[starbai]

Hey folks,

I'm currently between the A/B Class JL Audio JX360/4 Amp and the D Class XD400/4 amp.

Both have very similar power ratings, and the 360/4 is more than ample for what I need.

But there is about a $120 (on average) difference in cost.

Only thing I can see different is D class vs the A/B class...

This will be powering my 4 interior speakers (doors and rear deck) - i have something else for my mid basses and trunk sub.

I know you get what you pay for, but can anyone help enlighten me as to why i should nearly double my amp budget for this D class 400/4?

Thanks

[ctuna]

I was more concerned with the sound between the two.
But found a good Class D can sound pretty much as good as
a Class AB. The thing that is good about a class D is they are so much more efficient and smaller than a class AB. They are much less of a load on the already overtaxed BMW electrical system and the JL XD600/6 for example
can fit in the same spot as the Hi Fi amp an is 5 times as powerful.
If you are keeping the stock head unit you need to consider if the amp has balanced inputs and crossover adjustments built in.

Also there are a lot of cheap class AB's out there that should not be compared
to quality AB's and D's. This can be a case of you get what you pay for so read all the specs reviews and user comments you can.

[gte460z]

Class AB amplifiers have a much lower THD (total harmonic distortion) than class D amplifiers but class D amplifiers are much more efficient (less power draw for the same output power). The higher THD of the class D amplifier is caused by the modulation used. This is usually only noticeable (to the ear) at higher frequencies which is why they are popular for powering subs. Most of the nicer class D amplifiers have feedforward feedback networks to reduce the THD to almost equivalent levels making them much more appealing.

In summary, a nice class D amplifier will be more efficient than a class AB and have similar audio characteristics. A crappy class D amplifier will have a high THD. The JL XD400 will be of the nice variety of class D amplifiers.

[ctuna]

Well they make full range D now .
And even some snooty audiophiles use them .
The thing is are we talking about levels of distortion or types of
distortion the human ear can even distinguish especially with road , traffic
and engine noise.
I have to admit I was skeptical about class D but I really can't hear anything awful with mine in fact it sounds really good.

[Crusader]

Class D are more efficient, generate less heat for a given output. Historically they are noted for more THD than class AB, less so for more modern designs. Given the inherent issues in a moving automotive environment, the point is essentially moot; ours is hardly an ideal listening environment. (After all, Bose OEM systems sound pretty good in cars; ever hear them A/B compared to anything remotely good in the home?) So, decent power, decent speakers? You'll be fine.

[gte460z]

Originally Posted by ctuna

Well they make full range D now .
And even some snooty audiophiles use them .
The thing is are we talking about levels of distortion or types of
distortion the human ear can even distinguish especially with road , traffic
and engine noise.
I have to admit I was skeptical about class D but I really can't hear anything awful with mine in fact it sounds really good.

When I referenced the increased THD of class D amps, I'm specifically talking audiophile levels of distortion (1% vs 0.1% THD). Levels that you wouldn't be able to hear over engine noise/road noise. Like you said, nowadays you wouldn't be able to hear the difference between class AB and D in an automotive platform. I definitely agree with you and Crusader, class D is the way to go if you have the money.