Sonic Frontiers SFM-75 MK-II Operating Manual

SFM-75 MK II PRIV ATE
MONO TUBE AMPLIFIER
OPERATING MANUAL
We at Sonic Frontiers are sure that you will derive many years of listening pleasure with your new
SFM-75 MKII mono tube amplifiers. This brief operating manual contains important information
regarding the operation and care of the amplifiers, so be sure to read this manual carefully and fol-
low these simple instructions in order to keep them looking, operating and sounding their best!
VACUUM TUBES
Handling
We suggest that you do not handle the large power tubes with your bare hands or fingers as skin
oils deposited on the glass surface can "leach" through the glass envelope and cause the tube to
become "gassy." In other words, your tube life may be shortened unnecessarily. Use a paper towel
or one of the cotton gloves (supplied) instead. This is also the recommended procedure for handling
the small input tubes.
Installation
Whenever you remove or insert the input or power tubes into their sockets, handle them gently and
do not force them into the sockets. Instead, "rock" them slightly as you slowly push them into place,
making sure that they are properly seated.
Recommended Tube Types
Your SFM-75 MKII amplifiers are supplied from the factory with 6DJ8 tubes for the input and driver
stages (installed into the small sockets). You may also use tubes of the following designations:
ECC88, 6922, or 7308/E88CC.
The power tubes are factory supplied matched pair KT88's but you may also use 6550/6550A types.
EL34/6CA7 tubes may also be used but the available output power will be reduced by about 35% to
50 watts. Although not essential, we recommend the use of matched pairs of power output tubes for
lowest distortion.
Tube Biasing
This is a simple yet important function of the front panel meter, the selector switch and the two slot-
ted adjustment controls protruding above the top surface of the chassis.
It is essential that the following procedures be followed before you turn on your SFM-75 MKII ampli-
fiers.