Pioneer SA-6800II

Commentary

This is a pre-main amplifier developed by Pioneer using the know-how acquired from high-end machines.

The circuit system of the equalizer is a first stage differential and 3-stage direct coupled circuit with ± 2 power supply. The NFB element, which determines the frequency characteristics, uses carefully selected elements such as nichrome metal film resistance with 1% error and styrene condenser with 2% error.
The dynamic margin of the maximum allowable input of 200 mV is obtained by supplying two positive and negative power supplies of + 23 V and -19.5 V.

The flat amplifier uses a 2-PNP-NPN configuration with low noise and low distortion factor to increase the power supply utilization factor and expand the dynamic range.
And, the tone control circuit of the next stage is CR type, and a knob with a Klix/Klukš top is adopted.
It also has a tone on/off switch that instantly flattens the tone regardless of the position of the tone control knob.

The volume is a 32-step attenuator type.

The first stage of the power amplifier section is differential-amplified by dual transistors with uniform characteristics, and all stages are directly connected to the pure complimentary service OCL system.
In this circuit, a constant current load is applied to the pre-driver stage to eliminate the low-frequency time constant, making it possible to reproduce signals up to the ultra-low frequency range. In addition, this method reduces the load on the pre-driver, making it possible to obtain a large gain in the linear region of the transistor. In addition, by taking a large gain in the open-loop mode and applying sufficient NFB, distortion is reduced.

The power supply uses a large transformer and a 10,000 μ Fx2 large-capacity capacitor.
In this power supply section, the transformer windings for the final stage of the power amplifier and the stabilization power supply section before it are separately wound to reduce mutual interference.

The protection circuit has a built-in protection circuit using a power relay.
This circuit also functions as a muting circuit to cut off noise when the power is turned on/off.

Equipped with a loudness contour and a 2-system tape monitor.

Model Rating

Type	Stereo pre-main amplifier
Circuit system	Power Amplifier : Pure complimentary service OCL Equalizer : Two positive and negative power supply, first stage differential, 3-stage direct connection Tone control part : Positive / negative 2 power supply 2-stage direct connection flat amplifier, CR type tone
Effective power (Both channel drive, 20 Hz to 20 kHz)	50W + 50W (4 Ω) 45W + 45W (8 Ω)
Harmonic distortion factor (20 Hz to 20 kHz)	0.1% (Effective Output) 0.05% (8 Ω at 23W output) 0.05% (8 Ω at 1W output)
Cross modulation distortion factor (50Hz:7kHz=4:1)	0.1% (Effective Output) 0.05% (8 Ω at 23W output) 0.05% (8 Ω at 1W output)
Output Bandwidth (IHF, both channel drives)	5 Hz ~ 40 kHz (Distortion Factor 0.1%)
Damping factor	30 (20 Hz ~ 20 kHz, 8 Ω)
Input Sensitivity / Impedance	Phono : 2.5mV/50k Ω Tuner, Aux, Tape play1, 2 : 150mV/50k Ω
Phono maximum allowable input	200 mv (1 khz, 0.1% harmonic distortion rate)
Output Level / Impedance	Tape rec1, 2 : 150 mV Speaker AORb : 4 Ω ~ 16 Ω Speaker A + B : 8 Ω ~ 16 Ω Headphone : 4 Ω ~ 16 Ω
Frequency characteristic	Phono : 20 Hz to 20 kHz ± 0.3 dB Tuner, Aux, Tape play : 10 hz to 40 khz + 0 -1dB
Tone control	Bass:+9dB -8dB(100Hz) Treble:+8dB -6dB(10kHz)
Filter	Low : 15 Hz, 6dB/oct.
Loudness contour (Volume -40dB)	+6dB(100Hz) +3dB(10kHz)
S/N (IHF, A-network Short circuit)	Phono:73dB Tuner, Aux, Tape play : 95 dB
<General>
Semiconductor used	Transistor : 34 Diode, etc. : 17 pcs
AC outlet	Power switch interlock : 2 systems Power switch not linked : 2 systems
Power supply voltage	100 VAC, 50Hz/60Hz
Power consumption	110W (Electrical Appliance and Material Control Law) 300W maximum
External dimensions	Width 380x Height 139x Depth 308 mm
Weight	8.7kg