Krell KSA 50 PCB

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PB2

PB2

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Joined 2004
linkedin.com/in/petebasel
Mark Allen said:
One more question for you guys so I don't have to tear into my KSA-50 to find out. I have one set of main board and driver board hooked up and run up to 20 volts per rail on my small Tektronix Split bench supply. This amp oscillates at quite a high frequency! I was able to stop it by adding another 330pf across C-105 and C-106, base to collector. Its specified as 390 pf on the Delta schematic, 330 PF in the Delta parts list and only 39 pf on all the other schematics of the KSA-50 that I have. So whats the correct value? I also note that C-107 & C-108 (100 pf) do not have locations on the board, so if need be those can be soldered across the bottom of the driver PCB.... My amp does not have C-107 & C-108 and without substantial tear down I have no idea what value cap I installed at C-105 & C-106. Do any of you guys remember if you ran into this oscillation and what value did you use at C-105 & 106? Also, did you even bother with C-107 & 108?

Thanks in advance for any clues...

Mark
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Did you notice that the pre 83 schematic does not have a beta multiplier transistor in front
of the VAS? The later does, and the cap is only from C to B of the VAS not also around the
the beta multiplier where most would put it. The emitter follower provides current gain so the cap needs to be larger to offset that gain.
 
mpmarino

mpmarino

Member
Joined 2004
troystg said:
I second that!!!

Good to see (read) from everyone again!!!
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Timeless I guess :D

I really do enjoy listening to my KSA50.

So much so, that I'd like to do a fresh build using better components etc.

Is there an unused set of Pinkmouse boards out there looking for a home?

I also have a set of Peter Daniel Aleph boards to trade for them if someone is interested. (and maybe some other boards :confused:)
 
PB2

PB2

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Joined 2004
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DrNick said:
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.
Click to expand...

Does anyone know who did the LTspice simulation attached to the above post?
 
mpmarino

mpmarino

Member
Joined 2004
PB2 said:
There have been several different boards designed, as I understand it, which ones are
closest to the original factory design?
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Hmm - Regarding Pinkmouse's and Jan's boards; i think they were both pretty faithful to the original schematic.

Pinkmouse's had a separate driver board. This is the one I have experience with. I never did any formal measurements. It sounded great on power up, and I didn't want to spoil it :)

Except for the semis, mine was thrown together using parts from my drawer - the thing has paralleled resistors and no name caps all over the place. has been enjoyable for many years. I want to make a better one. Almost time to re-cap anyway!

Come on board hoards - Fess up :)
 
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still4given

still4given

Member
Joined 2004
troystg

troystg

Member
Joined 2004
pinkmouse said:
I did post the gerbers. They're in the thread...Somewhere...

Sorry Pete, no spare boards, I only designed it, I didn't look after production.
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Mark did the group buy but then got pulled away by work so I finished shipping the boards out for him. Every order was filled and the extras sold. I have a set of both boards but i am keeping them for "one day" when I can build them.

Sent from my SM-S975L using Tapatalk
 
PB2

PB2

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Joined 2004
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still4given said:
The Group Buys are long over and board houses have come way down in price. Maybe Pink Mouse would be willing to post the gerber files so guys can get boards made. I built Pink Mouse's boards and another set that used plastic outputs. Both play and sound beautiful.

http://img.photobucket.com/albums/v357/still4given/Krell/newKrell001.jpg

http://img.photobucket.com/albums/v357/still4given/Krell/Krell017.jpg
Click to expand...

Thanks for all the info everyone.

Those pics look great, nice work.
 
S

spurlte

Member
Joined 2011
Pinkmouse Boards

PB2 said:
Thanks for all the info everyone.

Those pics look great, nice work.
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I think I have a new pair that I got from Pinkmouse and few years back (I am assuming I got them from Pinkmouse). I don't remember what I paid for them then and wouldn't know what they are worth now. I built the, lately referred to as Stolen KSA-100 and the amp is still working great so I have never started the KSA-50 amp.
 

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B

bobgroger

Member
Joined 2005
Hi Guys, Been gone for a while after a Q-tip accident and broken ossicles rendered my audio days done. Left ear still works but listening is so distorted to be painful. ANyway I still love building stuff, and came to revisit this thread. I looked through my stuff and found a copy of the now missing Wiki, posted below. Also have schematica and build guide if they are gone as well. Not 100% sure but I might still have a pair of boards. Don't really want to sell them but I would donate to someone doing another GB to copy.
 

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  • Krell Clone pinkmouse parts list.pdf
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  • krell_TECHINF.pdf
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  • Krell-Clone Parts List.pdf
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  • Krell-Clone_Corrections_Copper_Side.pdf
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  • Krell-Clone_KSA-50_Schematic.pdf
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A

AndrewT

R.I.P.
Joined 2004
Thanks for all those links. Saved.
I really liked the way we had the Wiki set up back then. Shame it has fallen into disuse.
There were lots of complex projects stored in Wikis. Far better than the strung out Threads we have now, some with hundreds of different amplifiers/projects buried in a mire.
 
pinkmouse

pinkmouse

Ex-Moderator
Joined 2002
Sorry to hear about your accident Bob. :(

Hmm, I'm sure I posted the gerbers. Still most fabs should be able to use the Eagle files as is, though be sure to tell them about the router layer for the grooves. As I mentioned earlier, I don't have the files on this computer, but I'll try and track down the old hard drive I have the project on over the next week or so.
 
PB2

PB2

Member
Joined 2004
linkedin.com/in/petebasel
Thanks everyone. I don't have any plans to have more boards made so please don't go to
any trouble for my use, thanks.
Perhaps others do?
I'd like the boards just to make some measurements on the bench. If I build a clone
it has to fit in an old chassis so I might end up making new boards for that situation.
If there is a new group buy at a good price, I'd probably be in for one pair of boards.

I do have a few offers to buy boards, Mark Allen said he has a few of the Delta boards
left over.
 
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