sound processor, eq, line driver?

As mentioned before, if the input level (gain) of the amp is matched to the output of the HU then the amp will put out max power.

If you have an amp with an adjustable gain of 8v - 2v, then a HU that puts out anything in between that will allow the amp to reach full power. So, an amp with an adjustable gain of 8v - 2v can reach full power with EITHER a HU that puts out 8v OR 2v, period. This eliminates the use for line drivers etc...

What amps do you know of that won't accept less than 2v input?

I walked outside and checked my sub amps. They accept from 8v - .003v. Meaning, even 3/1000 of a volt will still give the amp enough to reach full power. My front stage amp goes from 5v - .2v.

Do you see what we're saying?

You have some things mixed up here. Regardless of how many stars and posts I have, I can assuredly tell you, you have been misinformed some where along the line.

1. As mentioned above, the gain is a level matching system. Your statements are contradictory in the above post. So you use an Eclispe deck that happens to have 8 volt pre-outs, great, you need only crack the gain on you amp a hair (read; you adjusted the gain ever so slightly), for it to reach FULL output wattage of the amp (Not going to adress impedance yet).

Here is the contradiction, you now swap that Eclispe deck with some off brand deck that only has 2 volt outputs, now in order for the to be level matched  and produce FULL wattage output, you must crank the gain, and again it is producing the same wattage as when the gain was only cracked with the 8 volt input.

Oh wait, the amp produces full power either way the gain is set (only when leve matched properly)?? Yes, so the amp works at the same "stress" level when levels are matched! It doesn't matter where the gain is set!

2. Yes, of course changing (lowering, going from a 4 ohm load to a 1 ohm load for eg. ) the impedance presented to the amp will require the amp to draw more current from its power source (cars charging system) hence the light dimming, etc.

I don't think you understand the concept of a gain control.  It isn't a volume control.  It is there to match the amplifier to the head unit being used.  Since output voltage isn't regulated like it is in home audio, signal levels from head units will be different, therefore an amplifier needs a gain knob to adjust to those differences.  An amplifier producing 500 watts with a 2 volt input will be just as efficient and produce the same amount of heat as an amplifier producing 500 watts with an 8 volt head unit.  The difference is the gain will be set at different points.

Here's a great link that explains gain controls: http://www.bcae1.com/gaincon2.htm

That's not true.  My deck/processor combination has a pre-out voltage less than 1 volt (as was seen with an oscilloscope) and I'd bet it produces cleaner sound than your 4v pre-out head unit.  Pre-out voltage is a marketing gimmick pure and simple.  And I believe it is responsible for quite a bit of confusion and damaged equipment throughout the industry because so many installers don't know how to set gains correctly, much less the DIY'ers out there installing their own equipment.

Why wouldn't you go past 3/4 if the amplifier never clips?  I set my gains with an oscilloscope and found I could turn the gains all the way up and never get clipping.  What do you think will happen by doing this?

For most people adjustments with bass and treble should be enough as they don't know what they are doing.  A processor in the wrong hands (the monkey I described above) can do far more damage to the sound with a tool like that than good.  Give a paint brush to a kindergartener and all you get is a mess.  But that brush in the hands of someone who knows what they are doing gives us the Sistine Chapel. 

There is a lot more going on there beyond the simple output differences.  You are talking about two different subs with different harmonic distortion characteristics and different frequency responses.  However with the same sub, try swapping an amplifier with one that produces twice the power and you will be surprised at how small the jump in audible output really is.  I know I was when I went from a Soundstream Reference 500 to my Arc 1500dr on my Brahma 10. 

Actually 10 dB is double the loudness. 

Actually Dave is highly respected around here because of the extensive research he does and the experience he has.  It helps having friends who happen to be engineers at Harman Kardon.  You really need to pick your fights more wisely.  This forum isn't like many of the others, with teenage kids blabbing their mouths trying to sound like they know something.  Many of the people here have extensive backgrounds in this field. 

The decibel is a unit of measurement relative to a specified level. 

No reason yet for locking this thread tcss, so please try to keep it that way. BTW, Rule # 3, rules created by tcss should be taken with a grain of salt ;)

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