MACKIE M800 - Manual (Page 13)

13
If you’re using low imped-
ance loads at high power
levels, we recommend that
you use the binding post
speaker outputs rather
than the 1/4" TS jacks. Al-
though 1/4" jacks and plugs are convenient and
easy to use, they are not designed to handle
high-level currents.
Make sure that the amplifier is off before
making connections or reconfiguring the signal
routing.
INPUT
The M•800 gives you a choice of inputs — it
has XLR as well as 1/4" TRS (Tip-Ring-Sleeve)
input jacks. Sonically (and electrically) they’re
identical, so choose either one. Since these two
inputs are in parallel, don’t use both at the same
time.
The amplifier expects to see a nominal sig-
nal level anywhere between the –10 dBV
“semipro” and +4 dBu “pro” standards, mean-
ing almost any line-level mixer or other device
can be plugged into the amp’s
INPUTs. Use the
GAIN controls to adjust the gain of the ampli-
fier to match the signal level you’re using.
Each type of input can be used with either
balanced or unbalanced signals.
Balanced
Use the balanced connections if your source
has balanced outputs. This will greatly reduce
any noise picked up in your system.
When connecting a balanced signal using
the XLR or 1/4" jacks, they’re wired thusly, per
AES (Audio Engineering Society) standards:
XLR TRS
Hot (+) Pin 2 Tip
Cold (–) Pin 3 Ring
Shield (Ground) Pin 1 Sleeve
2
2
3 1
1
SHIELD
COLD
HOT
SHIELD
COLD
HOT
3
SHIELD
COLD
HOT
3
2
1
TIP SLEEVE
TIP
SLEEVE
SLEEVE (SHIELD)
TIP (HOT)
RING (COLD)
SLEEVE (SHIELD)
TIP SLEEVE
TIP (HOT)
RING (COLD)
RING
TIP
SLEEVE RING
Balanced 1 ⁄ 4 " TRS Plug
Unbalanced 1/4" TS Plug
Balanced XLR Plug (prior to Lunar orbit insertion)
Unbalanced
Unbalanced TS (Tip-Sleeve) lines can be
accommodated via the TRS jack. Make sure
the cord terminates with a TS plug (like a gui-
tar plug), or if it’s a TRS plug (like a
headphone plug), make sure the ring is tied to
the shield, preferably at the source end.
THRU
The THRU jacks allow you to feed the input
signal to the inputs of other amplifiers. In this
way, multiple amplifiers can receive an input
signal from your single mixer or preamp. This
is accomplished as follows:
• Make sure all your equipment is turned
off before making any connections.
• Plug the signal source outputs into the
first amp’s INPUTs.
• Patch from that amp’s THRU jacks to the
next amp’s INPUT, and so on, daisy-chaining to
other amps in your system (assuming your
mixer has low impedance outputs).
To prevent excessive loading
of your source, a general rule
of thumb is to maintain a
load impedance 10 times or
more than the source imped-
ance . If your console has an
output impedance of 100 ohms, then you can
daisy-chain up to twenty M•800 amplifiers,
which presents a load of 1000 ohms to the con-
sole (input impedance of 20 kohms divided by
20 amplifiers = 1000 ohms).
The THRU jacks can also be used to relay
the input signals on to other devices such as a
DAT or cassette recorder. They are wired in
parallel with the XLR and TRS
INPUTs, so the
signals coming out of the THRU jacks are ex-
actly the same as the signals going into the
amp, unaffected by any of the amp’s switches
and controls.