Specifications

reference 0.5 volts output, and this too corresponds
exactly to the 250 mV spec called for by Mclntosh
for their referenced output level of 2.5 volts.
Figure 9 illustrates the range of control of each of
the three equalizer controls provided on the MX
117. The frequencies at which the three equalizer
controls are centered make for an extremely ver-
satile range of control. The action of the unique
loudness control found in the MX 1 1 7 is illustrated
in the series of response curves plotted by means of
our spectrum analyzer and reproduced in the 'scope
photo of Fig. 1 0. Note that only a moderate amount
of treble compensation comes into play as the con-
trol is advanced towards more contouring.
Fig. 10—Response obtained at various settings of
the independent loudness control of the
Mclntosh MX 117 Tuner-Preamp
Frequency response plots for the phono preamp-
equalizer section of the MX 117 were accurately
plotted using our new Sound Technology 1 500A
test instrument and an associated video printer. In
Fig. 1 1 we see the familiar RIAA playback curve ob-
tained by feeding a constant amplitude frequency-
swept signal into the phono inputs. The plot extends
Fig. 12 —Expanded-scale phono response, using
inverse RIAA input test signal
from 20 Hz at the left to 40 kHz, with double vertical
lines indicating 1 00, 1 000 and 1 0,000 Hz. 0 dB re-
ference has been established at 1 kHz as shown. In
Fig. 12 the vertical sensitivity of the plot has been
expanded so that it is 2 dB per vertical division (in-
stead of 10, as in the previous display). Also, the
signal applied to the phono inputs has not been
subjected to inverse RIAA equalization so that, in
theory, if perfect RIAA equalization were incorporat-
ed in the MX 1 1 7, a "straight line" response would
be obtained. As you can see, maximum deviation
from this ideal was 0.6 dB at 40 Hz (where the dot-
ted line cursor is positioned for a read-out at the
lower right of the display) while moving the cursor to
the maximum deviation in the high frequency region
(Fig. 13), shows a maximum deviation from "ab-
solute RIAA accuracy" of only 0.5 dB at 1 8.5 kHz.
Fig. 11—Phono preamp-equalizer response,
Mclntosh MX 117 Tuner-Preamp
Fig. 13 —Same as Fig. 12, except "cursor" has been
moved to read relative response at 18.5 kHz
Signal-to-noise ratio of the phono section was first
measured in accordance with the IHF/EIA standard,
which calls for a 5 mV input at 1 kHz and adjustment
of the volume control so as to produce an output of
0.5 volts. Under these conditions, and using an
"A-weighting" curve, a reading of 84.4 dB was ob-
44