How may add a CD/MP3 Line IN to my amp.

[polo16mi]

Hi there:

I made an amp using a sansamp clone http://www.pisotones.com/GT2/GT2.htm as preamp, and LM3886 Chipamp as amp. It is wired straight the output of sansamp to LM3886 input.


I wondering how can i add an CD/MP3 input as, say, MG15CD, so i can jam a backing track.

My first idea, is wire a jack in parallel with sansamp output, directly to poweramp input, join Left and Right channels to + signal input, and gnd-gnd. Not sure if any trouble in that way. 


I see MG15CDR squematics, and it use a 10uf cap in series with a 10K resistor from preamp output, and a 3.3K from cd input. Joins resistors terminals and go to the power amp input.

Why they use that resistors? Not sure if it is for protection purpose or impedance dealing.

Can any help?

[J M Fahey]

You can't just join outputs.
Use separation resistors.
A classic value for SS amps is around 10K each.