Speaker Jacks; Mode Selector Switch - Mesa/Boogie Mark IV Amplifier Owner's Manual

REAR VIEW MKIV
POWER TUBE SUBSTITUTION: (Continued)
ohm speaker should be plugged into the 4 ohm jack. However, please note that Mesa/Boogie cannot accept responsibility for
any blown 6V6's incurred during such usage! Proper operation depends totally on the correct setting of the aforementioned switches
and this will be impossible to verify for warranty tube coverage. So please exercise caution when using 6V6's! Incorrect setting of the
switches won't usually cause immediate tube failure, but the strain caused is far in excess of recommended ratings.
TRIODE SIMUL-CLASS HARMONICS
PENTODE MID GAIN
CLASS A
OUT
8 OHM 4 OHM
4 OHM
WHT NG 44 WHT NG
454 STR
454 STR
GC 6L6
GC 6L6

SPEAKER JACKS:

Speaker jacks for both 8 ohm and 4 ohm loads are provided. CAUTION: A speaker (or load resistor) must remain connected to
a speaker output on your MARK IV to prevent damage to the power tubes and transformer! (For silent recording, merely pull
the designated switch on the OUTPUT LEVEL control located on the Front Panel and do not disconnect the speaker.)
TRIODE SIMUL-CLASS
PENTODE
CLASS A
LEVEL OUT
8 OHM 4 OHM

MODE SELECTOR SWITCH:

This switch determines the method of control over your MARK IV'S switching functions. The first position activates the footswitch.
SIMUL-CLASS HARMONICS
RHY 2
RHY 1
FT SW
CLASS A MID GAIN
MODE SELECT
4 OHM 4 OHM
HANDBUILT IN PETALUMA CALIFORNIA
(Continued)
CLASS A/ SIMUL FX LOOP
RHY 2
LEAD
RHY 1
EX SW
FT SW
EXTERNAL SWITCHING JACKS
MODE SELECT
RHYTHM 1
HANDBUILT IN PETALUMA CALIFORNIA
44 WHT NG 44
454 STR
GC 6L6
NOTE:
Two 4 ohm jacks are provided and should be used when you wish to run two 8 ohm speakers
HARMONICS
or cabinets. (This is because two 8 ohm loads connected in parallel present a combined load
to the amplifier of 4 ohms.) Speaker mis-matching is not a cause for great concern - unless the
MID GAIN
combined load is considerably less than the rated impedance. If, for example, you run two 4
ohm cabinets - each plugged into a 4 ohm jack - the amplifier would "see" 2 ohms as the total
load. And while this will not cause immediate damage, it will result in shortened power tube
4 OHM
life. Mis-matching on the high side is always preferable, if you have no choice.
The next three positions select the individual modes manually.
LEAD
The last position enables the use of the EXTERNAL SWITCHING jacks. If ever the switching
EX SW
functions seem to operate incorrectly, always check that the MODE SELECTOR switch is set
to the proper position.
These two outer tubes can be substituted with EL-34's.
EQ
CAUTION: Place amp in STANDBY mode when changing
tubes.
CAUTION: Tubes can become very HOT...they can cause
injury. Use care in removing tubes that are warm/hot and
RHYTHM 2 LEAD
never remove a tube by pulling on the glass. Instead, grab
the tubes socket or base and rock the tube from side to
WHT NG 44
side while pulling gently downward.
454 STR
GC 6L6
PAGE 13