DAD FZ10004 User manual


USER MANUAL
FZ10004
SWITCHING POWER AMPLIFIER
EN
VL
VL
VL
VL

All rights reserved by Music & Lights S.r.l. No part of this instruction manual may be
reproduced in any form or by any means for any commercial use.
In order to improve the quality of products, Music&Lights S.r.l. reserves the right to modify the
characteristics stated in this instruction manual at any time and without prior notice.
All revisions and updates are available in the ‘manuals’ section on site www.musiclights.it
REV.001-04/14

1
FZ10004
Packing content • FZ10004
• Power cord
• User manual
TABLE OF CONTENTS Safety
General instructions
Warnings and installation precautions
General information
1 Introduction
1. 1 Description and technical specications
1. 2 Main features
1. 3 Front panel overview
1. 4 Rear panel overview
1. 5 Method for AMP module hot plug
2 Installation
2. 1 Unpacking
2. 2 Mounting
2. 3 Cooling
2. 4 Operating Voltage
2. 5 Grounding
3 Functions and settings
3. 1 Introduction
3. 2 Operation precautions
3. 3 Signal ow and head room
3. 4 Audio input and output connections
3. 5 Protection, faults and warnings
4 Maintenance and Specification
4. 1 Maintenance and cleaning the unit
4. 2 Techincal specication
Warranty
2
2
3
4
4
6
7
9
10
10
11
12
12
13
13
13
15
19
21
21

FZ10004
2
SAFETY
General instruction
• The products referred to in this manual conform to the European Community Directives and are there-
fore marked with .
• The unit is supplied with hazardous network voltage (230V~). Leave servicing to skilled personnel only.
Never make any modications on the unit not described in this instruction manual, otherwise you will
risk an electric shock.
• Connection must be made to a power supply system tted with ecient earthing (Class I appliance ac-
cording to standard EN 60598-1). It is, moreover, recommended to protect the supply lines of the units
from indirect contact and/or shorting to earth by using appropriately sized residual current devices.
• The connection to the main network of electric distribution must be carried out by a qualied electrical
installer. Check that the main frequency and voltage correspond to those for which the unit is designed
as given on the electrical data label.
• This unit is not for home use, only professional applications.
• Never use the xture under the following conditions:
- in places subject to vibrations or bumps;
- in places with a temperature of over 45 °C.
• Make certain that no inammable liquids, water or metal objects enter the xture.
• Do not dismantle or modify the xture.
• All work must always be carried out by qualied technical personnel. Contact the nearest sales point for
an inspection or contact the manufacturer directly.
• If the unit is to be put out of operation denitively, take it to a local recycling
plant for a disposal which is not harmful to the environment.
Warnings and installation precautions
• This product in combination with loudspeakers, may be capable of producing dangerous sound levels
that could cause permanent hearing loss. Do not operate for a long period of time at high volume level
or at a level that is uncomfortable.
• Do not install the xture near sources of heat.
• If this device will be operated in any way dierent to the one described in this manual, it may suer
damages and the guarantee becomes void. Furthermore, any other operation may lead to dangers like
short circuit, burns, electric shock, ect.
• The xture must be located in a place where a proper ventilation or thermal dissipation is not impeded.
Do not install the xture in a conned space.
• After connecting to the power supply, standby LED lights up to show that some components inside
have already been electried.
• Linking an output to an oscilloscope - when in “bridge” mode – is forbidden or it will cause damage to
the amplier and to the equipment.
• The output level of the amplier must never exceed the marked sensitivity.
• Do not link the output of any amplier channel back into another channel ‘s input. Do not parallel or
series connect an amplier’s output with any other amplier’s output.
• In system’s setup, amplier’s output power must be from 50% up to 100% greater than the loudspeak-
er’s rated power.
WARNING! Before carrying out any operations with the unit, carefully read this instruction
manual and keep it with cure for future reference. It contains important information about
the installation, usage and maintenance of the unit.

