Koch Multitone User manual

MULTITONE - USER MANUAL
FRONT PANEL FUNCTIONS
[1] INPUTS :
HIGH - Input for standard-level instruments, e.g. guitars with passive pickups.
LOW - Input for high-level instruments, e.g. guitars with high-output passive or
active pickups.
Both inputs ma be used for connecting two instruments simultaneousl .
[2] BASS, MID & TREBLE : Classic passive tone controls that regulate low,
mid and high frequencies respectivel , of the Clean and the Pre-EQ Overdrive
channel. In the Pre-EQ Overdrive channel the tone control circuit is located
before the overdrive stage, therefore pre-shaping the overdrive tone which
results in a blues t pe of distortion with lots of mid-range harmonics.
[3] VOLUME : Controls the volume level of the Clean channel.
[4] DRIVE : Controls the amount of amplification in the Pre-EQ Overdrive
channel. Cleaner sound is achieved at lower settings (3 to 5), at higher settings
(5 to 10) medium overdrive occurs which will produce more sustain and
distortion.
[5] VOLUME : Controls the volume level of the Pre-EQ Overdrive channel.
[6] GAIN : This ‘Dual-Gain’ is a ver powerful feature combining Drive and
Gain-Boost in one knob. This has been achieved b controling the amount of
amplification in the Post-EQ Overdrive channel preamp in two stages
simultaneousl . Cleaner sound is achieved at lower settings (3 to 5), at middle
settings (5 to 10) medium overdrive occurs which will produce more sustain and
distortion. At high settings (10-20) mega overdrive occurs, adding loads of
sustain and compression. Accurate pre and post shaping circuitr prevent the
low-end from getting mudd even at the highest settings.
NOTE: High gain settings may cause squealing and/or excessive hum and
noise, due to microphonic guitar pick-ups and insu icient screening o circuitry.
[ ] VOLUME : Controls the volume level of the Post-EQ Overdrive channel.
[8] PRESENCE : Controls the amount of boost in the upper mid frequenc
range of the Post-EQ Overdrive channel.
[9] BASS, MID & TREBLE : Classic post-distortion passive tone controls that
regulate low, mid and high frequencies respectivel , of the Post-EQ Overdrive
channel. In this channel the tone control circuit is located behind the overdrive
stage, therefore equalising the overdrive tone which results in better control
over the harmonics at high gain settings and a more rough-sounding distortion.
[10] RHYTHM VOLUME : When activated (see Footswitch), this control
functions as a master volume and can be preset at a lower (rh thm) volume.
NOTE: I the Footswitch is not connected, the RHM VOLUME is active.
[11] REV/FX MIX CONTROL : Controls the amount of the Spring Reverb or
Effects signal (see rear panel [5]) mixed with the original dr signal.
[13] DAMPING SWITCH : Switches speaker damping from High to Low. In High
(normal) position the power amp damps the speaker which results in a more
controlled sound. In Low position the power amp’s damping of the speaker’s
cone-movement is minimal, which results in a more open sound.
[13] STANDBY SWITCH : Allows the amp to be placed in standb or active
mode. In standb mode the tubes remain hot, but the amplifier is not
operational.
[14] POWER SWITCH : Turns AC power On and Off. When the switch is Off
the amplifier is completel shut down. When switching the amplifier On, allow
the tubes to get hot before switching to the active mode [13
MULTITONE - USER MANUAL

