Sony STR-7055

1 9 7 2 1972
1 9 7 6 1976

The 1970s near-equivalent to the 1960s STR-6120 and STR-6200F - same lineup near-topper status, same quality but a very different internal structure and componentry.

Gone was the lavish simplicity and cleanlisness of the cabling and PCB placing of the late 1960s ES units - in came the more... hectic connection between boards and stages : lots of inputs and outputs but lots of (very) hectic cabling, too.

Sony made up for this with the incredibly fine-tuned and classy design of the front.

The differences between the 7055 and the real topper STR-7065 lie in more power, a third output for an extra loudspeaker pair, the possibility to mix two microphones together (where the AUX input is on the 7055) and a supplementary meter to show FM input signal.

The rest is the same : DC structure (yes), FET-charged 4-gang varicap, all the possible connections, a big trafo powering everybody, large heatsinks protruding through the back, two pairs of Sony PNP / NPN power transistors, three pairs of loudspeakers' outputs and a separable pre/main loop.

At 3295FF (french Francs) in 1973, this was the high-fidelity of the fairly rich and this still shows today - in spades. Despite often higher list prices, Sony sold a lot and a lot of STR-7055.

Replaced by the very rare ES-II-like STR-7800SD and its more common STR-6800SD brother.

Sony STR-7055, image 1 Sony STR-7055, image 2 Sony STR-7055, image 3
Sony STR-7055 specifications
Title Value
General General
Circuit : FM-stereo / FM-AM superheterodyne tuner
DC quasi-complementary symmetry (SEPP OTL) amplifier
Semiconductors : 5 ICs
49 transistors
(4 FETs & 11 transistors for reception)
(34 transistors for auxiliary circuit)
29 diodes
Dimensions : 47,1 x 15,7 x 37,5cm
Weight : 15,3kg.
PRE/MAIN section PRE/MAIN section
Dynamic power output : 200W (4 Ohm, IHF constant ps method)
136W (8 Ohm, IHF constant ps method)
Continuous power output : 2x 45W (8 Ohm, 1Khz, 0,2% THD)
2x 55W (4 Ohm, 1Khz, 0,2% THD)
2x 35W (8 Ohm, 20Hz...20Khz, 0,2% THD)
2x 45W (8 Ohm, DIN 45500, 0,2% THD)
Power bandwidth : 15Hz...35Khz
THD : < 0,2% (rated output)
< 0,1% (1W output)
< 0,2% (rated output, 20Hz...20Khz)
IMD : < 0,2% (rated output)
< 0,1% (1W output)
Frequency response : ± 1dB (RIAA)
10Hz...70Khz (lines, +0 / -3dB)
10Hz...100Khz (main amp, 1W output, +0 / -3dB)
Inputs : 2mV / 47kOhm (phono)
150mV / 50kOhm (lines)
Outputs : 250mV / 10kOhm (RCA rec out)
1V / 4,7kOhm (pre out)
30mV / 82kOhm (DIN rec out)
8 Ohm...10kOhm (headphones load)
S/N ratio : 70dB (phono, 3mV input)
90dB (lines, 250mV input)
100dB (main amp, 1V input)
Damping factor : > 50 at 8 Ohm
Bass control : ± 10dB at 100Hz
Treble control : ± 10dB at 10Khz
High filter : 12dB/octave above 9Khz
Low filter : 12dB/octave below 50Hz
Loudness control : +10dB at 50Hz / +4dB at 10Khz
FM section FM section
Intermediate frequency : 10,7MHz
Sensitivity : 2,0µV (IHF)
1,6µV (S/N ratio = 30dB)
Image rejection : 70dB
IF rejection : 100dB
Spurious rejection : 90dB
AM suppression : 56dB
Capture ratio : 1,0dB
Selectivity : 70dB (IHF)
S/N ratio : 70dB
Frequency response : 20Hz...15Khz (± 1dB)
THD : 0,2% (400Hz, mono, 100% modulation)
0,5% (400Hz, stereo, 100% modulation)
Stereo separation : > 38dB at 400Hz
Carrier suppression : 40dB
AM section AM section
Intermediate frequency : 455Khz
Sensitivity : 53dB/m (built-in antenna, 1MHz)
30µV (external antenna)
Image rejection : 50dB at 1MHz
IF rejection : 40dB at 1MHz
S/N ratio : 50dB at 50mV/m
THD : 0,8% at 50mV/m
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page online since : october 2008
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