Pioneer SA-910

Commentary

A pre-main amplifier with improved sound quality by adopting a two power supply system for all circuits and a differential amplifier in the first stage of each section.

With the positive and negative two power supply system, the input / output point is always kept close to 0 potential, so the shock noise generated when the switch is switched is almost zero.
This is especially important in the low-level section, such as the equalizer stage, where a high-gain amplifier is placed at the rear.

The SEPP circuit is used for the output stage of the equalizer amplifier to increase the power utilization factor, to obtain high output with low distortion, to increase the allowable input, and to widen the dynamic margin.

A differential amplifier is used in the first stage and 100% DC NFB is applied to achieve low distortion and excellent DC stability over a wide range.
In addition, it is difficult to cause any deviation of the operating point for transient input.
The transistor uses a carefully selected low-noise can-shield type to prevent noise from changing over time due to humidity.

An NFB element for obtaining the RIAA curve and a Styrofoam capacitor (error 2%) and Nichrome evaporated metal film resistor (error 1%) with less error are used for the NFB receiving part.

There are two input circuits for both Phono and AUX. Phono1 and AUX1 are straight and Phono2 and AUX2 are level control circuits.
By applying the level control of the Phono2 in particular, you can adjust the level when comparing two types of cartridges with different output voltages using two players (or twin-tone arms).
Since the level control is adjusted according to the amount of NFB, consideration is given so that the dynamic margin is not insufficient even when this control is reduced for a high-output cartridge.
The input impedance of the Phono2 terminal can be selected in three levels : 25k Ω, 50k Ω and 100k Ω. The optimum value can be selected depending on the type of cartridge.

Two tape decks can be connected simultaneously to enable tape-to-tape duplication as well as alternate playback by switching between switches.

Both Bass and Treble have twin tone controls with smaller knobs on either side of each.
Turning the large middle knob (main) provides general tone control, while turning the flat main knob and turning the small left and right knobs (sub) controls the very low and high ranges.
In this way, by making the tone control capable of controlling two characteristics, it is possible to control characteristics that have not been possible until now.

The Main and Treble can be controlled in 11 positions with 2 dB steps. Bass can be controlled by ± 10 dB at 100 Hz, and Treble can be controlled by ± 10 dB at 10 kHz.
In the flat position, the NFB circuit has only a resistance without the capacitor, so the frequency characteristic becomes flat.

The Sub control can be controlled independently of the Main control within ± 6 dB in 2 dB steps and 7 positions at 50 Hz for Bass and 20 kHz for Treble.
When used in combination with Main, approximately 6000 types of controls are possible.

Equipped with a tone defeat switch that flattens the frequency response by quick action regardless of the position of the main and sub control.

Like the equalizer amplifier, the control amplifier uses a first stage differential 3-stage direct-coupled circuit to which DC NFB can be multiplied by 100%.
The first stage differential amplifier uses a can-shield transistor with less noise variation over time, and uses highly reliable and carefully selected parts.

The Low filter operates at 30 Hz, Subsonic, and Off in three stages, while the High filter operates at 12 kHz, 8 kHz, and Off in three positions, each at 12dB/oct, and sharply cuts unwanted ultra-low sound vibrations and tape hissing without losing the playback sound.
In particular, the High filter is composed of L and C passive elements and has excellent transient characteristics, which tend to be problematic in high frequency bands.

Equipped with a level set mechanism that can expand the adjustment range of volume.
The set knob on the same axis as the main volume lowers the level to -15dB and -30dB. You can adjust the volume near the center (at an angle around 12 o' clock on the clock) even when listening at a low volume.
Because the relationship between the volume level and the rotation angle of the volume changes when the level set is switched, the range of motion of the Loudness contour also changes in conjunction.
At a level set knob of 0 dB, the loudness is active from the volume control Min to 40% (approximately 11 o' clock), at a point of -15dB, it is active up to 60% (approximately 1 o' clock), and at a point of -30dB, it is active over all rotations.

All stages of the power amplifier are directly connected with pure complimentary service OCL circuit system. In addition, two stages of differential amplifier and bias guarantee circuit are used to obtain stability.
The first stage differential amplifier is equipped with a can-shield transistor to prevent noise and other changes over time due to humidity.

The power circuit receives two constant-current load circuits.
This circuit suppresses changes in idle current due to fluctuations in power supply voltage, etc., eliminates transient crossover distortion, and provides playback sound with low distortion rate from high power to minute output.
By inserting a current amplifier circuit between the constant current load circuit, the operating points of the two differential amplifiers can be selected optimally, reducing noise and increasing gain. Therefore, a large amount of NFB can be stably applied, so that low distortion and high power can be obtained over a wide bandwidth.

