Sonic Frontiers SFS-80 Owners manual
STEREO TUBE AMPLIFIER
O P E R A T I N G M A N U A L
S F S - 8 0
We at Sonic Frontiers are sure that you will derive many years of listening pleasure with your new SFS-80 Stereo Tube
Amplifier. This brief operating manual contains important information regarding the operation and care of the amplifier, so be sure to read this manual carefully and follow these simple instructions in order to keep it looking, operating
and sounding its 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. Also, check to be sure that none of the 6DJ8
tube pins are bent when you install them.
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 SFS-80 amplifier is 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 KT99a’s but you may also use 6550/6550A or KT90/KT99 types.
EL34/6CA7 tubes may also be used but the available output power will be reduced by about 50% to 40 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 four slotted adjustment controls protruding above the top surface of the chassis.
It is essential that the following procedures be followed before you turn on your SFS-80 amplifier.
O P E R AT I O N
1. Connect your speaker leads, input cables and power cord to the amplifier, making sure the power switch is in the
“OFF” position (down).
2. Using a long-handled slotted screwdriver, rotate all 4 of the adjustment controls fully counter-clockwise.
3. Turn “ON” the amplifiers. After approximately 5 seconds you should see an orange glow appearing inside each
tube. Wait one minute, then turn the selector switch to the “V3” position marked on the chassis. Insert the screwdriver into the corresponding bias control and watch the meter pointer as you slowly rotate your screwdriver clockwise.
Adjust the control until the pointer indicates “50” on the meter. Now rotate the selector switch to the “V4” position
and rotate the V4 bias control clockwise to set the meter pointer at “50.” Follow the same procedures for LV3 and
LV4. Wait a few minutes and recheck the settings for all 4 output tubes.
Once you have finished adjusting all 4 bias controls, return the selector switch to the “OFF” (centre) position.
Your SFS-80 amplifier is now ready for use.
NOTE:The red mark at the “50” point on the meter scale is the maximum recommended bias point for the KT99a output tubes. Setting the bias meter to read in excess of this value will exceed the rated dissipation rating of the tubes
and unnecessarily shorten your tube life with no redeeming sonic benefit. You may, if you wish, operate the tubes at
the “40” mark for somewhat longer tube life. If you are unable to perform the previous adjustments, turn to the
“Trouble-Shooting” section of this manual on Page 3.
C L E A N I N G
The beautiful stainless steel (non-magnetic) finish of the chassis and transformer top covers will last for years. A regular dusting with a soft, non-abrasive cloth will generally keep the finish looking like new. Fingerprints may be
removed with a small amount of silicon spray, such as WD-40 TM. Be sure to apply any liquid into a soft cleaning
cloth, not directly onto the chassis. At no time should you allow any liquids to drop onto the amplifiers; it may run
into the electronic circuitry underneath and cause damage which will not be covered under your warranty!
TROUBLE-SHOOT ING GU IDE
If at any time your SFS-80 amplifier fails to work, follow this simple checklist:
1. Make certain that the A.C. power cord is plugged in firmly, both at the A.C. wall socket and at the A.C. amplifier
socket.
2. Make sure that you have biased the output tubes.
3. Remove the A.C. power cord at the amplifier and open the fuse hatch on the A.C. input socket. Check that:
A. A “slo-blo” fuse, with a rating of 5 amps 250V (0.25” x 1.25”), is installed (or 2.5 Amp 250V (5mm x 20mm) for
European and Asian versions).
B. That the A.C. power fuse is intact and has not blown.
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