3
FZ10004
• Make sure that the signal is correctly connected to the amplier’s input channel and set to the proper input
mode.
• Please turn o the power switch before pulling o the power cord.
• At the beginning, please always set the volume at the -80dB position.
• Before starting any maintenance work or cleaning the unit, cut o power from the main supply.
• Please clean the dust lter placed on front panel.
GENERAL INFORMATION
Shipments and claims
The goods are sold “ex works” and always travel at the risk and danger of the distributor. Eventual dam-
age will have to be claimed to the freight forwarder. Any claim for broken packs will have to be forwarded
within 8 days from the reception of the goods.
Warranty and returns
The guarantee covers the xture in compliance with existing regulations. You can nd the full version of
the “General Guarantee Conditions” on our web site www.musiclights.it. Please remember to register the
piece of equipment soon after you purchase it, logging on www.musiclights.it. The product can be also
registered lling in and sending the form available on your guarantee certicate. For all purposes, the va-
lidity of the guarantee is endorsed solely on presentation of the guarantee certicate. Music & Lights will
verify the validity of the claim through examination of the defect in relation to proper use and the actual
validity of the guarantee. Music & Lights will eventually provide replacement or repair of the products de-
clining, however, any obligation of compensation for direct or indirect damage resulting from faultiness.

FZ10004
4
- 1 - INTRODUCTION
1.1 DESCRIPTION AND TECHNICAL SPECIFICATIONS
FZ10004 is a 4ch amplier capable to deliver 4x2500W @2Ohm and 4x2100W @4Ohm, in 2U rack mount
only.
These features make it ideal for professional full-range speakers and in multi-amplied system character-
ized by wide dynamics and high performance.
• The FZ ampliers series uses the technology of amplication in Class I with SMPS power stage.
• The operation in Class I is based on a continuous and automatic adjustment of the value of the supply
voltage of the nal stage. This optimizes the eciency up to 85%, reducing the weight and heat dis-
sipation comparing with other ampliers which deliver same output.
• The models of FZ serie are able to operate with loads from 2Ohm and are equipped with an extensive
set of protection circuits to satisfy the higher reliability parameters with high quality prole for xed
and mobile sonorizations.
1.2 MAIN FEATURES
The amplier incorporates a number of sophisticated technologies to ensure the best possible perform-
ance and many years of reliable operation. Familiarizing yourself with these technologies will prove in-
valuable in setting up and optimizing your loudspeaker system.
Class I amplifier Continuos and Automatic Adjustment Power Supply
Class I technology combines the exceptional eciency of a Class D amplier with the high sonic quality
associated with Class B designs. Class I also incorporates the same basic concepts behind Class H designs,
but here they are rened and pushed to a higher level to achieve greater eciency.
The Class I output sections work in concert Continuos and Automatic Adjustment Power Supply to create
a superior overall power amplier topology. Ensures stable, full output power over an extremely wide
range of mains voltage levels. Sagging or uctuating mains voltage will not aect the power output de-
livered to the loudspeakers.
Amplifier gain
For greater exibility in system Integration, amplier allow gain adjustment from +23dB to +44 dB in 3dB
steps. This feature accommodates any combination of input device and loudspeaker type.
For example, if the input signal is weak, the gain can be boosted to maintain maximum power output
while avoiding a poor signal-to-noise ratio. This gain adjustment feature makes it easier to achieve an
optimal balance between headroom and noise oor.
Voltage Limiter (VL)
The Voltage Limiter (VL) feature allows user adjustments that determine maximum voltage output, thus
matching the amplier to the connected speaker load. Regardless of load impedance, the VL feature can
be set to ensure that neither temperature nor current limitations are exceeded before reaching the de-
sired voltage threshold.
Protection and performance optimization
Appropriate and reliable power amplication is vital to any audio system. Inadequate or faulty power
amplication could cause damage to the loudspeakers or in some cases to the power ampliers them-
selves. To prevent any damage or costly service interruptions, the amplier oer advanced features to
protect both internal circuits and any connected loads. These features even protect the mains fuse that,
in extreme cases, could be overloaded. Following are short descriptions of standard built-in protection
features:

