New radio and JBL system

[406hdi110ex]

I replaced my execs normal cassette player with a cd player unit i got from an 03 406, my car has the jbl amplifier and i notice this new radio seems to have too high a volume ie 0 is nothing but 1 is where 6 would have been its very loud. Is there devices i could get such as a supressor which would tune down the signal going from somewhere, i dont know how to wire it up but do know where the amp is. All i need is someone to tell me what item i need and how to wire it up.
Thanks

[406hdi110ex]

some say its not solveable but i disagree

[newton]

I know it sounds silly but have you set the levels to match up with the radio volume control and the gain on the amp. if all speakers are running off the amp and its set to high compared to headunit then the moment u turn it up it will be really loud.. just a thought (i did it with my system first time i installed it)