amp input sensitivity

[Ludi Mali]

quick question. lets say my HU preouts put out an 8v signal, what happens if the rated input sensitivity of my amp is 0.2-5V?

[Ludi Mali]

anyone....anyone.....bueller.....bueller....

[pookypal15]

I doubt your head unit puts out that much signal, that's too much - that's like a regular signal to drive speakers. And if it really does, test it with a mutlimeter, since it comes out to almost twice what your amp is recommend to handle, your amp will probably be damaged in regular use, at least blow a fuse (cheap amps just fry, they don't even have fuses). If the voltage tester/mutlimeter comes to readings that don't rise above +/-5v, then it's probably a safe hookup and not much to worry about. Otherwise if they truly rise up to +/-8 and you have to use that HU, look into putting some kind of resistance into the line to shed off the power before it meets the amp, but problems with like adding passive resistors (though quickest and simplest) is the sound quality degenerates after it passes through it!

[Vanilla Sky]

what kind of HU do you have? higher end units do have insanely high line outputs... nakamichi, eclipse, high end alpine... i've seen outputs rated as high as 9 volts...

[Strugglebucket]

just set the amp inputs to the lowest gain setting and you'll be fine. only thing is the sweep of your volume control will be shorter, i.e. the amp will reach full volume at a lower volume on the head unit and your increments of adjustment will be larger as opposed to if you had the sensitivity matched perfectly.
good news is your signal to noise ratio will be great! just watch that you don't turn the head unit up so much that you clip the input.

[Ludi Mali]

yeah its an eclipse cd8454, friend of mine is selling his for 200. he only used it for 6 months. So you're saying it only puts out max voltage at max volume, and at a lower volume it'll just have a lower voltage?

[Strugglebucket]

yup.

[Vanilla Sky]

isn't that why it's rated as "max" level output?

[pookypal15]

just set the amp inputs to the lowest gain setting and you'll be fine. only thing is the sweep of your volume control will be shorter, i.e. the amp will reach full volume at a lower volume on the head unit and your increments of adjustment will be larger as opposed to if you had the sensitivity matched perfectly.
good news is your signal to noise ratio will be great! just watch that you don't turn the head unit up so much that you clip the input.

yeah that's good thinking... of course most people don't have their HU up at full blast since you hear high frequencies alot better and feel lower ones more, so you should never really reach that 8v max.. but you still wanna be VERY careful of NEVER clipping your amp - the amp will survive a few clips, but it's just as bad for the speakers since it puts them through frequencies they're not used to. You can bleed off some of that power as the volume gets louder on the HU by putting something between the preout and the input for maximum safety. you could put a variable resistor/attenuator (basically a passive volume control), that would be kinda cool cuz you can mount it on your dash and it's use would really be to turn down the amp, to keep it from getting too much juice as HU gets louder (depending on what your amps volume already is). Or/and you could put two (L/R) low voltage colored lights, so that as the signal passes through them they dissipate into the fillaments and continue to the amp - also got the coolness factor of lights that dance to music. The problem with that is too low voltage and they burn out quick, too high and the resistance is bad for the HU and they won't reproduce that much of the spectrum (have to use AC only). LEDs would be great, but those won't handle more than like a max of 2v and they're dc.

[Hash_man_Se_i]

Very very nice deck, wicked deal for 200 aswell, eclipse 8v decks are awesome.

[87DXHatch]

Your friend doesn't happen to have a second one, by chance? That's the very deck I was looking for, and you nabbed it for about $100 than the average price they go for on eBay or elsewhere.

Like others have mentioned, just minimize the gains on the amp and then be careful with the volume knob. With the 8454, you can also adjust the level of outputs for all the different pre-outs it has, so you can lower it to a level that you won't risk damaging the amp/speakers.

If you find that it's too much HU for you, feel free to drop me a PM and I'll take it off your hands.

[Hash_man_Se_i]

yeah its an eclipse cd8454, friend of mine is selling his for 200. he only used it for 6 months. So you're saying it only puts out max voltage at max volume, and at a lower volume it'll just have a lower voltage?

All eclipse decks put out either 5v or 8v RMS, so no matter what frequency, they will put out that voltage, so in turn, they sound awesome.

[87DXHatch]

All eclipse decks put out either 5v or 8v RMS, so no matter what frequency, they will put out that voltage, so in turn, they sound awesome.

That is incorrect. Some eclipse decks put out 16 volts (balanced). But when a deck is rated for 2v, or 4v, or 8v outputs, they aren't ALWAYS putting out the rated voltage... just like an amp isn't ALWAYS putting out 200 watts RMS or whatever it's rated at. It's only putting out the rated voltage at, or near, maximum volume. If it always put out the same voltage, you would have no use for a volume control, because it'd always be maxed out!

They don't vary as far as current goes (amperage), they vary as far as voltage goes. I'm not sure exactly why this is, but I know that if you were to take a DMM to your pre-outs, you will get varying voltages up to the maximum RMS voltage, depending on the volume level.