamp on the market today.
The XLR inputs are wired as follows:
Pin 1 = Shield or ground
Pin 2 = Positive (+ or hot)
Pin 3 = Negative (– or cold)
We use phantom-powered, balanced microphone
inputs just like the big studio mega-consoles, for exactly
the same reason: This kind of circuit is excellent at
rejecting hum and noise. You can plug in almost any
kind of mic that has a standard XLR-type male mic
connector.
Professional ribbon, dynamic, and condenser mics all
sound excellent through these inputs. The mic inputs
will handle any kind of mic level you can toss at them,
without overloading.
Microphone-level signals are passed through the
mixer's splendid microphone preamplifi ers to become
line-level signals.
See Appendix B (page 29) for further details and
some rather lovely drawings of the connectors you can
use with your mixer.
PHANTOM POWER
Most modern professional condenser mics require 48V
phantom power, which lets the mixer send
low-current DC voltage to the mic’s electronics through
the same wires that carry audio. (Semi-pro condenser
mics often have batteries to accomplish the same
thing.) “Phantom” owes its name to an ability to be
“unseen” by dynamic mics (Shure SM57/SM58, for
instance), which don’t need external power and aren’t
affected by it anyway.
Phantom power for each channel can be selected
using that channel's phantom [22] switch.
Never plug single-ended (unbalanced)
micro phones, or ribbon mics into the mic
input jacks if phantom power is on. Do not
plug instrument outputs into the mic XLR input jacks
with phantom power on, unless you are certain it is safe.
“tip”
This plug connects to one of the
mixer’s Channel Insert jacks.
“ring”
tip
ring
sleeve
SEND to processor
RETURN from processor
(TRS plug)