SANSUI QA-7000

Commentary

A 4-channel pre-main amplifier with a new QS synthesizer.

The QS regular matrix method is adopted for the synthesizer and decoder section.
This system consists of a 90 ° phase-shifter with a square matrix as the reference, and the signal is transmitted through a QS Barrio matrix at the time of playback to improve acoustic separation and musical performance.
In addition, the newly developed 2-4 conversion encoder circuit can convert conventional 2-channel sources into 4-channel sources.

It is equipped with a 90 degree phase shifter developed by SANSUI.
In the conventional matrix method, the phase relationship between the two rear speakers is said to be opposite to each other, resulting in poor sound connection. To solve this problem, a 90-degree phase shifter shifts the phase of the decoder side by -90 degrees from the left rear and by + 90 degrees from the right rear to the positive phase.
This improves the orientation of the sound image in all directions.

Equipped with QS Barrio matrix circuit.
This circuit is an application of the directional masking phenomenon. It changes the matrix coefficient at every moment, controls the matrix to clarify the directivity of the main signal at that moment, and improves the separation between each channel.
Theoretically, the Barrio matrix circuit can obtain infinite channel separation if the control level of the matrix coefficient is selected. In QA-7000, the separation is set to the most audible value for music playback.

It features a new QS synthesizer and an improved 2-4 conversion encoder circuit that performs special processing when playing back a 2-channel source and enables 4-channel conversion in the subsequent QS Barrio matrix circuit.

It is equipped with a phase matrix function and supports 4-channel sources created by the SQ method.
You can also play 4-channel discrete sources.

The equalizer amplifier section uses a 3-stage direct connection circuit of PNP-NPN-PNP configuration.
In addition, excellent RIAA deviation is secured by adopting resistors and capacitors with less error as feedback elements.

The tone control amplifier section has a 4-chip configuration with a 2-stage direct-coupled circuit using PNP-NPN transistor in the front stage, ensuring a large dynamic range and stability even when tone control is boosted.
A 4-channel volume is installed in the latter stage, and S/N is improved by using the volume where the signal is large.

An emitter-follower circuit is used for the output stage of the preamplifier section, and the output impedance is designed to be low.
The pop noise generated during power ON/OFF is removed by a transient canceler using a relay.

A constant voltage power supply circuit using five transistors and a zener diode is used for the power supply of the preamplifier section.

All stages are directly connected OCL pure complimentary service circuit of ± 2 power supply configuration using a differential amplifier for the power amplifier section.

The power supply section is equipped with a large power transformer and 10,000 μ Fx2 capacitor.

The 4-channel main amplifier can be used as a 2-channel high-power amplifier via the BTL connection.

It is equipped with an electronic protection circuit using a relay circuit and a short-cut fuse to protect the amplifier and speaker from accidental application of DC voltage. This circuit also serves as muting and eliminates pop noise.

Equipped with independent tone control for front and rear respectively.
In addition, it is equipped with functions such as balance control and loudness control which affect the whole front and rear, and the left and right independently.

Equipped with 4-channel headphone jack.

Equipped with a large level meter and level set knob to adjust the overall input level.

Equipped with a 4-channel tape recording function, a 2-channel source can be converted into four signals using the new QS synthesizer and recorded as four channels.

Model Rating

4-channel pre-main amplifier
Effective power	12W + 12W + 12W + 12W + 12W (8 ohm, 4-channel operation, 20 hz to 20 khz) 15W + 15W + 15W + 15W + 15W (8 Ω, 4 ch operation, 1 khz) 40W + 40W (8 ω, 2 ch operation, BTL connection, 1 khz) 20W/20W/20W/20W / 20 w (8 Ω, 1 ch operation, 1 khz) 50W/50W (8 ω, 1 ch operation, BTL connection, 1 kHz)
Music Power (IHF)	108W (4 Ω, 1 kHz)
Total harmonic distortion factor (rated output)	Not more than 0.1% 0.3% or Less (BTL Connected)
Cross modulation distortion factor (rated output)	0.15% or Less (70 Hz : 7 kHz = 4 : 1, SMPTE)
Power Band With (IHF)	10 Hz to 30 kHz
Frequency characteristic	10 Hz ~ 50 kHz ± 1 dB (at 1W output, main amplifier)
RIAA deviation	Phono1/2 : 30 Hz to 15 kHz ± 0.5 dB
Damping factor	100 (8 Ω)
Input Sensitivity / Impedance (1 kHz)	Phono1/2 : 2.5mV/50k Ω 2 ch Tape mon (Pin, Din) : 100mV/50k Ω 4 ch Tape mon, Tuner, Aux : 100mV/50k Ω Main in : 800mV/50k Ω
Phono maximum allowable input	270 mV (THD 0.5% or less)
Output Level / Impedance	2 ch Tape rec (Pin) : 100mV/2k Ω 2 ch Tape rec (Din) : 30mV/65k Ω Pre out : 800mV/600 Ω (Maximum output 6.5 v, THD 0.5% or less)
Hum and noise (IHF)	Phono1/2 : 70 dB or more 4 ch Tuner, 4 ch Aux1/2 : 80 dB or more Main amp : 90 dB or higher
Tone control	Bass : ± 15 dB (50 Hz) Treble : ± 15 dB (15 kHz)
Loudness (Volume -30dB)	+ 8 dB at 50 Hz, + 3 dB at 10 kHz
Synthesizer / decoder	Sansui QS Regular Matrix Method Built-in QS Barrio matrix circuit
Semiconductor used	Transistor : 97 FET : 2 Diode : 64 units
Rated power consumption	115W 340 VA (max)
External dimensions	Width 440x Height 140x Depth 322 mm
Weight	14kg