With my new head unit avic f700 I have hissing from amp with motor off if I lower gain on amp it goes away but I can not get music as loud as I like. running alpine 55 watt x 4. Am wanting a pdx 5 anyway which is 100 per channel will that allow me to keep gain on amp lower thus less hissing but still achieve amount of sound I like?

 

If you have the gain turned all the way up it will get that hiss you talk about. You want an amp with more RMS power than the speakers RMS. This helps with sound quality and it keeps the amp cooler. The Amp with amplify anything it gets through the RCA's. If your deck is a cheaper model it maybe putting out that hiss signal and the amp is amplifying it. Want you want to do is turn the volume to about 3/4 of max and set the amps gain to a level that would be your max volume you would be comfortable with. This goes for High's and Lows amps. If you have to turn the gain on your amp up beyond 70% or so you need a bigger amp. General rule of thumb is if anything is turned up beyond 70% you get into THD issues and sound quality will suffer.

 

Amp gain is NOT a volume control. It is there to match the output of the source with the input of the amp. Ideally you would set it up with test tones and a scope. Basically you need to determine the highest output of the head unit before clipping. If your head amp has a volume scale of 1 to 100 and you find it clips at 87 you would set it just below at 85. Now turn up the gain on the amp until the amp output clips and back it off until it stops. That is the correct way. It is normally done with 1Khz test tones for full range amps and something lower for sub amps, maybe somewhere around 80 - 120 Hz.

You should always buy speakers that can handle the full output of your amp not less. 01 gt has it backwards. THD is not the same as clipping. It is ok to turn your gain up over 70% as long as you are not clipping the outputs.

 

I never claimed to be an expert on the matter. I stated what has worked for me for 25 years without computer programs and test equipment. I have done competitions and blown windsheilds out of trucks, and made pants crawl on your skin from 100 feet away at 10 cycles. I also know that by the book is not neccesarily the best way to do anything. It's a guide. For me It's what works everyday all day in any temperature, windows up or down, parked or going down the freeway at 70+. I choose my equipment and tune by ear. Many factors, many blown speakers,amps,fuses and broken windows has made my formula over a long time. In the end You can hear ever nuance at high volume or low with any type of music and nothing gets to hot and nothing blows, something was done right. Alot of people build systems that taylor to a specific type of music. I like pretty much all types of music and that is a more difficult system to perfect.

 

you both have good points

and norm I have heard the gain is not a volume control but if you turn down the gain you get less volume. when I turn mine down to were it is matched good it is not loud enuf.
but if I increase the gain I get poor quality. My question was If I get a higher watt amp will I be able to acheive both?

Also are the alpine pdx 5's good amps? Looking for a good 5 channel that is smallish in size.

 

That would depend on your speakers. The Amp you have now is around 25 watts RMS...not very much. The Alpine pdx5 is a decent ampm from what I read on it. I prefer amps with a better signal to noise ratio. It is a class D amp which means it should run pretty cool. I didn't see a spec on dampening factors on the sub output. The higher the dampening the better it can control your sub.

 

Well I have decided I need a sub just one 10 with 200-300 watts i think.
And I really want just one amp so 5 channel but some of them are so large I am
Afraid they will over heat behind the seat. I would also like more like 75-100 per channel
To door so I can upgrade them down the road I am running db571's now.
Any suggestions not loaded with cash and not looking for any professional class
Stuff just normal driving use.

 

I've used this online Amplifier Voltage Calculator with a multimeter to get good results before.

 

I would modify your doors to fit in 6" components or polk x9's. I love the sound the polk DB's put out. clear and loud. set the highs X-over point at 100-120hz and the same with your sub. that should leave you little to no gap in sound. placement of your sub is important to. What type of truck do you have, IE standard, supercrew, extended cab.

 

Supercrew

 

If you turn it down you will get less volume because you are using less of your amp. If you turn it up too high you will get poor quality because you are either clipping or driving your speakers too hard and there are mechanical noises. This is what happens when the speakers cannot handle the output of the amp. If you set up your gain structure correctly you will get the best your system can provide. If that is still not good enough then you are correct: You need to upgrade.

 

Look at my pics. I got my Subs behind the seat. If you want I could give you some pointers on how I did it.

 

You can not get subs behind the seats in an 06 I believe the only place would be under seats.

I am thinking get 5 channel AMP sell old amp then few months later get sub see how it sounds then decide about upgrading door speakers.

 

I was also looking at this amp
http://www.crutchfield.com/s_136XD70....html?tp=35808

 

The JL has a way better signal to noise ratio. You would be happier with that one over the alpine any day. Your plan sounds solid. I say go for it.