The Marantz 4400 is a classic quadraphonic 4 channel receiver into which Marantz pretty much threw everything they had. Offered from about 1974 until 1978, it pushed out 125 watts RMS per channel into 8 ohms in 2 channel mode and 50 watts per channel into 4 channels which was pretty powerful for a quad receiver. It did this with under 0.15% total harmonic distortion from 20 Hz to 20 KHz. A buyer could all this for the retail price of $1250.00.
Marantz also not only incorporated built in Dolby Noise Reduction into the 4400 but gave it six different controls.
Probably the most iconic aspect of the 4400 and some other Marantz receivers is the built in oscilloscope. The scope, located at the top left corner of the front of the receiver has 3 basic functions. First, it acts as a tuning meter and graphically represents channel separation. Second, you can see the signal source and third you can see the effect of antenna position in order to reduce distortion. The oscilloscope utilized a Hitachi 50TB31 tube for the display.
The new price was $1,350.00 in 1978!
Content from http://classicreceivers.com/marantz-4400