Capacitors? Where's the proof?

[helotaxi 5,000+ posts]

Mono by itself means nothing. The class of amp matters a lot. In reality, though you're not running a lot of power even though it is A/B power (I've run a good bit more than that at times in the past) and you shouldn't be getting bad dimming. Are you using a chassis ground?

 

[audioholic 5,000+ posts]

Mono by itself means nothing. The class of amp matters a lot. In reality, though you're not running a lot of power even though it is A/B power (I've run a good bit more than that at times in the past) and you shouldn't be getting bad dimming. Are you using a chassis ground?

I wish I could find that old chart I saw a few years ago showing amplifier efficiency between several bench tested class A/B's and class D's. It showed that at low to moderate output levels, the difference between an A/B and D was drastic. But by the time they reach full tilt output, the efficiency difference was about 10% (80% versus 90% iirc). Not the huge difference most people equate to comparing the two topologies.

I agree with you that if I were the OP Id probably still chose a class D, but just reminding people that amplifier efficiency is not constant, or even linear.

 

[helotaxi 5,000+ posts]

Either way, his smallish system shouldn't be placing that big a strain on his electrical. He's getting some losses somewhere in the power delivery chain. I'm guessing o the ground.

 

[soldiermedic 10+ year member]

yes, all grounds are 1/0 as well. It isn't bad dimming, but it's dimming just enough at those heavy bass hits to annoy me.

 

[helotaxi 5,000+ posts]

Grounds run how? Chassis or back to the battery?

 

[sooperxtool 10+ year member]

Jesus... 10 pages later....

So from what I gather, a cap doesn't really DO anything, but then it doesn't really HURT anything either? Cosmetics and extra weight?

 

[soldiermedic 10+ year member]

Grounds run how? Chassis or back to the battery?

One ground running from the battery, another running from the chassis. they are on opposite sides of the vehicle from each other. Grounds running from both amps are 3 feet from each other.

 

[Haunz 10+ year member]

I wish I could find that old chart I saw a few years ago showing amplifier efficiency between several bench tested class A/B's and class D's. It showed that at low to moderate output levels, the difference between an A/B and D was drastic. But by the time they reach full tilt output, the efficiency difference was about 10% (80% versus 90% iirc). Not the huge difference most people equate to comparing the two topologies.

The efficiency numbers were probably closer to 65% and 75% if there was only a 10% difference between them... it's worth noting that many older class D amps were only around 75% efficient at full clip (some even less)... but more modern designs are often more then 90% efficient.. At the same time the best efficiency you are going to see out a class A/B is still only going to be around 65%...

But I digress...

 

[helotaxi 5,000+ posts]

One ground running from the battery, another running from the chassis. they are on opposite sides of the vehicle from each other. Grounds running from both amps are 3 feet from each other.

What I meant is are the grounds for the amps run to the battery directly or connected to the chassis. With the amount of current that you are drawing, using the chassis as a grounding point might be causing part of your problem.

 

[soldiermedic 10+ year member]

What I meant is are the grounds for the amps run to the battery directly or connected to the chassis. With the amount of current that you are drawing, using the chassis as a grounding point might be causing part of your problem.

Ah. I see. The grounds from the amps are to the chassis; one is using a bolt from where my rear seat is bolted down, the other is in the trunk area on a tie-down bolt.

 

[audioholic 5,000+ posts]

The efficiency numbers were probably closer to 65% and 75% if there was only a 10% difference between them... it's worth noting that many older class D amps were only around 75% efficient at full clip (some even less)... but more modern designs are often more then 90% efficient.. At the same time the best efficiency you are going to see out a class A/B is still only going to be around 65%...

But I digress...

If we are talking about comparisons at full output, we might as well look at the efficiency of a Class B, because that's how an A/B will react. A class B's efficiency can reach close to 80%.

"A Class B amplifier can attain an efficiency of up to 78.5%." - Amplifier Classes : Class A, B, AB, C, D, E/F

"Class B has a maximum theoretical efficiency of 78.5% (i.e., π/4)." - Electronic amplifier - Wikipedia, the free encyclopedia

 

[helotaxi 5,000+ posts]

Have to consider the losses in the power supply as well which that 78.5% figure isn't accounting for.

 

[helotaxi 5,000+ posts]

Have to consider the losses in the power supply as well which that 78.5% figure isn't accounting for.

 

[Subcut]

Alright so this is my first post...... but I was searching the internet high and low for what I needed to do to solidify my car's electronic capabilities. I have seen capacitors used and hoped they would be able to bandaid my system, but now I doubt it...

Background: I just bought an Alpine type E subwoofer, and a pioneer gm5400t(380rms 760 max) amp, and I don't even have the stuff yet just trying to prepare properly. I read the whole thread almost, and I know your thinking now "why the F@%# is this guy worried about his +-300 rms setup?!" The answer may astonish you!

My truck is an old Isuzu four cylinder truck with the fewest available options, no power locks, steering, windows, not even a stereo till now. 30 or 40A stock alternator depending on my luck. Is there any easy way to tell how much extra power I have available? I've already looked into upgrading the alternator and it's not going to be fun or cheap if it's necessary. Ideas input appreciated.

Also over the course of the thread I feel I have gained a fine understanding or capacitors, and even a much firmer understanding of the whole relationship between alternator and battery. Overall I would add an extra battery sooner than I tried wasting time on a Cap, and overall I'd just upgrade the alternator if it proved necessary.

 

[-01limited- 10+ year member]

Alright so this is my first post...... but I was searching the internet high and low for what I needed to do to solidify my car's electronic capabilities. I have seen capacitors used and hoped they would be able to bandaid my system, but now I doubt it...
Background: I just bought an Alpine type E subwoofer, and a pioneer gm5400t(380rms 760 max) amp, and I don't even have the stuff yet just trying to prepare properly. I read the whole thread almost, and I know your thinking now "why the F@%# is this guy worried about his +-300 rms setup?!" The answer may astonish you!

My truck is an old Isuzu four cylinder truck with the fewest available options, no power locks, steering, windows, not even a stereo till now. 30 or 40A stock alternator depending on my luck. Is there any easy way to tell how much extra power I have available? I've already looked into upgrading the alternator and it's not going to be fun or cheap if it's necessary. Ideas input appreciated.

Also over the course of the thread I feel I have gained a fine understanding or capacitors, and even a much firmer understanding of the whole relationship between alternator and battery. Overall I would add an extra battery sooner than I tried wasting time on a Cap, and overall I'd just upgrade the alternator if it proved necessary.

If you really only have a 30 or 40 amp alt I would be all over upgrading that puppy. That will benefit you I think more than adding another battery.