There’s no denying that wiring in a car amplifier is a difficult task, especially when you’re dealing with a factory car stereo. The situation just gets more complex when you add multiple amplifiers into the mix. And yes, you can wire two amplifiers, or even multiple amps, in one car audio system, but this takes some extra planning.
Generally speaking, the most crucial factors that you need to take into account when you wire in two or more amps are how to connect multiple amplifiers to one power source, how to properly ground each amp, and whether or not the remote turn-on signal from your head unit is strong enough to split between multiple amps. This is not to mention how to hook up two amps with one RCA jack.
Speaking of which, you can do this amps wiring in one of two ways. The most common is to daisy-chain the amplifiers by taking the signal from the RCA output of one amplifier and sending it over to the input on the next one.
The other way to hook up two amps with one RCA jack is to use RCA splitters (one female to two male) to split the RCA signal between the amplifiers. The second option allows you to easily gain match the amplifiers because the same input signal is sent to both amps.
How to Hook up Two Amps With One RCA Jack
#1. Daisy-Chaining Amplifiers
Daisy chaining amplifiers refers to running the outputs of one amplifier into the inputs of another. This is done by running one line signal through the amps using their bypassed input and output circuits. It’s essentially the equivalent of using a RCA Y-splitter to split a signal so the same signal can be sent to more than one amp channel.
By daisy chaining two or more amplifiers, these amps share the same signal, however, each one will work separately. In other words, you can run each amp separately than the other. What this means is that you can control your speakers and subs individually.
Daisy chaining is a great way to hook up two or multiple amplifiers with only one RCA pre-amp output. The downside, however, is that if one amp is off, it won’t be able to pass the signal through.
Additionally, when you adjust the gain on one amplifier, you must also check the other amp(s) to make sure your gains are perfectly matched.
It must be noted that daisy-chaining neither increases nor decreases the impedance load nor power output on any given amp. What changes the load is what you’re doing with the speaker outputs of the amplifier and how the speakers are wired together.
That said, do not confuse “amp strapping” with “amp daisy chaining”. The former is done to get double the power rating of one amp, while the latter is done to share the signal from one RCA jack between two or more amplifiers.
#2. RCA Splitting
As its name suggests, RCA splitting refers to using Y-splitters (one female to two male) to split the signal coming from the head unit, so the same signal can be sent to more than one amplifier.
RCA splitting does make it a little bit less complicated to gain match the amplifiers because you have the same input signal on both of them.
Some people think that by using a Y-splitter, the voltage will be divided in half, which is completely wrong. By using a Y-splitter, you’re essentially wiring two circuits in parallel, which means voltage stays the same.
Fundamentals of parallel circuits say that voltage is equal at all points, it’s the current that changes. So, since line level signals operate at such small current, the head unit will no have any difficulties trying to double the current output several times.
I mean, think of it like the battery in your car. When you add an external amp to your audio system, does the vehicle now only receive 6V and the amp receives the other 6V? What about when you add a second amplifier, do they all now receive 4V (12V/3)? No, they all receive 12V but the electrical system provides the additional current to support the added load (the amplifier). And when the electrical system is no longer able to keep up with the increased power demand, the voltage begins to drop drastically.
There’s no denying that there may be an imperceptibly small voltage drop. And if you wire a sheer number of amplifiers off of a single RCA jack, there may come a point at which the voltage begins to be noticeably affected. However, this would realistically never happen as no one would ever wire so many amplifiers off of a single RCA jack.
How to Split RCA for Multiple Amps
Splitting RCA signal for multiple amplifiers isn’t rocket science. All it takes is to invest in a Y-splitter (one female to two male), plug it into the head unit so that it looks like a branch coming out of a stem (as shown in the diagram above).
Next, hook up two more Y splitters (one female to two male) to each end, and you’ll end up with four “male” jacks. These jacks are to be connected to your amplifiers.