My KSA-50 runs 39 volt rails ising a 1.2kva transformer. This transformer has dual secondaries. Also a single CL-60 current limiter on the AC side of the transformer to limit inrush. Caps are 68,000 @ 63vdc caps. Bleeders were chosen so both rails drop to close to zero at the same time. I would have to open up the amp to see the value. Its been so long. I do tear it apart every few years to clean the dust out....
Mark
Mark
I used 2 800va Avels Y236901 30+30v per monoblk. ( order form 10/24/05!! Sshh! ) time flies!
Loaded dc rail was 41 v. A little more heat produced
Interesting price back then 76.30 $ each now 109$
Special order at parts express ( not in catalog )
Used the same ps caps as Mark 68 k but dual rectifiers per mono
Loaded dc rail was 41 v. A little more heat produced
Interesting price back then 76.30 $ each now 109$
Special order at parts express ( not in catalog )
Used the same ps caps as Mark 68 k but dual rectifiers per mono
Krell Ksa 50 PSU
I'm looking for the original schematic (or similar) of the power supply (PSU) krell Ksa 50, but can not find. can you help me? thank you
I'm looking for the original schematic (or similar) of the power supply (PSU) krell Ksa 50, but can not find. can you help me? thank you
IIRC, I don't think we ever saw the official PSU schematic, but it isn't that complicated, as Mark said above, transformer, rectifiers, lots of caps and some bleeder resistors to drain the cap bank on power off. A bit of inrush protection like a CL60 helps if you have a really meaty traffo.
One day, I'll have to dig out my Krell stuff from one of my old hard drives, the current one it was on died recently, and my first backup NAS then dropped dead as well. I do have it all on the original HD, but that's buried in a box somewhere with about a dozen others, so would take some tracking down.
One day, I'll have to dig out my Krell stuff from one of my old hard drives, the current one it was on died recently, and my first backup NAS then dropped dead as well. I do have it all on the original HD, but that's buried in a box somewhere with about a dozen others, so would take some tracking down.
Am building up a pair of KSA-50 boards to send to a friend and I noticed there is no value stated for R-124 in any of the info. Does anyone know what value this is supposed to be? Short of opening up my own KSA-50 and taking a look, I can not remember what we did here. A search did not turn up anything either... and it for sure can not be just left out or jumpered.
Thanks in advance for any input!
Mark
Thanks in advance for any input!
Mark
Thanks for that! Do you know off hand the bias setting? 680 mv across a positive emitter resistor at 40 volt rails sounds right to me for three OP devices per rail, just want to be sure.
Thanks again!
Thanks again!
Are there any boards for these still out there? I've taken apart some old potentiostats that were going to be thrown away at work and have 7 pairs of MJ15003's and 4's on reasonable sized heatsinks, and 2 frame transformers of about 450 VA each (as well as two smaller ones not labelled). I was looking for a way to use them for a nice project, and found this thread. I've spent a week reading most of it, drooling over the pictures.
As the Delta Audio website is no longer live, I found what I think is the final version of the schematic prepared by Jan Dupont which was at http://www.hobbielektronika.hu/forum/getfile.php?id=34222. This is attached, as I could not find it in this thread, only links to the Delta Audio address from the post http://www.diyaudio.com/forums/solid-state/31077-krell-ksa-50-pcb-16.html#post516893, apologies if it is somewhere already.
I'm was planning on using this, but saw the updated values used by Pinkmouse. I'm curious as to which changes resulted from changing the transistors used, and which are improvements even if you use the original transistors. I've only just started with LTSpice for modelling, but I thought if I knocked up a model in LTSpice to check my understanding of the circuit, it might help to check what effect the changes had. Anyway, I've attached this in case it's useful to anyone, with the .lib files in a zip file.
