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Discussion Starter · #1 ·
I have an Avic HU which has max 2v outputs. I run this to an alpine pdx 4.150. Two of the amp channels power my PPI 356comps.

The gain on the amp is turned all the way down, and I cant turn the head unit up beyond half or it is too loud. This means that most of the time I am playing the HU at 10/40 or so, and the signal from the HU is low voltage and not ideal s/n.

I would like to run the HU hotter, but I cant turn the gains on the amp down any furhter. Any solutions?
 

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That is perfectly fine. HU is most of the time is worse then the amp (unless you get some flea-bay or some really cheap stuff). Bottom line is, your fine. I run my amp gains at 90% and test my HU with different songs so I have a general idea how loud I can play it. I have a clip meter and have found this to be 100% true (HU is worse then using amp gains).
 

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In the sense that you can add resistance to the sub, yes but the sub with draw less power from the amp and the sub can only handle what it was designed for. The subs thermal capacity can only be so much. Also in doing so, you might change the subs T/S perameters.
 

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You don't want to add resistors because this will effectively just be working your amp harder for no reason. The resistors can also get hot and that can cause problems, although the chance of this happening is much less than it used to be, when finding high quality resistors capable of handling high powered amplifiers was more difficult. The amp will also react different to a load with a resistor wired into it. A resistor gives the amp a static value, whereas the sub's resistance is dynamic. If you are simply looking for a solution that would allow you to use more of your head unit's volume control, I'd recommend the attenuators that stores like parts express sell. They plug into your RCA inputs and attenuate the signal so that you can just your gains more. However, if you are getting the volume you want and the system is balanced the way you want it, you are doing just fine the way things are. I would only add attenuators if you need to be able to use the volume and gain controls to better control the balance of your system.
 

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the majority of the worlds resistors are 1/4w. some of the power resistors are 5-20w. what do you think will happen if you send them 150w?
 

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You'd need what's called a dummy resistor and they do make them to handle a lot of power, but andrave is correct - any power that the resistor will take is merely power that is being wasted by the amplifier. There is no way to use a resistor that will make the speaker take more power. All it can do is make the amp work harder. The only way to increase power to the speaker is to modify the amp or to lower the impedance of the speaker (usually not possible, unless for example it's a DVC sub and the coils are currently wired in series - then you could wire them in parallel if the amp supports that load)
 

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Strange because a new PDX should be good for 8V or something new HUs and have less gain.

Normally you turn the amp gain way down and turn the HU way up to see if the HU clips but at a low output. Then you only use the volume range on the HU that is clean, and set gains back up to use that range. Cheaper HU do clip, but better ones will not at least at zero EQ.

Something still seems amiss here, how would you run a higher voltage HU on this amp then, and everyone does. When I test amps I find new amps have less gain, some I can't even get to clip on a 2v HU while every old amp will.
 

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Strange because a new PDX should be good for 8V or something new HUs and have less gain.

Normally you turn the amp gain way down and turn the HU way up to see if the HU clips but at a low output. Then you only use the volume range on the HU that is clean, and set gains back up to use that range. Cheaper HU do clip, but better ones will not at least at zero EQ.

Something still seems amiss here, how would you run a higher voltage HU on this amp then, and everyone does. When I test amps I find new amps have less gain, some I can't even get to clip on a 2v HU while every old amp will.
I agree. I think we are missing something....does the OP have a line driver and not know it? Is the OP turning the Gain adjustment the wrong way and not know it? This just seems wrong and I have never heard of this happening, even from a 4volt deck or higher.
 

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I agree, how high voltage can those alpine amplifiers set?

most I have seen will take 5-10V input turned all the way down and even on 4V HU, if you set it for 10V you will not be able to drive the amp full out.
 

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Discussion Starter · #14 ·
OP here. . .

There is nothing "wrong" here, with my HU or my amp. I am running a set of PPI comps, that I think are 75rms, but I am hitting them with twice that, per other users on this forum.

The problem is that I have little granularity of volume control from the HU. A volume of "8" is too soft, and a volume of 15 is pretty darn loud. 20 is uncomfortably loud.

If I can stretch out the volume range, I can have a more usable volume control, also I will be operating in the proper range of the HU and maximize s/n for better fidelity.

Thanks for suggesting on volume attenuator. Nothing is wrong with volume settings or hook up, the amp is just twice rated the speakers.
 

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