Akai GX-65 MKII

Dolby NR system
Set the proper Dolby Noise Reduction sys-
tem before ali recording and playback Op-
erations
When playing back a tape, set the noise reduction selector
switch to the setting that was used when the tape was re-
corded. Set the noise reduction selector switch to OFF for
tapes that were recorded without the use of the Dolby NR
system.
What is the Dolby Noise Reduction (NR)
System?
The DOLBY NR system is a noise reduction system de-
signed to reduce tape noise caused when high frequency
soft sounds are recorded. The DOLBY NR system does this
by lowering the noise floor in order to increase the dynamic
room in the high frequency range above 5kHz.
During recording, the DOLBY NR encoder circuit boosts soft
high frequency sounds, and then during playback the
DOLBY NR decoder circuit lowers what was boosted by ex-
actly the same amount to restore the high frequencies to
their original levels. At the same time, tape noise is lowered .
by the same amount.
The result is reduction of up to 10dB in unwanted tape noise
in the high frequencies. :
What is the difference between Dolby
B-type and C-type NR systems?
B-type : This is the conventional Délby NR system. It boosts
or lowers the low-level signals at high frequencies
‘only (more than 5kHz) and reduces tape noise by
10dB.
Compared to Dolby B NR, it operates at lower fre-
quencies (from 500HZz) for uniform noise reduction
across more of the audible spectrum. Tape noise
is reduced by as much as 20GB.
C-type :
Double process noise reduction system
In a conventional noise reduction system, one circuit acts
both as an encoder and decoder, and is switched to one or
the other accordingly.
The double process noise reduction system has an encoder
circuit in the recording amplifier section, and a decoder in
the playback amplifier section. The double process noise re-
duction system is used in cassette decks with 3 independent
heads (recording, playback, and erase). Therefore, when re-
cording with a noise reduction system, you can immediately
confirm the effect of the noise reduction by monitoring the
just recorded music.
A rding Source Result
Loud Encoded tape
| Loud | Encoder eg
sounds |> og 4 (<=)
Soft sounds ie
soft
sounds i
Playback
Tape
Result
.
bier NR system
Encoded tape
Ear
Boosted
soft
sounds
Decoder
> 00 9
Loud sounds
Restored
soft sounds
Tape noise Lowered tape noise