I have a Magnavox era V4B that has two ext. amp jacks in the rear. I have one going to my Korg tuner and would like to use the other to go to the house PA. I have searched for a document to tell me which jack does what, but so far haven't found anything. I have the original sales brochure and it only says, "Patching Jacks In and Out". Have looked at the Ampeg site on the newer V4BH, but it is not the same. Hate to experiment and blow something either on the amp or PA. Any wisdom out there on the operation of the two jacks and which is which? Thanks.