Installed Aftermarket Amp And Sub

[carascod2000]

i installed a aftermarket amp to my factory radio and it sounds great but when i put the volume down on my headunit the door speakers go down but not the sub so if i want to put the volume down i got to pop the trunk and lower the gain somebody please help

[carascod2000]

I HAVE A 1992 LEXUS LS400

[Gaugster]

i installed a aftermarket amp to my factory radio and it sounds great but when i put the volume down on my headunit the door speakers go down but not the sub so if i want to put the volume down i got to pop the trunk and lower the gain somebody please help

I don't have any direct experience with your car but it sounds like the input to your amp is being fed by a audio signal that does not adjust it volume. This is common with the ML systems. The low level inputs to the external OEM amp do not control the volume. Rather the OEM amp changes the volume by adjusting its own high level outputs via a separate control signal from the radio.

In this case you would need to tap into the high level outputs of the OEM amp to have the volume function properly. A high level (Speaker wires) to low level (RCA Jacks) converter can be used to do this. The converters should be available at many electroncis stores.

Good Luck