Pure complimentary service pair transistors of driver and power stage are carefully selected PNP and NPN types with excellent characteristics.
In addition to using materials with high breaking strength, we also use a large radiator, current limiting circuit and electronic protective circuit to improve stability and reliability of operation.

Equipped with a full-scale protection circuit that combines relays and electronic circuits.
When the protection circuit operates, the protection lamp on the front panel lights up to indicate an error.
This protection circuit also functions as a power muting when the power is turned on, so that no shock noise is generated when the switch is turned on.

The power supply section uses a highly regulated power transformer and 15,000 μ Fx2 large-capacity power supply capacitor, and the driver stage uses a constant voltage power supply circuit to eliminate unstable elements caused by the power supply.

You can switch between three pairs of speakers (A, B and C), or two pairs of speakers (A + B and A + C) at the same time.
In addition, the B position has a level control that allows you to control the volume of only the speakers connected to the B position. You can also compare two sets of speakers with different efficiency at the same level.
Since the level control circuit is located before the power amplifier section, there is no change in the output impedance that drives the speaker system depending on the control.

Basic performance such as power, distortion factor and residual noise was measured for all units, and the data is attached to each unit.

Model Rating

Type	Stereo pre-main amplifier
Power Amplifier Unit
Circuit system	Pure complimentary service OCL directly connected to all 2-stage differentials
Effective power	20 Hz to 20000 Hz, both channel drive : 60W + 60W (8 Ω) 75W + 75W (4 Ω) 1 kHz, both channel drive : 65W + 65W (8 Ω) 85W + 85W (4 Ω) 1 kHz, single-channel drive : 75W/75W (8 Ω) 100W/100W (4 Ω)
Harmonic distortion factor	Effective power : 0.1% or less 1W output : 0.04% or less
Cross modulation distortion factor	Effective power : 0.1% or less 1W output : 0.04% or less
Output Bandwidth (IHF, both channel drives)	5 Hz ~ 40 kHz (Distortion Factor 0.1%)
Frequency characteristic	7 Hz to 80 kHz, + 0 -1dB
Input Sensitivity / Impedance	Power Amp In : 500mV/50k Ω
Output terminal	Speaker : A, B, C, A + B, A + C (4 Ω ~ 16 Ω) Head Phones : 4 Ω ~ 16 Ω
Damping factor (1 kHz, 8 Ω)	70 or more
S/N (IHF, short circuit A network)	95 dB or more
Residual noise (8 Ω, pre + power amplifier)	1 mV (0.13 μ W) or less
Subsonic filter	8Hz(12dB/oct)
Preamplifier Section
Circuit system	Equalizer amplifier : first stage differential 3-stage direct connection SEPPP NF-type Control Amplifier : First stage differential 3-stage direct connection NF type
Input Sensitivity / Impedance	Phono1 : 2.5mV/50k Ω Phono2 : 2.5 mV to 10mV/25k Ω, 50k Ω, 100k Ω Phono maximum allowable input (rms/p-p) : 250mV/700mV MIC : 2.0mV/50k Ω Tuner : 150mV/100k Ω AUX1 : 150mV/100k Ω AUX2 : 150 mv ~ 1.5V/50k Ω ~ 100k Ω Tape Monitor1, 2 : 150mV/100k Ω Tape Monitor2 (DIN) : 150mV/100k Ω
Output Level / Impedance	Tape Rec1, 2 : 150 mv Tape Rec2 (DIN) : 30mV/80k Ω Pre Out : 2V/8 Ω
Harmonic distortion factor (20 Hz to 20 kHz)	Not more than 0.03%
Frequency characteristic	Phono (RIAA deviation) : 30 Hz to 15 kHz, ± 0.2 dB MIC : 7 Hz to 10 kHz, + 0 -1dB Tuner, AUX, TapeMonitor : 7 hz to 70 khz, + 0 -1dB
Tone control	Bass Main : ± 10 dB (100 Hz) Sub : + / - 6 dB at 50 Hz Treble Main : ± 10 dB at 10 kHz Sub : ± 6 dB (20 kHz)
Filter	Subsonic:8Hz(12dB/oct) Low:30Hz(12dB/oct) High : 8 kHz, 12 kHz (12dB/oct.)
Loudness contour at volume -40dB	+10dB(100Hz)
S/N (IHF, short circuit A network)	Phono : 80 dB or more MIC : 70 dB or more Tuner, AUX, Tape Monitor : 90 dB or higher
Muting	-20dB
Level Set (3-Step Switching)	0 db, -15dB, -30dB
<General>
Semiconductor used	Transistor : 63 Diode and others : 30
Power supply voltage	100 VAC, 50Hz/60Hz
Rated power consumption	152W
Maximum Power Consumption	400W
Power outlet	Power switch interlock 1, non-interlock 2
External dimensions	Width 430x Height 138x Depth 341 mm
Weight	13.6kg