Krell KSA 100mkII Clone

[awpagan]

Originally posted by jacco vermeulen


btw: i've heard both the kSA50 and the KSA100 on proper loudspeakers.
The KSA100MKII may have been better on Apogee's, i've never understood the charm of those metal washboards.

or very big cheese graters
"family size"
or morgue table

allan

[Flodstroem]

Mark:

As for the PCB if we make up a MK-2 board straight over it would be easily reverse-adaptable to building any of the earlier KSA-100 circuits. Neither myself, Al, or my friend Dave have time to adapt or figure out a universal pcb to accomodate all the versions. I am only willing to foot the bill to have 100 boards made up. Its easy to envision that the Mk-2 board straight over can be very adaptable in itself just by jumpering out certain devices and changing some part values to building the earlier versions of the amp. Hopefully those that are going that route would take the time to share that in a future chart with all of us. However it should be up to each individual building the amp to figure out for him self..... Otherwise this PCB deisgn might go on for two years! So in simple terms the universal board would already exist in the from of the MK-2 board!!

Yes, to me it sounds like a good idea to make a MK-2 board with only minor changes due to the component substitutions and output board connections etc. Then the boards could be made in a relative decent time period and also to an acceptable fair price, dont you think?

Im in for 6 boards of the KSA100 MK-2.

Regards

[Mark A. Gulbrandsen]

It seems the logical way to go to me Flodstroem. The Mk-2 board is certainly able to please all others merely by jumpering out components and changing other parts values.

Mark

[Upupa Epops]

Andrew, if exist something like recomendation about impedance of speaker and somebody wittingly ignore it, how do you can term it ?
Mark : Some more, some less....Krell markedly...

[Mark A. Gulbrandsen]

Here are a couple of photos of the inside of the KMA-100. It appears that the power supply regulator and the main board aare stacked together on one side and the power supply also looks a tad larger.

Mark

[Mark A. Gulbrandsen]

Another vuew of the power supply regulator board and main caps.

[Flodstroem]

Hi Mark

Any idea for what reason Krell used a power supply regulator ?
Was its purpose to rise the efficiency of the output stage
(this could be done by having a 5-10V higher rails on the input/driver stage)
Or was the purpose to lowering power supply ripple noise/buzzing?
Maybe both.

A long time ago I built a Pass 40W Class-A and implemented a solution similar like the Krells (I think but Im not sure about that). I think I used a regulator for ± 7-8 volt higher/lower than for the power devices who was darlingtons).
The benefit for doing it for me was lowering power supply noise AND a rise in power output capability, thus rising the efficiency of the amp (also: rising the total audio quality )

Wandering if this implementation should be located together on the amps driver board ?
It could be done though its not a high power circuit. Or is it impractical?
(benefit: you only need to make one board, not two. drawback: a more complex board/circuit)

What do you think?

Regards

[BillWW]

Originally posted by Mark A. Gulbrandsen


So that being said all that need be changed are those devices over to the Zetex unless anyone knows of a better device (I had originally thought of IRF9610 and 610 but the Zetex's spec better).


Mark

I have been experimenting with jfets on my Aleph 3 and found those are much more musical than the zvp3310a.

I am using the j176 jfet and do not know its complimentary version, but there are a whole range of mA versions for more or less driver power. It seems to be more spacious and much more extended in the highs with less distortion.

I have compared the j176 to the zvp3310a and found the zvp3310a is still very nice sounding, but not quite as sweet.

Since, we are designing a new board, I think this would be a good time to check on jfets. They do make a great big improvement on my Aleph 3.

Mark, when your ready, I could bring my Aleph 3 over to let you compare the zvp3310a in your mini Aleph vs the j176 in my Aleph 3, so you can decide what you like.

Regards, Bill

[dung0981]

I am in for 4 set MKII
Thanks

[AndrewT]

Hi Mark,
do you still have that KMA? to take measurements and read off the psu data (+-80mF?)