Digital and HC amps....what's the real diff?

[LoneRanger 10+ year member]

I just went out and bought an Ultimate Sound Digitalis on a whim for my girlfriend's car. It's supposed to put out 750w RMS into two channels or 1500 into a 1 ohm mono load, and the maximum current draw is supposed to be 4v DC. If these stats are accurate, I think I just got the best deal ever ($299 shipped). However, if this amp won't put out what it says, i have thirty days to ship it back, so no real loss. I chose this amp mainly because I don't want to upgrade her alternator or electrical system. She doesn't want a "boom car", but I'd like to use her car for a few local comps before the end of the season. My question is, other than efficiency (an HC amp that puts out 1500w RMS will usually draw about 80-120 amps, whereas this one should never draw more than 4v), is there any other advantages to digital amplifiers over HC's? Are there any specific problems with this amp or digital amps in general? Did i do the right thing?!?!

PS: This amp will be driving a pair of Audiobahn AW1208Q's in a 4.5cuft slot-ported box.

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[nismo 10+ year member]

Originally posted by LoneRanger I just went out and bought an Ultimate Sound Digitalis on a whim for my girlfriend's car. It's supposed to put out 750w RMS into two channels or 1500 into a 1 ohm mono load, and the maximum current draw is supposed to be 4v DC. If these stats are accurate, I think I just got the best deal ever ($299 shipped). However, if this amp won't put out what it says, i have thirty days to ship it back, so no real loss. I chose this amp mainly because I don't want to upgrade her alternator or electrical system. She doesn't want a "boom car", but I'd like to use her car for a few local comps before the end of the season. My question is, other than efficiency (an HC amp that puts out 1500w RMS will usually draw about 80-120 amps, whereas this one should never draw more than 4v), is there any other advantages to digital amplifiers over HC's? Are there any specific problems with this amp or digital amps in general? Did i do the right thing?!?!

 

PS: This amp will be driving a pair of Audiobahn AW1208Q's in a 4.5cuft slot-ported box.

first things first...you WILL get flamed talking about 'digital' amps, cuz they arent digital...they are class d--theres your fair warning //content.invisioncic.com/y282845/emoticons/wink.gif.608e3ea05f1a9f98611af0861652f8fb.gif

your girlfriends amp doesnt draw 4v....it will draw amps. another thing is that as you move toward a higher volume (and full output), the class d amps dont have anything on the a/b's...as they are only more efficient at lower volumes. as for high current amps...that just means they can handle low impedances. you can have class d high current amps, as that is becoming the norm.

as for the amp, i dunno whether id keep it or not. if you really wanna know youve got 1500 watts+ on tap, in a fairly efficient package, try the resonant engineering 1500 watt amp. its about 350, and you just about cant find a better deal, that will be as solid, and deliver that much power. itll be the best 350 you can spend. //content.invisioncic.com/y282845/emoticons/smile.gif.1ebc41e1811405b213edfc4622c41e27.gif

eric

 

[LoneRanger 10+ year member]

Class D - Digital.....same thing......okay.

the class d amps dont have anything on the a/b's...as they are only more efficient at lower volumes.

So are they more or less efficient at high volumes than a class a/b?

your girlfriends amp doesnt draw 4v....it will draw amps.

i know that volts can be converted into amps, and i used to have the formula

somewhere.......

I'm sure 4v isn't a whole lot in amperes. I had a JBL 600.1 before this amp, and i had to keep it at 13.5v constant power to keep it happy. My train of thought was that this amp would operate to it's fullest potential at only 4v.......maybe i misunderstood. If it would operate to it's fullest at 4v, it would draw far fewer amperes off the alternator......right? I also read on a data sheet that the amp was more than 80% efficient than class a/b's at two and one ohm. Are they talking about heat dissipation, current draw, or what?

if you really wanna know youve got 1500 watts+ on tap, in a fairly efficient package, try the resonant engineering 1500 watt amp. its about 350, and you just about cant find a better deal, that will be as solid, and deliver that much power. itll be the best 350 you can spend

I've been told a couple times that i'm a dumbass, but if i can get 1500w RMS outta this one, wouldn't it be the best $300 i could spend? by my modest calculations, 300 shipped is less than $350. I don't know much about ultimate amps, nor do i know much about RE's amps, but i guess i'll just take my chances......

I'd like to hear from someone who owns an ultimate digitalis amp, or has owned one. what was it like? did it put out the power it stated? thanks in advance

Donn

 

[nismo 10+ year member]

Originally posted by LoneRanger Class D - Digital.....same thing......okay.

