Harman Kardon Citation 12 Stereo Power Amplifier

Citation 12 Power Amplifier

About the Citation 12

The Citation 12 was Harman Kardon's first big transistorized power amplifier. It was rated at 60 Watts per channel. It was based on a design published in the RCA Solid State Handbook. It's a relatively modern design in that it has a differential input stage. Many other things are a bit old-fashioned, like a boot-strap capacitor rather than a current source in the voltage gain stage. This was common practice in an age when transistors were still relatively expensive. The output stage used two NPN transistors, a quasi-complementary output stage.

It used separate power transformers, bridge rectifiers, and filter caps for the left and right channel. As such it was a dual-mono design. This also helped maintain the output power as the two transformers can typically offer better regulation than a single transformer.

There are big heatsinks, a thermal cut-out on each heat-sink, and a fuse for each power supply. There is no DC fault protection, so a big fault in the output stage might put up to plus or minus 41.5 volts right onto the loudspeaker. I don't think this happened often, as the Citation 12 doesn't have a reputation as a speaker killer.

Technical Information and Other Interesting Stuff

I was able to buy an original Technical Manual on Ebay. I've included a

Looking at the schematic, it refers to a number of long obsolete RCA transistors. I found copies of the old RCA transistor manuals, and have excerpted the RCA transistors.

The Citation 12 was based on an RCA design found in their semiconductor data books.

The amplifier circuit board plugs into a socket. It's retained in place by 4 screws and two plastic brackets. Both amplifier channels are on one long circuit board.


Equivalent Replacement Transistors

under construction

Improved Replacement Transistors

under construction

Upgraded Amplifier Design

The Citation 12 is a nice platform for improvements. We could probably drop in a modern amplifier design, and improve the distortion and signal to noise ratio. under construction

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