REAR PANEL FUNCTIONS
[1] A.C. POWER :
INPUT- Power cord input. The amp is equipped with a worldwide power suppl .
It is possible to rewire for selecting one of two voltages, 115 or 230
inside the amp. Either of these voltages will work worldwide with minor
power differences. The amp will work on either 50 or 60 hertz. After
rewiring MAKE SURE FUSES ARE REPLACED WITH PRINTED
RATINGS ON REAR OF AMP.
FUSE - Both fuse and spare fuse are located within the cap 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 repeatedl blows fuses, check for a bad power tube. If tube-
failure is not the cause, 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 ONLY BE REPLACED WHEN THE POWER
CORD HAS BEEN DISCONNECTED FROM ITS POWER SOURCE.
[2] CHANNELS SWITCH : Selects the Clean, the Pre-EQ or the Post-EQ
Overdrive channel if the Footswitch is not connected.
[3] FOOTSWITCH CONNECTOR : Provides an input for the FOOTSWITCH and
automaticall disconnects the Channels Switch [2].
THE FS-5 FOOTSWITCH
The Footswitch is equipped with five switches:
- three CHANNEL switches for selecting the Clean channel, the Pre-EQ
Overdrive channel or the Post-EQ Overdrive channel (red LED indicators).
- a SOLO/RHYTHM switch for activating (green LED on) or b passing the
RHYTHM VOLUME control [11].
- a REV/FX switch for switching the Parallel Effects Loop on/off ( ellow LED).
Thus functioning as a Reverb on/off switch or, if an effects unit is plugged in to
this loop, as an Effects on/off switch [5].
[4] PARALLEL EFFECTS LOOP SEND (TO FX) : This jack provides a buffered
mono output from the preamp and can be used in conjunction with the
RETURN (FROM FX) [5] jack as a patch point for external effects units. (see
CONNECTION DIAGRAM page.)
[5] PARALLEL EFFECTS LOOP RETURN (FROM FX) : This jack disconnects
the internal spring reverb and inputs external (effects) signal via the REV/FX
MIX control at the front panel directl to the power amp where it is mixed with
the original dr signal from the preamp.
IF THIS LOOP IS USED, DIRECT SIGNAL MUST BE TAKEN OFF THE
EFFECTS UNITS SIGNAL FOR EXAMPLE WITH ITS DRY/WET MIX CONTROL.
[6] SERIAL EFFECTS LOOP SEND (TO FX) : This jack provides a buffered
mono output from the preamp and can be used in conjunction with the
RETURN (FROM FX) [7] jack as a patch point for external effects units. (see
CONNECTION DIAGRAM page.)
[ ] SERIAL EFFECTS LOOP RETURN (FROM FX) : This jack inputs external
(direct+effects) signal directl to the power amp and automaticall disconnects
the preamp.
NOTE: The EFFECT LOOPS operate on a -10dBV SIGNAL LEVEL which
guarantees compatibility with both instrument-level e ects like loor-pedals and
guitar-processors, as well as line-level e ects like pro essional 19 inch rack
mount devices.
NOTE: I the connecting o an e ects unit to the MULTITONE causes hum, a
ground-loop may be the reason or it. This ground-loop may be eliminated by
isolating or disconnecting the e ects units earth rom the mains sockets earth.
[8] TRIODE/PENTHODE POWER SWITCH : Selects half (triode) or full
(penthode) output power. In the Triode position the amp also has a more
vintage tone.
[9] SPEAKER OUTPUT JACKS : Provided for connection of speaker(s) or
speaker cabinet(s) with a minimum total impedance of 4, 8 or 16 ohms.
[10] RECORDING OUTPUT : ThIs jack provides a mono output from the power
amp and includes Reverb and External Effects signals. The signal is derived
from the speaker output and filtered b a special Speaker Simulating Filter
which simulates the sound coming from the speaker. Now the signal can be fed
directl to a recording or sound reinforcement mixer while the amp will sound
as if it is miked.
POWER TUBE OPTIONS
Each t pe of power tube has its own distinctive sound character, therefore
changing to a different t pe (or mix of t pes) of power tubes also changes our
amp’s overall sound.
50W VERSION

The MULTITONE-50 accepts either 2xEL34 or 4x6V6.
100W VERSION
Due to special bias control circuitr the MULTITONE-100 accepts almost an
t pe of power tube for example: EL34, 6CA7, 6L6, 6550, KT66, KT77, KT88,
KT90, KT100. Also the MULTITONE-100 is provided with two seperate bias
control trimmers (on the PC board), one for the inner two power tubes and one
for the outer two power tubes, thus enabling the use of mixed sets of power
tubes (two + two). So for example the two outer tubes ma be EL34’s while the
two inner tubes are 6L6’s or 6550’s.
(see REPLACING TUBES)
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 WARRANTEE OBLIGATION EXPIRES)
•BEFORE REPLACING THE POWER TUBES, FIRST REMOVE THE CE
SAFETY CAP.
•AFTER REPLACING THE POWER TUBES, PUT THE CE SAFETY CAP
BACK IN PLACE.
NOTE: ALWAYS HAVE THE AMP REBIASED AFTER PEPLACING THE
POWER TUBES. BIASING INSTRUCTIONS CAN BE FOUND INSIDE THE
AMP.
REBIASING THE AMP IS NOT NECCESSARY ONLY IF KOCH POWER TUBES
ARE USED WITH THE SAME TYPE AND BIAS-CLASS NUMBER.
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, the loose
highs, lows and d namics and after a period of time the have to be changed.
Exactl when is hard to sa but this is an indication: if ou pla almost ever
da change tubes each ear, if ou pla once or twice a week change tubes
ever 2-3 ears.
Tubes rarel fail. If the are bad, these might be the s mptoms:
PREAMP TUBES (ECC83/12AX7A, 7025/12AX7WA):
- 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:
- Loud crackling that is not affected b 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 our amp.
In case of failure, just one or more POWER TUBES can be replaced without
rebiasing onl if KOCH tubes with the SAME TYPE AND BIAS-CLASS NUMBER
are used.
If power tubes with a different or unknown bias-class number are used for
replacement, the two inner and/or the two outer tubes have to be replaced
simultaneousl and the amp has to be REBIASED.
Please alwa s use four or two + two (see above) matched replacement power
tubes to obtain the amps best performance.

SAMPLE SETTINGS

CONNECTION DIAGRAM
BLOCK DIAGRAM
TECHNICAL SPECIFICATIONS

INPUT IMPEDANCES Input HIGH 1 M ohms
Input LOW 136 K ohms
From FX 100 K ohms
OUTPUT IMPEDANCES To FX 1K ohms
SIGNAL LEVELS Effect Loops -10 dBV
TUBES - Preamp tubes 1x 12AX7WA/7025
3x 12AX7A/ECC83
- Power tubes 50W version 2x EL34 or 4x 6V6 (see text)
100W version 4x EL34 / 6L6 / 6550 / (see text)
OUTPUT POWER 50W version 50 Watts in 4, 8 and 16 ohms
100W version 100 Watts in 4, 8 and 16 ohms
MAINS 50W version 125 Watts
230VAC, 50Hz or 115VAC, 60Hz 100W version 250 Watts
Multitone Front and Rear Panel