Early ones had the fan on top, later ones had the fan on the bottom, and separate left and right transistor/fan assemblies
Stupid question for those who have build clones on the JimsAudio/ZeroZone boards: What have you used for the "onboard" heatsinks on the main PCB?
I seem to struggle to find something that fits without major modifcations to either board or heatsink (or both 🙂 )
I seem to struggle to find something that fits without major modifcations to either board or heatsink (or both 🙂 )
Are you talking about the driver heatsink? Took me ages to find one that fitted and I had to drill and tap it to attach it to the PCB.
Try this one SK68-75-SA
SK68-75-SA | Heatsink, 3.9K/W, 75 x 46 x 33mm, Screw | RS Components
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Yes, exactly. I did think the one in your pictures looked like an SK68 but I couldn't really make that fit with the boards - your mods explain it 😀
Hi everyone, here are some pictures of a project I started a couple of years ago. For various reasons I won’t be able to finish, so I have decided to sell.
As you can see, all good quality components have been used. The heatsinks are virtually identical to original Krell and I decided to use two sets as per the KSA100 even though I required only about 60W of class A. This allows the cooling fans to be run at a lower speed, so very quiet in operation.
Both channels have been tested and offset and bias set up perfectly.
Papst fans are new, as are the two 30-0-30-0 500Va transformers.
The case is from a server, in very good condition but will need finishing.
If anyone is interested in finishing this project could they pm me.
Regard
Alan
As you can see, all good quality components have been used. The heatsinks are virtually identical to original Krell and I decided to use two sets as per the KSA100 even though I required only about 60W of class A. This allows the cooling fans to be run at a lower speed, so very quiet in operation.
Both channels have been tested and offset and bias set up perfectly.
Papst fans are new, as are the two 30-0-30-0 500Va transformers.
The case is from a server, in very good condition but will need finishing.
If anyone is interested in finishing this project could they pm me.
Regard
Alan
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KSA50 Monoblock
Attached is a picture of a KSA50 Monoblock that I am almost finished assembling (waiting on some mounting hardware for the boards).
I am quite enjoying listening to a pair of these. I was wondering if someone could point me to the "official" or "best" KSA50 (MkII?) schematic and orderable/reliable gerber files? I have searched and found the pink mouse boards as one example but it is not clear that those are the best ones.
I ask since the second attached image is my schematic and the third attached image is "another" KSA50 schematic that I found online which has what appears to be two additional transistors. (And various values changes plus two added Zener diodes.) Are those two additional transistors emitter followers to reduce loading? Which design is better? Which is the best/real KSA schematic? (And gerber file?)
Attached is a picture of a KSA50 Monoblock that I am almost finished assembling (waiting on some mounting hardware for the boards).
I am quite enjoying listening to a pair of these. I was wondering if someone could point me to the "official" or "best" KSA50 (MkII?) schematic and orderable/reliable gerber files? I have searched and found the pink mouse boards as one example but it is not clear that those are the best ones.
I ask since the second attached image is my schematic and the third attached image is "another" KSA50 schematic that I found online which has what appears to be two additional transistors. (And various values changes plus two added Zener diodes.) Are those two additional transistors emitter followers to reduce loading? Which design is better? Which is the best/real KSA schematic? (And gerber file?)
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So after lots of broken links (and the website from the first 300 posts which no longer exist) I found post #8815: Krell KSA 50 pcb
So should I conclude that the Pink Mouse boards are the best or "official" clone boards of this KSA50 clone thread? Are they considered KSA50 or KSA50 Mk II?
But I don't understand what posts #9310 and #9315 mean. Is something wrong with the gerbers or this version? Is it safe to go order the gerbers from post #9305?
So should I conclude that the Pink Mouse boards are the best or "official" clone boards of this KSA50 clone thread? Are they considered KSA50 or KSA50 Mk II?
But I don't understand what posts #9310 and #9315 mean. Is something wrong with the gerbers or this version? Is it safe to go order the gerbers from post #9305?
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I've not built the PinkMouse boards, but they were developed to use flat pack outputs and more modern transistors. I have some boards spare if you are in the UK.
Mine was the #9310 post and I had used the gerbers from post #9305 to order them As far as I'm aware there aren't any problems with the boards. Jen's previous boards did have problems.
Mine was the #9310 post and I had used the gerbers from post #9305 to order them As far as I'm aware there aren't any problems with the boards. Jen's previous boards did have problems.
Just looking at the cct in https://www.diyaudio.com/forums/solid-state/31077-krell-ksa-50-pcb-309.html#post6239875 it has the same extra transistors that you've highlighted in your blue boxes.
Ok. So I am concluding that the extra transistors are for a Mk II. That would make the boards in this thread (and my HM2S boards) Mk II variants. My existing KSA50 clone would indeed be a Mk I then.