5
FZ10004
• CPL , (Current Peak Limiter) ensures that the amplier’s Output does not exceed the safe current han-
dling parameters of amplier components.
• Temperature protection ensures that the amplier will not be damaged by exceeding thermal limits.
• VHF , (Very High Frequency) protection circuits mute the output of the amplier when non dynamic
continuous signals above 10 KHz are detected.
• DC protection ensures destructive DC signals will not appear at the amplier outputs. If such condi-
tions occur an internal fuse opens and fault indication is displayed.
• Low-impedance (short circuit) protection provides a fault warning indication and shuts down the out-
put stage when, for example, an input signal is present and a malfunctioning cable or driver is short
circuiting the output.
• High-impedance warning reports an alert when, at the same time, output signal is high and no cur-
rent draw is measured. This situation might occur when no speakers are connected, or when a driver
is blown.
• Low inrush current ensures that the mains breaker will not trip when several power ampliers are
turned on simultaneously.
Patent AMP Module hot plug in/out technology
Plug in or out directly, so there is no need to switch the power o or turn down signal of the device during
the operation of AMP module.
2Ω Heavy duty non-heat protection
In the condition of 2 heavy duty, the power module will decrease power automatically before thermal
protection to make amplier outputs normally with without mute. The power module will increase auto-
matically to the preset value after over-heat disappeared.

FZ10004
6
1.3 FRONT-PANEL OVERVIEW
The amplier’s front panel presents the performance and fault condition indicators, power and remote
switches, and a removable dust-lter cover. Level potentiometers provide individual attenuation for the
amplier channels. Range is 0dB to - innity. (The 12 o’clock position indicates -10dB attenuation.) A con-
venient label strip with writing surface is provided adjacent to each level potentiometer.
To remove the dust-lter covers, loosen the thumbscrews located underneath the front handles. This al-
lows removal of the dust-lters for cleaning. The covers may be made tamper resistant by replacing the
thumbscrews with Philips head or safety Torx screw. Thread size is M3.
The amplier never should be operated without the dust-lters in place.
Front
The front-panel LED area includes the following indicators per channel:
SIG -20 -15 -10 -4 VL CPL
HI - IMP
VHF
TEM
MUTE
• VHF - Very High Frequency protection active (output muted) (Red constant)
• TEM - Temperature mute (Red constant)
• MUTE - Channel muted due to a fault condition(yellow)
• C P L - (yellow cons tant with output muted): Low impedance / short circuit detection fault
• VL - Voltage Limiter (VL) active
• S IG - Signal levels - 40dB (Sig) to -4dB
• Hi-IMP - High-impedance/open load detected (Red)
When no VL, CPL or PAL indicators are illuminated, and the VL DIP-switch is set to maximum at the speci-
ed nominal load, the amplier channel is able to deliver maximum rated output power.
It’s normal light has been shown “BLUE”during power on.
Fig.2 - Power LED
Fig.1 - Front-panel LED area
(
PWR) Power on (BLUE)
POWER

7
FZ10004
1.4 REAR-PANEL OVERVIEW
Fig.3Rear panel
AC 110 V /2 2 0V , 5 0- 6 0 H z ; 2 5 00 W~
MA D E I N C H I N A
S E R IA L N U MB E R :
32dB
29dB
26dB
23dB
MODE
VL
CH 4
VL VL
CH 3 CH 2
VL
CH 1
MODE MODE MODE
CH 4 CH 3 CH 2 CH 1
CH 4 CH 3 CH 2 CH 1
44dB
41dB
38dB
35dB GAIN
VL- VO L TA G E LIMIT E R
150V
121V
101V
83V
70V
56V
47V
38V
MOD E
SWITCH
SOFT
HARD
GA I N
31 24
BRIDGE
3+4
BRIDGE
1+2
1. MAINS INPUT 110V OR 220V OPERATION (NOT SELECTABLE).
2. DIP-SWITCHES FOR ADJUSTING KEY FEATURES.
3. DMX IN (3-pole XLR):
1 = ground, 2 = DMX -, 3 = DMX +
4. 4 CHANNEL VERSION SHOWN WITH NEUTRIK SPEAKON OUTPUT CONNECTORS.
Configuration section
Four-channel model shown. The amplier has dierent VL values. Functions are otherwise identical.
DIP-switch features
Fig.4 - DIP-switches on the rear panel
32dB
29dB
26dB
23dB
MODE
VL
CH 4
VL VL
CH 3 CH 2
VL
CH 1
MODE MODE MODE
44dB
41dB
38dB
35dB GAIN
VL -V O LT A G E L IMIT E R
150V
121V
101V
83V
70V
56V
47V
38V
MO DE
SWITCH
SOFT
HARD
G A IN
BRIDGE
3+4
BRIDGE
1+2
The following features may be adjusted using the DIP-switches on the rear panel of the amplier.
• Gain - Globally set for all channels, from +23dB to +44 dB in 3dB steps.
• Option active - Not currently implemented.
• Fan Masked - When on, engages the intelligent fan feature; fan speed is lowered when no signal is
present.
• Bridge A+B and C+D - Switches the channel pairs into bridge mode operation An automatic - 6dB gain
compensation is applied.
• VL - The Voltage Limiter provides optimum peak voltage settings for each channel . Eight discrete levels
are selectable.
• Mode - Select VL mode to either Hard or Soft operation. For channels driving sub-woofers and low-
frequency drivers, it is recommended to use the hard setting for optimal operation. For mid- and high-
frequency drivers, always select Soft.

