Sonic Frontiers Sonic Frontiers SFM-75 MK-II User 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.

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 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 counter-clockwise. Adjust the control until the
pointer indicates “50” on the dial. Now rotate the selector switch to the “V4” position and rotate the
V4 bias control counter-clockwise to set the meter pointer at “50.” Wait a few minutes and recheck
the settings for both tubes.
Once you have finished adjusting both bias controls, return the selector switch to the “OFF”
(centre) position.
Your SFM-75 amplifiers are now ready for use.
NOTE: The red mark at the “60” point on the meter scale is the maximum recommended bias point
for the 6550/KT88 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 satin chrome finish of the chassis and transformer top covers will last for years. A reg-
ular dusting with a soft, non-abrasive cloth will generally keep the finish looking like new.
Fingerprints may be removed with a small amount of window cleaner, such as Windex 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 your SFM-75 amplifiers fail 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. 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 2 l/2 amps 250V, is installed (or l.25 Amp 250V. for

European and Asian versions).
B. That the A.C. power fuse is intact and has not blown.
3. If the power line fuse has blown, replace it with a same size and type fuse of the same rating
(2 l/2 amp. 250V. slo-blo - 110 to 120 Volt Countries / 1.25 Amp 250V. - 220 to 240 Volt
Countries).
4. Turn on the amplifier. If the amplifier fails to operate, turn off the amplifier, remove the two
6550/KT88 power tubes (using a glove, cloth or paper towel) and turn the amp on again. If the two
small 6DJ8 type tubes glow and the A.C. line fuse remains intact, it is likely that one (or both) of the
power tubes has shorted and should be replaced.
5. If the fuse blows again without the power tubes installed, then you should return the
amplifier to your dealer or to a service depot for repair.
NOTE: Under no circumstances should you replace the A.C. power fuse with one of a higher
current rating! Doing so may cause further damage to the amplifier in the event of a fault condition
and will also void your warranty! In addition, your continued protection from the risk of fire or shock
would be seriously compromised.
6. If at anytime you are unable to adjust the meter pointer to read at least “35” on the meter, for
either or both of the power tubes, you should replace the tube as it is nearing the end of its useful
life.
TUBE CAGES
The tube cages serve to both protect the vacuum tubes in the SFM-75 amplifiers from physical
damage and to prevent small children or pets from burning themselves. The tube cages snap easily
into the four sockets located at the edge of the chassis, but ar quite difficult to remove. This is inten-
tional in order to maintain safety while allowing quick user access to tubes and bias controls when
needed. (Please refer to the TOP COVER REMOVAL insert in your literature package).
If possible, the SFM-75 amplifiers should be operated without the cages as the tubes will have
somewhat better thermal cooling.
VENTILATION
Your SFM-75 MKII amplifiers must be placed on a flat hard surface to allow proper air flow through
the ventilation slots in the bottom panel. Failure to do so may result in overheating of electronic
components inside the units and possible damage to your amplifiers.
PACKING MATERIAL
We recommend that you retain all of the packing material and shipping boxes for your SFM-75 MKII
amplifiers. They are custom designed to prevent shipping damage from occurring. SONIC FRON-
TIERS INC. will accept no responsibility for any damage occurring to amplifiers that are shipped in

packing material other than the original SONIC FRONTIERS INC. packing material.
SAFETY INSTRUCTIONS
1. WATER AND MOISTURE - This product should not be used near water. Do not expose this
product to rain or moisture to prevent fire or shock hazard.
2. HEAT - This product should be situated away from heat sources such as radiators, heat
registers, stoves, or other appliances which produce heat.
3. POWER SOURCES - This product should be connected to an AC power source of the same
rated voltage. The original shipping containers will stipulate the AC voltage this unit can operate
on.
4. CLEANING - see previous section in this manual.
5. SERVICING - Do not open this product. NO USER SERVICEABLE PARTS INSIDE. Refer
servicing to qualified service technician.
6. NON-USE PERIODS - The power cord of this product should be unplugged from the outlet
when left unused for an extended period of time.
DISCLAIMER OF LIABILITY
Under no circumstances does SONIC FRONTIERS INC. assume liability or responsibility for injury
or damages sustained in the use or operation of this equipment or for damages to any other equip-
ment connect to it.
SONIC FRONTIERS INC. reserves the right to make design changes or improvements without the
obligation to revise prior versions.
All specifications are subject to change without notice.

LIMITED FIVE YEAR WARRANTY
SONIC FRONTIERS INC. warrants to the purchaser that each SFM-75 MKII Mono Tube Amplifier is
free of manufacturing defects for a period of five (5) years from the date of purchase. This five (5)
year limited non-transferable warranty excludes all vacuum tubes, which we warrant for a period of
six (6) months. To receive this warranty, the original purchaser must mail to SONIC FRONTIERS
INC. within thirty (30) days from date of purchase, the enclosed WARRANTY REGISTRATION
FORM completed, along with a copy of the bill of sale from an authorized SONIC FRONTIERS deal-
er. SONIC FRONTIERS INC. will then validate the warranty to the original purchaser. This warranty
is subject to the following conditions and limitations:
1. This warranty applies only to the original purchaser.
2. This warranty is void and inapplicable if the product has been handled other than in
accordance with the instructions in the OPERATING MANUAL, abused or misused, damaged by
accident or neglect or in being transported, or the defect is due the product being tampered with,
modified or repaired by anyone other than SONIC FRONTIERS INC. or an authorized SONIC
FRONTIERS repair depot.
3. This warranty does not cover normal maintenance.
4. SONIC FRONTIERS INC. shall not be responsible in any way for consequential or indirect
damages or liabilities resulting from the use and operation of the product covered herein or
resulting from any breach of this warranty or any implied warranty relating to said product.
During this period, SONIC FRONTIERS INC. will repair or replace any defective components free of
charge. A Return Authorization Number is required before any amplifier is returned to our factory for
any reason. This number must be visible on the exterior of the shipping container(s) for SONIC
FRONTIERS INC. to accept the return.
Units shipped to us without a Return Authorization Number or without a visible RA number on the
exterior of the shipping container(s) will be returned to the sender, freight collect.
Units to be repaired by SONIC FRONTIERS INC. must be sent shipping and insurance prepaid by
the original purchaser in the original packing material. A returned product should be accompanied
by a written description of the defect. Repaired units will be returned by SONIC FRONTIERS INC.
shipping and insurance prepaid.
All other warranties or conditions either written or implied are void.

TECHNICAL SPECIFICATIONS
Power 75 watts RMS from 20 Hz to 20 kHz
Frequency Response 5 Hz to 60 kHz + 0.5 dB
(1 watt into 8 ohms) 3 Hz to 110 kHz - 3.0 dB
Input Impedance 475 Kohms
Input Sensitivity 1.4V RMS at 1 kHz for 75 watts
Power Requirements 225 VA 50/60 Hz (Maximum)
Fuse Requirements 2.5 Amp 250V slo-blo - 100V to 120V Countries
1.25 Amp 250V slo-blo - 220V to 240V Countries
Tube Complement 1 - Matched pair KT88 2 - 6DJ8
Dimensions 18 in. Wide x 14.5 in. Deep x 9 in. Wide
Weight 45 lbs. (21 kg) per Mono Amp