RSD AX 3500 User manual

AX
1500
2500
3500
USER GUIDE
Professional Power Amplifiers

Contents
Instructions
Unpacking 1
Safety Instructions 1
Front panel controls and features 2
Rear panel controls and features 3 - 5
Operation 6
Ventilation 6
Protect LEDs 6
Cables 7
Rack Mounting 7
Trouble Shooting 7
Service Information 8
Technical Information
Technical Specification 9 - 10
Glossary of Terms 11
Set-up Diagrams
Mono Mix 12
Stereo Mix 12
Mono Bi-amp 13
Stereo Bi-amp 13
2-way Monitor Mix 14
Stereo Bi-amp with Mono sub bass 14
2-way stereo with additional amplifiers 15
Notes 16
STUDIOMASTER AX Amplifier Series
STUDIOMASTER AX Amplifier Series

Congratulations on your purchase of a Studiomaster AX Series power amplifier. Like
all Studiomaster products, it has been designed to meet the highest standards of
performance, safety and reliability. We are confident that this amplifier will fully meet
your needs for many years to come. Please read this guide carefully and keep it safe
in case you need to refer to it in the future.
Unpacking
Remove your AX amplifier from its packing. Check that the carton includes an
AC power cord/mains lead and a warranty card. It is important to retain the carton
and all packing material in the event that the unit needs to be returned to your dealer
for service or repair. Please complete and return your warranty card. Returning the
completed warranty card does not diminish your statutory rights in any way.
Safety instructions
1. Make sure you have the correct product for your local supply Voltage. This will be marked on
the rear panel of the amplifier.
2. Only use the A.C. power cord/mains lead supplied with the product. If it becomes damaged in
any way it should be replaced.
3. Never operate without, or remove, the safety ground (earth) from the A.C. power cord/mains
lead.
4. Do not attempt to remove screws or panels. There are no user serviceable parts inside.
5. Do not operate the unit next to heat sources such as electric fires, central heating etc.
Note : Exposure to strong sunlight (eg outdoors) could cause the amplifier to over heat.
6. The unit should not be operated or stored near rain or moisture.
7. This equipment must not be exposed to dripping or splashing and no objects filled with liquids
should be placed on top of it.
8. Always ensure that both front and rear ventilation holes are clear of obstructions.
9. Write the serial number in the box provided below for future reference.
10. If the unit gets damaged or appears to have developed a fault refer to the Service Information
section for details.
WARNING: THIS APPARATUS MUST BE EARTHED (GROUNDED)
STUDIOMASTER AX Amplifier Series
STUDIOMASTER AX Amplifier Series 1

8
0dB
-30
-20
-15
-3 SIG
AB
POWER
-6dB PEAK PROTECT
CHANNEL A
CHANNEL B BRIDGE
AX
2500
P r o f e s s i o n a l P o w e r A m p l i f i e r
8
0dB
-30
-20
-15
-3
I
O
1. LEVEL controls adjust signal levels for channels A and B.
2. Status LEDS indicate the following:
a SIG indicates a signal is present and sound should be heard from the
speakers.
b -6 shows a strong signal is present.
c PEAK shows maximum output power has been reached. Increasing
the level control or input signal will not increase the output power.
d PROTECT illuminates when the amplifier is muted at switch on. After a
couple of seconds they will turn off and the speakers are connected for
normal operation. If at any stage, they stay illuminated, a fault has
occurred. See section under PROTECT LEDs for more information.
e POWER shows the amplifier is switched on.
f BRIDGE indicates the amplifier is in BRIDGE mode.
3. POWER switch.
4. Fan ventilation holes. Do not obstruct.
Front panel controls and features
STUDIOMASTER AX Amplifier Series
STUDIOMASTER AX Amplifier Series2
1234
4
-10
-5
-10
-5

