Nothing exotic or erotic. Good 1980s Japanese design. A lot like an oversize effects pedal.
DO NOT SHORT THE OUTPUT!! There is NO protection for the power transistors.
Input amp is NFET-PNP working from quite high voltages. Volume pot, and clipping diodes with high part-numbers suggesting a late revision. NFET buffer. Fender-like tonestack. Tone recovery with another NFET-PNP pair. More clipper diodes. Reverb feed, NPN buffer, reverb mix, power amp.
Spirit 30 and Spirit 50 differ in supply voltages, appropriate gain change, and frills. The 50 has overdrive knob and Pre-Out Main-In jacks. The connections are on the PCB, just not used on the 30.
I got the manual from the link above: http://www.stereomanuals.com/man/rep/roland/index.htm
The site has instructions for PayPal-ing an order. Get his pay-to email address. Be sure your PayPal account has your proper mailing address. Send 5 bucks with this info in the "Additional Notes":
Roland SPIRIT-30 Guitar Amp Service Manual
Item #101219090038 $4.00 Shipping $1.00 TOTAL $5.00