FZ10004
8
Fig.5 - Input / Output connectors
Input and Output connectors
The amplier is equipped with balanced XLR-F input connectors. Speakon output connectors (SP).
For specic conguration and wiring information, see section 3.4.
VL VL in Bridge Mode
150V 300V
121V 242V
101V 202V
83V 166V
70V 140V
56V 112V
47V 94V
38V 76V
Speakon outputs - four-channel models
CH 4 CH 3 CH 2 CH 1
Audio inputs - four-channel models
CH 4 CH 3 CH 2 CH 1

9
FZ10004
1.5 METHOD FOR AMP MODULE HOT PLUG
How to:
Push in: - Stir the plug in/out bar to the handle (right side), and then push into the bottom of slot directly.
It’s only can be used after an indicative sound from the auto-lock switch that means the module is posi-
tioned. (It is very important to make sure that the module has been pushed in completely).
Pull out: - When need to pull out the module, stirring the plug in/out bar to the handle (right side), the
module will draw out from the position automatically, and then pull out the module easily and simple.
Please insert/pull by one time only due to AMP module featuring high power connection.
Fig.6
Idling Auto-lock Device
Handle
Auto-Lock Switch
Plug In/out Bar
Idling Auto-Lock in

FZ10004
10
- 2 - INSTALLATION
2.1 UNPACKING
Carefully open the shipping carton and check for any noticeable damage. The power amplier is tested
and inspected before leaving the factory and should arrive in perfect condition. If any damage is discov-
ered, please notify the shipping company immediately. Only the consignee may institute a claim with the
carrier for damage incurred during shipping. Save the carton and packing materials. Inspection. Should
you ever need to ship the amplier, always use the original packaging materials.
2.2 MOUNTING
Free airow from front-to-rear of the amplier must be possible. Therefore, no doors or rack-lids should
be mounted in front of or behind the ampliers. Ampliers may be stacked directly on top of each other.
There is no need for spacing in between units, though this might enable more convenient installation
of cabling on the rear panel. It is recommended that rear supports be mounted for maximum long-term
stability. Rear support brackets are included.
MA D E I N C H IN A
MA D E I N C H IN A
Standard Accessories (package Included)
Alternative 1:
use washer for xed installation.
Fig.7 - Rear support bracket
Alternative 2:
use tube for exible - depth installation.

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FZ10004
2.3 COOLING
The amplier uses a forced-air cooling system with air ow from front to rear, maintaining a low operating
temperature within dened limits. Front-to-rear airow is preferred as cooler air is present at the front in
nearly all applications. (This allows higher continuous power levels without encountering thermal prob-
lems). Never attempt to reverse the airow. The amplier modules require a pressure chamber between
the fans and heat sink, and this eect functions only in one direction.
Make sure that there is an adequate air supply in front of the amplier, and that the rear of the amplier
has sucient space to allow the exhaust to escape. If the amplier is rack-mounted, do not use covers or
doors on the front or rear of the rack.
Should a heat sink overheat, the temperature sensing circuits will mute the overheating channel.
If the power supply overheats, another sensing circuit will mute all output channels until the power sup-
ply cools to safe operating temperature. An early warning before shut down will be indicated on the front
panel LEDs.
Always make sure that the dust-lters behind the detachable front panel are clean to ensure maximum
possible airow.
If the amplier malfunctions due to dirty dust lters, any required repairs are not covered by the warranty.
Fig.8 - Cooling system

