Bryston 11B - Page 2

Congratulations on your selection
of the very finest sound equipment.
Your Bryston preamplifier has been
engineered to provide many years
of trouble-free, highly musical lis¬
tening enjoyment.
This instruction manual refers to
the Model 12B. With the exception
of the phono inputs, the Model 11B
preamplifier is identical, and the
instructions pertain to it in exactly
the same way. Where a difference
occurs, it will be noted in the text.
The Model 12B is a basic signal
preamplifier with switching facilities
for all the sources likely to be used
by even the most elaborate domestic
sound system, including dubbing
capability for two tape recorders,
and the convenience of recording
from any source while simultan¬
eously listening to any other through
the speakers. The included diagram
will illustrate the switching functions
of the Bryston Model 12B preampli¬
fier.
Phono Inputs; Including Moving
Coil
The Model 12B is supplied with
an internal moving-coil step-up
transformer. This extremely wide¬
band transformer, with almost no
added noise or distortion, increases
the voltage gain through the phono
section by 22.5dB, and adjusts the
in put i m pedance to suit the vast ma¬
jority of moving-coil cartridges. (It is
available on special order with 6dB
less gain, and a higher input im¬
pedance, for those few high-output
MC cartridges which may perform
better with these settings).
The 12B will also accept moving-
magnet cartridges by switching the
MC transformer out via a switch on
the front panel. In this case, the
cartridge is plugged into the MM
inputs on the rear panel. The MM
inputs (only) are equipped with input
loading capacitors of about 275 pf
per channel. When added to the
normal turntable wiring capacitance,
this yields about 300-400 pf, which
is in the optimum range for most
cartridges. (This internal phono
capacitance may be special-ordered
to any value at no extra charge).
The Model 11B is identical to the
Model 12B except that it is not
equipped with the MC transformer.
Thus both .phono inputs become
MM inputs, as above. They may be
selected between Phono 1 and
Phono 2 via the switch on the front
panel. (The MC tranformer may be
retrofitted at any time, converting
the preamp to a 12B). Since the
phono stage on the Model 12B in¬
verts absolute phase, the MC trans¬
former is connected to invert phase
also. Thus, MC cartridges play in
proper phase with no special con¬
nection necessary. In case of MM
cartridges, reversing the hot and
ground leads on the cartridge pins
is a convenient way of obtaining the
same function.
Tape Monitor Function
Although the 12B's tape monitor
function is arranged differently from
most standard preamplifiers, it is not
complicated to use. The two selector
switches operate independently, and
affect only the outputs to which their
labels refer. Thus the “MAIN
OUTPUT” switch is used as the
tape monitor, also. Include yourtape
deck in the preamp’s tape loop in
the normal way (i.e., its record head
is connected to Tape 1 output, and
its playback head is plugged back
into Tape 1 input). To monitor the
recording, just move the MAIN
OUTPUT switch to “Tape 1 ” A sec¬
ond tape deck may be included in
the tape loop in a similar manner,
using Tape 2 input and output, and
“Tape 2” selector position for mon¬
itoring.
Two Tape Recorders; Dubbing
Facility
Plug in the playback and record
heads of the two decks to their res¬
pective tape inputs and outputs, as
above. Normally, both decks will
receive the same signal for record¬
ing When “Tape 1” is selected on
the TAPE OUTPUT switch, how¬
ever, the playback head of deck 1
is connected to the record head of
deck 2, via Tape 2 output. This
obviously allows direct dubbing
from Tape Deck 1 to Tape Deck 2.
Selecting “Tape 2” on the TAPE
OUTPUT switch allows dubbing in
the opposite direction by reversing
these connections.
External Equalizer, Noise Re¬
duction, or Other Audio Pro¬
cessor
An equalizer, noise reducer, etc.,
may be included in the tape loop
(as shown in the diagram) by con¬
necting its input to one of the tape
outputs, and its output back to (the
same numeral) tape input. Turn the
MAIN OUTPUT switch to (that
numeral) "Tape” position whenever
you wish to use the audio proces¬
sor in the signal path. During that
time, the TAPE OUTPUT switch is
used as the selector for whichever
source is to be processed. Turning
the MAIN OUTPUT switch back to
this source position will bypass the
processor.
Headphone Jack
The Model 12B is equipped with
a headphone jack for convenient,
private listening. The signal is taken
directly from the output circuit which
normally feeds the power amplifier,
and is thus controlled by the volume
knob. This output will drive head¬
phones of any type, but lower
impedance headphones may re¬
quire somewhat more volume
control rotation for the desired
loudness. To facilitate headphone
listening without disturbing others,
the preamplifier automatically dis¬
connects thedirect feed to the power
amplifier. (This is indicated by the
green pilot light on the front panel
changing to red whenever the out¬
put relay is opened). This circuit does
not disconnect the remote outputs.
(See under“RemoteOutput”). Since
sqme headphones may require
substantial volume control rotation,
be sure to reduce the volume
before removing the headphone
plug, or you may be startled by the
high sound level when the relay
re-connects the amplifier.
Remote Output
The 12B preamplifier is equipped
with a special remote output, which
is switched via the “Main Output”
selector, but which exits ahead of
the volume control. This line-level
output may then be used to drive
amplifiers in remote locations, with
local volume controls. This allows
remote systems to function inde¬
pendently of the volume level set in
the main system. The automatic
amplifier disconnect which is part
of the headphone circuit does not
affect these remote outputs. (As an
option, this function may be replaced
by a second set of main outputs,
connected in parallel with the first.
Thisallowstheconvenientconnec-
tion of two amplifiers which are
desired to be controlled together,
such as subwoofer installations, or
passively biamplified systems).