@raikkonen:
are there any other changes than the mentioned 10/56pf
compared to this one?
http://www.audio.webd.pl/pdf/lm4780_sch.pdf
are there any other changes than the mentioned 10/56pf
compared to this one?
http://www.audio.webd.pl/pdf/lm4780_sch.pdf
Many manufacturers of consumer audio equipment are in the far east, like China, Taiwan, etc. They are extremely cost sensitive so National's typical application circuits are usually for this type of market. DIY and higher end guys will know better and use more expensive components to get better sound quality. I have been to China and Hong Kong and it is amazing how they throw things together and if it works OK and sounds OK it is good enough. Been a few years so many things have changed some but quite different.
If you really want the best sound don't use the Ci capacitor (what National calls it) at all. This cap is ONLY for setting DC gain to unity. You will have more DC offset but it is typically still low enough (mV) to be fine. If you want to use the cap then using a larger value gets better bass response but more importantly pushes the distortion this cap creates further away. You can also parallel a small value high quality poly cap for better sound on the high frequencies.
The other caps, 10pF/56pF are probably for noise. I often use a 15 - 47pF cap on the input to signal GND to clean up the input. A cap across the inputs can be used also. Or if they are in the feedback path then they are there to reduce gain at higher frequencies to impove stability. Personally, I have never had stability issues with the LM3886.
-SL
If you really want the best sound don't use the Ci capacitor (what National calls it) at all. This cap is ONLY for setting DC gain to unity. You will have more DC offset but it is typically still low enough (mV) to be fine. If you want to use the cap then using a larger value gets better bass response but more importantly pushes the distortion this cap creates further away. You can also parallel a small value high quality poly cap for better sound on the high frequencies.
The other caps, 10pF/56pF are probably for noise. I often use a 15 - 47pF cap on the input to signal GND to clean up the input. A cap across the inputs can be used also. Or if they are in the feedback path then they are there to reduce gain at higher frequencies to impove stability. Personally, I have never had stability issues with the LM3886.
-SL
