Krell KSA 100mkII Clone

[Mark A. Gulbrandsen]

It's tempting to adapt the input stage of the KMA, just so we have a balanced option.

Al,

Actually neither the KSA-100 nor the KMA 100 had a balanced input stage at all but they did somehow eliminate ALL capacitors from the signal path probably including the caps in the feedback path. The write up at Krell History about the KMA-100 says.......

"KMA-100 and KMA-200 mono amplifiers introduce DC coupling from input to output, eliminating capacitors from the signal path. They also contain fully regulated power supplies for the front-end voltage gain stages and sophisticated protection circuitry for the output amplifiers. These innovations, coupled with massive power supplies, enable Krell amplifiers to drive any speakers."

The KSA-80 not only had a balanced input but was fully balanced differential from input to output.

" With the KSA-80 and KSA-200 amplifiers, Krell introduced fully balanced amplifier design, which maintains balanced operation from input to output."

I believe the KSA-80 would be pretty difficult to build and it would require alot of device matching......although the gerbers for a board design does already exist here .


Adapting the balanced part alone from the KSA-80 would be very difficult, adapting a balanced inoput to the KSA-100 MK-2 might be possible but is not true to the original. Anyway I doubt that many of us would be using a balanced input were it to be added....

Really, we should keep to the original design anyway if this is really going to be a klone just with the exceptions of adding more bypass caps as you did for the KSA-50... that can never hurt to have!

Mark

[jacco vermeulen]

Do a fully biased KMA160 with vents.

[AndrewT]

Hi,
the KMA160 shows 3pair repeated as the output stage.
Is it repeated twice making 6pair or is it quads making 12pair for each channel? The pics seem to show 6BJTs on each sink and 4 sinks in total coming to just 6pair per channel.

In Krell's KSA80 & 200, KMA 160 & 400 manual it shows 325mV bias for all models. This equates to 0.975A per 3pair.

So what is the Iq? 1.95A or 3.9A? 1.9A gives ClassA =60W, 3.9A gives ClassA=240W

Is the KSA100mk2 a 4 pair output stage? Re=1r0? Bias voltage =325mV? or 575mV? Iq=1.3A or 2.3A? This gives 27W or 84W of ClassA.

Are we getting closer to some design numbers?

[Mark A. Gulbrandsen]

The KSA-100 MK-2 is a 4 pair O.P. stage. The KSA-80 is 6 pair per channel. The LMA 160 is 12 pairs that are driven from one main board. JWB's KMA 160 thread was all about building extra main boards to convert his KMA 160 monoblocks into KSA-80 stereo amps. Both share the same chassis, same power supply, same heat sinks.


Mark

[jacco vermeulen]

To make it more complicated, the KSA-80B was a KSA-100 overhere. Confusing ? Of course not.

[Upupa Epops]

Try to think economically, guys... and make this model like washdryer.... your wives will bless you....

[darkfenriz]

Class A washdryer ?

[Mark A. Gulbrandsen]

To make it more complicated, the KSA-80B was a KSA-100 overhere. Confusing ? Of course not.

Probably a mixup with the language barrier. All of the Krell's that I have seen for sale in Europe are exactly the same as over here in the states excepting the 220 volt primary.

Class A washdryer ?

My Dryer runs on natural gas... how do we make a Krell to do that?

Mark

[Upupa Epops]

Relationship between " power to speaker " vs producing heat is by normal listening levels app. 1:100, so why not...

[Flodstroem]

Adapting the balanced part alone from the KSA-80 would be very difficult, adapting a balanced inoput to the KSA-100 MK-2 might be possible but is not true to the original. Anyway I doubt that many of us would be using a balanced input were it to be added....

Really, we should keep to the original design anyway if this is really going to be a klone just with the exceptions of adding more bypass caps as you did for the KSA-50... that can never hurt to have!

Original is fine for me.

Now, if a decision will go for a KSA 100 mk-2 original, then it is not a big issue regarding designing of the front/driver board but what about the power supply?

In the schematic there is no information about what was the rail voltage for the front end /driver board except for those 39V zener diodes. Was Vcc/Vee ± 52V, 70V or 87V ? Was the front/driver board fed by the same rail as for the OP devices?

Does it exist a schematics for the power supply or was it same as for the KSA-80? Or have I missed something?

What transformer could be used for the KSA 100, mk-2, a custom or a standard? Just mention this because the original Krell main transformers for the KSA 80 etc..., could hardly be substituted with standard industrial types or could they?

Do we need to start a GB for a main transformer (I can do it).

Regards