Use Of The Dolby System On Fm Broadcasts; Fm De-Emphasis Switch; Dolby Mode Chart - Marantz 4270 Instructions Manual

Mark the calibration positions on the recorder's
record and playback level controls to avoid the
necessity of re-calibrating after making a non­
Dolby recording.
IMPORTANT:
It will be necessary to re-calibrate the Dolby
levels when a change in tape speed has been made
or when a different brand or type of tape is used.
When the Dolby process is not desired on a re­
cording, record in the normal manner - adjusting
the record levels with the recorder's record level
controls. DO NOT change the 4270's PLAY
CAL controls.
USE OF THE DOLBY SYSTEM ON FM BROAD ­
CASTS
Your Model 4270 is equipped to receive Dolbyiz­
ed FM broadcasts.
Most FM broadcasts do not currently use the
Dolby Noise-Reduction system. To receive these
broadcasts, leave the DOLBY Switch in the
"OFF" position. However, if a local station is
broadcasting a Dolbyized FM signal, full advan­
tage of the increase in signal-to -noise ratio may
be obtained by putting the DOLBY Switch in
the "DOLBY FM" position. The rear panel
DOLBY FM PRESET LEVEL controls are fac­
tory-adjusted. Do not change the position of
these controls.
FM DE-EMPHASIS SWITCH
This rear panel switch operates only when the
front panel DOLBY Switch is in the "DOLBY
FM" position. It alters the frequency response
of the FM signal. Normally, this switch should
be left in the 7511S position. However, if the
station is broadcasting the Dolbyized signal using
a 2511S pre-emphasis, put this switch in the
"25I1S" position to obtain flat FM frequency
response. If in doubt, call the station.
DOLBY MODE CHART
This chart indicates the correct DOLBY Switch
positions for various types of input material.
The input format is indicated in the left column
and the appropriate DOLBY Switch position,
together with FM DE-EMPHASIS Switch posit ion,
is shown under the appropriate mode of opera­
tion.
'~
De-Emphasis
Dolby Switch Position
Mode
Sw itch
Listen ing
Record
Input Position
Without Dolby With Dolby
F.M.
75J1.S
"Off" "Off" "Record I"
(Normal)
F.M.
with Dolby
7511s
"Dolby FM" "Record II" "Dolby FM"
If
7511s
Pre-emphasis
the
F.M.
with Dolby
25J1.S
"Dolby FM" "Record II" "Dolby FM"
rect
25J1.S
Pre-emphasis
Non Dolbyized
sources
"Off"
(Phone, Tape, -
"Off" "Record I"
Aux inputs,
"Record I"
A.M.)
terial
Dolbyized
sources (de­
rived from
"Play"
"Record II" "Play"
to
"Tape" or
-
"Record II" mode.
"Aux" inputs
etc.)
For initial calibration, utilizing the Dolby standard alignment tape, see detailed instructions
on Pages 14 thru 16 of this manual.
Notes :
-
there is a doubt regard­
ing the pre-emphasis used on
transmission,
the F.M.
station should be contacted,
where possible, to ensure cor -
pos ition for de-emphasis
switch.
Pre-recorded tape manufac­
turers indicate when the rna­
has been recorded in a
Dolbyized format. Home reo
corded tapes should also be
clearly marked as to format,
ensure correct play back
Table 1. Dolby Mode Chart
16