You can feed the JBL’s from your head phone output. You’ll need a 3.5mm TRS to L & R 6mm or 1/4″ tip sleeve connectors with wire of appropriate length. For more control over level I would suggest a Pyramid SEA-2500x preamplifier. It has RCA in & outs. Check it out on line to see all the features it offers, about $100.
\”I push the RECORD button and hope for the best\”