I finally found someone else with the HM2S boards:
Proper KSA-50 bias setting???
So perhaps it is safe to assemble the HM2S boards and only if necessary I can later order the pink mouse boards with the gerber files. (I am not in the UK, across the pond instead.)
I finally found someone else with the HM2S boards:
Proper KSA-50 bias setting???
So perhaps it is safe to assemble the HM2S boards and only if necessary I can later order the pink mouse boards with the gerber files. (I am not in the UK, across the pond instead.)
Thank you. Lots of info there.
Unfortunately 3 of the 4 links on Chapter 4 are broken (Chapter 4: Krell Facts and Reviews).
Does anyone know who is currently maintaining that Wiki? I would suggest to them to include (near the beginning) a statement regarding which KSA50 version the Wiki pertains to. For example, is it a KSA50 Mk II? Perhaps a schematic of the original (Mk I), the schematic of the Mk II and a few sentences on the difference (in schematic and sound) would be appropriate.
I am assuming most are looking for a KSA50 Mk II. (Even if they don't know the difference between the two or even know there were multiple versions with schematic differences and two additional transistors.) Does this sound correct?
Unfortunately 3 of the 4 links on Chapter 4 are broken (Chapter 4: Krell Facts and Reviews).
Does anyone know who is currently maintaining that Wiki? I would suggest to them to include (near the beginning) a statement regarding which KSA50 version the Wiki pertains to. For example, is it a KSA50 Mk II? Perhaps a schematic of the original (Mk I), the schematic of the Mk II and a few sentences on the difference (in schematic and sound) would be appropriate.
I am assuming most are looking for a KSA50 Mk II. (Even if they don't know the difference between the two or even know there were multiple versions with schematic differences and two additional transistors.) Does this sound correct?
Boy, that stirs up some memories. There was a KSA-100 GB going on at the same time, with 2X the drivers on a heat sink. IIRC it was the MK I version but that was a lot of brain cells ago. I still have a pair of GB2+ boards. I would offer to scan and photograph them if that is OK with Pinkmouse and someone wants to run with this. Mine never got past the breadboard on the bench stage but you have reminded me to finish the project.
I confirmed the Gerbers in post 9303 are identical to my Pinkmouse boards even to the 17/5/05 date....
can you make? please make and send it to me , roimark3568@yahoo.co.uk. i will give payment after i received
thanks
Hi guys.
I am considering assembling the KSA 50 myself. I'm on page 70 currently, but wanted to ask this quetion:
The torroids will be the most expensive part, unless I get REALLY fancy with the case.
I managed to find a pair of 480V to 277V torroids rated at 300VA.
If I use a 120V input, my remedial math skills indicate I'd have a 69.25V output, which I think might be useful; and certainly leaves room for volt drop during filtering etc.
ANYWAY, if you could get said transformers quite inexpensively, would you? I mean, for less than $40 each, it seems prudent to make them work to me (but I'm not an EE, and why I'm asking the question.)
Thanks in advance!
I am considering assembling the KSA 50 myself. I'm on page 70 currently, but wanted to ask this quetion:
The torroids will be the most expensive part, unless I get REALLY fancy with the case.
I managed to find a pair of 480V to 277V torroids rated at 300VA.
If I use a 120V input, my remedial math skills indicate I'd have a 69.25V output, which I think might be useful; and certainly leaves room for volt drop during filtering etc.
ANYWAY, if you could get said transformers quite inexpensively, would you? I mean, for less than $40 each, it seems prudent to make them work to me (but I'm not an EE, and why I'm asking the question.)
Thanks in advance!
On eBay Antek sells new 300VA for $35 with free shipping:
300VA 45V 3A + 45V 3A 90VCT Power Transformer Antek AN-3245
300VA 36V 4A + 36V 4A 72VCT Power Transformer Antek AN-3236
But for Class A make sure you get a large enough transformer and do calculations for the supply voltage, bias and heaksinks depending on your speaker impedance. (Are they 8 Ohms or 4 Ohms?)
300VA 45V 3A + 45V 3A 90VCT Power Transformer Antek AN-3245
300VA 36V 4A + 36V 4A 72VCT Power Transformer Antek AN-3236
But for Class A make sure you get a large enough transformer and do calculations for the supply voltage, bias and heaksinks depending on your speaker impedance. (Are they 8 Ohms or 4 Ohms?)
Main speakers are rated at 8 ohms but drop to around 6 at some frequencies (Thiel CS 2.2)
I’m not sure I’ll even use those with this amp but most likely the most critical listening will be with those.
I probably need more current. I’ll check the ones you suggested, but continue the search for meatier ones. The ones I found are not suitable I think.
I’m not sure I’ll even use those with this amp but most likely the most critical listening will be with those.
I probably need more current. I’ll check the ones you suggested, but continue the search for meatier ones. The ones I found are not suitable I think.