From the Rain City Audio Repair Blog:
The first Bose® 402E Active Equalizer, for the Panaray speaker system, just came through the Rain City Audio repair bench. It’s a small speaker array system, designed around similar drivers in the 901, and uses an Active Equalizer for the same effect. They’re designed for a limited frequency response, 90 Hz – 16 kHz, up to 120W at 8 Ohms.
It’s a small box with two channels of 1/4″ TRS. There are no adjustments. Inside, there’s a power supply similar to that found on a Series III or IV, three op-amp chips, and a handful of electrolytic capacitors. This unit was noisy and had uneven volume when it came to the bench, and those should components should have it good as new again.
The board was produced in early 1985 in Atlanta, apparently.
It was time for some tests. It sounded pretty good, but how was it performing? I ran a frequency response sweep on the Audio Precision System One:
Both channels perfectly matched, in an interesting saddle curve rolling off sharply at 100 Hz down past -30 dB at 20 Hz, and a healthy boost to the high end. Comparing with the service manual,
Identical. This 402E Active Equalizer is performing perfectly and should work great for years to come.
RETROVOLTAGE 
hello,
thanks for the content
what did you replace exactly in your 402e ?
I have the same and it’s noisy, if I remove the 402e from my amp the noise stops, making me think about some capacitors are in a bad state…
thanks for the help
Arnaud
I need to buy a Bose 402 Controller
Not clear Are you selling these?
No.
OK thanks
How do you patch-in the unit? i have a Makie 12VLC mixer and a QSC 2406 Amp and two 402 BOSE speakers.
I’m not sure. You’d probably have better luck consulting the manual for the mixer for the best connection method for that one.