Krell KSA 100mkII Clone

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Mark A. Gulbrandsen

Member
Joined 2001
It's tempting to adapt the input stage of the KMA, just so we have a balanced option.
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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
 
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AndrewT

R.I.P.
Joined 2004
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?
 
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Mark A. Gulbrandsen

Member
Joined 2001
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
 
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Mark A. Gulbrandsen

Member
Joined 2001
To make it more complicated, the KSA-80B was a KSA-100 overhere. Confusing ? Of course not.
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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 ?
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My Dryer runs on natural gas:hot:... how do we make a Krell to do that?

Mark
 
F

Flodstroem

Member
Joined 2004
Balanced or not, is not the big issue

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!
Click to expand...

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 :cool:
 
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Mark A. Gulbrandsen

Member
Joined 2001
Foldtrroem,

If this does end up going another way to something completely different both you and I can also still do the original MK-2 version although you and I would just split the proto run of baords as I doubt a production run would be worth it. I just got an e-mail from Dave and he is willing to do it. He says its a tiny project compared to what he's used to. I just have to get a list of component parts and types and get that to him along with the schematic. He will use "Pads" to do the files so we may have to post a viewer to be able to look at it.

As for the Xformer I would think that Plitron must have something that would work but I have not checked. A G.B. on that might be worthwhile for all interested in building it. Another possible might be Victoria Magnetics if they are still around. They were VERY reasonable to have custom trannys made. They stock an 8 amp transformer for the larger Dr. Leach amp... I wonder what the secondary voltage is on that tranny?

Mark
 
F

Flodstroem

Member
Joined 2004
I have already wrote to Victoria Mag.

Did ask them about possibilities (Custom design, steel can, shielding etc...). Ill post their answer in here later.

Mark:
If this does end up going another way to something completely different both you and I can also still do the original MK-2 version although you and I would just split the proto run of baords as I doubt a production run would be worth it. I just got an e-mail from Dave and he is willing to do it. He says its a tiny project compared to what he's used to. I just have to get a list of component parts and types and get that to him along with the schematic. He will use "Pads" to do the files so we may have to post a viewer to be able to look at it.
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Absolutely Mark. I also agree to your suggestion regarding a proto run of boards.
Mark, have you ever seen a schematics for the mk-2´s power supply ? If not available then we had to measure some amps some where, or is there another possibility ?

Regards :cool:
 
gerhard

gerhard

Member
Joined 2005
hoffmann-hochfrequenz.de
Re: Balanced or not, is not the big issue

Flodstroem said:


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?
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Why not, if the voltage & current ratings are right?
Quality-wise, standard industry transformers probably won't be inferior to that thing that sits in my Krell KST 100 and that annoys me with its loud hum.

Does anybody out there have circuit diagrams etc of the KST 100 ? I bought that used Krell because I really don't have the time to start yet another project. I'm already working on a PreAmp plus some RF / phase noise stuff and a day has only 28 hours... But it looks like the Krell is going onto the operation table RSN.

regards, Gerhard
 
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Mark A. Gulbrandsen

Member
Joined 2001
Does anybody out there have circuit diagrams etc of the KST 100 ?
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Gerhard,

Throw out the KST-100 guts, it was never a very good amp but it is a great classic chassis! really, you've got the chassis and heat sinks to build your KSA-50 in! That should shorten your construction time to two days or less:) .

Everyone,

As far as a balanced input version I feel that is up to the individual to do that him/her self. Only a very few will be building this amp anyway and even fewer will want to make it balanced and then actually use it that way. Like Stuart Easson did up the current source for the front end of the KSA-50 you could also do up a balanced input board that could be piggybacked to it for a balanced input option. Having owned complete balanced systems in past years(Krell included) I can tell you how greatly unimportant balanced is in a home system. If you really want balanced then we need to do the KSA-80/KMA-160, but I feel that is a year down the road for us as a project. It will be quite dofficult and the j-fets needed will be somewhat difficult to obtain.

Lets make this a many sided project with those wanting options doing the design work themselves and posting it in the thread.... then we can do a small piggyback board for it. But above all lets at least keep the main board as clean as in the original or should I say lets keep it a klone and not branch out into outer space where the original board never went. Someone else could also do the power supply for the main board and I feel that looking at the KSA-80 regulated power supply diagram is a good starting point. Power supplies don't get much simpler than that! Perhaps it could be made even better.

Al,

You've hardly been griddled..... er... ah.... sacked. I only sack potatoes and you're peachy keen! Dave only agreed to do the main board. What would be nice would be if you also did one and we combined the best of the two together. Keep in mind that Dave knows all the standard PCB criteria for high voltage/high current boards, component spacing, copper clearance, etc. We also will still need the driver and output board files done as well. He did not agree to do those too. It couldn't possibly take you more than an hour to modify the existing KSA-50 driver board files for two extra driver devices...... Dave could use them to work backwards with that board in his mind so the terminals, rail connection points, etc match up the forst time around. The KSA-50 output board file is also easily modified for the 100. A TO-3 board would have to come from scratch. Since you say you're very busy I was only considering that the main board was more than your time allotment could tackle??? Its probably a couple hour job for Dave. But if you wanna tackle the whole thing its fine with me also. I am just attempting to get this going in as short of time as possible to keep this thread going and I am still willing to foot the bill to make up 100 board sets. Perhaps I could ship you half the boards in return for you doing the files and you could do overseas sales of them and I would take care of this part of the globe. That way we both might break even. Presently the KSA-50 board sales I'm running about $600 US negative with most of the second batch still sitting here, but thats ok too. I didn't expect them to disappear overnight like the forst batch did, neither will the run of 100 KSA-100 boards disappear very fast.

Mark
 
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Luke

Member
Joined 2001
Has anyone compared this to the KSA50 we just built? I like the idea but not sure its a much better performer. People here seem to think the KSA50 was the better krell. Also, I never understood why the drivers were on a separate board in Als version of the KSA50. Isn't it easier to have the front end and drivers on one board?
Im not knocking, just trying to decide if I get boards for this project, I really want my Aleph-X to be next, but I have too little time these days and too long a wish list:)


seeya ab
 
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