bbtri

Here is my solution to using the stock head unit to turn on and off an aftermarket amp. The stock head unit uses 2 wires to control the stock amp, the red and yellow amp on wire and the yellow and green ACC wire. The 'amp on' wire goes to 10-12 volts when the ignition is turned on. The ACC wire turns off the stock amp with a 4-5V signal if the head unit is off or the volume is zero. The signal goes to zero at a volume of 1 or higher, turning on the amp. To control an aftermarket amp, I needed to use a zero voltage signal to create the positive voltage signal needed to turn on an aftermarket amp. Here is the circuit diagram of how I did it:


The way it works is 1) voltage from the ignition-switched wire passes through the resistor to the remote switch turning on the amp. 2) if the ACC wire is at zero (volume on), the transistor is turned off, and the reed relay stays open and the remote stays at 12V and the amp is on 3) if volume is zero or off, the 4V of the ACC wire passes through the other resistor and activates the transistor. This closes the reed relay, which grounds the remote terminal on the amp, shutting it off. Current from the ignition-switched wire passes through the resistor to ground (about 60 mA, much less than an idling amp). I used the yellow/red input to the head unit for remote voltage rather than the 'amp on' output because the remote on the 2nd amp would nearly ground the amp on wire.
Parts list:
Reed relay - Radio Shack 275-0233, $2.49
Transistor, 2N4401 - Radio Shack 276-2058, $1.19
Resistors - Radio Shack 271-1325, $1.19 for 5

Here's the transistor soldered up:

Feel free to ridicule my soldering skills. If you do you got to post pics of your soldering on miniature items.
Here's the reed relay wired:

Here's the assembly. Don't laugh, it's a prototype. I'm going to do a neat one and pot it in silicone.

It's working well so far.

rockstar143

iTrader: (6)

Really interesting, thanks for posting this...I'd like to understand the schematic better...for the time being I actually wired in an ON/OFF toggle that kills power to the relays.

I'll also say this, I'm not 100% on the wiring and voltage, but I can say that using the stock remote turn on wire for the OEM amp to turn it on and my aftermarket amp (which is substantial) the oem wire for remote was not sending strong enough signal to turn the amp on. I had to run another from a ACC fuse.

jda123

Do you lose the navi and HFL with the HU off? ...or do you not care?

The stock amp is on all of the time for the navi and/or HFL.

rockstar143

iTrader: (6)

^^^that's a good point!

flyromeo3

wow..
I just did my aftermarket amp install this weekend and only thing I needed was a low voltage remote turn on trigger.

the remote turn on from the factory amp isnt 12v.
which is why you need the low voltage trigger.

RBeachTL

What the OP is trying to say is that the HU doesn't turn off, only the stock amp mutes or goes into standby. I've never checked what the Amp Mute signal from the HU to the amp does but BBTri is saying that if the HU is off or has the volume turned down that the amp is muted. I don't know how the amp uses this signal; if it goes into standby of activates a mute circuit but it must do something different from just powering off or Acura would have just grounded the Amp on signal.

bbtri

I don't have navi. I'll have to try the HFL.

bbtri

HFL works.

bbtri

Here's a simplified circuit - no relay required. The transistor acts as a switch. The purpose of the resistor to the remote is to limit current when the amp is muted. The purpose of the resistor to the transistor is to prevent exceeding the max base-emitter voltage of 6 volts.

rockstar143

iTrader: (6)

Ummm...you're a badass. Thanks for sharing.

Frosty

iTrader: (7)

thread bump!

Thank you, bbtri, for this DIY. I just did this today and it works perfectly. I would like to add that a reed relay IS NECESSARY for this circuit to function properly. I tried it using the simplified method with a transistor only, and the amp was on at all times (regardless of the headunit state). Also, unlike bbtri, I did not use the 2 HU input wires, but rather the 2 headunit output wires. Everything works the same way. Side note - I'm not sure why people say the factory 'amp on' wire doesn't provide enough juice to turn on an aftermarket amp. It does just fine with its continuous 12v signal.

Anyways, thanks again for the DIY. I'm happy this worked.

I Wanna Go Fast

bump bump this DIY is on point shout out to op bbtri

i was lost as to what the amp mute wire does...

just tested it out and found out that while playing tunes amp mute wire has 4.6-4.7v...when call incoming or bluetooth activated voltage drops to 0.0-0.1v.

so according to the diadgram and my test it seems as if the amp mute takes away the ground from the amp still not sure on how u still hear audio during a call if the amp is dead but this fix from bbtri seems as if it works as factory standard with aftermarket amp.

I Wanna Go Fast

I'm a dumb ass....the remote gets grounded. Duh