Adding Aux input to solid state guitar amp

[ccnw]

I'd like to tap in just before the TDA2030H power amp chip to insert backing tracks from a phone or mp3 player. (Amplifier schematic attached) From what I understand I could insert a resistor in the existing preamp line and place a similar resistor in line with the additional incoming line, tie them together and send them into the existing power amp input, creating a summing point Just a guess from what I understand and can google. Are the resistors actually necessary or could I just put a healthy sized cap in the incoming and line and hack it in? The other alternative I'm wondering about would be to bring the auxiliary input in at the negative input (labeled input 2). Might this work? Please school me here. Thanks!

[P90]

Another option would be to get a multieffects pedal, such a a zoom g1on and plug into the built-in aux jack...

[ccnw]

Thanks, but in this case I'm trying to go minimalist and not bring out anything from my typical overstuffed "gear closet".