1. There are two INPUT CONNECTORS per channel. One is a combination 3
pin XLR and 3 pole (TRS) ¼" jack socket, the other a male XLR for linking to
other amplifiers. Both balanced and unbalanced signals can be used to drive
the amplifier.
XLR connector wiring
Balanced Operation Unbalanced operation
PIN 1 Ground PIN 1 Ground
PIN 2 +Ve/in-phase signal PIN 2 +Ve/in-phase signal
PIN 3 -Ve/out-phase signal PIN 3 Link to ground (pin1)
Jack connector wiring
Balanced Operation Unbalanced operation
3 pole/TRS/stereo ¼ " jack 2 pole/TS/mono ¼ " jack
TIP +Ve/in-phase signal TIP +Ve/in-phase signal
RING -Ve/out-phase signal SLEEVE Ground
SLEEVE Ground
2. Input GND LIFT (ground lift) switch removes the ground connection to all input
connectors. This can solve hum loop problems when connecting equipment
with different A.C. supplies.
Under no circumstances should the electrical safety ground (earth) from the
A.C. supply be disconnected.
3. PARALLEL INPUTS links Channel A input to Channel B. A single input signal
will now supply both channels. The volume levels of each channel can still be
adjusted individually.
4. 35Hz high pass filter reduces the level of very low frequency signals
reaching the speakers, improving bass clarity and power handling. It is
recommended that this filter is always used for live P.A/Sound re-inforcement.
Ported / Vented / 'bass reflex' speaker cabinets can be damaged if driven with
high power low frequency. For Studio monitoring where a totally flat response
is required, deselect the High Pass Filter. The filter has an 18dB / octave cut-
off slope.
Rear panel controls and features
STUDIOMASTER AX Amplifier Series
STUDIOMASTER AX Amplifier Series 3
1
234
230V
RISK OF ELECTRIC SHOCK
DO NOT OPEN
CAUTION
A
I
R
V
E
N
T
S
F
R
O
N
T
A
N
D
R
E
A
R
M
U
S
T
N
O
T
B
E
O
B
S
T
R
U
C
T
E
D
C
A
U
T
I
O
N
CIRCUIT
BREAKER
GND
LIFT
PARALLEL
INPUTS
INPUT B LINK
B
CH
BRIDGE
CH. A
PIN 1+ =
PIN 2+ =
+
-
P
IN 1+ =
P
IN 1- =
+
-
ASSEMBLED IN CHINA
35Hz
LIMITER
OFF
HI
LO
INPUT
A
LINK
A
CH
HI
LO
35Hz
LIMITER
OFF
HI
LO
XOVER
TO CH A - AMP
XOVER OUTPUT
OFF
ON
HI
LO
XOVER
TO CH B - AMP
OFF
ON
PIN 1+ =
PIN 1- =
+
-
XOVER OUTPUT
100Hz
150Hz

5. LIMITER OFF disables the clip limiter circuit. At maximum power output, the
limiter virtually prevents amplifier clipping, minimising audible distortion. It
should only be turned off in specific applications, as serious speaker damage
can occur if the amplifier is allowed to clip regularly.
6. X-OVER turns on the internal two way crossover circuit. The crossover splits
the audio band into high frequencies, suitable for mid/high speakers and low
frequencies suitable for bass speakers. If the crossover function is not
required this switch should remain off (out position).
7. The frequency switch selects the crossover frequency between 150Hz and
100Hz. For most systems 150Hz is recommended although some, typically
when using 18" subs, will work better with 100Hz. The internal crossover has
a '3rd order' response.
8. HI LO selects which signal from the crossover the amplifier receives. When
HI (out position) is selected only frequencies above 100 or 150Hz feed the
amplifier. When LO (in position) is selected only frequencies below 100 or
150Hz feed the amplifier.
9. XOVER OUTPUT sockets allow the high or low frequencies from the
crossover circuit to feed additional amplifiers. See examples in the Set Ups
section.
10. BRIDGE mode combines the output power of both amplifier channels into one
load. This is useful when driving a single, high powered speaker. Only channel
A output socket connects to the speaker but has to be wired in a different way.
See the section below regarding speaker wiring.
In this mode only Channel A input and level control are used.
Rear panel controls and features
STUDIOMASTER AX Amplifier Series
STUDIOMASTER AX Amplifier Series4
5
976
230V
RISK OF ELECTRIC SHOCK
DO NOT OPEN
CAUTION
A
I
R
V
E
N
T
S
F
R
O
N
T
A
N
D
R
E
A
R
M
U
S
T
N
O
T
B
E
O
B
S
T
R
U
C
T
E
D
C
A
U
T
I
O
N
CIRCUIT
BREAKER
GND
LIFT
PARALLEL
INPUTS
INPUT
B
LINK
B
CH
BRIDGE
CH. A
PIN 1+ =
PIN 2+ =
+
-
PIN 1+ =
PIN 1- =
+
-
ASSEMBLED IN CHINA
35Hz
LIMITER
OFF
HI
LO
INPUT A LINK
A
CH
HI
LO
35Hz
LIMITER
OFF
HI
LO
XOVER
TO CH A - AMP
XOVER OUTPUT
OFF
ON
HI
LO
XOVER
TO CH B - AMP
OFF
ON
PIN 1+ =
PIN 1- =
+
-
XOVER OUTPUT
100Hz
150Hz
8 10

