National/Panasonic SA-73

Commentary

Solid state pre-main amplifier with all stages directly connected by OCL circuit.

OCL circuit is used in the main amplifier section.
In this circuit, the capacitor used in the signal circuit has been eliminated. In addition, by adopting a two power supply system, the capacitor of the speaker output circuit has been eliminated and all stages are directly connected to each other to improve the sound quality.
A differential amplifier is used in the first stage to improve DC stability and linearity.

All of the preamp sections use low-noise PNP silicon transistors to eliminate noise and noise problems.

It is equipped with a protection circuit, detects when the load is short-circuited, and limits the current flowing to the power transistor. It is also an instantaneous recovery type, and when the load is short-circuited, it returns to normal status.
This circuit is independent of the left and right channels.

Equipped with a program indicator.

Uses a slide control system.

The preamp section and main amplifier section can be used separately.

Model Rating

Type	Pre-main amplifier
Main Amplifier Section
Music Power (IHF)	52W (4 Ω) 40W (8 Ω)
Effective power	12W/12W (8 Ω)
Total harmonic distortion factor	Not more than 0.5%
Output bandwidth	4 Hz ~ 50 kHz (Distortion Factor 0.5%)
Frequency characteristic	10 Hz to 60 kHz
Residual noise	0.8 mV or less
Input Sensitivity / Impedance	240mV/100k Ω
Damping factor	16.5 (4 Ω) 33 (8 Ω)
Load impedance	8 Ω ~ 16 Ω
Preamplifier Section
Maximum output voltage	1V
Rated output voltage	240mV
Signal-to-noise ratio (IHF)	Phono:74dB Aux:88dB
Control switch	Bass Treble Loudness control Mode switch Function switch
Low filter	200 Hz, -6dB/oct.
High filter	6 kHz, -6dB/oct.
<Others>
Accessory function	Tape monitor DIN terminal Headphone port Speaker switch Sliding tone control Pre-out / Main in terminal Program selection indicator Protection circuit AC outlet
Pwer	AC100V
External dimensions	Width 407x Height 127x Depth 300 mm
Weight	8.1kg