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Old 27th April 2006, 06:51 AM   #101
AndrewT is offline AndrewT  Scotland
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Hi,
Stuart is right and supports Kamps. I cannot disagree that Iq=2.76A gives MORE than 100W of ClassA into 8r.

I think we are also agreed that KSA100mk2 will safely deliver a lot more than 100W into 8r. Mark has stated 160W.

I also will not/cannot dispute Kamps measurements and calculations leading to
Quote:
690mv across the 1 ohm emitter resistors meant it was biased to 122 watts pure class-A into 8 ohms
On the same basis that both the KSA50mk2 and our 50 Klone will push a lot more than 50W into 8r does not stop us specifying an Iq=1.9A giving about 58W ClassA for an amp capable of a maximum of about 70W to 80W.
I think we are all agreed that our 50 Klone is fully biased to ClassA just as a Klone of the 100Mk2 biased to 2.76A will be fully biased to ClassA. These levels of bias separate the Klone and their originals from the high bias designs that CLAIM to be ClassA. Keep in mind that a less than scrupulous retailer could under specify the output power of a high bias amp and then rightly (or wrongly depending on the method of measurement) claim they had a ClassA design. I believe that neither Krell nor the Klone builders need to resort to this style of chicanery.

From some of the information I have seen the 100Mk1 was a high bias design. That distinction was the main purpose of my original statement.

But, I thank Kamps again for the info, it gets the designers/builders closer to specifying the Klone requirements.
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Old 27th April 2006, 12:49 PM   #102
K-amps is offline K-amps  United States
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Quote:
Originally posted by AndrewT
Hi Kamps,
not quite, your measured Vrail supports the contention of Mark that the peak output of the 100Mk2 is nearer 160W (50.6Vpk) into 8r.

0.69V bias gives Iq=2.76A.
Peak voltage in ClassA will be just below 2*2.76*8= 44.16Vpk.

I would expect the KSA100mk2 to manage quite a bit than 44.1Vpk into 8r.

ps what is the rated input voltage for the rated (specification) output voltage?
44.16v peak is about 31.2v RMS class-A or 31.2 X 31.2 /8 = 121.5 watts RMS pure class-A. Supports the previous.

Also the 160 watt figure seems to be the class AB max output prior to clipping, not pure class-A max (which at Iq of 2.76A is limited to 122 watts into 8 ohms).

Stuart is right, my calculations were based on a purely resistive load.

Thank you all for helping clarify this.
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Old 7th May 2006, 06:18 PM   #103
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Am finally back after a long winded service trip through Nevada. Nothing is close together in that state!

Many have asked or denied they need to build the larger Krell....however......

Yesterday we had the opportunity to compare my KSA-50 MK-2 Klone to Bill WW's Krell KST-100 Class A-B amp. Clearly the KSA-50 clobbered the KST-100 in high frequency end of things... it was much more refined while the Krell KST was colder fomr about 5K up and just a tad bit gritty sounding. HOWEVER... the KST-100 blew the KSA-50 out of the water in the low end department driving my Dynaudios with a slam factor that never seemed to run out. The KST was literally able to make my floors shake playing back track 1 from Crystal Method, clearly the KST was definately more like my old KSA-80B. Also the KST-100 was not lagging that far behind in the midrange department as compared to the KSA-50, it was close with the KSA-50 taking the edge. The KSA-50 MK-2 kas really amazing bass response for a 50 watt amp but is nothing compared to the KST-100! This only re-affirms to me that the KSA-100MK-2 is the next thing on my list to build. Clearly my Dynaudios and a larger Krell are a much better match and I will continue to go ahead with the KSA-100 MK-2 amp.

Those of you that have speakers in the 86 to 90db sensitivity range also really need a larger amp to get the results I have been able to get with the larger Krells.

The KST looks like a pretty complicated circuit to attempt to Klone and I don't think it would be worthwhile to do. At that point going to the KSA-80 would be the better route to take for the time and $$ involved. Here is a photo of the inside of the KST.

Mark
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Old 8th May 2006, 08:40 AM   #104
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Default Hi Mark

Quote:
This only re-affirms to me that the KSA-100MK-2 is the next thing on my list to build. Clearly my Dynaudios and a larger Krell are a much better match and I will continue to go ahead with the KSA-100 MK-2 amp.
I liked that, and I am very interested to join this project.
BTW, interesting picture, every component placed on one board (it looks like that). If building an amp like the one on the pictures it demands a chassis that fits perfect for the board, dont you think?

