car audio ignorant...

Systems

hey guys,
I just bought a new car and the first thing I want to do to it is upgrade the sound system.
No subs, just some good aftermarket speakers and an amp.
Anyways, I've been looking through a few posts here and decided that I don't want momo, but I don't want the cheapest line Polk makes either.
I have 6 1/2's in the front and 6x9's in the back.
I was at a stero shop last weekend looking at multichannel amps and the guy beside me asked what class they were and he said they were analog. Is that what I need...I think he also mentioned a class d but it was made for subwoofers and that they were digital so they could make them smaller but by making them digital they lost sound quality which is why they only make them for subs...because the sound quality doesn't matter as much. What is he talking about?
Thanks for all the feedback!

PoweredByDodge

*BASHING HEAD AGAINST THE WALLLLLL*


AAAAAAGHHHHHHHHhh HEY JUSTIN WHERE IS THE ANGRY SMILEY EMOTICON!!!!!!!!!!!!!!!!!!!!!!!!!!!! ***INSERT ANGRY EMOTICON***

*cough cough* -- well... the gentleman beside you - whether he worked for the store or not - is smoking something from the 1960's.

First - there is no such thing as a digital amp... all amplifiers for audio are ANALOG. now... some of these amplifiers have DIGITAL PROCESSING, which includes crossovers / equalizers / bass boost / and other controls... however that signal must then be converted back to analog and then sent to the "amplifier portion" of the amp -- which like all other amps -- is ANALOG. now -- those digitally processed amps i spoke of -- htose are actually more expensive and have equivelant sound quality -- some would argue better.. i would argue similar... but thats debatable... and... they cost more... and they're not for subs -- they're for anything.

class "D" is not for "digital" -- its for "d"...

class D amps are analog -- 90% of them dont have digital processors -- let me rephrase -- 90% of hte amps on themarket today or any kind do not have digital processing -- class D amps only play a frequency range of up to 250 hertz (give or take), they are mono (one channel not two), and can usually drive very low impedance loads and put out a disgusting amount of power (which is usually coupled with higher distortion and lowered damping, but in the long run, its cheaper and more efficient to build a 1000 watt class D amp than a 1000 watt "other class" amp.)

For your regular 4 speakers, you will want a class AB amp... or... ifyou're full of money -- a class A amp.

Class A amps utilize vaccuum tube technology -- contrary to popular belief, the 1950's were not the end of tube tech. class a amps use tubes in either the output stage or the input... or both. few to none still use them in the power stage as its ultimately irrelevant. tube amps are regarded as the absolute best in teh sound quality competition world and usually retail as low as 700 dollars for a single one piece 75 x 4 watts into 4 ohms model up to thousands and thousands of dollars for a parcel-ed unit (separate power supply and output stages). you will not find any of this at circuit city.

class AB's are the everyday man's standard and the most common amp used for both relatively high power and good sound quality. while 1000, 2000, 3000, or ten thousand watt class AB amps are built regularly, you will not find them at circuit city either... however you will find their lower power counterparts... a decent class ab 4 channel that'll do 75 x 4 at 4 ohms will probably cost you about 350 - 400 dollars retail at CC / Best buy / etc etc.
Look for factors like low THD (total harmonic distortion), high damping factor, and a high slew rate.

something with a damping factor of at least 400 and a slew rate of at least 40v/ms would be nice... but chances are, circuit city / best buy wont have anything even that good (which isn't even good at all) on the shelf... however... we all end up buying something from there anyway -- lord knows i've got more amps that i can shake a stick at and none of them have the kind of specs i'd hope that they would have.... a "pimp" amp will have a damping factor of up near 1,000 and a slew rate of 80+ v/ms ... ask circuit city what the slew rate is -- they'll be like "dude -- that's not important... none of those numbers matter -- what matters is that master P endorses these new bazooka brand amps.... and if master p says they're good.. then dammit you need to buy it".

i suggest a class AB amp // less than 0.1% thd @ 4 ohms // doing at least 50 x 4 at 12.5 volts -- this will turn out more like 60 x 4 at 14.4 volts.

brands --> alpine / hifonics / usamps / cadence ... mtx and rockford aren't exactly "clean" but they'll do as well... if u want to hunt the used section ... mtx blue thunder amps were great **** and they're dirt cheap now online... blue thunder pro 754 would be ideal for you -- 90 x 4 at 4 ohms and 14.4v. (yes, i'm brand wh*** but i'll be hte first to tell u that mtx isn't the best thing for high's anymore - not for the last few years - the other brands listed would do a much better job based on current model products offered by manufacturers). i've skirted the issue of having clean amps by having amps that are "dirty" but have vastly so much more power than i need than i can run them at half to 60% of their output and thus end up with "clean" power because they're not even coming near their limit.

