Denon PMA-770
Spec
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Denon PMA-770 Manufacture..................... Foster, Japan
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Futures
The Integrated Amplifier
which supplied original technology, such as amplifier unreturned [ of 0dB ], a
direct A system, a super equalizer, and was developed.
MC input terminal to the speaker output terminal considered it as the whole page
Capacitor-Less (perfect direct-current composition) which uses not a capacitor
for the main signal course, and has formed the signal course into pure & high
speed thoroughly.
This perfect Capacitor-Less composition suppressed direct-current drift by
adopting the direct direct-current servo circuit carried in PMA-970 or PMA-950,
and has secured super-low-pass stability.
The MC/MM super equalizer is carried and the outstanding RIAA deflection
characteristic of 20Hz-100kHz±0.2dB exceeding the high region play threshold
frequency of a high-class cartridge is acquired.
Composition consists of the NF form direct-current amplifier and CR form
equalizing filter by newly developed low noise dual FET, and the first rank has
composition of the parallel differential amplification by dual FET of a direct
direct-current servo system.
The amplifier unreturned [ of 0dB ] is adopted as a power amplifier part.
The amplifier unreturned [ of 0dB ] takes out ingredients (distortion, noise,
etc.) other than an incoming signal for the signals (main signal + distorted
ingredient etc.) acquired from the output side of the main amplifier in a direct
distortion servo circuit as compared with an incoming signal.
This distorted ingredient is amplified in a direct distortion servo circuit, and
also phase inversion is carried out, and it is added to the input side of the
main amplifier. By this, a distorted ingredient is negated and static distortion
is suppressed.
Furthermore, with the amplifier unreturned [ of 0dB ], since [ through which a
signal flows only into one way ] a direct-pass, dynamic distortion does not
occur. Moreover, noise ingredients other than static distortion are also
cancellable as a difference of an incoming signal by the effect of a direct
distortion servo circuit. Furthermore, the buffer (emitter-follower) which
separates a voltage magnification stage and an electric power magnification
stage is designed, and in order that there may moreover be no NFB loop, a
voltage magnification stage is not influenced by a speaker. Furthermore, since
the excessive amplification degree by NFB is not needed, it has the various
features -- an intermediary coarse magnification stage can constitute simply
Circuit composition of the power amplifier part was used as the 3 steps of
differential current mirror by first rank low noise FET, by the complimentary
emitter-follower, attained low impedance-ization and has separated it completely
with the electric power magnification stage.
Moreover, an electric power magnification stage is used as the output stage of a
high-speed power transistor 2 parallel push pull, from the output terminal, it
applies a direct direct-current servo to the first rank of a voltage amplifier
at overalls, suppresses direct-current drift, and is attaining super-low-pass
stabilization.
Furthermore, the zero crossing linear bias circuit of DENON original is adopted
as an output stage, and generating of the switching distortion by cutoff of a
power transistor is canceled.
In order to reduce the distortion at the time of speaker real load, the real
drive circuit is carried.
In a real drive circuit, the real drive line by an electronic device is set up,
and it writes with an A.S.O. (Area of Safety Operating: safe operation domain)
line and the protection line approached extremely,Even if a speaker load
operation line becomes large at the time of the Oide power, a protection line is
not contacted but the thing of the engine performance of a transistor done for a
high power drive up until last minute is possible.
This is reducing the distortion at the time of speaker real load to 50 by about
1/.
The aluminum radiator was made to separate equalizer amplifier and power
amplifier, and the mutual intervention is eliminated.
Moreover, the input change is attaining shortening of wiring as remote control.
The large-sized toroidal transformer which thought the rate of voltage
fluctuation and the leakage flux as important, and a 44,000-micro F mass
capacitor are adopted as a power-source part.
Real-time tone control is adopted as tone control.
This consists of only passive devices required for tone control, has neither a
distortion of the tone circuit itself, nor a problem of S/N, and is suppressing
the influence on a main circuit.
The comparison audition of two MC or two MM is also possible by switch operation
of the front panel.
A Rec out selector, the Subsonic Filter, the direct couple switch, the mode
switch in which a stereo reverse play and a monophonic play are possible, and
the loudness control switch are carried.
The high-speed protection circuit is carried.
Translation via Audio-Database.com
from-Japanese spec page on this unit
From audioinvest.no
. They contain 4 PDF's from the PMA-770
Service Manual, to which they do not have a complete copy.
pma770_adjust.pdf
(439.5k) - contains instructions for idle current adjustment for the tone &
power board and adjustment of the input eq board.
pma770_board.pdf (1.4M)
- printed PCB layout with parts overlay for tone/power board.
pma770_connect.pdf
(483.7k) - various board connections in the PMA-770.
pma770cd.pdf (529.1k) -
schematic of most of the tone and power amp board. does not show power supply,
input selection, input eq, etc.
