Fosgate Audionics Signature User manual

Fosgate Signature
Tube Headphone Amplifier
Owner’s Manual

1
Table of Contents
Read This First…………………………………….2
Introduction by Jim Fosgate……………………3,4
Unpacking………………………………………….5
Tubes Installation………………………….………5
Product Placement………………………………..5
Connections………………………....………….....6
Use………………………………………………….7
Features………………..…………………………..7
Special Features…………………………………..8
Tube Rolling………………………………………..9
Specifications……………………………………..10
Warranty and Service……………………………11

2
Read This First
Please read carefully the following safety instructions,
which have been included in compliance with
international safety regulations.
•Read this instruction manual prior to connecting and
operating this unit. Retain this manual for future reference.
•Retain all packing materials and carton for future need.
•To prevent fire or shock hazard, do not expose this unit to
rain or moisture or operate in these conditions.
•This unit contains voltages that can cause serious injury or
death. Do not remove the bottom cover at any time.
•To avoid risk of burns, do not touch vacuum tubes when the
unit is powered on or within 30 minutes of powering down.
•No user serviceable parts are inside. Service should only be
performed by Musical Surroundings or our authorized repair
agents.
•In case of fuse replacement (located in IEC receptacle),
disconnect AC cord prior to replacement and replace ONLY
with fuse of identical type and rating.
•Never place any object or material over this unit, which
would restrict ventilation, to avoid risk of fire.

3
Introduction
World-class audio engineer Jim Fosgate is the vision and expertise
behind the Fosgate Signature Tube Headphone Amplifier. The
Fosgate Signature embodies unique and patented circuit topologies,
elevating the headphone listening experience. The genesis of the
design started over 2 decades ago. Countless man-hours of working
with every possible major circuit approach was not just explored, but
designed, built, and auditioned byJim Fosgate himself.
The circuit incorporates 12AX7 vacuum tube amplification in the low
distortion SRPP configuration, similar to our Signature Phono
Preamplifier, winner of the 2011 Golden Ear Award from The
Absolute Sound magazine. High speed, high current video buffers are
used to drive headphones directly. This provides a pure audio path
with low output impedance, low distortion, and wide signal bandwidth.
The Video Buffers are not Op Amps and have no voltage gain. They
offer high input impedance so the vacuum tubes are not loaded
down, and low output impedance capable of driving most
headphones to high volume levels with no audible distortion or
colorations. The smooth, natural sound of the 12AX7 vacuum tubes
passes straight through to the outputs.
The bass boost equalizer circuit is designed to give the headphone

4
listener defined low frequency bass impact without bass boom. This
circuit has been used in different forms in many products including
Rockford Fosgate Car amplifiers. Jim Fosgate received US patent
number 3,883,832 for this circuit in 1975. It is called a "SINGLE
ELEMENT CONTROLLED TWIN T FILTER" and has a much steeper
curve than a bass or loudness control. It changes frequency and
amplitude (Boost) with a single control. When the control is set in the
“Min”position, the boost is applied at a lower frequency than when
the control is set to the “Max”position.
In order to infuse the sound with a natural sound stage, Jim
integrated his surround circuitry design, part of his US patent
5,307,415 “Panorama Control” filed in April 1994. This circuit applies
an out of phase cross blend to create a sense of depth and space
and moves the dimensional soundstage outside of your head. The
control has “Min”, “Max”, and “Off”positions. In the center “Off”
position the surround circuit is bypassed so the signal is unaffected
and provides normal stereo output.
The Fosgate Signature Tube Headphone Amplifier’s elegant circuit
has the tube amplifiers, buffers, bass EQ, and surround processing
configured in a single stage. Negative feedback is applied around this
stage in a single loop. Output offset is controlled with DC servos,
allowing the video buffers to directly drive the headphones with no
output capacitors in the signal path. There is only one coupling
capacitor per channel in the signal path, and it is enclosed within the
feedback loop, thus capacitor colorations are eliminated. Distortion
and noise are below the threshold of hearing. The bandwidth is very
wide allowing audio signals to pass through without colorations.
Bandwidth is an amazing “ten times” the threshold of human hearing,
2 HZ to 200KHZ at -3DB.
The power supply is similar to the one used in our Fosgate Signature
Tube Phono stage. It uses separate oversize storage capacitors on
each amplification path of each channel to provide a rock solid supply
voltage without voltage regulators to affect the signal. The circuit is
configured so that audio signal from one channel cannot couple to
signal from the other, preserving soundstage width and depth. This
power supply provides the benefits of both dual mono and batteries
but in a simple AC powered circuit.
A 35 second muting circuit eliminates turn on/off thumps fromthe
direct coupled output circuit. Two stereo inputs and a stereo tape
output are provided for added flexibility.

