Differences in the revisions of HK Citation 16?

When I got back into audio a few yrs ago, I foolishly bought a Citation 16 and ended up sticking it the closet after I bought an upgraded modified one (dah!) which was always a thorn in my side with its fuzzy definition. I finally sold it lately and pulled out the original to sell as well. It still worked!

The last time I listened to it my only source was an HK DVD 25 the sound quality of which would be indistinguishable from a cow. Now I had a spare vintage HK HD7600--granted agey but was very high quality--and my Morrison ELAD line stage. I connected the amp to my vintage AR91's, a bear to drive which will make a lot of amps sound pretty sick.

It sounds not bad at all. It sounds a lot better than the upgraded modified one that I sold. I googled it and got that the original 16 like mine had only 10k input impedence, so oh yeah I forgot to plug in the Rothwell attentuators which I usually do with vintage hk since input impedence is usually 22k. The Rothwells really cleaned up the high end. Now I'm impressed and excited. I haven't even cleaned it up yet. Don't even know if its caps are leaking their insides.

My info was that the original 16 was capacitor coupled and that the A and S were direct coupled. Now I read that the original has an IC on the driver board and the A does not.
Does anyone know if the A and S sound better than the original? And what is the connection between an IC and coupling? And now I read that there was an AS version as well. Any tidbits or an entire expose' would be very interesting to me.

First off, given the age of the amp you may wish to replace the filter caps in the amp. Allowing an amp to sit for years is not good for the electrolytic caps. Regarding the IC based unit; it is possible that the IC based input circuit is still capacitor coupled. It would be interesting to see if there may be a new IC that may sound better and run quieter then the one in there. I would suggest installing an IC socket in that case. Interesting that it would use an IC as the Citation 12, the amp designed before the 16, had a discrete input that utilized a bipolar differential circuit. I believe that was the first amp to use that circuit topology. If I'm not mistaken it was designed by Matti Otala. It also was one of the first solid state wide bandwidth amplifiers ever designed.
OK. Thanks for clarifying the IC in regard to cap coupling. I read in the search that the A revision "went back to" all discrete which must be a reference to the 12. I have it apart and am cleaning. Can't see any leaky caps. Two smaller caps were blackened. Couldn't tell why or understand why. They wiped clean.
I believe Nelson Pass designed the 12, and I don't know who gets credit for the 16. Matti Otala designed the XX in 1981, the almost mythical (expensive) amp that almost no one has ever seen or heard. The hk775 mono amps were the commercially priced version of the XX. I have a pair of those. Also need work.
Thanks. Good to know about the filter caps.
I did see and XX when it was new at my local audio store when I was in middle school and it was a very pretty looking amp. Edge lit glass in the faceplate. It was a true show piece. It also had some kind of laser trimmed device in it as well as gold plated circuit boards. I'm guessing it was a very wide bandwidth amplifier and therefore used a ground plane circuit board a la Spectral. Sonically, I believe it was unremarkable.
Wow! I have pictures, and I remember reading about a prototype and a lazer. So that solves the mystery (to me) about the lazer. I think the reason for its sonic reputation is that one of the magazines--was there a Stereo Times ?--did a blind listening test of the most expensive amps or top amps and it won. It was Sidney Harman's comeback after he sold the company to be Sec of Commerce under Carter to Beatrice Foods who ran it into the ground and then Sidney bought it back.
It probably was a wide bandwith. The 775 monos were less than a cycle to 300k. Otala had written a paper on current demands in loudspeakers, and I think high current was his biggest contribution.