Koch Classictone-II Bedienungsanleitung Seite 5

This fuse also must be replaced with the same type
and value in order to avoid damage to the amp and
to prevent voiding the warranty.
[4] FOOTSWITCH: Provides an input for the KOCH
FS2 FOOTPEDAL or for a remote channel switching
unit, e.g. a MIDI switcher. It automatically disconnects
the 'Channels' switch [2] on the front panel.
This jack is a stereo jack. The TIP controls switching
between Clean and OD, the RING controls the Gain
Boost. Both TIP and RING must be switched on/off to
ground, to realise switching.
COMBO ONLY:
[5] SPEAKER OUTPUT JACK: For connecting the
internal speaker of the Combo
[6] EFFECTS LOOP
SEND: This jack provides a buffered mono output from
the preamp of the CLASSICTONE-II and can be used
to connect an external effects unit. This jack must be
connected with the input of the effects unit (see also
CONNECTION DIAGRAM).
RETURN: This jack provides an input for an external
effects unit and must be connected to the output of the
unit. When used, it disconnects the preamp from the
power amp and therefore it also allows the
CLASSICTONE-II to be used as a "satellite" for other
preamps.
NOTE: The EFFECTS LOOP's mode is serial. Its
10dBV SIGNAL LEVEL guarantees compatibility with
both instrument-level effects like floor-pedals and guitar
processors, as well as line-level effects like
professional 19 inch rack mount devices.
NOTE: If the connection of an effects unit to the
CLASSICTONE-II gives more hum, a ground-loop
may be the cause of it.
RECORDING SECTION
This section provides mono outputs suitable for
recording. Its signal is derived from the speaker output
so the typical tube saturation of the power amp will be
included; it also includes Reverb and External Effects
signals. This signal is shaped by a special filter that
simulates the typical recording characteristic of a
microphone placed in front of a guitar speaker.
[7] OUTPUT: This jack is an unbalanced output for
recording (or PA) and provides the filtered and voiced
signal as described above. The output signal is at line
level (-10 to 0 dBV).
[8] LIFT/GND SWITCH: Connects or disconnects pin 1
from the XLR connector [9] to ground. Can be used to
eliminate hum caused by a ground-loop.
[9] DI OUTPUT: This XLR connector provides a 600
ohms fully balanced direct output for recording or PA.
The filtered output signal is at line level.
[10] SPEAKER ON/OFF: This switch disconnects the
output of the amp from all Speaker Output jacks and
loads it with an internal 50W dummy load. This allows
you to play the amp at full power without hearing
anything while using the outputs [7] [9] for recording or
other purposes.
WARNING: Never play the CLASSICTONE-II without
a speaker connected if the Speaker On/Off switch
[9] is in the "On" position. This may cause serious
damage to either the power tubes and/or the output
transformer.
COMBO ONLY:
[11] EXTENSION SPEAKER OUTPUT: For connecting
an 8 ohms extension speaker cabinet to the Combo. The
output impedance of the amp switches automatically to
the correct impedance of 4 ohms.
HEAD ONLY:
[12] SPEAKER OUTPUT: Provided for connection of
speaker(s) or speaker cabinet(s) with a minimum total
impedance of 4, 8 or 16 ohms.
Always use speaker cable!
REPLACING TUBES

SAFETY FIRST: DISCONNECT THE POWER CORD
FROM ITS POWER SOURCE AND LET HOT TUBES
COOL.

CHECK THE 'TUBE LOCATION DIAGRAM' ON THE
CHASSIS FOR THE CORRECT TYPE NUMBERS
AND LOCATIONS.

REPLACE TUBES ONLY WITH ORIGINAL KOCH
HIGH QUALITY TUBES. (IF OTHER TUBES ARE
USED THE WARANTEE OBLIGATION EXPIRES)

BEFORE REPLACING THE POWER TUBES,
REMOVE THE SAFETY CAP FIRST.

AFTER REPLACING THE POWER TUBES, PUT
THE SAFETY CAP BACK IN PLACE.NOTE: The
CLASSICTONE-II has an auto-bias circuit so it does
not have to be re-biased after replacing the EL84
power tubes.
If you have any doubts, please take no risks and let a
qualified technician do the job.
Preamp and Power tubes wear out and have to be
changed from time to time to maintain the amps best
performance. Tubes behave like strings, they lose highs,
lows and dynamics and after a period of time they have to
be changed. 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.
Tubes rarely fail. If they are bad, these might be the
symptoms:
PREAMP TUBES (ECC83, 12AX7, 7025):
- 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.
POWER TUBES (EL84):
- Loud crackling that is not affected by front panel controls.
- Intermittent or regular blowing fuses.
- Weird amp 'distorting'.
- Hum.
Changing a tube is a simple and quick fix for most
problems in your amp.
In case of failure, just one or all POWER TUBES can be
replaced without rebiasing.
Please always use two or four matched EL84 (=
one duet/quartet) replacement tubes to obtain the
amps best performance.
Again, if you have any doubts, please take no risks
and consult your dealer and/or a qualified technician.