I've seen some different boards available commercially, https://world.taobao.com/item/9797282148.htm?spm=a312a.7728556.201601086188259.3.BQS6Kg&scm=1007.12679.20634.9797282148 but not to the exact same schematic, so I'm wondering if it's best to make my own. I've got access to the kit to etch some boards, but I'll have to look into what is required.
Just wanted to post to thank all the people that have given their time to make this thread, it's been a real eye opener.
As the Delta Audio website is no longer live, I found what I think is the final version of the schematic prepared by Jan Dupont which was at http://www.hobbielektronika.hu/forum/getfile.php?id=34222. This is attached, as I could not find it in this thread, only links to the Delta Audio address from the post http://www.diyaudio.com/forums/solid-state/31077-krell-ksa-50-pcb-16.html#post516893, apologies if it is somewhere already.
I'm was planning on using this, but saw the updated values used by Pinkmouse. I'm curious as to which changes resulted from changing the transistors used, and which are improvements even if you use the original transistors. I've only just started with LTSpice for modelling, but I thought if I knocked up a model in LTSpice to check my understanding of the circuit, it might help to check what effect the changes had. Anyway, I've attached this in case it's useful to anyone, with the .lib files in a zip file.
I've seen some different boards available commercially, https://world.taobao.com/item/9797282148.htm?spm=a312a.7728556.201601086188259.3.BQS6Kg&scm=1007.12679.20634.9797282148 but not to the exact same schematic, so I'm wondering if it's best to make my own. I've got access to the kit to etch some boards, but I'll have to look into what is required.
Just wanted to post to thank all the people that have given their time to make this thread, it's been a real eye opener.
Mark
That was the max as I recall and depends on proper heat sinking at these levels.
I have built all versions, 50/100/150 monos of each wattage and never ran the maximum unless it proved sonically superior.
I fan cooled all and run a little less for longevity overall
No reason to stress anything if it didn't make a difference..,
Regards
David
That was the max as I recall and depends on proper heat sinking at these levels.
I have built all versions, 50/100/150 monos of each wattage and never ran the maximum unless it proved sonically superior.
I fan cooled all and run a little less for longevity overall
No reason to stress anything if it didn't make a difference..,
Regards
David
Here is a 2007 version... The errors Andrew refers to were simulations not hard calculations. It's row 23 just ignore it. Already explained this to him years ago, but his brain is tuned to point out mistakes of others more than remember whats important...
https://drive.google.com/open?id=0Bz2OUywabAjkOUhsQS1faHFLSVE
good luck boys.
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row 15 says Total Amplifier bias is 3.64Aps and yet row 14 says different.
The total output bias of the 4pair stage is 1.82Amps, as derived in the upper rows of the sheet.
The total output bias of the 4pair stage is 1.82Amps, as derived in the upper rows of the sheet.
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remove row 15.
It gives no useful information.
It does worse, it gives misleading information.
It's a long time since this came up so I don't have any recall of the discussion at that time, although Kamps does recall.
I wonder if this row was what was being discussed?
It gives no useful information.
It does worse, it gives misleading information.
It's a long time since this came up so I don't have any recall of the discussion at that time, although Kamps does recall.
I wonder if this row was what was being discussed?
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I wonder if we put it there either to simulate 2 channels or to estimate load on the PSU at idle...?
I think the spreadsheet is considering one channel with a multiple pair output stage.
The load at idle (no signal) is total Ibias (Ib) plus front end current consumption.
This total is sometimes referred to as quiescent current (Iq)
I have a feeling that row15 is simply a mistake that a few Members make when totalling up the current flows in a quiescent amplifier.
Some mistakenly add the upper device current/s to the lower device current/s and come up with a wrong answer.
The load at idle (no signal) is total Ibias (Ib) plus front end current consumption.
This total is sometimes referred to as quiescent current (Iq)
I have a feeling that row15 is simply a mistake that a few Members make when totalling up the current flows in a quiescent amplifier.
Some mistakenly add the upper device current/s to the lower device current/s and come up with a wrong answer.