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Head units with digital amps  

post #1 of 6
Thread Starter 
I've been watching the market casually for a couple of years, mulling an upgrade from my factory system to something that would play MP3/WMA. One of the features that I've been expecting to see more of, but haven't, is digital amps in head units. Panasonic has produced a couple of models, but as far as I can tell that's it. Sony & JVC have been using digital amps in home receivers for a while now but have nothing similar in the car arena. Anybody know of others? Or, why digital amps haven't taken the car stereo world by storm? It would seem like an obvious, no-brainer application but that clearly isn't happening.
post #2 of 6
What do you mean by digital amps? I am an installer so I am curious. I have two of the Kicker SX amps, which have digital sound processors, but I dont think thats what you mean.
post #3 of 6
Thread Starter 
I'm talking about what's called switching or sometimes "Class T" amps, such as in the Panasonic CQ-C8803U. Panasonic also uses similar digital amps in some of their HT receivers. This type of design can produce more clean power with less heat and requires a correspondingly smaller space.

More info in this Crutchfield article, and note that article is over 2 years old now.
post #4 of 6
Thread Starter 

Anybody have any comments, info, hot tips, wild rumors about digital amps in head units?
post #5 of 6
I have been asking this question to factory reps this past couple weeks, since you posted.

Basically the concenses is that a class "T" amp is nothing different than a class "d" amp, just somebody wanted to have there own letter. Class D amps are quite common, though not in headunits. There is nothing digital about class d or class t amps.

The problem with these amps is that they basically reproduce noice at a certain frequency that's very audible, has something to do with the reproduction of the sound wave, it was over my head when it was told to me. Very audible meaning around 1k or so. Thats why most class "d or t" amps are used for sub amps, because they can crossover below this frequency so it wont be heard.

There are companies who have figuired it out, like eclipse has a full range class d amp, but it sounds llke the money for the r & d and tooling isnt worth it, thats probably why you dont see them in headunits, manufacturing costs dont meet the demand or the justification of raising prices for a more effeciant amp.

It has also been the consensus that these amps, although super efficiant, are no where near the sound quality of class "ab" amps. This is why most companies have only incorporated them as sub amps. Some campanies have class d amps that produce very clean power and some that produce very dirty power, um audiobahn.

Alto mobile has been making these amps for probably ten years, some have said they were the first, but I doubt it, and they are pretty respectable for sound quality.

Hope that helps, Ive been meaning to pass this info along, you peaked my curiousity with your post, I will continue to ask people this question.
post #6 of 6
Thread Starter 
Hammer28, thanks for the comments and I really appreciate you taking the time to talk to reps on this topic.

My understanding is that yes, the Class D (or T or whatever a particular maker may call it) amps are not technically truly digital, but that they do approximate a digital behaviour due to the fast switching and can interface more directly to a digital input.

Also, on the sound quality concerns I'm also aware that these amps have for a long time been used strictly as sub amps because of what you said, but that seems to no longer be the case. As I mentioned in my first post, Sony, JVC and Panasonic make pretty well regarded home theater receivers that use digital amps. In fact I have one sitting right next to me, a Sony DA3000ES, and while I use it mainly for playing MP3s from my PC, I also have an Onkyo SACD/DVD-A player hooked up to it and there doesn't seem to be an issue with an obviously noticeable spurious frequency. The sound may not be quite audiophile high end, but it's pretty darn good and I don't notice any obvious noise or distortions that would be allegedly introduced by a digital amp.

And to be honest, and I don't mean this in an argumentative way or anything, but I just have a hard time buying the spurious frequency thing as a problem in the car. With all the road and other noise in the car environment, it makes no sense that it would be a worse problem in a car head unit than in a HT receiver.

It just seems like there is a ton of upside to this design that is directly applicable to the mobile environment, and it surprises me to see it in several HT units but not car units.
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