I bought a used 4412G but no manual came with it, so maybe someone on the list can help. This is the 1st TE amp I've ever owned so I'm not familiar with the DC pwr jack on the back panel--why are there two pairs of terminals? Is there a special plug that is made to fit over it and connect to the terminals? Also, any info on hard-keying this amp would be appreciated. Tnx.