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BMW 3-Series (E90 E92) Forum > E90 / E92 / E93 3-series Technical Forums > AUDIO/VIDEO + BLUETOOTH + Electronics/Alarm/Software > Attack of the class D amps!



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      05-03-2009, 01:10 PM   #1
scooby9
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Attack of the class D amps!

There are so many new class D amps out now that are for full range applications. Some of these are even smaller than the Alpine PDX amps so you can get pretty creative with a stealth install. I guess the big question about using this class of amp is the sound quality...

http://www.crutchfield.com/p_113XR4S...owAll=Y&tp=115

http://www.crutchfield.com/p_130D420...owAll=Y&tp=115

http://www.crutchfield.com/p_105AR80...owAll=Y&tp=115
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      05-03-2009, 01:36 PM   #2
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I have the Alpine 5 channel one in my DD. Works fine for my application. I wouldn't hesitate to run a couple of these amps anywhere. Runs cool and is very compact. I run a pair of Polk MOMO separates in the front and some Polk coaxials in the rear doors. I run a RF shallow sub in a MTX thunderform. Plenty of power for my Frontier.
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      05-03-2009, 01:57 PM   #3
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The classic problem with full-range Class D amps is that there is ultrasonic noise generated by the Class D power supply which requires filtering - so the audio output is run through a low-pass filter which is usually much lower than you would want.

Even though the notes involved are above what we can hear, tests have shown that such filtering has a couple of undesired side effects on the notes we CAN hear. Whether you are talking about the phase shift effects of the crossover filter or the missing harmonics or whatever you are talking about, this is a problem which relates back to the early days of CD players. (Google "double oversampling"). The steeper the analog lowpass filter, the more audible effects it has.

So as a general rule Class D amps are good for basss, but took a long time to get into full-range applications.

I don't like Alpine PDX amps much. They feel cheap. That said, they have a great WP$ and they sound better than some others. I have not heard of any tech in the PDX amps which make them sound better than other full-range Class D amps, but they may have some and I just haven't cared to look...

I have heard the JL Class D amps sound better than the others and there is some tech involved which they license. I have read up on that and it might be worthwhile - open to the idea.

But as a rule I am not getting on the Class D bandwagon. I can afford to own the traditional approach, so I will stay with it.

I am interested in Arc Audio Mini amps.
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      05-03-2009, 05:12 PM   #4
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Quote:
Originally Posted by VP Electricity View Post

So as a general rule Class D amps are good for basss, but took a long time to get into full-range applications.

I don't like Alpine PDX amps much. They feel cheap. That said, they have a great WP$ and they sound better than some others. I have not heard of any tech in the PDX amps which make them sound better than other full-range Class D amps, but they may have some and I just haven't cared to look...

I have heard the JL Class D amps sound better than the others and there is some tech involved which they license. I have read up on that and it might be worthwhile - open to the idea.

But as a rule I am not getting on the Class D bandwagon. I can afford to own the traditional approach, so I will stay with it.

I am interested in Arc Audio Mini amps.
what's that A and B amps?

I stumbled across a couple of sites for diy component upgrades. These guys were changing opamps and psu's I'm sure you could do the same thing to the PDX's or any other amp to improve their performance. It's a lot of work and a bit of a gamble for those uninitiated in the soldering thing. I don't think my ear is trained enough to hear the diff..
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      05-03-2009, 09:50 PM   #5
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Quote:
Originally Posted by VP Electricity View Post

I am interested in Arc Audio Mini amps.
I had an Arc Audio in my Harley Road Glide. that is the best sounding amp ive heard for the size and output. im not a real audio guru, but that was one bad ass amp. I can put you in contact with a rep of theirs, this guy is good people.
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      05-03-2009, 11:15 PM   #6
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Quote:
Originally Posted by JoeyFiasco View Post
what's that A and B amps?

I stumbled across a couple of sites for diy component upgrades. These guys were changing opamps and psu's I'm sure you could do the same thing to the PDX's or any other amp to improve their performance. It's a lot of work and a bit of a gamble for those uninitiated in the soldering thing. I don't think my ear is trained enough to hear the diff..
Thinking you can't hear good sound is like being a high school girl thinking you suck at math...
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      05-04-2009, 02:56 AM   #7
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Quote:
Originally Posted by VP Electricity View Post
Thinking you can't hear good sound is like being a high school girl thinking you suck at math...
Are you calling me a mathematically challenged girl?

Have you done any OpAmp/PSU upgrades before? Is it worth it? I'm pretty sure I can hear good sound, it's just being able to differentiate between good(store bought unit) and "great" sound(unit with upgraded components) that I was talking about. Maybe I should have worn hearing protection during all the shooting and heavy machinery. I really want to get stated on upgrading my Hi-Fi Pro system just low on funds and I'm using the time to educate myself.
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      05-04-2009, 10:47 AM   #8
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Quote:
Originally Posted by JoeyFiasco View Post
Are you calling me a mathematically challenged girl?


[QUOTE=JoeyFiasco;5048282]
Have you done any OpAmp/PSU upgrades before? Is it worth it? /QUOTE]

I have not done the soldering but I have heard some of the results. It is certainly NOT worth it until you know what things sound like without, and while such an upgrade can improve a given device, there are other improvements which are larger impacts:

- drivers selected

- installation means

- system design

- source signal (HU or integration)

All those make a bigger impact on the sound than the PCB upgrades, and you can't get the benefits of the PCB upgrades without those being executed well.
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