I hope this helps you in some way -- i'm sorry if i ramble -- i'm just really sick and tired of the mentallity of "just tell the customer anything to make a sale" -- i've been refused audio sales jobs because i'm "too intelligent to allow the customer to buy whatever they first look at even if its the absolute wrong thing that would set their car on fire" or "push expensive garbage on people who dont know any better"... salesmen suck -- and i've fixed enough broken amps to know that dumbass ones dont help the situation any.

Systems

thank you for clearing things up.
The guy beside me was the sales advisor from the store. So are all amps "analog class" amps? What is damping and slew rate?
I think I'm going to go with an "ab" amp because I am on somewhat of a budget.
Thanks again.

PoweredByDodge

glad to be of service...



all audio amplifiers that are current production models to date are analog -- its got nothin to do with class -- there are a few difft classes and there are surely to be more classes invented as tech gets better... but they're all analog

---

someday, maybe, we'll have digital amplifiers... i dont quite know how... but we might... it would involve having to convert the signal from analog - to digital, back to analog so it's gonna require some marked benefits to justify doing such a laborious circuit.

the damping factor of an amplifier is a number which indicates (in short) how well an amplifier can control the speaker it is driving. indirectly it's related to distortion -- if an amplifier has a high distortion rating, it's gonna have a low damping factor -- low distortion, high damping factor -- but to get to it ... it is an expression of an amplifier's "grip" on a speaker -- a loose grip and your speaker may get sloppy at high power levels and not be nearly as accurate as you'd want... a tight one and that speaker isn't gonna do anything anomalous. high power with very low damping factors is something that usually spells trouble for a loudspeaker.

as far as slew rate -- it is the rate as which the amplifier can alter its output signal -- this goes in tune with the notion that voltage cannot change instantaneiously -- if your lights are on in your house, and you flip the switch off there will be a delay (could be something like 0.000000000000001 seconds... but its something, however miniscule) before they actually go off -- it is just a basic property of energy.

so lets say you're playing a song -- hell not even a song -- lets make it simplier -- you're playing a 60 hertz bass note -- just a test cd... and for 10 seconds that 60 hz note is loud (say a "10" on our imaginary loud scale) then it gets quieter (only a "5") at 10.1 seconds into the track -- then at 15.1 seconds it gets back up to 10... then it goes loud / soft / loud / soft / loud / soft repeatedly with 0.5 seconds between transitions.

well -- where we have the same amplitude of a given frequency for a few seconds -- slew rate isn't that important... the amp can "juice up" to its necessary output voltage and maintain it... then it flips for about 5 seconds to the quieter amplitude.... but that's still ok.

but what about when you've got half a second between loud and soft loud and soft? -- well slew rate is very important, if you have a junk amp and the transition is fast enough, you may never even know that the song was suppose to go from loud to soft and back -- it may just play loud, or just soft, or some varying degree of this extreme.

it takes the amp a certain amount of time to say "ok - this was a 10, now i have to make it a 5, ok i gotta close my power valve... *grunt grunt grunt* ok its closed" -- the slew rate is the measure of the amoutn of time that it takes for the amp to do that.

100 mV/s is fantastic -- 70 is great - 50 is very good / 35-40 is still good / 30 is "adequate" for an amp for highs... good / 20 is "adequate" for a subwoofer amp .... below 20 and i would not buy that amplifier.

the reason lower slew rates are ok for sub amps is not because "no one cares how the bass sounds" -- it is because the higher the frequency of the sound, the more essential it is for the slew rate to be adequate so as that the listener does not hear any degredation of the music -- the slower the frequency, the easier it is for the amp -- so a 20mv rating for a sub amp is going to give probably the same "quality of sound" as a 30mv rating for the amp you're using on your highs... use that sub amp on your highs and you may notice it is not quite as good sounding as the other one.

if you post a price range and how much power you are looking for, i'd be happy to try to find you a link to a website or a store where you could get an amp that would fit both of your needs.

sntnsupermen131

Originally posted by PoweredByDodge
it takes the amp a certain amount of time to say "ok - this was a 10, now i have to make it a 5, ok i gotta close my power valve... *grunt grunt grunt* ok its closed"

lol...
-Cody