Krell KSA 50 PCB

[Upupa Epops]

Jan, this biasing circuit is nonsens !

 

[Jan Dupont]

Goodmorning Pavel

Please tell
To me it seems quite normal, if you make a connection between C of TR8 to B of TR10, and again from C of TR7 to B of TR11.....
Or did I miss omething ????

 

[Jan Dupont]

Pic of a "normal" biasing circuit...
Sorry but it has to wait, as it seems as the pics I got here at my labtop doesn´t show well when published here...

 

[Upupa Epops]

To Jan : That will be correct .

 

[Jan Dupont]

Thanks Pavel
For a moment I thougt that I was gone crazy

 

[Upupa Epops]

To Jan : P.S. : If you will make a PCB, give capacitors on position CB of drivers and serial resistors to the basis of output devices - amp will be more stable .

 

[Upupa Epops]

P.P.S.: Try to think to give there a protector for overcurrent ( same as you have in your amp ) - amp without this circuit is crime .

 

[Jan Dupont]

Pavel

Thanks for your suggestions
I will sure put in the output protection circuit, base resistors and CB caps on the drivers

 

[jarek]

Could someone tell me what for a resistors R1 in the PSU is?

 

[PMik]

It was a "smart trick"
it hides the basic sound quality of the incredeble poor schematics......its called "floating ground"

Musical Fidelity used "floating ground" as well for there P270 and A370



Removed my comments on Krell engineering or lack of same

Should not spoile your fun

 

[Jan Dupont]

Hi all,
I have now drawn the KSA-50 mk.II schematic in my CAD software: http://www.delta-audio.com/temp_acd/Krell-Clone_KSA-50.pdf
Please let me know your comments before I start the PCB-layout

To PMik:
I agree, however we do diy for fun

 

[Upupa Epops]

C 107, 108 must be on CB not on BE.

 

[fcel]

Can anybody comment on how much it'll cost to built this clone - using non-exotic parts and excluding chassis cost.

 

[zcolic2]

Yes, there is an obvious (symetrical) error on schematic that I gave link to. Base of TR10 should be connected with collector of TR8. As T11 with TR7. Thats, it. Waiting for suggestions on low power transistor replacements. Thanks all for contributing.

Regards,
Zoran

 

[Jan Dupont]

Pavel

You are absolutely right
Please comment other errors, as I was drawing this schematic last night

 

[Jan Dupont]

Schematic has been updated

 

[Upupa Epops]

Jan, it must to stay Krell, not to be DuDu ( Dupont - Dudek ) , so only little notices : Q 105 - MPSA 92, Q 106 - MPSA 42 - Pc in this position is not big, so there is 0,5 W Pc enough ( MPSA .. or MPSW .. family ). Q 111 - give there some transistor in TO 126 ML ( full insulated - easy mounting ), such as 2 SC 3955 or similar. C 109 - give bigger value ( cca M1 - 1 M / 63 V). Current sense ( R 301, 302 ) is better to lead from both emiters of power devices ( value 4*200 R ). Give on rails blocking capacity ( + to G, - to G and + to - ). Other improvement are not required, 'cos Daniel d' Agostino is boss .

 

[Jan Dupont]

Pavel

Your suggestions sounds ok to me
And as you say, we must take care that we don't move the "project" too far away from original Krell (otherwise we could just make a new ourself a new amp) The "DU-DU Amp"

 

[Jan Dupont]

zcolic2

Sorry for this late comment to your input....
If you look at the schematic I have uploaded, you see that this error in the schematic provided by you has been corrected

 

[Jan Dupont]

Pavel

By the way.............
Which Pc's do you suggest instead of MPSA 42 and MPSA 92 ???


I think it's possible to choose between a lot of different Pc's with the same pin configuration as the 42/92's So the printed name in the schematic doesn't matter