HI ACD & all,
In my eye,the copy of KSA50 have a mistake like the post #33 of jwb show here:http://www.diyaudio.com/forums/showthread.php?s=&threadid=42357&pagenumber=4
Although I am an amateur audio DIYer in China, I had viewed several hundreds power amp schematics
.I had found that no power amp has a miller cap which is over 100pF in this situation (the gain of VAS stage is very high).If I am wrong,the open loop freq band of kas50 will be worse than the 741 op amp
I think that the value of C105,106 should be 39pF,not 390 pF.
good luck
X.G.
In my eye,the copy of KSA50 have a mistake like the post #33 of jwb show here:http://www.diyaudio.com/forums/showthread.php?s=&threadid=42357&pagenumber=4
Although I am an amateur audio DIYer in China, I had viewed several hundreds power amp schematics
.I had found that no power amp has a miller cap which is over 100pF in this situation (the gain of VAS stage is very high).If I am wrong,the open loop freq band of kas50 will be worse than the 741 op ampI think that the value of C105,106 should be 39pF,not 390 pF.
good luck
X.G.
X.G.
You might be right. I haven't made any calcs yet
I have made the first "rough" layout.
Size app. 7.5x10,75 cm or 3"x4.2"
Please let me know your suggestions for any improvements, before I go further.....
However... NO
and please clearly explain your reasons for your suggested improvements, so all can participate and so I don't have to make a mill. minor changes with no effect
You might be right. I haven't made any calcs yet
I have made the first "rough" layout.
Size app. 7.5x10,75 cm or 3"x4.2"
Please let me know your suggestions for any improvements, before I go further.....
However... NO
and please clearly explain your reasons for your suggested improvements, so all can participate and so I don't have to make a mill. minor changes with no effect
May be it will be possible to co-operate with wladl, an author of a preliminary Krell 50 PCB showed at Polish forum.
Look at post dated 2004-10-21 08:18:21
http://audiostereo.pl/forum_wpisy.html?temat=11843&p=3#k
Look at post dated 2004-10-21 08:18:21
http://audiostereo.pl/forum_wpisy.html?temat=11843&p=3#k
First of all i am not good at layout and i have never done any myself so thake this more as questions than any kind of critique.
1: The feedbacksensing shares the copper on the PCB with some other parts on its way t R130 and R145 is that ok. Couldn't you have the sensing wire taken directly from before the Zobel to directly connecting to R130 and R145?
2: As i see it an emitter follower is less suceptible to powersupply noise than a common emitter so woud there be any benefit of not sharing the supply for q107 q108 emitterresistors with the rest of the early amp stages, like a star ground for the power rails.
Not bashing more like asking questions to learn.
Hjelm
1: The feedbacksensing shares the copper on the PCB with some other parts on its way t R130 and R145 is that ok. Couldn't you have the sensing wire taken directly from before the Zobel to directly connecting to R130 and R145?
2: As i see it an emitter follower is less suceptible to powersupply noise than a common emitter so woud there be any benefit of not sharing the supply for q107 q108 emitterresistors with the rest of the early amp stages, like a star ground for the power rails.
Not bashing more like asking questions to learn.
Hjelm
Luke
Just use 0.2 Ohm value if you prefere to do that
I prefere 0.1 or 0.15 Ohm emitter resistors,
if the power-transistors are pretty good match regarding Hfe....why not go for high effeciency, better peak current and not to forget lower THD
But a hint you better use:
when using low Ohm Emitters for hi-power/class A amps....use multiturn-pots for bias and DC-offset adjustments, this detail gives the last drop of stability.
AuroraB
True class A for 50watt/8Ohm demands 3.5 Amps idle current
A more "human" approach is to go for 2.5 amps idle
Check the math out....true Class A amps aint "cheapo" to play around with
Just use 0.2 Ohm value if you prefere to do that
I prefere 0.1 or 0.15 Ohm emitter resistors,
if the power-transistors are pretty good match regarding Hfe....why not go for high effeciency, better peak current and not to forget lower THD
But a hint you better use:
when using low Ohm Emitters for hi-power/class A amps....use multiturn-pots for bias and DC-offset adjustments, this detail gives the last drop of stability.
AuroraB
True class A for 50watt/8Ohm demands 3.5 Amps idle current
A more "human" approach is to go for 2.5 amps idle
Check the math out....true Class A amps aint "cheapo" to play around with
bremen nacht said:
Paralelling 0.1 is 0.05 ohms not 0.4 ;-)
By the way, the KSA-100 and the KSA-250 both use 1 ohm emitter resistors. I have seen manufacturer's use higher rated ER's in class-A amps than in Clas-AB. (There are always the exceptions, right?). Even though you will get higher efficiency and TDH with lower ER's, I suspect your will cause the sound to be different than what the KSA-50 sounded like.
Remember, many people still think the KSA-50 is one of Krell's best sounding and one of Stereophile's top 10 power amps of all time. ;-)
I would stick with the stock ER's unless you want to play around.