Sonic Frontiers SFM-75 Mk2 Owners manual
SFM-160 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-160 Mono Tube Amplifiers. 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. Over-enthusiastic “rocking” may result in the cracking or
breaking off of the keying lug (orientation pin) of the output tube (this is not covered under your 1
year tube warranty).
Recommended Tube Types
Your SFM-160 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/E188CC.
The power tubes are factory supplied matched pair KT99/KT99(a)’s but you may also use
6550/6550A (GOLD AERO or GE, not a CHINESE type) or KT90/KT90(a) types. Although not
essential, we recommend the use of matched pairs or matched quads of power output tubes for lowest distortion.
NOTE: A true KT88 tube, built to the original British M.O. Valve/Genelex/Gold Lion standards,
may become available in the near future. Until then, the only warranty authorized
KT88 type tube that can be used is the M.O. Valve/Genelex/Gold Lion version - NOT
THE CHINESE version!!!!
\We do not authorize the use of the CHINESE KT88 or 6550 in the SFM-160 amplifiers as the amplifier runs with over 625V dc on the plates. The CHINESE power tubes will likely fail under these
operating conditions; any damage caused to the SFM-160’s through the use of these tubes will not
be covered under warranty! Use only the tube types and brands recommended above.
STANDBY/OPERATE Switch
On the right front panel of the amplifier, you will find a rocker switch which controls the operating
mode of the amplifier. In the “DOWN” position, the amplifier is in STANDBY.
STANDBY
In this position, your amplifier is ON but the tubes are “Idling” at a very low bias setting. The amplifier will not pass an audible input signal. This switch is very useful in prolonging the life of your output tubes.
OPERATE
In this position, the amplifier will bring the bias setting up to the preset level, allowing the signal to
be amplified. Anytime the amp is not being actively used, either switch the amp OFF or switch the
amp into STANDBY.
OPERATE/MUTE Switch
On the back panel of the amplifier, you will see a toggle switch labeled OPERATE/MUTE. This is
used to MUTE the input signal. The primary use of this switch is to allow the user to remove (or
connect) INPUT interconnect cable from the amplifier, preamplifier (or signal source) without the
need to “power down” the amp.
This feature will prevent “speaker destroying” bangs, hums, buzzes and thumps from being passed
through the amplifier during these cabling changes.
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 SFM-160 amplifiers.
OPERATION
1. Connect your speaker leads, input cable and power cord to each amplifier, making sure the
power switch is in the “OFF” position (down).
2. Using a long-handled slotted screwdriver, rotate both 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 “V5” 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 “V6” position and rotate the V6
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 SFM-160 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 KT99(a)/6550A 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.
CLEANING
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-SHOOTING GUIDE
If at any time a SFM-160 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.
4. If the power line fuse has blown, replace it with a same size and type fuse of the same rating
(5 Amp 250V. slo-blo - 100 to 120 Volt Countries / 2.5 Amp 250V. - 200 to 240 Volt
Countries).
Loading...