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Krell KSA 50 pcb
Krell KSA 50 pcb
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Old 12th January 2019, 07:33 PM   #8991
Blitz is offline Blitz  Germany
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And you would recommend this version of the PCB ? I see that this one has the LM339 CCS on board, while the green ones above do not have them on board and I guess the ones of ounkmouse neither ?

I am asking if you think which version to pick as Jim is charging a hefty margin on the red board (80$ for a stereo set)...you could get for that money a fully stuffed set of boards incl. speaker protection from aliexpress.
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Old 12th January 2019, 08:22 PM   #8992
Dave murrey is offline Dave murrey  England
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Quote:
Originally Posted by Blitz View Post
And you would recommend this version of the PCB ? I see that this one has the LM339 CCS on board, while the green ones above do not have them on board and I guess the ones of ounkmouse neither ?

I am asking if you think which version to pick as Jim is charging a hefty margin on the red board (80$ for a stereo set)...you could get for that money a fully stuffed set of boards incl. speaker protection from aliexpress.
I got the green boards from ebay item number 112435193237 18.50
They seem to be good quality boards and look similar to original krell ksa50 mk2.
I personally would components separately from mouser, RS components, hifi collective, airlink transformers or digikey.

Last edited by Dave murrey; 12th January 2019 at 08:36 PM.
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Old 12th January 2019, 11:12 PM   #8993
Blitz is offline Blitz  Germany
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Ok, Guys you got me believe in this, thanks for bringing me on speed...

...as I have many (too many) projects going on at the same time, I ask myself: Should I order a set of these assembled boards:

YJ KSA50 Class A Krell 50W+50W 2SA1943/2SC5200 MJE15034/MJE15035 Completed Amplifier board in YJ KSA50 Class A Krell 50W+50W 2SA1943/2SC5200 MJE15034/MJE15035 Completed Amplifier board aus Verstarker auf AliExpress.com | Alibaba Group

or its sister

YJ KSA50 Class A Krell 50W+50W MJ15024G/MJ15025G MJE15034/MJE15035 Completed Amplifier board in YJ KSA50 Class A Krell 50W+50W MJ15024G/MJ15025G MJE15034/MJE15035 Completed Amplifier board aus Verstarker auf AliExpress.com | Alibaba Group

...and have a playing amplifier rather fast. If it is good and I could imagine it could become great with more careful parts selection etc.: Wonderful. Lets invest more time and money. If it is soso: Lets move on...100 Euro for two stuffed boards are hard to beat...enclosure, transformer and caps I do always have from previous projects

Makes sense ? Any preference for one or the other version above ?

Last edited by Blitz; 12th January 2019 at 11:18 PM.
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Old 14th January 2019, 07:09 AM   #8994
neychi is offline neychi  Croatia
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Quote:
Originally Posted by Blitz View Post
And you would recommend this version of the PCB ? I see that this one has the LM339 CCS on board, while the green ones above do not have them on board and I guess the ones of ounkmouse neither ?

I am asking if you think which version to pick as Jim is charging a hefty margin on the red board (80$ for a stereo set)...you could get for that money a fully stuffed set of boards incl. speaker protection from aliexpress.
LM334

I can't give you a recommendation for other boards that you mentioned, but I can tell you my experience with boards that i have and they are very positive.
If you want to go a simpler way then buy green boards without mosfet-ccs, but if you want the option of upgrading to ksa100mk2 some day then buy Jims boards.
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Old 14th January 2019, 08:00 AM   #8995
Blitz is offline Blitz  Germany
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Damned...you know how to convince...Ok, will do. I was not sure, how much the CCS is needed or not.

By the way: I understand that most of you guys do not use speaker protection, correct ?

I have two big 800VA toroids with 30V*2 on the shelf from a former project...may not give me the 48V you proposed, I would guess more like 43V...but I guess a good start.

I always wonderd if 22K input impedance has any particular reason ? Why not 100K ? My line-stage would like that. Can anything go south when taking a different value ?
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Old 14th January 2019, 10:37 AM   #8996
danieljw is offline danieljw  Australia
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Quote:
Originally Posted by Blitz View Post
Damned...you know how to convince...Ok, will do. I was not sure, how much the CCS is needed or not.

By the way: I understand that most of you guys do not use speaker protection, correct ?

I have two big 800VA toroids with 30V*2 on the shelf from a former project...may not give me the 48V you proposed, I would guess more like 43V...but I guess a good start.

I always wonderd if 22K input impedance has any particular reason ? Why not 100K ? My line-stage would like that. Can anything go south when taking a different value ?
You will change the characteristics of the input filter somewhat.
And you will find there is somewhat less noise with 22k than 100k.

I would be surprised if a line stage can't deal with 22k ?
Is it a special configuration?

-Dan
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Old 14th January 2019, 11:06 AM   #8997
Blitz is offline Blitz  Germany
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Yes, it is...its a DHT tube outputstage with OPTs, output impedqnce approx. 1K. Lots of current, but that is at the moment what it is...depending on the sensitivity of the KSA, I could bring output impedance down to 250ohm. Nevertheless I tested the sound of the OPT with different impedances of the input side of my power amp (300B) and you can hear quiet a bit of differnces...funny enough with the grid choke of 7000H/1.2kohm being the best...maybe a grid choke as well for the KSA ? This may drive its DC path to 1.2k and its AC impedance into the megaohm area...
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Old 14th January 2019, 12:39 PM   #8998
danieljw is offline danieljw  Australia
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Whatever works for you, that certainly sounds like a special pre!
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Old 14th January 2019, 03:53 PM   #8999
AVWERK is offline AVWERK  United States
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[QUOTE=Blitz

By the way: I understand that most of you guys do not use speaker protection, correct ?

Never used protection on any of my 6 monoblocks ( 50-100-150 watt versions)
And never had an issue except on my 150 pair that started to give me signs and was shut down quickly ( power supply caps age )

Torture testing and living with it on the bench for an extended time should cover most bets before putting it on your favorite speaks

Dont like the signal output path and willing to live dangerously yes

Regards
David
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Old 14th January 2019, 05:32 PM   #9000
Blitz is offline Blitz  Germany
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I have the same philosophy.

I do not want anything in the signal path which does not have to be there. In my tube equipment, I found even gridstopper resistor sound bad, destroy the micro-dynamics/ musical energy...a small HF bread which has around 1k impedance at 10Mhz sounds much, much better...not sure I want the 1k series resistor in the input section. What is the purpose ? HF filter ? I have a natural HF filter in my line stage (output transformer).
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