Koch Guitar Electronics ATR-4502 User manual

OPERATING INSTRUCTIONS GB
BEDIENUNGSANLEITUNG DE
GEBRUIKSAANWIJZING NL
2013 Koch Guitar Electronics

EC DECLARATION OF CONFORMITY
We, Koch Guitar Electronics, Amersfoort, The Netherlands, declare under our sole responsibility that the product:
ATR4502 Guitar Power Amplifier
to which this declaration relates is in conformity with the following harmonized standards:
* EN 50081-1 [1991] Electromagnetic compatibility. Generic emission standard.
Part 1 : residential, commercial and light industry;
* EN 50082-1 [1991] Electromagnetic compatibility. General immunity standard.
Part 1 : residential, domestic and light industrial environment;
* EN 60065-1 [1993] Household electronic apparatus
Part 7 : Heating under normal operating conditions
* EN 60335-1 [1988] Safety of household and similar electrical appliances.
Part 1 : general requirements
following the provisions of Council Directive 98/336/EEC on the approximation of the laws of the Member States relating
to electromagnetic compatibility and the provisions of Council Directive 73/23/EEC on the approximation of the laws of
the Member States relating to low voltage and electrical safety.
Amersfoort, 1 july 2005
Dolf Koch

Dual Guitar Tube Response Power Amp
Volume
Channel A Channel B
Voicing Voicing
Depth
Thermal Thermal
CH-A
CH-B
-10dB MONO (bridged)
90 Watt in 8 ohm
70 Watt in 16 ohm
STEREO (CH-A/CH-B)
2x 50 Watt in 4 ohm
2x 45 Watt in 8 ohm
2x 35 Watt in 16 ohm
0dB
Input Levels
OUTPUT POWER
Depth
+ ++ +
Pres-
ence
Pres-
ence
Volume
Inputs
ATR-4502
0 0
10 10
5 5
6 6
7 7
8 8
9 9
4 4
3 3
2 2
1 1
Mains
On Off
100/120V - T5A
220/240V - T2.5A
Fuse:
VAC
115 230
100
~
Channel A
MONO
Channel B
Speaker
Outputs MONO
(bridged)
CH-B CH-A
4 Ohms
Minimum Load
8 ohm
Minimum
Load 4 ohm
STEREO
STEREO
17
5
3
26
4
1
4
5678
23
Front panel
Back panel

E N G L I S H
Thank you for choosing the ATR4502 from KOCH. You now own a "state-of-the-art" guitar power amplifier of the highest quality. The ATR4502 features the unique and totally new
KOCH ATR  Technology (Authentic Tube Response) that makes the amp sound completely like a vintage all-tube amplifier, but with lesser weight and higher reliability. The ATR4502
has been designed and built by people who - from their own experience as musicians - take guitar sound and quality very seriously. That is why this product was designed and built with
the utmost care in order to meet all professional standards. Our goal was not only to design an amp which sounds fantastic and is easy to operate, but also to build it in such a way that it
will serve you loyally for many years to come. Please take your time to read this manual carefully before you switch on the ATR4502.
Thanks and lots of succes with your new ATR4502 !
CAUTION:
* BEFORE PUTTING INTO OPERATION READ
THESE OPERATING INSTRUCTIONS
CAREFULLY.
* NO USER SERVICEABLE PARTS INSIDE.
* REFER SERVICING TO QUALIFIED SERVICE
PERSONNEL ONLY.
WARNING:
* DO NOT BLOCK THE VENTILATION OPENINGS ON THE
FRONT & BACK PANELS.
* TO REDUCE THE RISKS OF ELECTRICAL SHOCK, DO
NOT REMOVE THE COVER.
* TO REDUCE THE RISK OF FIRE OR SHOCK HAZARD, DO
NOT EXPOSE AMPLIFIER TO RAIN OR MOISTURE.
* THIS APPARATUS MUST BE EARTHED.
FRONT PANEL FUNCTIONS
[1] VOLUME: Controls the volume levels of both channels in MONO mode, or the volume
of channel A in STEREO mode.
[2] VOLUME: Controls the volume of channel B in STEREO mode.
[3 & 4] VOICING SWITCHES:
DEPTH - With this switch a filter can be activated that boosts the lowest frequencies. The
effect is subtle but therefore always instantly useable without having to re-adjust the tone
controls.
PRESENCE - With this switch a filter can be activated that boosts the upper mid
frequencies.
[5 & 6] THERMAL: These LEDs indicate that the amp has been shut down because of
overheating.
PLEASE CHECK IF THE FANS ARE FUNCTIONING AND IF THE FAN OPENINGS ARE
CLEAN AND FREE.
After cooling down the amp will automatically switch on.
[7] POWER: Turns AC power On (red LED on) and Off (red LED off). When the switch is
Off the amplifier is completely shut down.
Note: After switching the amp on please allow the tubes to heat up (5-10 seconds).
BACK PANEL FUNCTIONS
[1] A.C. POWER:
INPUT: Power cord input. The ATR4502 is equipped with a worldwide power supply.
Inside the amp a mains selector switch can be set on one of three voltages, 100, 115 or
230. Either of these voltages will work worldwide with minor power differences. The amp
will work on either 50 or 60 hertz. After resetting the internal mains selector switch make
sure fuses are replaced with printed ratings on rear of amp.
FUSE: Both fuse and spare fuse are located on the sled of the fuseholder. Fuse sled can
be removed with a screwdriver. If the fuse should fail, it must be replaced with the same
type and value in order to avoid damage to the amp and to prevent voiding the
warranty.
If the amp repeatedly blows fuses the amp should be taken to a qualified service center
for repair.
WARNING: Only a qualified technician should attempt an input voltage change.
Personel injury or equipment damage may occur if done incorrectly.
WARNING: The fuse should be replaced or the voltage should be reset only when
the power cord has been disconnected from its power source.

