Technics SU-8055K amplifier

The main function of an amplifier is to amplify the input signal without adding to or subtracting anything from the waveforms of the original music. In other often-heard words, the ideal amplifier should be a straight piece of wire that provides gain without phase shifts, transient and other types of distortion over a wide frequency range. Technics sums all this up and calls it "waveform fidelity" and the SU-8055K is a good example of what we have done to make this kind of fidelity a reality. A glance at the specifications will show that what we say is not an idle boast. But we don't want you to just look. Listen to the SU-8055K and we're confident that you'll hear the qualities we're talking about.

 

DC Power Amplifier Helps Preserve Waveform Fidelity

Waveform fidelity has been greatly enhanced in Technics SU-8055K by the elimination of coupling capacitors not only in the signal path but also in the NFB loop. The lack of something is often a defect. But here, the absence of coupling capacitors means gain all the way down to 0 Hz and phase linearity in the bass frequencies. The result, in this DC power amplifier, is waveform fidelity - the accurate reproduction of musical waveforms.

Big Power and Matching High Fidelity

This amp offers plenty of power even if your special interest is thundering popular music with a lot of bass. It delivers 47 W at 8 Ω, from 20 Hz to 20 kHz with no more than 0,02% Total Harmonic Distortion. Reasons for this high fidelity are manu. A single-packed, low-noise dual transistor is used in the differential amplifier first stage for low noise and precise thermal tracking. Current mirror loading provides high open loop gain without increasing the level of noise. This stage gets help from the emitter-follower, in driving the Class A voltage amplification stage. The end result is minimal distortion in the high frequency range. In addition,, a 2-stage Darlington connection is used in the power stage, comprising a pure complementary circuit that provides high damping factor and low distrtion.

Super Quiet Phono Equalizer

The SU-8055K has an unbelievably high Signal-to-Noise ratio of 85 dB (at 2,5 mV sens. IHF A) when using an MM type cartridge, something rerely found in this amplifier's price class. There is a 3-stage, direct-coupling MM phono equalizer section, with direct coupling of the PNP-NPN transistors, plus a PNP transistor in the emitter follower. Low-output MC cartridges, which are growing in popularity, can also be used without adding an extra pre-preamp (another rarity in a moderate price amp). For the MC input, S/N ratio is 66 dB (at 170 µV sens. IHF A). A few of the reasons for low distortion and high gain are the separation of DC and AC in the negative feedback loop of the equalizer, 100% DC feedback, and the use of narrow tolerance components for negative feedback.

Treble and Bass Controls

An advaanced operatonal IC is used for negative-feedback-type tone controls. Bass and treble can be easily boosted or attenuated to suit individual tastes without  introducing distortion

Accurate Peak Power Indicators

These easy-to-read FL meters are used instead of conventional power output meters. They feature superior accuracy and near-instantaneous response time, and can be switched between two ranges: 0,1 W- 100 W when you are metering for full peak power: 0,01W - 10 W when metering in the more usual listening range. Brightness of the meters is switchable between bright and dim.

 

Versatile Recording Selector

The SU-8055K has two tape positions on the input selector as well as on the recording selector in a logical and practical layout. With this complete separation, you can do such things as dub from tape to tape while listening to your favorite disc. Or tape from your tuner while listening to music on another tape.

Rugged Stable Power Supply

The power supply is designed to handle the sudden current demands of high energy musical transient without losing sound clarity or introducing transient crosstalk. This is done by using two large-capacity 8,200 µF electrolytic capacitors in the bridged full-wave rectifier circuit and by employing a recently-developed transformer. It also supplies regulated voltage to the phono equalizer circcuit. The transformer coils are floated in a special resin to absorb unwanted vibrations. Even at soft volume levels you can enjoy your favorite music without being bothered by a noisy transformer.

Other Features

Muting circuit eliminates shock noise when the power is turned on and off, providing added speaker protection.

High filter to cut out high frequency noise such as record scratches and tape hiss. Subsonic filter reduces low-frequency noise.

