Hello TB'ers - first timer; please be gentle Upgraded gear about 3 weeks with Aguilar DB750 and Whappo Jr. Sounded very good up until yesterday when tone went dull - kind of muted with perceived loss of overall range & clarity, and strange hissing rattle sound in tweeter at certain notes (consistent as note sustains - fairly loud), mostly in upper register of my 4 str Alembic Spoiler. Have not run head past 12:00 - gentle use at home practicing. Any ideas on where you would start to isolate the problem (other than contacting AG and Aguilar - in process). Could it be anything in the head? Hope not - bought used. Strange in that the tweeter doesn't seem to rattle with my SWR 350x head or GK800RB, but those have much less power and the cab still just doesn't sound right. BTW - changed the battery in the Alembic and put new strings on right away - problem still there. Thanks for any thoughts - I promise to contribute along the way for others after I get my selfish needs taken care of!