DYNAMIC SOUNDS ASSOCIATES Phono III
Page 18 of 38
USER MANUAL
used during the recording process was available in the current literature. The recording equalization
used by RCA in the early years of LP development became the RIAA equalization with the addition of the
t1 time constant which flattens the LF rise starting at 50Hz.
From
Figure 1B
, shown here for reference,
the switches within the “Equalization”
section on the center-lower section of the
Phono III
front panel allow selection of the
playback equalizations in
Table 2
. The first
switch in the section has three options: RIAA
(center “off”), G1 (down), or G2 (up). The
second switch selects either EQ1 or EQ2
within either group G1 or G2. The “EQ
Group” LED shown in Figure 1A will be blue
when the RIAA equalization is selected, it
will be green with group G1, and red with
group G2. (These colors are selected to alert
the user that non-RIAA equalization is being used.) Likewise, the EQ1 or EQ2 LEDs will illuminate
depending on which is selected within the equalization group G1 or G2. The EQ1 and EQ2 LEDs will not
illuminate if the RIAA equalization is selected
.
Appendix B
presents design curves and typical measured responses of the
Phono III
for all of the
equalization curves shown in Table 2. It will also show how the different curves were incorporated
within the
Phono III
architecture. Precision matched components are used for all of the equalization
curves. As seen in
Appendix B,
the measured responses for the RIAA and group G1 curves are accurate
to ≤
±
0.2 dB from 20Hz to 20KHz and, at many frequencies, the error is <
±
0.1 dB.
Appendix B
also
shows that the curves of group G2 are accurate to
±
0.2 dB from 100Hz to 20KHz, but are low by < 1dB
at 50Hz, 2.5-3dB at 20Hz, and are low by ≈ 8dB at 10Hz.
Note:
When the G1 or G2 curves are selected, the overall gain of the
Phono III
will change by ± 1-2dB
relative to the RIAA equalization gain, depending on which EQ selection is made. This is to be expected
and is not a fault of the unit.
NOTE: Charts with playback equalization measurements made on this particular unit are found at the
end of Appendix B.
8
A General Observation
:
To meet special requirements, it is possible that other equalization curves can
be incorporated in lieu of the four that come as standard in the
Phono III
.
4.5
Noise Levels
There are three basic sources for noise at the output of the
Phono III
:
8
The measurements are performed using the CLIOwin7 measurement system which is calibrated prior to making
each set of measurements. CLIOwin7 is a registered Trademark of Automatica.