 

 

 

So are they more or less efficient at high volumes than a class a/b?

 

 

 

i know that volts can be converted into amps, and i used to have the formula

 

somewhere.......

 

I'm sure 4v isn't a whole lot in amperes. I had a JBL 600.1 before this amp, and i had to keep it at 13.5v constant power to keep it happy. My train of thought was that this amp would operate to it's fullest potential at only 4v.......maybe i misunderstood. If it would operate to it's fullest at 4v, it would draw far fewer amperes off the alternator......right? I also read on a data sheet that the amp was more than 80% efficient than class a/b's at two and one ohm. Are they talking about heat dissipation, current draw, or what?

 

 

 

I've been told a couple times that i'm a dumbass, but if i can get 1500w RMS outta this one, wouldn't it be the best $300 i could spend? by my modest calculations, 300 shipped is less than $350. I don't know much about ultimate amps, nor do i know much about RE's amps, but i guess i'll just take my chances......

 

I'd like to hear from someone who owns an ultimate digitalis amp, or has owned one. what was it like? did it put out the power it stated? thanks in advance

 

Donn

where are you getting this 4v from? if its 1500 watts (assuming 100% efficiency--and that its ACTUALLY doing 1500 watts), it will draw 1500w=14.4v*104a ... thats at 100% efficiency, so taking approximately 70% efficiency into account, that means it will draw 149 amps. i HIGHLY doubt the ultimate amp is doing 1500 watts, and whether it is or not, its not gonna be able to get full power from your g/f's electrical system.

id like to see word for word what youre getting the efficiency ratings from. if you are using full power (sine waves especially), bumping full volume, etc...you are better off with an a/b amp. class d's get less and less efficient as they go up in volume. that is why so many competitors are switching back to class a/b.

as for which amps are more solid, id put my money on re any day, even tho they are fairly new at making amps. the know what theyre doing, and imho, they know more what theyre doing than ultimate.

eric

 

[kottonmouth 10+ year member]

class d amps are more efficient at higher volumes than a/b...where do u get that ab is more effieient from?

 

[nismo 10+ year member]

Originally posted by kottonmouth class d amps are more efficient at higher volumes than a/b...where do u get that ab is more effieient from?

that is a misconception. as the duty cycle increases on the class d's, they increase in current draw to the point where they draw as much current at full volume as a/b's...and the a/b topology is a better design. the only benefits of class d are at lower volumes where it doesnt really matter as much anyway.

eric

 

[audiolife 5,000+ posts]

only real clear cut advantage to class d is at 1/3rd volume they are more eff. by 20+% after that it falls way off into class ab relm. on a reactive load at high power ab is better even though many will argue all i can say in direct comparisions car audio and electronics did a monster amp shoot out ...the winner was a class ab us amp. if you study the charts and learn what it means then learn about how each amp works you can see why...... class d is CHEAPER to produce as the electronics to do so are made more and more.... a/b is generally safer to run on subs at high volume as it seems to be cleaner and doesnt produce the "wicked clip" as easy.. btw there are exceptions but i think this holds true in vast majority of cases.

 

[bigbassman Premium Member]

Originally posted by audiolife a/b is generally safer to run on subs at high volume as it seems to be cleaner and doesnt produce the "wicked clip" as easy.. btw there are exceptions but i think this holds true in vast majority of cases.

Class D amps compress, when the power supply reaches its limits.. You can only clip one, if you overdrive its input, with excessive signal voltage..

http://www.e-insite.net/ednmag/index.asp?layout=article&articleid=CA152804&pubdate=8/30/01

Read the "At a Glance" section on the right, in gray..

It's much easier to tear a woofer up, with a giant class A/b...

Loyd L.

 

[audiolife 5,000+ posts]

my class d memphis will go almost straight clock when over driven lol my other memphis doesnt (ab) never hooked it up to a speaker under these conditions but i dont think an osiloscope would lie.... resistive and reactive are different though i know. if i had a scanner id show you some of the graphs..a sony explode class d will do the same thing but the abs will do it also

 

[bigbassman Premium Member]

Originally posted by audiolife my class d memphis will go almost straight clock when over driven lol my other memphis doesnt (ab) never hooked it up to a speaker under these conditions but i dont think an osiloscope would lie.... resistive and reactive are different though i know. if i had a scanner id show you some of the graphs..a sony explode class d will do the same thing but the abs will do it also

An o-scope shows you the wave, but gives you nothing about the power potential of it...

Repeat your test with the Class D's, making sure not to overdrive the inputs, and throw a DMM on the leads, and watch what happens when you crank volume... //content.invisioncic.com/y282845/emoticons/smile.gif.1ebc41e1811405b213edfc4622c41e27.gif

Loyd L.

