Sound impact of including the output coupling capacitor in feedback loop


2008-10-28 8:55 am
Hello.I was wondering what is the impact on sound when including the output coupling capacitor inside feedback loop of a single ended power amp?
Ihav seen many amps from seventies where the output cap is inside feedback and on others it is outside.
Two examples are Sansui 2000X main amp unit and Sansui 4000
The reason there are two nfb points is simple. On the 4000.
R844/9 provides global AC coupled feedback in an attempt to make the response more linear and R845/6 adds a proportion of the current drawn by the loudspeaker as voltage, the more efficient the loudspeaker is at certain frequencies, the less out of phase nfb is added to the driver section, reducing the nfb at certain points in an attempt to get the best out of both worlds; poor linearity and poor responses from the loudspeaker.
This method has been and is still widely used by Yamaha and other well known makers.
Adding a small amount of positive feedback in with negative feedback has the advantage of bending the response to suit the result. If that makes any sense.


2008-10-28 8:55 am
Thank it seems a bit more clear to me.
Does this kind of 'dual' feedback affects dumping factor?it makes it higher?
does it corrects the capacitor distortion at low frequencies?i would say yes because the capacitor is part of he feedback now.

And what effect on sound does this 'dual' feedback have?
more/less detailed?
more/less warmth?
deeper bass?

I have many questions..:confused:
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