Harman Kardon Citation 12 input amplifier

Harman Kardon revised Citation 12 input to use two 43027722 transistors. Original circuit used 8K2 tail resistor for original 43024217 dual transistor, but revised circuit used 12K tail resistor to reduce current trough new input devices.

Does anybody know if 12K resistor was used for get better linearity from new devices, or is it true that this 12K tail resistor with original dual transistor will reduce turn off thump and also DC offset, as it has been suggested?

Best Regards


80mV L ch offset
140mV R ch offset¨
That is a bit more offset than I would like to see. 30mV is a better number. Before playing with the input, check the power supply rails. I have seen the main filter capacitors fail in Citation 12s. (I have also seen failures in the white molded Mallory capacitors.)

As this is one of the best designed amplifiers ever made, I wouldn't change values. There are of course better amplifiers, but a great deal of that is due to better parts coming along.

Do you have the dual transistor version?

The only really useful service tweak is to use some high grade conductive plastic lubricant on the open carbon film bias trim pot. (Caig etc. make these chemicals.)
Citation 12 caps

My Citation is made in 1971 and is earlier dual transistor version.

Main reservoirs seems to be OK. I am planning to replace them anyway when I find suitable replacements, 1 3/4 x 3 5/8 case seems quite hard to find. I replaced other electrolytics on PCB and also bias pots, as bias adjustment didn´t work on one channel. However, dirt on PCB connectors was most likely reason for this.

I measured all resistors on the PCB and they seems to be within 3% target values. Horror stories about off spec carbon comp resistors seems not to be true.

My other mostly tube gear is performing considerably better. Even then this amp seems to quite nice when properly adjusted and considering early solid state design.

Best Regards

The trick to replacing the power supply capacitors is to carefully open the cans for the old ones and remove the guts. Then you can place new ones inside the cans and keep the look of the amplifier.

The resistors are film not carbon composition on the units I have seen.

It is a solid state amplifier. What was new was the circuit topology and the use of linear beta transistors. What is outstanding is the use of rubber insulated dual power transformers, grounding scheme, high quality parts throughout and very nice heatsinking.

What is dated is the geometric circuit card and connectors. It is a 40 year old design. Tube amplifiers of the era and earlier rarely used such high quality layout or parts.
Carbon comp resistors

They have probably used carbon comps first. Service manual specifies 10% carbon comp 0,5W resistors, even for 12K tail resistor for revised input amplifier. Maybe they did upgrade resistors to carbon films later.

This seems quite odd as Quad 22 did use carbon film resistors in critical positions in 1959. As far as I remember, there were 2-6 positions considered to be critical. Both amps were quite expensive when they were introduced.

Best Regards

Citation 12 rebuild

I have now replaced original input RCA connectors to better quality ones. Originals were not too good design originally, with 40 years oxidation they were clearly out of order. I did no see no reason to replace speaker terminals, as they have not oxidized too much and they are pretty good design even today.

I replaced C705 and C706 with Nichon Muse electrolytics. For input coupling caps I used axial Vishay polar electrolytics intented for coupling duties. For other PCB locations I used ordinary power supply electrolytics.

Amplifier performs now pretty well, even highs are a bit edgy and there is not too much depth in soundstage. When I upgraded input RCA:s and C705/706 and input caps from ordinary power supply electrolytics, I had used first time, to audio types, it was odd to note that wooly LF improved considerably but HF reproduction remained roughly same.

Main reservoirs are still original ones. They have not leaked, but I suppose ESR must be off spec after 40 years use or age. Authority of LF is not too good on considerable LF transients... Or is it too much to expect this from 60W amp?

Best Regards

Remember this is the grandfather of most modern solid state amplifiers. I would go after the power supply capacitors. Just for a listen you might temporarily put in one that are case size too small. If you like it then you can decide if you want to hollow out the originals to keep the look.
Citation 12

LF performance of 12 is nice and detailed, but lacking authority when driven hard. LF is actually very close to my ARC CL60 tube amp. Maybe not so datailed and tight... but very close anyway.

I was only wondering where the current limiting of output devices has been figured. ATC 100 speakers I used, are reflex loaded and impedance minimum can cause clipping. Power transformers have also been figured for continious 8 ohm opereration.

I have found correct dia CDE 13000uf/63V caps from Mouser. I will order these soon, but they will not help if the outputstage is limiting current.

Best Regards

CDE caps worked without any trouble. They look nice as they fill the original holes and sound quality also improved considerably. Citation 12 is now quite smooth sounding amp, hf-reproduction is a bit one dimensional and not too smooth compared to midband. LF is a bit round like vintage tube amp. I like it very much... maybe I should sort this DC-offset some time, but actually only time when there has been any harm with DC-offset was when it saturated cores of my Audio Technica AT-706 electret headphone transformers and they sounded like crap due core saturation.

Harman Kardon Citation 12 cap replacement

I have a 12 and a 16 and want to replace the main caps they are original
on the 16 i can understand how to remove the screws on the caps
on the 12 there is a screw on the 12 but its a strange connector
cant find anything on the web discussion how to remove. Do i need to desolder?
also testing them connected (dont think im supposed to do this way)
all caps measure 8764 7697 7571 8400 uf for a 6K cap
vloss shows 1.6 1.6 2.2
ESR .18 .17 .20
any help appreciated
Citation 12 6000uf cap replacement

This is a very stupid question but how do i remove the wires from the caps
they look like screw on caps but there does not seem to be anyway to remove these other than desoldering
I also have a citation 16 and the caps have screws on the bottom and were very easy

Any suggestions?
I took a look at the one I have here, I see what you mean. Those are the oddest fasteners ever. Regardless, those are still standard threaded connections on top of the capacitors.
I was able to wiggle one of the ring terminals from side to side, so I'm betting that weird fastener is actually a faceless screw that sits inside teeth in the ring connector, and the whole thing is meant to be spun tight as a unit and then held in place by wire tension. I think perhaps the best thing to do is desolder a single terminal and see if you can spin the lug counter-clockwise once its free of the heavy gauge wire connected to it.