14
14
11. Speaker Wiring. Each channel uses SPEAKON NL4 connectors. Using cable
as specified (See CABLES) speaker connections are as follows:-
Each channel connected individually to a speaker:
PIN 1+ Positive (+) PIN 2+ Not used
PIN 1- Negative (-) PIN 2- Not used
Two Speakers connected to both channels in a single 4 core cable:
Use only Channel A connector wired:
Channel A PIN 1+Positive (+) Channel B PIN 2+ Positive (+)
Channel A PIN 1- Negative (-) Channel B PIN 2- Negative (-)
Bridged operation:
Use only Channel A connector wired:
PIN 1+ Positive (+) PIN 2+ Negative (-)
PIN 1- Not used PIN 2- Not used
Always ensure speaker cables are wired the same way. When any cable has
the pin wiring reversed, some speakers will be out of phase, usually resulting
in a loss of volume or bass.
12. Circuit Breaker will only activate if the amplifier has developed a fault or been
driven too hard into very low speaker impedances. The button on the circuit
breaker will protrude approximately 6mm when tripped. Check speaker wiring
and load before re-setting. To reset turn off the amplifier power switch and
push in the reset button. If the breaker trips again, the amplifier could have
developed a fault. If this happens refer to the Service Information section.
13. A.C. power inlet.
14. Fan ventilation holes. Do not obstruct.
Rear panel controls and features
STUDIOMASTER AX Amplifier Series
STUDIOMASTER AX Amplifier Series 5
11
230V
RISK OF ELECTRIC SHOCK
DO NOT OPEN
CAUTION
A
I
R
V
E
N
T
S
F
R
O
N
T
A
N
D
R
E
A
R
M
U
S
T
N
O
T
B
E
O
B
S
T
R
U
C
T
E
D
C
A
U
T
I
O
N
CIRCUIT
BREAKER
GND
LIFT
PARALLEL
INPUTS
INPUT B LINK
B
CH
BRIDGE
CH. A
PIN 1+ =
PIN 2+ =
+
-
PIN 1+ =
PIN 1- =
+
-
ASSEMBLED IN CHINA
35Hz
LIMITER
OFF
HI
LO
INPUT
A
LINK
A
CH
HI
LO
35Hz
LIMITER
OFF
HI
LO
XOVER
TO CH A - AMP
XOVER OUTPUT
OFF
ON
HI
LO
XOVER
TO CH B - AMP
OFF
ON
PIN 1+ =
PIN 1- =
+
-
XOVER OUTPUT
100Hz
150Hz
1312

Operation
Decide the required mode for the amplifier and select the appropriate rear panel
switches. The set up diagrams later in this guide will help.
Always ensure that all signal and power connections to the amplifier are properly
made before switching on. It is recommended to turn the level controls to minimum
initially as well.
Any amplifier(s) in a system should always be switched on LAST and switched off
FIRST to prevent damaging thumps, originating from other equipment.
Hints and tips
1. Make sure that the speakers being used have the correct power rating for the
amplifier. This will help avoid possible damage to the speakers.
2. The optimal speaker load impedance for power delivery and long term operation is 4
ohms per channel; 8 ohms in bridged mode.
The amplifier will operate into 2 ohm loads; 4 ohms bridged, although continuous
flashing of the PEAK LED should be avoided to prevent thermal protection shutting
down the amplifier.
3. Always use the LIMITER (rear panel switch in the out position) as it helps prevent
distortion on large signal peaks.
4. Use the 35Hz filter (rear panel switch 'in' position) as it will improve the bass power
handling and clarity of the system. This is especially important with vented / ported /
'bass reflex' cabinets.
5. When used with a pro-audio mixer, adjust the level controls to a position compatible
with the mixer metering. A suggested starting position for the level controls is '-10'.
Ventilation
It is essential that air can circulate freely around the amplifier to provide adequate
cooling. The fans take air in from the rear of the amplifier and exhaust through the
front panel. Both the front and rear ventilation holes must not be obstructed.
When the amplifier is rack mounted, care must be taken to ensure that the rack is
open at the front and rear to allow sufficient air flow.
In some installations, racks are fitted with covers for security reasons. If these restrict
the air flow in any way they must be removed while the amplifier is in operation.
Where multiple amplifiers are installed in a rack, additional forced ventilation or a
source of fresh cooling air may be required.
Protect LEDs
Operate independently and show that the speaker outputs have been muted
resulting in no sound. They illuminate under the following conditions:
1. When the amplifier is turned on. After a couple of seconds the LEDs will turn off
showing normal operation.
2. If the amplifier has reached an over temperature condition the volume of one or both
channels will rapidly reduce resulting in little or no sound. Once the fans cool down
the heatsinks, normal operation will resume. However, if the transformer has
overheated then it can take a few hours to cool.
3. If a fault has occurred on one or both channels the relevent PROTECT LED(s) will
stay illuminated and there will be no output. The amplifier should be returned to an
authorised Studiomaster service centre in the original packing, to prevent shipping
damage. See Service Information.
STUDIOMASTER AX Amplifier Series
STUDIOMASTER AX Amplifier Series6

