Anthem AMP-1 Brochure

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P R E 1P

P R E 2L

I N T 2

A M P 1

A M P 2

Amp 1

“These 40 watts mean business ...it had no apparent trouble with the

Thiel’s nasty little 2 ohm load, controlling the bass admirably. ...This amp’s

greatest strength comes from its overall high level of performance. ...it

sounds much better than many costing a great deal more (I know I’ve
heard them). It has control. It has balance. It has refinement. I think it is
extraordinary. There’s just one thing I want to know. How much is Sonic
Frontiers losing on each one?”

– Audio Adventure

November 1996, Vol. 3 Issue 10

“Sonic Frontiers Anthem Amp 1 excels at just about every parameter. It’s tonally
clean, with everything from the low lows to the high highs rendered just right,

and it’s boss man at the information retrieval game. ...But the best part is the

Amp 1’s sheer musicality — it doesn’t just get the notes right it plays the tune.”

– Lonnie Brownell, Stereophile

February 1998 Vol.21 No.2

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A M P 1

Stereo Tube Power Amplifier - 40 watts/ch

value without equal
performance beyond

e x p e c t a t i o n s

Developed as the mate to our award-winning PRE 1 and PRE 1L
preamplifiers, the AMP 1 combines a robust, regulated power
s u p p l y, sophisticated circuit topology, conservative operating
parameters and efficient industrial design practices, into one
uncompromising, yet affordable, stereo power amplifier product.
The sonic result is an amplifier which is both fast, tonally
neutral with the real power and control to adequately drive a
surprisingly vast array of demanding speakers.

Design Features

POWER SUPPLY: The heavy duty power transformer is

c o n s e rvatively designed for low temperature rise and moderate flux
d e n s i t y, resulting in cool operation, low acoustic noise and long life. In
a d d i t i o n, a large power supply reservoir for the high voltage is utilized,
along with two solid state voltage regulators which provide electronic
filtering, decoupling and voltage regulation for the low level input stages
and the phase splitter/driver circuitry. A well filtered unregulated
negative supply is also provided for fixed bias of the output stages so
as to track any variation or drift in the AC mains voltage, keeping the
quiescent current in the output relatively constant.

BIAS CIRCUIT: Individual potentiometers are provided for bias
adjustment of each of the 4 output tubes. The use of individual bias
controls allows balancing of the operating characteristics of each
output tube for optimum performance and compensation for tube aging
e f f e c t s .

OUTPUT STA G E : The heart of a vacuum tube power amplifier,
the output transformer, is the key to great performance. Utilizing the
best materials (5.25 lbs of M6 grain-oriented silicon steel and soft drawn
OHFC copper) and incorporating advanced bobbin winding techniques,
we have been able to dramatically improve the performance of this, our
latest generation, output transformer. Carefully balanced and interleaved
windings insure the widest bandwidth, with the lowest phase shift and
d i s t o rtion performance. The output stage consists of a pair of
EL34/6CA7 power pentodes biased into class AB1 and configured in
an “Ultra Linear” manner. This “Ultra Linear” connection provides an
intermediate operating point between a pentode and a triode, with the
power output of a pentode and the low internal output impedance of a
triode. Under these operating conditions, the tube functions as a
pentode with a small amount of negative feedback applied to the
screen grid, resulting in lower distortion products at the higher levels of
o p e r a t i o n.

OUTPUT TERMINATION: Separate 4 and 8 ohm taps,
which are available via convenient rear panel output binding posts,
allow the user to optimize the power output of the AMP 1 into any load.
An additional 16 ohm tap is provided internally which may be optionally
connected in place of the 4 ohm tap. A special compensation
network in each output channel maintains constant load impedance at
ultrasonic frequencies, making the AMP-1 ultra stable into difficult
loads such as electrostatic speake r s .

F E E D B A C K : A moderate amount of overall negative feedback
is used in the AMP 1. The benefits of this design practice
include a reduction in the AMP 1’s output impedance for
increased damping factor, reduction of output distortion and
increased bandwidth.

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