5
Unpacking
Opening the cartons:Use caution when opening the cartons.
Using a sharp edged tool could cause damage to the contents.
Foam packing:
When you open the
inner carton, you will
see a layer of foam
covering the
headphone
amplifier. There are
cut outs in the foam
containing each
vacuum tube,
located in the
appropriate position.
Be careful when lifting the foam so that the tubes do not fall out.
Alternately, you can remove the tubes from the foam before removing
the foam itself. Please note the location and marking for each tube.
Refer to the next page for specifics on tube installation.
Install the tubes:Included with your Fosgate Signature Tube
Headphone Amplifier is a pair of white gloves for handling both the
unit as well as the tubes. This will prevent any finger oil from getting
on the tubes. The unit should be powered off with AC cable
disconnected. When inserting tubes into their sockets, be very careful
not to bend the metal pins.
Placement: The Fosgate Signature headphone amplifier is
dimensioned for convenient placement when listening with
headphones. It should be placed close to where you will be enjoying
your music. It is best to position the headphone amplifier away from
hum producing sources such as motors, transformers and power
cords. Good ventilation is essential for safety and the life of the
headphone amplifier. Allow at least 2” of clearance above the unit,
and avoid placement on a shelf directly above a heat and noise
source such as a power amplifier. Ideally, the shelf or table where it is
placed should be constructed of non-resonant material to minimize
microphonics.

6
Audio connections: Your headphone amplifier features 2 line
level stereo inputs with RCA jacks. You can connect to these the
outputs of a phono stage, CD player, DA converter. etc. You may
also connect the tape output or loop output of a preamplifier or
receiver. These choices will be determined by your listening
preferences and system configuration. If you chose to connect your
source component directly to your headphone amplifier, you can
connect the headphone amplifier’s output jacks to an input of your
preamplifier or receiver. This is a pass through circuit, similar to a
tape loop, and the level is independent of the volume control of the
headphone amplifier (unity gain). Due to the high quality sound of
your headphone amplifier, we recommend using quality interconnect
cables. Consult your Musical Surroundings dealer in this regard.
AC power cord connections: Your Fosgate Signature
headphone amplifier is fitted with a male IEC AC input connector and
supplied with a high gauge IEC grounded power cord. With the
headphone amplifier power switch in the off (down) position, attach
the female end of the power cord to the unit andthe 3 prong AC plug
to a suitable AC outlet. Due to the high performance of this unit, you
may prefer a high quality after-market AC cord. Consult your Musical
Surroundings dealer in this regard.
Headphone connection:Your Fosgate Signature
headphone amplifier is fitted with a high quality ¼inch
phone plug input. This is the industry standard for high
quality headphones. Insert the male ¼phone plug from
your headphones completely into the female jack. If you
are using headphones with a “mini” connector, you must use a mini to
¼” adapter. Consult your Musical Surroundings dealer in this regard.

7
Powering up: Make sure all connections are in place and your
volume control is completely turned down prior to powering up your
headphone amplifier. When the unit is powered up, the amber LEDs
under the tubes will be illuminated. A 35 second muting circuit
eliminates turn on/off thumps fromthe direct coupled output circuit.
Now you are ready to listen. The sound will improve after several
minutes of warm up.
Input selection: Make sure all connections are in place and
your volume control is completely turned down prior. Select the
appropriate input for the source you want to listen to.
Volume adjust: Make sure your volume control is completely
turned down.Slowly increase the volume to the appropriate and
comfortable listening level
A note about headphone listening levels: Headphone
listening is the most direct and immediate way of enjoying music.
Please use caution when adjusting volume levels, especially when
listening over an extended period of time. Excessive volume levels
may result in listener fatigue and potential hearing damage.

8
SPECIAL FEATURES
Surround Circuit: Jim Fosgate integrated his surround circuitry
design, part of his US patent 5,307,415 “Panorama Control” filed in
April 1994 in his Signature headphone amplifier. This circuit applies
an out of phase cross blend to create a sense of depth and space
and moves the dimensional soundstage outside of your head. The
control has Min, Max,and Off positions. In the center off position,the
surround circuit is bypassed so the signal is unaffected and provides
normal stereo.
Bass Equalizer: The bass boost equalizer circuit
is designed to give the headphone listener defined, low
frequency bass impact without bass boom. There are
three positions on the bass control, Min, Max,and Off.
When the control is in the center Off position, the bass
boost is bypassed. This circuit has been used in
different forms in many products including Rockford
Fosgate Car amplifiers. Jim Fosgate received US
patent number 3,883,832 for this circuit in 1975. It is
called a "SINGLE ELEMENT CONTROLLED TWIN T
FILTER" and has a much steeper curve then a typical
bass or loudness control. It changes frequency and amplitude (Boost)
with a single control.
When the control is set in the Min position, the maximum boost is
applied at a lower frequency.
When the control is set in the Max position, the maximum boost is
applied at a higher frequency.
Using the special features: Depending on the type of
headphones you prefer, your listening habits,and the musical selection you
chose, experiment with these special features for the greatest listening
pleasure. Both features may be used in conjunction. You may find that
using the surround circuit for classical recordings will better recreate the
ambience of the concert hall and the bass eq will .