FZ10004
12
2.4 OPERATING VOLTAGE
The label placed to the right of the mains cable on the rear of the amplier indicates the AC mains volt-
age for which the amplier is wired and approved: 110V or 220V. Connect the power cable only to the
AC source type referred to on the label. The warranty will not cover damage caused by connecting to an
incorrect type of AC mains.
The switch mode ampliers use primary switching. Because the mains power is rectied directly in front
of the transformer, the amplier is insensitive to mains frequency. It may be connected to 50 or 60 Hz
sources, and actually will operate on line frequencies from DC to 400 Hz.
The amplier uses POWERCON connection. If the power plug mounted at the factory is not appropriate for
your country, it can be removed and the proper connector wired in its place as follows:
Wire Distribution:
WHITE LIVE
BLACK NEUTRAL
GREEN EARTH(GROUND)
If you are not 100% condent of your competence to replace the mains plug, engage qualied personnel
to do the job.
Once a suitable AC supply is connected, the amplier can be turned on using the front panel power switch.
The amplier then goes through a soft-start. The fans will blow at high speed before dropping to idle, and
the power LED will illuminate.
Inrush power is controlled and limited during soft start , enabling multiple ampliers to be powered up
simultaneously.
2.5 GROUNDING
There is no ground lift switch or terminal on the ampliers. The signal ground is always oating, via a res-
tor, to chassis and therefore the grounding system is automatic.
In the interests of safety, never disconnect the earth (ground) pin on the AC power cord.
Use balanced input connections to avoid hum and interference.

13
FZ10004
- 3 - FUNCTIONS AND SETTINGS
3.1 INTRODUCTION
The following sections provide comprehensive information on amplier connection, setup, operation,
and performance. The detailed information included here is essential to realizing the full functionality of
the ampliers.
3.2 OPERATION PRECAUTIONS
• Make sure that the Power switch on the amplier front panel are set to o before making any input,
output, and also before manipulating the DIP-switches on the rear panel.
• Make sure that the AC mains voltage is correct and matches the voltage printed on the rear panel of
the amplier (110V or 220V).
• Make sure that no signal is present at the input to the amplier when powering up. An input signal
could produce an unintentionally loud initial volume from the speakers.
3.3 SIGNAL FLOW AND HEAD ROOM
Signal flow blocks
The input stage of ampliers has a high sensitivity to provide ample system headroom. This in eect
means that the input stage is almost impossible to clip.
Overall amplier input gain is adjusted using the input stage DIP-switches. Please note that the gain set-
ting is global, aecting all channels. Following the input stage, the dedicated level control on each chan-
nel allows signal attenuation from 0dB to minus innity.
The Current Peak Limiter (CPL) section dynamically limits the input signal based on three parameters:
sensed current level, feedback from the output stage, and sensed voltage clip from the VL (and output
amplier voltage clip if Soft Clip is activated). This ensures that power output is maintained within the
design limits of the amplier.
The adjustable Voltage Peak Limiter (VL) sets the maximum output voltage and therefore also the maxi-
mum output power. Eight dierent voltage stages are available using the DIP-switches on the rear panel
of all models.
The sophisticated output section monitors faults and generates appropriate warnings, which are dis-
played on the amplier front panel. In the rare event that conditions are extraordinarily severe, the ampli-
er will shut down until the fault or problem setting has been rectied or adjusted. These sensing circuits
are also employed to feed back voltage and current level information, via a side chain, to the limiters.
Sensing circuits also transmit local amplier module temperature and power supply temperature to the
appropriate protection mechanisms. Read the Protection, Faults and Warnings section for further details.
Fig.9
I

