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Item location: Italy | Ships to: Worldwide
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This is a very nice Harman Kardon A30K amplifier, serial number 6041830. The 30K is the kit version of the A300 amplifier. Electrically the 30K and 300 are identical. I never put power to these amps without first replacing the electrolytic and coupling capacitors and diodes. It is strongly recommended (Google ‘recapping radios’) that the electrolytic and coupling capacitors be replaced in old tube units. For the A300 there are a total of seven electrolytic capacitor sections in the power supply and a total of eight coupling capacitors to be replaced, which I have done. After restoration I also verified the B+ voltages and critical components are to specification. I also replace the rectifying diodes with more modern units that have fast turnoff/soft recovery, characteristics that provide a little less noise– makes for a cleaner power supply. No change in the sound of the amp, only just a cleaner power supply.
These restorations do not modify the wonderful ‘tube sound’–no real modifications, but rather put back the way the HK engineers designed it, only make the unit safer and more reliable. See pictures, showing new components and before and after chassis refurb. (bottom cover removed for picture).
In addition to replacing the electrolytic and coupling capacitors, using premium 716 Series Sprague Orange Drops for the coupling capacitors, I have tested all the tubes on my B&K 707 tube tester—and replaced any that were marginal. I also have cleaned the tubes, tube sockets, controls and switches (Deoxit D5 contact cleaner for the tube sockets and switches, F5 Fader Lube for the potentiometers). The output tubes are performance matched Sylvania 7408’s with identical date codes of 1962, 26th week. The 7408 is a more rugged version of the 6V6, which are highly prized in tube amplifiers. For tube rollers, the 6V6 is a direct replacement for the 7408.
I have verified all the operations. The controls and switches all function as designed. All the inputs are operational. I have run this unit 8 hours without any issues after the refurbishing. This unit has a very nice appearance, the faceplate is excellent for it’s age, the issue is a scratch on the upper LH corner, see pic. The vertical lines on the faceplate are from the lighting. This is one of the best A30K’s that I’ve had. The knobs also are in very good condition. Chassis has a few stains, chassis lettering is sharp and legible–see pictures. As a stereo integrated amplifier, there are inputs for lo level (magnetic) phono or tape head, hi level (ceramic) phono, tuner and auxiliary inputs. The controls are: Source Selector, Loudness (Volume), Bass, Treble, Balance, and Blend. Switches are provided for power, rumble filter, contour, equalization and stereo reverse