Now, that is nice - thanks Alec.
The PSU will be 19 volts (laptop power supply) - will that change any of the values?
I assume, when using the battery pack to power the speaker, I would just unplug the above circuit output from the amp, and plug in the battery pack. That is the easiest.
Since I'm a novice at this, what value do I need for the M1 (P-Mosfet) = 20PCS New AO4606 AO 4606 SI4606 MT4606 N+P MOSFET SOP-8 ($1.05). I will just be soldering the circuit raw, so do I need special ends that will accept the solder?
and D1 MBR735 = 2 x MBR735G MBR735 Schottky Barrier Diode 35V 7.5A = OK?
Thanks

 

The PSU will be 19 volts (laptop power supply) - will that change any of the values?

No.

I assume, when using the battery pack to power the speaker, I would just unplug the above circuit output from the amp, and plug in the battery pack. That is the easiest.

That's one way. Or the battery pack could simply connect in place of the PSU.

AO4606 AO 4606 SI4606 MT4606 N+P MOSFET SOP-8

I wouldn't use that one. Go for something beefier (at least 10A rated), in a TO-220 package rather than a tiny SOP-8 package.

I'm not sure how effective this circuit or any of the other proposed current-boosting arrangements discussed in the previous posts will be in practice. A lot will depend on how the PSU responds to sudden demands for current beyond its capabilities. Will it shut down, go into current-limiting mode, or what? Also, sharing the current load between two sources will be affected by their equivalent series resistances; the one with the lower resistance will tend to provide the greater current.