Mackie 1640I User Manual

Owner's Manual   

11

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.

 

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.

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. 

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.