[2 & 3] SPEAKER OUTPUT JACKS: Provided for connection of (a) speaker cabinet(s) to
Channel A and/or Channel B in the STEREO or (SINGLE/DUAL) MONO mode, with a
minimum load of 4 ohms.
The output power of each channel changes with different loads as follows:
50 Watt: 1x 4 ohms or 2x 8 ohms speaker cabinet(s)
45 Watt: 1x 8 ohms or 2x 16 ohms speaker cabinet (s)
35 Watt: 1x 16 ohms speaker cabinet
[4] SPEAKER OUTPUT JACKS: Provided for connection of (a) speaker cabinet(s) in the
MONO (bridged) mode, with a minimum load of 8 ohms.
The output power changes with different loads as follows:
90 Watt: 1x 8 ohms or 2x 16 ohms speaker cabinet(s)
70 Watt: 1x 16 ohms speaker cabinet
DO NOT CONNECT A 4 OHMS OR TWO 8 OHMS SPEAKER CABINETS TO THIS
OUTPUT!
DO NOT USE GUITAR CABLE TO CONNECT THE SPEAKER CABINETS.
Use KOCH Dynacon SC608 speaker cable for the best results.
The ATR4502 can be used safely without a speaker connected.
Disconnecting the speaker(s) will NOT cause any damage to the amplifier.
[5] INPUT: Input for channel B.
[6] INPUT: Input for channel A in STEREO mode and for both channels in MONO mode.
[7 & 8] LEVEL: Switches for setting the signal level of channel A & B.
In the ‘down’ position the input level is 0dBV, which is well suited for mains operated
(studio) equipment.
In the ‘up’ position the input level is -10dBV, which is well suited for battery operated
equipment.
REPLACING TUBES
The ATR4502 has two 12AX7 tubes, one for each channel.
These tubes behave like strings, they lose highs, lows and dynamics and after a period of
time they have to be replaced to maintain the amps best performance. Exactly when is
hard to say but this is an indication: if you play almost every day change tubes each year,
if you play once or twice a week change tubes every 2-3 years.
12AX7 tubes rarely fail. But if they are bad, these might be the symptoms:
- Microphonic whistling or squealing on one or both channels.
- No or low amp volume on one or both channels.
- Excessive noise on one or both channels.
- Excessive hum on one or both channels.
Changing a tube can be a simple and quick fix for most problems in your amp.
SAFETY FIRST: DISCONNECT THE POWER CORD FROM ITS POWER SOURCE
AND LET HOT TUBES COOL.
REPLACE TUBES ONLY WITH ORIGINAL KOCH HIGH QUALITY TUBES. (IF
OTHER TUBES ARE USED THE WARRANTEE OBLIGATION EXPIRES)
If you have any doubts, please take no risks and let a qualified technician do the
job.