Car Stereos: New Mono amp not making my sub play, mono amp, rca output

Question
QUESTION: So I just got a Hifonics HFi10001D amplifier to upgrade my current power acoustik one. I also am running a 4 channel amp off of my head unit which is a KDC 138 (only 1 set of RCA output) so i run the RCA's to my mono amp and use the outputs on the mono to share the RCA to the 4channel and use Y splitters to get the connection to my 4 channel which requires 2 sets of RCA's. Everything turns on and grounds are solid. The problem is that when i hook my sub to my mono amp no sound comes out. If i hook the sub up to the 4 channel sound comes out.. What is the problem? is it the amp? or is the RCA not giving a clear signal? with that question i feel like it should be getting a clear signal since my 4 channel amp gets a clear signal from the outputs on the mono amp. Hopefully this makes sense.

ANSWER: Hi Nathan,

Being that you said you get sound from the subwoofer just fine when you hook it up to the 4 channel whose getting its sound through piggybacked and y-splitted cables, that would lead me to strongly believe that your mono amp is not working correctly.

Does the mono amp have a light to tell you its on?  If so, make sure it's turning on at all (ie the remote wire is doing its job).

The likelihood that you're having signal issues is highly unlikely, since, like you said, the sound is getting to the 4 channel amp just fine.

Justin

---------- FOLLOW-UP ----------

QUESTION: Hey thanks for replying and yes the mono amp turns on fully no safety mode either its all green and the face light turns on also. So I'm not sure why the signal does not go through to the sub.. because the 4 channel is getting the signal through the mono amp.. just the mono amp isnt pushing the sub.. I was reading the manual for Hifonics and it says something about needing to use a y splitter for the RCA that comes from the head unit if it is full range speaker RCA signals and split only one of the RCA's either right or left and plug the splitted right or left into the input of the mono.. if that makes sense? or just use a mono sub woofer RCA port for the mono. so im going to wait for my new Head unit to come in and hook the amp up to the mono sub RCA and see if that fixes it. if not im going to return it and try to get a replacement..

Answer
Hi Nathan,

All a mono output does is mix the two channels into one... if you're not getting any sound out of the sub right now at all, unless you have some sort of high pass filter blocking out the frequencies going to the subwoofer running on the deck, that's not going to fix your issue.

It sounds to me like you have a bad amplifier.

Justin