 

[audiolife 5,000+ posts]

but isnt that hang -flatline- on a clock type spike bad?

also we have a nimrod at work with a planet audio class d .... he goes through 2-3 woofers a month (not kidding either) talking near flame type smoke lol i know he a volume master but geezus i have never seen anything fry a sub quite that way funny thing is they keep givin him new subs ever stinkin time you set the gain right he comes back with it turned all the way up lol

 

[bigbassman Premium Member]

Originally posted by audiolife but isnt that hang -flatline- on a clock type spike bad?

it can be... but if you've got 50 volts on the leads, from a pure sine wave, and only 40 volts from a "square" wave...

Example: Nominal 2 ohm woofer, on a class D amp

voltage squared / impedence = wattage

50x50 = 2500 / 2 = 1250 watts

40x40 = 1600 / 2 = 800 watts

this is what happens to a Class D amp....

Loyd L.

 

[bigbassman Premium Member]

it could depend on a couple varibles as to why he's destroying woofers.. but the little dirty secret about D class amps.. they usually have a very limited input stage, and will usually be driven to clip with anything over 2 volts..

Loyd L.

 

[audiolife 5,000+ posts]

so its more "input" problem than anything else? i can believe that as to why it does but i will say this... that is more of a problem than the actual amp clipping impropper settings are about 70+% of the problems i see.... i help service 2-5 customers daily who just dont understand that turning their deck all the way up on an amp that is set wrong (most of these people turn the gain up after they leave) causes damage.... they just dont understand if they want more volume they need better bigger amps and speakers they figure hey if i can turn it that high it should work....basic idiots.

 

[LoneRanger 10+ year member]

Here are the specs on this amp from Ultimate's website:

Bridged Output- 4 Ohms N/A

Output Power- 1 Ohms 1,300 Watts RMS

Output Power - 2 Ohms 900 Watts RMS

Output Power - 4 Ohms 500 Watts RMS

THD

Signal to Noise Ratio >90dBA

Frequency Response 15Hz - 250Hz

Bass Boost Remote, Variable, 0-18dB @ 45Hz.

Low Pass Crossover Variable, 50Hz - 250Hz, 24dB/Oct.

High Pass Crossover N/A

Band Pass Crossover N/A

Sub-Sonic Filter Variable, 15Hz - 50Hz, 24dB/Oct.

Protection Thermal/Short/ DC/Cross-Wire/Fuse

Dimensions/mm 401 X 269.2 X 50.8

Dimensions/inches 15.75 X 10.6 X 2

Here are some quotes from reviewers that aren't stated in the stats, but influienced my purchase:

With overall efficiencies of 80% or more, and fully regulated power supplies, these digital power plants really deliver. Unlike conventional "High Current" amplifiers that waste as much power heating up your trunk as they deliver to your speakers, the Digitalis Amplifiers keep their cool and put the power to work where it does the most good- Moving those voice coils!

Quite the sleeper amp. It's rated at a mono output of 1200w RMS into 1ohm, however the output is more like 1400w RMS on the bench.

. Using pulse width modulation techniques, these new amplifiers make it possible to deliver enormous power to your speakers and do it efficiently without the need for special high power alternators or a trunk full of batteries.

I really enjoyed reading your dialogue about the advantages of class d vs class a/b, however, I still haven't gotten my "Amplifiers And Subwoofers For Dummies" book off barnes and noble yet, so I'd like someone to awnser these questions in a simple non-technical manor.

1. Are Ultimate Sound amps worth a ****? *PLEASE NOTE* Do not awnser this question if you don't own or have owned an ultimate sound amp. Nothing pisses me off more than replies where someone says "Well, my buddy had this amp and it sucked" You'll never know the full potential of an amplifier until you own it and have time to play with it.

2. How many amperes will this thing draw if it puts out 1200w RMS @ 1 ohm @ 80% efficiency? Will her stock 110 amp alternator keep up with it?

3. WTF is "Pulse Width Modulation"?

4. Is there anything I should know about maintaining/installing a class D over the class A/B's I've owned in the past? Is there any real physical difference?

5. Do class D's tend to clip more than a/b's? The last thing I need is some clip-happy amp ruining my beautiful 'bahns a week after I install them.

6. This one is especially for Lloyd: What subwoofers work best as hats? I tried a Kicker L5, but it clashed with my shoes. I tried an Audiobahn piston, but it kept falling off. The shocker 2 fit nicely, and it even matched my outfit, however the 60lb magnet caused undue neck strain.