BOSE 4702

Commentary

A 4-channel pre-main amplifier developed to bring out the capabilities of Bose speakers such as 301 mm and 101 mm.

The 4702 has four independent power amplifiers.

The preamplifier circuit consists of two channels. Normal stereo signals are output from channels 1 and 3 on the L side and from channels 2 and 4 on the R side.

Equipped with a master control volume that controls the volume level of all channels.

The rear panel mode selector switches between 2, 3 and 4 channels, and the gain of each channel can be controlled individually.
For 3 channels, channels 1 through L signal, 2 through R signal, and channels 3 and 4 are BTL connected to output a monaural signal. The monaural signal passed through a low-pass filter that cuts frequencies above 90 Hz. You can add a subwoofer to create a 3D system.
For 2-channel operation, channels 1 and 3 and 2 and 4 are BTL connected and can be used as a high-power stereo amplifier.

The 4702 has a built-in equalizer that matches the characteristics of the 301 mm and 101 mm. You can use the selector to select one of the two positions to bring out the individual capabilities.
This equalizer circuit can be bypassed and used on other speakers.

The microphone input is provided in the Route 3 so that 3 microphones can be connected at the same time, and mixing is possible by the microphone volume.

Equipped with an announcement switch, the source input can be attenuated by 20 dB with one touch operation.

Effects of using a microphone It is equipped with an input jack for the source and a dedicated level control, and an echo device can be connected.

Model Rating

Type	Pre-main amplifier
Rated output	For 2 ch operation : 3 ch Operation : 4 ch Operation : 80W + 80W (8 Ω, 20 Hz to 20 kHz) 40W + 40W (8 Ω, 20 Hz to 20 kHz) 80W (8 Ω, 20 Hz to 100 Hz) 40Wx4 (8 Ω, 20 Hz ~ 20 kHz)
Output bandwidth	15 Hz to 50 kHz
Total harmonic distortion factor	0.03% (at rated output)
Cross modulation distortion factor	0.03%
Frequency characteristic	10 Hz to 40 kHz ± 1 dB
3-channel low-pass filter characteristics	-3dB (12dB/oct) from 125 Hz
Phono RIAA deviation	20 Hz to 20 kHz ± 0.3 dB
Input Sensitivity / Impedance	Phono MM : 2.5mV/47k Ω Phono MC : 0.25mV/100 Ω Tuner, CD, Aux, Tape : 150mV/47k Ω Mic : 0.75mV/2k Ω
S/N (IHF-A at rated output)	Phono MM:85dB Phono MC:75dB Tuner, CD, Aux, Tape : 95 dB
Tone control characteristics	Bass : ± 10 dB (100 Hz) Treble : ± 10 dB (10 kHz)
Loudness property	+6dB(100Hz) +4dB(10kHz)
Pwer	100 VAC, 50Hz/60Hz
Rated power consumption (Electrical Appliance and Material Control Law)	175W
External dimensions	Width 474x Height 150x Depth 370 mm
Weight	14kg