Well, not an amplifer but still places itself in the solidstate category.
Read about this and obviosly this is a classical issue, EQ section sound really bad, constant hum (50hz) and hiss on high volume. if bypassed with bypass switch it actually sounds pretty nice.
Now.... this is an early model whitout any mods, and! i also read about HK being very productive in this era, solving problems etc etc.
So maybe there is some awesome! HK fanatic lurking in theese forums sitting on the answer how to overcome this issue the correct, or "the HK way" since the later models seems to have a totally different pcb layout and so on.
i have measured every elytic capacitator in the unit, the PS board and the big 1000uf caps really measue good but still old, for the rest they have been changed to better ones (some had esr over 10ohms), the goal is to solve the hum problem and then recap with proper hq caps everywhere.
Have a nice day, and thanks in advance! //Jonas
Read about this and obviosly this is a classical issue, EQ section sound really bad, constant hum (50hz) and hiss on high volume. if bypassed with bypass switch it actually sounds pretty nice.
Now.... this is an early model whitout any mods, and! i also read about HK being very productive in this era, solving problems etc etc.
So maybe there is some awesome! HK fanatic lurking in theese forums sitting on the answer how to overcome this issue the correct, or "the HK way" since the later models seems to have a totally different pcb layout and so on.
i have measured every elytic capacitator in the unit, the PS board and the big 1000uf caps really measue good but still old, for the rest they have been changed to better ones (some had esr over 10ohms), the goal is to solve the hum problem and then recap with proper hq caps everywhere.
Have a nice day, and thanks in advance! //Jonas
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Hum and hiss are two different symptoms.
Unless you follow the preamp with a power amp of Too Much Gain. So tell about that.
Have you read the several Service Bulletins? (I don't think you can download them all in one day, space it out.)
https://www.hifiengine.com/manual_library/harman-kardon/citation-11.shtml
It seems a remarkably cheap circuit (5-band EQ on ONE transistor?) in a very very nice case. Am I wrong?
Unless you follow the preamp with a power amp of Too Much Gain. So tell about that.
Have you read the several Service Bulletins? (I don't think you can download them all in one day, space it out.)
https://www.hifiengine.com/manual_library/harman-kardon/citation-11.shtml
It seems a remarkably cheap circuit (5-band EQ on ONE transistor?) in a very very nice case. Am I wrong?
Yes, hum and hiss is two different symptoms.
The hiss isnt thay much of a problem, gain related as you say. The hum is most probably ground related, thats why hoped that someone already dug into this.
Yes, i have seen them avalible there, but arent able to download them since they dont allow registration from my isp (sweden).
Yes, it is very cheap, build quality and case is awesome! there is multiple versions of theese and they get more components along with that and probably many many production adjustments not documented. This would be the very first version, early 1970 i think.
The hiss isnt thay much of a problem, gain related as you say. The hum is most probably ground related, thats why hoped that someone already dug into this.
Yes, i have seen them avalible there, but arent able to download them since they dont allow registration from my isp (sweden).
Yes, it is very cheap, build quality and case is awesome! there is multiple versions of theese and they get more components along with that and probably many many production adjustments not documented. This would be the very first version, early 1970 i think.
You have at least 2 carbon comp resistors over 100kohms, a brown green yellow and a yellow violet yellow. Both will have a lot of thermal noise & you could easily replace them with 1/4 watt or bigger metal film resistors which are much quieter. I didn't need double blind testing to hear the hiss improvement in my dynaco ST70 when I replaced the 220 k ohm resistors. You might also buy the orange band metal film resistors as opposed to the old carbon comps, although the improvement will not be nearly as drastic as yellow band. I've had good luck with vishay, international, multicomp(farnell) welwyn metal film resistors.
Almost any 2020 transistor from On or ST could be quieter than an average 1970 transistor, but those gate drain source transistors would take a lot of thought to replace. There was dmos from Signetics & PMI in those big round packages and I don't know if nmos or pmos fets can replace that. Modern fab areas are squeaky clean, and 1978 fab areas were not.
Almost any 2020 transistor from On or ST could be quieter than an average 1970 transistor, but those gate drain source transistors would take a lot of thought to replace. There was dmos from Signetics & PMI in those big round packages and I don't know if nmos or pmos fets can replace that. Modern fab areas are squeaky clean, and 1978 fab areas were not.