Gain Settings -
This is another topic where it is easier to defer to more informational pages. I will however try to give a very rudimentary summary though; I will try to explain the purpose for gain settings. Basically when dealing with RCA inputs on amplifiers, the amp has to be flexible in how much power it is expecting to get through the RCAs from the head unit. Different head units can supply different amounts of voltage. The most common amount now for mid-level quality decks is four volts. Since the input voltage varies in different situations amplifiers have a gain adjustment that is used to 'match' what the head unit is sending with what the amplifier is expecting. For more info on how gains actually work go to www.BCAE1.com section 63. Gain Controls.
Some people make the mistake of using the gain as a volume knob, thinking that 50% gain means 50% power and 100% gain means 100% power. The problem is that in doing so is there is a very good chance they will actually go beyond the amp's capabilities and force it into clipping, as was discussed above in the section "Power Requirements". I can't emphasize enough how bad clipping can be, it is easily the #1 cause of blown speakers and is also a leading cause of blown amps. Also keep in mind that even with properly set gains, using a bass boost or similar feature will greatly increase the chance of clipping. The best idea is to leave all bass boosts off, they are actually detrimental to sound quality and increase the chance of blowing your speakers. Below are some links that show the proper ways to adjust the gain settings so things work correctly
http://www.jlaudio.com/tutorials/Inp...nsitivity.html
http://forum.sounddomain.com/ubb/ult...c;f=2;t=030419
Amplifier brands -
Most manufacturers have various lines of equipment, and these categorizations are based on overall offerings (the low-end of a line might still not be worth buying even though the mid or upper models are good quality; while some companies top tier model is the only item of exceptional quality). Elite brands are typically thought to be an amplifier whose price puts it beyond the accessibility of the general car audio consumer. Quality brands are for those people who are willing to spend the money to get an above average audio system that will be of good quality and reliability. Value brands are for people who want something superior to most all OEM systems, but are limited by budget (best bang for the buck). Those amps listed as Poor are a brand with known reliability or quality problems.
I can't emphasize enough how rough this generalization is, and that it just attempts to throw out names and let people have some rough idea what the GENERAL feelings are toward a brand of amplifier. There are some cases where as a brand they are significantly toward the top or bottom of the category they have been placed into as well. For example, the JL "slash" series are on the high end of quality and on the high end of the pricing for that category; while Alpine amps are usually ultra reliable and cheaper than some of the other offerings, but the SQ is questioned by those who prefer upper quality or Elite level amps. The worst part is that there really are issues between the Elite and Quality level amps where they blend together, but again this perspective is based on an average for all lines made by that manufacturer. There are also situations where a brand such as Lanzar has a really poor line like the Vibe but the old Opti line is decent quality for the money.
Also, these opinions are limited to the current lines. Some things change drastically over time (a lot of that can be due to a company being bought by a competitor buy still using the same old name with lower quality products). Some of the older specific model lines worth mentioning are Alpine 35xx, Orion HCCA, Phoenix Gold ZPA, PPI Art, Soundstream Reference, and several of the old Rockford Fosgate amps. Lastly all brands are listed alphabetically in their respective category. Another odd situation is that some people feel US Acoustics mono and 2ch amps are 'Value' while the 4ch amps should be categorized as 'Poor'.
Elite - Arc, Audison, Brax, Helix, Linear Power, McIntosh, Milbert, Phass, Sinfoni, Tru Technology, US Amps, Zapco
Quality - Alpine, Cadence, Infinity, JL Audio, Kicker, Memphis, MTX, Phoenix Gold, Rockford Fosgate, Soundstream
Value - Clarion, HiFonics, JBL, Profile,
Poor - Audiobahn, Boss, Lighting Audio, MA Audio, Pyramid, Road Gear, Rockwood, Sony
Closing Thoughts - This FAQ & Buyer's Guide started out as an attempt to try and help people with some basic knowledge on this topic. After running through all of this I am a little concerned that there is so much information that the people who need it the most won't read through it. On top of that, I still feel like the information only scratches the surface. Any more pertinent information or especially links that might help shed more light on this topic is much appreciated. Please just don't turn this thread into an argument which amp is the best. I really hope that this might help some people out there. Thanks to all of the knowledgeable regulars on here who have contributed so much and a special thanks to BryanH and the suicidal eggroll for advice on this FAQ.
