Capacitor in the KSA 100 ltp

Mambo · 2nd September 2003, 08:32 AM

I'm looking at the schema of the Krell KSA 100 amp, and i'm puzzled with the 470uF caps in the emitter legs of the input stage, after the degeneration resistors...
What is their real use ? it seems, from simulation, that it can reduce the first harmonics level.

Thank You,

hatasa · 4th September 2003, 07:15 AM

Hi,

As I undersand, for increase the open loop gain there....

Regards,
Hatasa

Charles Hansen · 6th September 2003, 02:20 AM

Hello -

I agree with Hatasa. Increased gain from the first stage, but also increased distortion from the first stage due to lack of degeneration.

But then the increased overall loop gain translates to increased overall loop feedback, which reduces the closed loop distortion again.

Personally I prefer to keep the distortion to a minimum at each stage. Also, if the schematic is drawn correctly, there is a small AC signal across an unbiased electrolytic capacitor. This will also increase the distortion as the cap can be slightly reverse biased. Also, many people can hear the sonic signature from the electrolytic capacitor.

As always, there are lots of tradeoffs to choose from. Each person will make different choices.

Hope this helps,
Charles Hansen

2nd September 2003, 08:32 AM	#1
Mambo diyAudio Member Join Date: Feb 2002 Location: Italy	Capacitor in the KSA 100 ltp I'm looking at the schema of the Krell KSA 100 amp, and i'm puzzled with the 470uF caps in the emitter legs of the input stage, after the degeneration resistors... What is their real use ? it seems, from simulation, that it can reduce the first harmonics level. Thank You,

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4th September 2003, 07:15 AM	#2
hatasa diyAudio Member Join Date: Oct 2001 Location: Hong Kong	Hi, As I undersand, for increase the open loop gain there.... Regards, Hatasa

6th September 2003, 02:20 AM	#3
Charles Hansen diyAudio Member Join Date: May 2003 Location: Colorado	Hello - I agree with Hatasa. Increased gain from the first stage, but also increased distortion from the first stage due to lack of degeneration. But then the increased overall loop gain translates to increased overall loop feedback, which reduces the closed loop distortion again. Personally I prefer to keep the distortion to a minimum at each stage. Also, if the schematic is drawn correctly, there is a small AC signal across an unbiased electrolytic capacitor. This will also increase the distortion as the cap can be slightly reverse biased. Also, many people can hear the sonic signature from the electrolytic capacitor. As always, there are lots of tradeoffs to choose from. Each person will make different choices. Hope this helps, Charles Hansen