9
Tube Rolling:Your Fosgate Signature headphone amplifier ships with
two carefully selected, new production 12AX7 tubes.
Do not change tubes when the unit is powered on. To avoid risk of
burns, do not touch vacuum tubes when the unit is powered on or
within 30 minutes of powering down.
Below is a list of equivalent tubes used in your Fosgate Signature
headphone amplifier if you wish to tube roll. Please check with your
Musical Surroundings’ dealer regarding availability of tubes for this
purpose.
Please note that tubes obtained from an independent source that
causes damage to your Fosgate Signature headphone amplifier is not
covered under the warranty.
Below, we provide a space to notate your personal notes on sonic
differences with tube rolling.
V1 and V2 -12AX7/ ECC83
Equivalent: 7025, 5751
My Notes on Tube Rolling

10
SPECIFICATIONS
Frequency response: 2 HZ to 200KHZ at -3DB
Voltage Gain: 15DB
Signal to noise ratio:95DB
Headphone impedance drive range: 30 - 500 ohms
Maximum output voltage: 26 volts p-p into 500 Ohm load
Maximum power output: 180MW RMS 500 Ohm load
Maximum power output: 387MW RMS 200 Ohm load
Maximum power output: 1000MW RMS 30 Ohm load
Distortion: .05% @ 165MW 1KHZ 500 Ohm load
Distortion: .05% @ 387MW 1KHZ 200 Ohm load
Distortion: .1% @ 250MW 1KHZ 30 Ohm load
Maximum Bass Boost: 9DB @ 30 HZ
Minimum Bass Boost: 6DB @ 30 HZ
Dimensions: 7" W x 11" D x 5.5" H
Weight: 5 lbs
5662 Shattuck Ave
Oakland, CA 94609
510 547-5006
fax [phone]
[email protected]
www.musicalsurroundings.com

11
90 DAY LIMITED WARRANTY TERMS AND CONDITIONS
(2 Year optional extended service contract)
1. Musical Surroundings warrants the product designated herein to be free of manufacturing
defects in material and workmanship, subject to the conditions herein set forth, for a period of 90
days from the date of purchase by the original purchaser. If the purchaser registers the unit with
Musical Surroundings by mailing in the warranty card, together with a copy of the bill of sale,
within 14 days of the date of purchase, said purchaser will be registered for an extended service
contract. The extended service contract extends the 90 days to a period of 2 years from the date
of purchase by the original purchaser or no later than 3 years from the date of shipment to the
authorized Musical Surroundings dealer, whichever comes first. Tubes carry a 90 day warranty
only.
2. CONDITIONS - This warranty is subject to the following conditions and limitations. The
warranty is void and inapplicable if the product has been used or handled other than in
accordance with the instructions in the owner's manual, abused or misused, damaged by
accident or neglect or in being transported, or the defect is due to the product being repaired or
tampered with or modified by anyone other than Musical Surroundings or their authorized repair
stations. To obtain warranty service, you must first contact Musical Surroundings at 510 547-5006
or [email protected] to obtain a Return Authorization (RA) number. The
product must be packed in its original carton and returned to Musical Surroundings or authorized
repair station by the customer at his or her sole expense. A returned product must be
accompanied by a written description of the defect and a photocopy of the original purchase
receipt. This receipt must clearly list model and serial number, the date of purchase, the name
and address of the purchaser and authorized dealer and the purchase price. Musical
Surroundings reserves the right to modify the design of any product without obligation to
purchasers of previously manufactured products and to change the prices or specifications of any
product without notice or obligation to any person.
3. REMEDY - In the event the above product fails to meet the warranty, and the above conditions
have been met, the purchaser's sole remedy under the limited warranty shall be to return the
product to Musical Surroundings where the defect will be rectified without charge for parts or
labor.
4. LIMITED TO ORIGINAL PURCHASER - This warranty is for the sole benefit of the original
purchaser of the covered product and is NOT TRANSFERRABLE.
5. DURATION OF WARRANTY - This warranty expires 90 days after the date of original
purchase. If Musical Surroundings receives the warranty registration card, this period is extended
to the second anniversary of the date of purchase or no later that the third anniversary of the
shipment to the authorized Musical Surroundings dealer, whichever comes first.
6. MISCELLANEOUS - ANY IMPLIED WARRANTIES RELATING TO THE ABOVE PRODUCT
SHALL BE LIMITED TO THE DURATION OF THIS WARRANTY. THE WARRANTY DOES NOT
EXTEND TO ANY INCIDENTAL OR CONSEQUENTIAL COSTS OR DAMAGES TO THE
PURCHASER. Some states do not allow limitations on how long an implied warranty lasts or an
exclusion or limitation of incidental or consequential damages, so the above limitations or
exclusions may not apply to you. This Warranty gives you specific legal rights, and you may also
have other rights which vary from state to state.
7. WARRANTY OUTSIDE THE USA - Musical Surroundings has formal distribution in many of
the countries of the free world, in each country the Musical Surroundings importer has
contractually accepted the responsibility for product warranty. Warranty should normally be
obtained from the importing dealer or distributor from whom you obtain your product.