Zen Mod said:
More/better pictures.
There are only 4 MOx power resisors between the heatsinks.
The SCG devices are not mounted on both sides of the heatsinks, like regulator devices in some of Krell's pre-amp models.
Between the capacitor bank and the heatsinks : a parallel TO92 VAS pair, a silvermica cap, again a pair of TO92 drivers in parallel.
There's no bipolar cap visible for DC-blocking in the NFB path, no DIP8 opamp.
There are too many small signal devices in the front end for the TO-5 to be the input stage, a metal can LF411 is the first to come to mind.
That also explains the small green foil cap adjacent to the TO-5 critter.
No zeners visible in the front end, the device count suggests a front end a la KSA with all-bjt semi shunt voltage regulators and CCS's.
Complementary differential input + parallel VAS pair + parallel driver pair=> 300i
Could be the reason why the KSA-5 doesn't live up to expection, as the very first real sota Class A SS headphone amp you'd expect it to be a benchmark.
Sounds pretty good through a high efficiency large loudspeaker system. heard the KSA-5V on bigga bucka Alfred Rudolph horns.
oh man.... nothing probaly out of this one....oh well, back to my drawing board.....😕 simulator 🙂
Jacco,could you elaborate more about Krell all bjt semi-shunt regulators and CCS. Any schematic?
Zen Mod,I am interested in older high end solid state preamps and power supply topologies and how to incorporate good designs ideas in my own projects. Also, i like to compare them to more modern approaches.BTW term "semi shunt" is unknown to me.
kamis said:
well , maybe I'm not so well informed , but I can't see much differences between modern and old good preamps ;
differences in topology between various manufacturer are obvious, but I can't place them in time frame ;
anyway - that's not really issue 😉
like you - I'm always interested to see new (to me ) schematic ; I resume that's more passion than anything else .
"semi shunt" ......... Jacco is always playin' with words ............ dunno what is that......
most interesting shunt reg I saw lately on DiyA is certainly reg for driver stage in this thread
hehe
, not counting Shunty ........ from obvious reasons - it is fave to me 
Zen Mod said:
Correctomundo.
A common use for a zener diode is as shunt voltage regulator, exchange the zener by a bjt circuit and you have a semi-shunt.
As in semi-conductor, not pseudo. (Krill is boring, word and mind games are not)
Seems that Mihai joined the exotic nfb number club.
Ksa 5
I am out of the office but will post in the next day or two.
FYI the To-5 is a dual FET and the op-27 is used as a servo.
This is from about 1991 - 1994. It was done by Todd Eichenbaum if I guess correctly. He is now head of engineering at Krell. A fine engineer and a helluva a nice guy.
I reverse engineered it off of a unit I repaired. Cat hair and pee will screw up a servos operation.
I am out of the office but will post in the next day or two.
FYI the To-5 is a dual FET and the op-27 is used as a servo.
This is from about 1991 - 1994. It was done by Todd Eichenbaum if I guess correctly. He is now head of engineering at Krell. A fine engineer and a helluva a nice guy.
I reverse engineered it off of a unit I repaired. Cat hair and pee will screw up a servos operation.
KSA 5 Schematic
Here is the schematic. This is most of it. Not shown is bias or servo circuit.
Power supply is an R core in an external box OP27 a reference and pass transistors. + - 22 Volts
Here is the schematic. This is most of it. Not shown is bias or servo circuit.
Power supply is an R core in an external box OP27 a reference and pass transistors. + - 22 Volts
Thank you for you effort, but CCS for input differential is missing as well as type of output transistors. I guess a DC servo circuit would be of interest for many of us, if it's not plane-Jane-insert-current-at-inverting-input.😉
I see the pair of CCS for the inputs (which are followers) as
well as the numbers of the output devices.
😎