FZ10004
14
Headroom, sensitivity and VL/Gain settings
The input amplier and limiter system is designed to accommodate extremes of performance. Typically,
exceeding maximum input by much as +10dB will only result in a 1% increase in distortion. The following
schematics illustrate how the adjustable VL and Gain circuitry aect input sensitivity and output power.
The chart to the follow of the drawing below show input sensitivity with a 8 ohm load ad and 150V peak
(max.) and 38V peak (min.) respectively for the eight dierent gain stages between +23dB and +44dB. The
resulting output power is displayed in dBu, Vrms and watts in the tables to the far right.
The headroom available through the input stage to the clip limiter is shown by the dotted lines as +10
dB at 150V peak and +16.1dB at 38V peak. These lines illustrate the additional signal level that can be ac-
cepted at the input before any signicant distortion will appear at the input stage.
If you use the level potentiometer in the signal chain to reduce the level by an amount greater than the
headroom relative to input sensitivity, AND you drive the amplier to clip level, you are in danger of clip-
ping the input stage before the current or voltage peak limiters are activated.
When bridging two channels, you must add +6dB to the input sensitivity to achieve maximum output
voltage due to the automatic - 6dB gain compensation inserted by the amplier.
Fig.10
I
VL set to 150 V
PEAK
Input
sensitivity
dBu / V
rms
1,0 / 0,87
4,0 /
1,23
7,0 / 1,7
10,0 /
2,5
13,0 /
3,5
16,0 /
4,9
19,0 /
6,9
22,0 /
9,8
Gain set to:
(DIP-switches)
+ 44 dB
+ 41 dB
+ 38 dB
+ 35 dB
+ 32 dB
+ 29 dB
+ 26 dB
+ 23 dB
+ 10 dB headroom to clip
relative to input sensitivity *)
Voltage Limiter
set to:
(DIP-switches)
150 V
peak
121 V
peak
101 V
peak
83 V
peak
Output
power
dBu /
V
rms
45,0 / 106
43,8 / 86
42,1 /
72
40,5 / 59
Output Power
@ 8 Ohm
1300 W
924 W
648 W
435 W
VL set to 38 V
PEAK
Input
70 V
peak
56 V
peak
39,2 / 50
37,3 / 40
312 W
200 W
sensitivity
dBu / V
rms
-10,1 / 0,24
-7,1 / 0,34
-4,1 / 0,5
-1,1 / 0,7
1,9 / 1,0
4,9 / 1,4
7,9 /
1,9
10,9, / 2,7
Gain set to:
(DIP-switches)
+ 44 dB
+ 41 dB
+ 38 dB
+ 35 dB
+ 32 dB
+ 29 dB
+ 26 dB
+ 23 dB
+ 16,1 dB headroom to clip
relative to input sensitivity*)
*) Headrom limited to +5dB at Gain set to +23 dB at Max. VL
47 V
peak
38 V
peak
35,6 / 33
33,9 / 27
130 W
91 W
VL and GAIN settings

15
FZ10004
3.4 AUDIO INPUT AND OUTPUT CONNECTIONS
Balanced Input connections
The XLR input connectors are electronically balanced, and wired according to the IEC 268 standard (pin 2
= hot). XLR input connectors should be wired as follows:
Pin 1 Ground/Shield
Pin 2 Hot (+)
Pin 3 Cold (-).
Fig.11
CH 4 CH 3 CH 2 CH 1
XLR input connectors
Audio inputs - four-channel models
When linking the same source signal to several input channels, be aware that there is a limit to the number
of channels an output source Can drive . A typical output source (e.g. a DSP crossover unit) can drive up to
four amplier channels before external line-drivers might be required to buer the signal.
Unbalanced Input connections
To connect an input to an unbalanced source, it is possible to connect pins 1 and 3 in the XLR plug at the
amplier end of the cable. However, a better method is to connect pin 3 to the shield at the source end of
the cable, as this usually results in better hum and noise rejection. Balanced input connections are recom-
mended whenever possible.
Fig.12
Unbalanced Input connections

FZ10004
16
Speakon Output connections
Amplier is equipped with the Speakon output connectors.
Fig.13
CH 4 CH 3 CH 2 CH 1
Speakon outputs - four-channel models
Never connect an output terminal to ground, or to any other input or output. Observe relative loudspeak-
er polarity: loudspeakers connected in reverse polarity will exhibit degraded performance, particularly in
bass frequencies, and may be damaged as a consequence.
Use a high-quality stranded loudspeaker cable, and keep cable runs as short as possible.
Four -channel ampliers are wired in the following manner. The right Speakon connector, Channel A+B,
provides outputs for both Channel A and Channel B. This output is useful when wiring the amplier for
bridged mono operation. See section 3.4. The left Speakon connector provides an output for Channel B
only. Connect the + and -loudspeaker cables as shown in the illustrations below.
Fig.14
Channel A and B into one Speakon
(Channel C and D into One Speakon)
Bridge mode connects to1+/2+ of Channel
1+/2+ of Channel C
Channel A, B, C, D for each separate Speakons
A

