Application Hints
STABILITY
The LM1875 is designed to be stable when operated at a
closed-loop gain of 10 or greater, but, as with any other
high-current amplifier, the LM1875 can be made to oscillate
under certain conditions. These usually involve printed circuit
board layout or output/input coupling.
carlosfm is banned and will not answer
For a lower supply like +-15V a gain of 10 would be good
Around 1 Vrms input would give maximum power peaks.
For schematic the recommended standard circuit from National datasheet would work best.
Reason?
Because National want their chips to work good and become popular

So, if they would NOT publish optimal standard circuit,
they would not act in there own interest of selling many chips.
Customers staisfied = Best advertising
We should not have any doubts, that this standard circuit has been carefully tested
in very advanced electronical laboratory with test personel with high education/knowledge
and that have
testing gears we DIY members can only dream of
Such a big company as world leading National Semiconductors
does not pick amateurs of the streeet when selecting their technical staff.
They can afford to handpick only the best.
This is why you should FIRST consider the standard circut.
From this you can make small adjustments, if your system have some special need.
Also for PCB study the recommended PCB layout for LM1875.
It is not done by chance by some unqualified person
and not without careful consideration and testing
Let us not fool our selves too much, in thinking we know better than best qualified people.
After all, they do this for their profession. With the experience that comes from years.
-------------------------
Some DIY members here are good.
But I do not for one minute think
that National handpicked laboratory personel is inferior in any aspect of Audio electronics.
Links:
http://www.national.com/ds/LM/LM1875.pdf
Search www.diyaudio.com for LM1875, via google:
http://www.google.com/search?q=+site:diyaudio.com+diyaudio+LM1875
Attachment.
LM1875 PCB layout.
note: Should be mirrored, as is shown from component side.