Cables
Speaker cables should be as short and as heavy gauge as possible to prevent unwanted
power loss caused by high resistance, which can result in loss of both signal level and
quality. Heavy duty, twin core A.C. power cable is generally suitable.
Cable with a conductor size of 1.5mm² / 16AWG, 2.5mm² / 14AWG or 4.0mm² / 12AWG
is recommended. Note the losses caused by using thinner cable:
Cable length Wire size Loss @ 8 ohms Loss @ 4 ohms Loss @ 2 ohms
5 metres 1.0mm²/17AWG 2.15% 4.1% 7.75%
10 metres 1.0mm²/17AWG 4.12% 7.75% 14%
Rack Mounting
The AX series amplifiers are designed to be fitted into a standard 19" rack. They each
occupy 2 Units (2U) of rack space. If the amplifier is to be used in a mobile application, a
good quality, flight cased amp rack is essential if damage is to be prevented. We
recommend the use of 6mm rack screws with plastic or nylon washers underneath the
screw heads to avoid damaging the front panel.
Always use both the front and rear mounting holes, especially for mobile and touring
applications.
Trouble Shooting
No power on LED...
1. Check A.C. power cord/mains lead is connected to the wall supply and switched on.
2. Check A.C. power cord/mains lead is fully pushed into the amplifier socket.
3. Check that the amplifier is switched on.
4. UK only - Check fuse in the 'mains' plug.
5. Check A.C. supply house breaker / fuse.
No sound…
1. Check that the signal source (from mixer, CD player etc.) is working.
2. Check that the LEVEL control(s) are not in the minimum (anti clockwise) position.
3. Check that the speakers are connected correctly.
Distorted sound and PEAK LED(s) illuminated...
1. Possible short circuit on speaker cable or cabinet. Change speaker cable and check
cabinet.
2. If only on channel A, check a 4 core speaker cable is not being used with a speaker that
links PIN1+ to PIN2+ of the Speakon connector.
One or Both Amplifier channels stop working briefly…
(one or both Protect LEDs illuminate briefly)
1. Check the ventilation holes both front and rear for good air flow.
2. Check that the speaker load on each channel is not less than 2 ohms.
3. Check that the amplifier is not being over driven - red peak LEDs should not be illuminated
'continuously'.
Amplifier stops working and one or more PROTECT LEDs are illuminated…
1. The amplifier is in an over temperature or fault condition. See PROTECT LED section for
more information.
STUDIOMASTER AX Amplifier Series
STUDIOMASTER AX Amplifier Series 7

Service Information
If you have a problem with your Studiomaster product or think it has developed a
fault you should first carefully check the Trouble Shooting section in this guide. If this
does not solve the problem or if the product is physically damaged, contact your local
dealer or distributor for service details.
Should it be recommended you return the product to your nearest Studiomaster
Service Centre you must first contact them.
You will be asked for the product type and serial number. You will then be given a
Returns Authorisation (RA) number.
Pack the unit in its original carton to protect it from shipping damage.
You must have the Returns Authorisation number clearly marked on the outside of
the carton or we may refuse the delivery. Studiomaster cannot be held responsible
for damage resulting from the equipment being packed incorrectly.
Label the equipment clearly with your name and address and include a clear
description of the fault. The more information you supply helps the service engineer,
minimising repair cost when out of warranty.
Please write your Serial number here for future reference....
STUDIOMASTER AX Amplifier Series
STUDIOMASTER AX Amplifier Series8