17
FZ10004
Output bridge mode
When bridged, the input source must be connected to input A (A+B) or C (C+D) respectively.
Output speakon cables must be connected to the bridge on channel 1+/2+ of channel 1 and 3+/4.+
of channel 4. The main benet of bridging the output is a doubling of output voltage. Bridging can be
used to turn a four-channel by amplier, for example into a three-channel amplier with 2 x 1300W and 1
x 4200W at 8 ohms or 2 x 2100W and 1 x 5000W at 4 ohms
Most power amplier designs, when bridged, automatically introduce a +6 dB input gain boost which
can lead the user to conclude that said amplier delivers more than double the power when in bridge
mode. This is clearly not the case, as the gain boost articially enhances perceived power at the cost of
headroom. The ampliers work on globally set constant gain, and automatically compensate the input
gain by -6dB. For example, if the amplier is congured in a three-channel mode, then the selected gain is
maintained from input to output on all channels.
Amplifier Gain
The ampliers feature adjustable input gain. This versatility enables the amplier to accommodate a multi-
tude of system congurations with various input sources and speaker layouts. Amplier gain is set globally
for all channels.The range is +23dB to +44dB in 3dB steps. Individual channel ne level adjustment is avail-
able using the potentiometers on the front panel.
The unique adjustable input gain feature of the amplier makes it easier to attain the optimum balance
between headroom and signal-to noise ratio in the signal path. A weak signal at the input might require
the gain to be raised in order to achieve maxi- mum output power with the lowest signal -to-noise ratio. A
hot input signal, however, would require a lowering of the gain to avoid sending the amplier into Voltage
or Current clipping. See Appendix to review the table containing Gain versus VL setting implications for
input sensitivity and output power. Bridge mode operation automatically compensates by -6dB, keeping
all channels at the same gain.
Channel gain/level (front-panel pots)
Individual channel gain (level) may be adjusted using the potentiometers located on the front panel.
Range is from 0dB to -innity. The attenuation is -10dB.
If the level control is used to attenuate to a lower level than the headroom relative to input sensitivity AND
the amplier input is driven into clip, there is a danger of clipping the input stage before the current or
voltage limiters are activated.
Amplifier sensitivity
Sensitivity is dened as how many Volts (rms) or dBu (referred to 0.775V rms) are required to achieve full
(maximum) output power. As the output power varies with the load impedance, 4 ohms is usually the
common reference. Since the ampliers are capable of providing multiple maximum output power levels
through use of the VL feature, many sensitivity calculations may be required for a single amplier.
Output Voltage Limiter (VL)
Voltage Limiter (VL) is a unique feature in ampliers. It is used to select the maxi- mum power available on
each output channel. VL levels are set using the rear-panel DIP-switches; eight level positions are oered.
The values for VL are displayed as maximum Voltage Peak. To translate Voltage Peak into Vrms, you must
divide the Voltage Peak values by 1.41 (see table). The VL allows you to set the correct maximum output
peak power for optimum performance with the connected speakers. The correct setting depends on the
system type and the specic load connected to the channel. Since each channel can be congured to
deliver either very high voltage peak power OR high current draw at low-impedances, it is important to
set the VL correctly. If you choose a lower VL setting, you only reduce the maximum output voltage. At the
same time, this allows more current headroom for low-impedance loads. The amplier thus runs at higher
eciency, with a signicantly reduced risk of going into thermal protection.

FZ10004
18
Output Current Peak Limiter (CPL)
The Current Peak Limiter (CPL) ensures that the amplier will not be damaged by forcing the amplier to
deliver current levels to the outputs that exceed the physical limits of the transistors. The CPL keeps the
amplier within the Safe Operating Area (SOA.)
The CPL is non-adjustable and has dierent limit values depending on model type.
CPL activity is indicated by illumination of an orange LED for each channel on the front panel.
A steadily illuminated orange CPL LED (with MUTE illuminated) indicates a short circuit situation (or very
low-impedance). The output will mute for 6 seconds before measuring the output impedance again. This
will continue until the short circuit is xed, at which time the output will automatically un-mute. An input
signal must be present to allow detection of short circuit or low-impedance conditions.
The problem can be solved by checking input and output cables and examining the state of the loud-
speaker load. If there is no short circuit present, then the condition may be rectied by lowering the VL or
input levels.
V peak (VL) V rms
150 106
121 86
101 72
83 59
70 50
56 40
47 33
38 27