Running a older Alpine CDA-7995 competition head unit using 1 rca pre-out to one Alpine PDX 1.1000 and 2 rca's to another PDX 4.150.

Things had been working "ok" for a while but the PDX 1.150 had been cutting out. PDX 1.1000 is brand new and was just installed. Was told it could could have been a wiring issue as i was only running 8ga. I upgraded to 4ga from the engine to the trunk today when i installed the PDX 1.1000. I put all new 4ga grounds in the engine bay and have 8ga power and grounds after my distribution block which is located in the trunk.

after i got everything upgraded and installed today, my mid range cut out all together. Using balance and fade i can confirm that all for 4 mid range speakers work, but they all sound like tweeters. All the mid range is gone. I have unpowered and reset the deck, the pdx 1.150 must be working if all 4 cabin speakers have sound. I have tried everything i can think of. the PDX amp and all speakers are about 8mos old.

could this be a head unit issue is there a way i can test the amp to see if its putting out any mid-range?

i am at a loss. thanks for your help!