Hello... the Spider Jam's onboard sound processing options (Amp Model, FX) are really geared towards electric guitar input primarily. While it's possible to put some Reverb to the AUX input (for say, acoustic guitar IN), this FX won't necessary provide you with "natural and loud" qualities. To achieve those qualities, a good pickup system on the guitar itself, along with some EQ (tone control) and perhaps some Compression (to balance the gain-- but in a "clean" way without introducing a tube amplifier's overdriven tendencies) will probably be the tools. Unfortunately those do not natively exist within the Spider Jam amplifier. These would have to be 3rd party components (the pickup/preamp of the guitar and pedal or rack-mount FX's) prior to the acoustic guitar signal hitting the AUX input jack.