Harman Kardon refurbed A10 mono tube amplifier EL84 1

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LISTING IS FOR ONE HARMAN KARDON A10 ALLEGRO MONO TUBE AMPLIFIER, TWO TOTAL AVAILABLE. I've restored over 25 Harman Kardon amplifiers and sold many of them on EBay, 100% positive feedback. (Check my several restored HK tube amps I now have listed on EBay). This is a time capsule Harman Kardon refurbished tube type A10 integrated amplifier, called the Allegro, serial number 3241584. As this is a mono amp, two are required for stereo, (I have a second A10 listed). An alternative is to use a companion mono receiver (HK FA10) for the second channel, see next to last picture and also my EBay listing the for a FA10 receiver. I had a HK tube in college in the 1960's and always loved it's sound. I am a retired electrical engineer and have been restoring HK amps for a couple of years now as a hobby. Not any real money in it, but I enjoy making these amps reliable and available to a new generation of tube folks. I've learned all that I can about these amps and have been successful in their restoration. I never put power to these amps without first replacing the electrolytic and paper/ plastic coupling capacitors. It is strongly recommended (Google ‘recapping radios’) that the electrolytic and paper or molded (original disc mica type are OK) coupling capacitors be replaced in old tube units. Some people say it's OK just to 'reform' the power supply caps. (bring them up very slowly over a couple of days on a variac). While this is a much simpler and less costly alternative, I'm not convinced that it is a good as replacing dried out caps with new current fresh stock. After restoration I also verified the B+ voltages and critical components are to specification. This restoration does 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 the last picture, showing the replacement capacitors.In addition to replacing the electrolytic and coupling capacitors (using premium Orange Drop 716's 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 two output tubes are performance matched EL84's. In addition, I replaced the original frayed power cord with a new one. I have verified all the operations. The controls and switches have no noise. All the inputs are operational. I have run this unit 8 hours without any issues after the refurbishing. This amp dates from about 1958, and for it's age is in very good condition cosmetically. The faceplate has a few dings and one scratch by the volume control, see pictures. The case has been stripped and repainted, there is some unevenness in the metal, and some loss of lettering on the back--see pictures. The A10, as a tube unit has a sound unlike solid state units. These were (and are) highly regarded amplifiers, and have that highly desired ‘tube sound’. Interesting that HK is one of the very few hi-fi companies of the 1960's to still be in business. As a mono integrated amplifier, there are inputs for lo level (magnetic) phono or tape head, hi level (ceramic) phono, tuner /auxiliary input. The controls are: Source Selector, (Phono, Tape Head, Aux/tuner) Volume (with power switch), Bass and Treble. I will include a copy the Sam's Photofact service manual for this amp. The major specs are:IMHF music output power—10 watts—this was back when power ratings meant something. Works best with efficient speakers, I like Electrovoice 12TRXB's--a very nice horn type triax.Output impedance—8 and 16 ohm speaker output.Mono inputs—low level—RIAA (phono) and NARTB (tape head) equilizationsMono inputs—high level –Aux/tuner —this is suitable input for tuners, CD decks, and some MP3 p... read more

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