Loudness switch for use when listening at low volume levels. Lows and highs are boosted to make up for "deficiencies" in the way the human ear responds at low volume levels.

Front-panel speaker selector lets you select either of two speaker systems (AorB) both or at once (A + B).

 

Specifications

Specifications

Amplifier Section (IHF)

Continuous Power both Channel Driven

From 20 Hz - 20 kHz

2 x 48 W  at 4 Ω

2 x 47 W at 8 Ω

From 40 Hz - 16 kHz

2 x 48 W at 4 Ω

2 x 47 W at 8 Ω

At 1 kHz

2 x 56 W at 4 Ω

2 x 50 W at 8 Ω

Total Harmonic Distortion:

Rated Power (20 Hz to 20 kHz)

0,03% at 4 Ω

0,02% at 8 Ω

Rated Power (40 Hz - 16 kHz)

0,03% at 4 Ω

0,02% at 8 Ω

Rated Power (1 kHz)

0,03% at 4 Ω

 0,02% at 8 Ω

Half Power (1 kHz) :   0,008% (8 Ω)

Half Power (20 Hz - 20 kHz) :  0,01% (8 Ω)

-26 dB Power (at 1 kHz) :  0,15% (4 Ω)

50 mW Power (at 1 kHz) :  0,2% (4 Ω)

Intermodulation Distortion:

Rated Power (250 Hz : 8 kHz = 4 : 1 ) :  0,03%

Rated Power (60 Hz  : 7 kHz = 4 : 1 SMPTE 8 Ω) :  0,02%

Power Bandwidth( both channel driven -3 dB): 

At 4 Ω :  5 Hz - 30 kHz

At 8 Ω :  5 Hz - 50 kHz

Residual Hum and Noise:  0,8 mV (0,8 mV, IHF  A)

Damping Factor:  18 (4 Ω);  36 (8 Ω)

Headphones Output Level/Impedance:  440 mV/330 Ω

Load Impedance

Main or Remote:  4 Ω - 16 Ω

Main and Remote:  8 Ω - 16 Ω

Input Sensitivity/Impedance

Phono MM :  2,5 mV/47 k Ω

Phono MC :  170 µV/100 Ω

Tuner, Aux :  150 mV/47 k Ω

Tape 1, Rec/Play :  180 mV/33 k Ω

Tape 2 :  150 mV/33 k Ω

Phono Max.input Voltage (1 kHz RMS): 

MM :  150 mV

MC :  6,5 MV

Signal-to-Noise Ratio

Rated Power (4 Ω)

Phono MM:  73 dB (85 dB IHF A)

Phono MC :  60 dB (66 dB, IHF A)

Tuner, Aux, Tape :  86 dB (97 dB, IHF A)

-26 dB Power (4 Ω)

Phono MM :  62 dB

Phono MC :  58 dB

Tuner, Aux, Tape :  63 dB

50 mW Power (4 Ω)

Phono MM :  58 dB

Phono MC :  56 dB

Tuner. Aux, tape :  60 dB

Frequency Response;

Phono :  30 Hz - 15 kHz (RIAA standard curve ±0,5 dB)

Tuner, Aux, Tape :  10 Hz - 60 kHz (-1 dB) ±0,5 dB (20 Hz - 20 kHz)

Tone Controls

Bass :  50 Hz +10 dB /-10 dB

Treble ;  20 kHz +10 dB / -10 dB

High Filter:  7 kHz, -6 dB/oct

Subsonic Filter:  30 Hz, -6 dB/oct

Loudness Control (Volume at -30 dB):  50 Hz , +9 dB

Output Voltage/Impedance

Rec Out :  150 mV

Rec /Play :  30 mV/82 k Ω

Channel Balance

Aux (250 Hz - 6300 Hz) ±1 dB

Channel Separation

Aux (1 kHz) 60 dB

General

Power Consumption: 500 W

Power Supply:  AC 110/120/220/240 V 50/60 Hz

Dimensions (W x H x D):  430 x 142 x 255 mm 916-15/16" x 5-19/32" x 10-1/32")

Weight:  7,7 kg (17,0 lb)