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TE CH NI C AL O VE RV I EW
The Sonic Frontiers Phono 1 is a single chassis phono stage with an
equalized gain of 62dB at 1kHz. The circuit topology is non-invert-
ing, and uses a single high quality J-Fet for the input amplifier, and a
special series amplifier for the second amplifying stage. In order to
provide a low output impedance, a cathode follower is used after
the second stage, transforming the high output impedance from the
second stage to a lower output impedance suitable for driving any
preamplifier with a reasonable input impedance. The input amplifier
is a common source amplifier with a high drain load. This provides a
gain that is (almost) the drain load divided by the source load, in this
case 100X. The second stage uses one section of a 6922 as an
active load element, and this minimizes the distortion in this stage
regardless of tube variations. The equalization is accomplished by
the use of frequency dependent feedback. Only one compensation
T EC H NI CAL S PE C IF I CAT I ON S
FREQUENCY RESPONSE:
NOISE:
DISTORTION:
TUBE COMPLEMENT:
GAIN:
POWER REQUIREMENTS:
INPUT IMPEDANCE:
DIMENSIONS:
OUTPUT IMPEDANCE:
NET WEIGHT:
MAXIMUM INPUT:
RATED OUTPUT:
+/- .1dB, 20Hz to 20kHz, RIAA equalized
0.07uV equivalent input noise,
-83 dB below a 1mV 1kHz input.
IHF - A-weighted , shorted input.
Less than .01% THD at 1kHz, 1VRMS output, IHF load - 10K ohms, 1000pf.
(4) 6922/E88CC Dual triodes.
62dB at 1kHz. (1200 X) - recommended for cartridges with 1mV or less output.
(optional 54dB version available from the factory for cartridges with >1mV output)
100V - 135VAC 50/60 Hz, (200 - 270VAC 50/60Hz).
60 VA maximum. Line fuse .75A SLO BLO (.375A 240V)
47K ohms/10pf standard. 10, 100, 1K, 10K ohms resistance
and 47, 47, 100, 100pf capacitance available by user selected
DIP switches on rear of unit. Two positions available per channel for
user selected components via solder posts.
19" Wide x 14.25" Deep x 4.5"
High (48cm x36cm x 11.5cm)
175 ohms at 1kHz unbalanced.
21.5lbs. (9.75kg) - Unpacked
50mV at 1kHz and 280mV at 20kHz.
1.2VRMS 20Hz to 20kHz, 10K ohm load
network is used, and this is fed from a relatively low impedance,
thereby avoiding slew limiting at high frequencies, with its attendant
d i s t o r t i o n s .
Despite the high technical performance achieved by this innovative
approach, it was realized that noise would be the final barrier to the fin-
ished products performance. Great strides were made in reducing noise
from both the circuit and the power supply. Circuit noise reduction tech-
niques such as careful component selection and ground planes as well
as advanced power supply noise reduction schemes has helped the
PHONO 1 achieve excellent noise specifications, on par with many of
the best solid-state units.
Note: All measurements performed with an Audio Precision
System Two test center.
Due to Sonic Frontiers desire to continually improve its
products, specifications are subject to change without notice.
9
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