It must be easier to build an amp (clone?) where you could have different options for to choose the chassis you like ( or maybe already have) ?

The project must go for one main/driver board per channel. thats only my opinion.

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Old 14th June 2006, 11:15 PM   #105
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Default Hi Mark

Any news from the KSA-100 mk-II clone design project ?

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Old 22nd September 2006, 07:18 AM   #106
PWatts is offline PWatts  South Africa
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If there is no designated designer yet, I have experience with both the KSA50 and KSA100 (commercial and clone) and use P-CAD PCB software for my day job - I'm an electronic engineer specializing in audio. Maybe PinkMouse is a bit tired of all the board layouts by now
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Old 22nd September 2006, 07:50 AM   #107
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You're more than welcome to have a go. I haven't, because I have been too busy in the real world, and have too many other projects in the queue.
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Old 22nd September 2006, 08:13 AM   #108
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Default Hi PWatts

Are you going to design a PCB for the KSA 100mkII clone?

If yes, im wery interested to joining in and help if I can.

Also, I must admit that the long delay between posts in this thread had lead me to design a PCB on my own software. PCB design is not finished, only component placing and outer physical format of the board is done. No routing of traces and no ground-plane is done yet. (board outline ca 5.50" x 5.00").

I dont know if this could be of interest or you would like to start from scratch(or maybe you already have started).

BTW, right now Im searching for computer grade caps for this project( see this thread: http://www.diyaudio.com/forums/showt...27#post1011227 )

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Old 22nd September 2006, 09:30 AM   #109
AndrewT is offline AndrewT  Scotland
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Hi Flod,
Quote:
no ground-plane is done yet
Is that a power ground plane, or a signal (clean) ground plane, or a zero current electrostatic screen ground plane? Have you considered when a ground plane might be useful? Do any of the pros apply to audio amplifiers? Do any of the cons work against audio amplifiers?

Or, are you just jumping on a fad, used by others that have never reviewed the need, for an audio amplifier ground plane?
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Old 22nd September 2006, 10:12 AM   #110
PWatts is offline PWatts  South Africa
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I haven't done any work yet on the board, but since there seems to be a lot of interest on a KSA100 clone and as I think that Al has made more than his share of contributions, somebody else might take it further.

There's no need to do a completely new design since his KSA50 boards are well designed and also work well. The same general layout could be used as basis; otherwise the genuine KSA100 MK2 board can simply be copied and adapted for the modern components.

I'd suggest that all the comments of what should be included on this clone compared to the KSA50 should come in within the next two weeks or so, after which design can start. Component identification should be one of the first choices, especially the MOSFET's. The BJT's can stay the same as with the KSA50. The protection, fan controllers etc. are all off-board and not part of the board itself.

It will be too expensive to start a group buy from South Africa since all the boards will have to be sent overseas, so I'd suggest that someone abroad with access to a PCB manufacturing facility handle that part, supplied with the Gerbers.

AndrewT raises a very important point, often (OK usually) overlooked by many designers, both DIY and professional. Grounding principles on a PCB is a very touchy subject for some, and opinions vary on what works best. Particularly in a mixed-signal environment there are a plethora of ideas and methods used, some with disastrous results.

The fact of the matter is that just by doing lots of copper pours, dedicated ground plane on a multilayer board or exotic copper plate shielding or similar can lead to worse performance than a much simpler well-designed ground scheme.

For a power amplifier ground and power planes are largely unnecessary. Proper care needs to be taken to prevent signal ground as the return for power ground, and to a certain extent screening of the signal ground should work well. A dedicated ground or power plane for power isn't really necessary, but will reduce DC resistance that may be a problem. Thick traces are sufficient for even very demanding amps though and a plane is overkill. The reason why power and ground planes are popular is due to digital electronics where the small inductance of the trace DO make a difference at high frequencies that are not the case here. A dedicated ground plane in a multilayer board is also used as a screen between the top and bottom layers to prevent signal coupling through the board substrate.

For normal non-switching amplifiers a double-sided board is more than sufficient as most of the advantages mentioned are not applicable. A properly designed copper pour for signal ground is unlikely to do any harm though, but a dedicated ground plane on an expensive 4-layer board is definitely overkill, and can even count against you.
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