Can someone please explain to me what a class D amp is and what the diference is between it and a regular amp? The reason I ask is because I am considering the sony 1,000 mono amp to power my two 12's Mb quartz and I noticed it said class D.

 

Classes of Amplifiers

Amplifiers do not actually increase the strength of an electronic signal. What happens instead, the signal is copied and enlarged. There are different schemes for amplifying the signal. There are different classes of amplifiers. These classes are A, AB, and C. There have been some special classes such as G, created by Hatachi. Class H created by Soundcraftsman. Class D for the so-called digital amps and Class T for Tripath's digital amplifiers.

Class A amplifiers use one or more transistors that conduct during both the positive and negative cycles of the signal. This Class of amplifier has the lowest distortion but it is very inefficient and generates a lot of heat. A Class A amplifier requires that the amplifier generate the full current no matter what the output is. If you were simply listening to FM or watching a movie, the amplifier would be consuming as much power as if you had it turned up to full volume.

In order to increase efficiency, Class B amplifiers use one transistor to conduct the positive portion of the waveform and another transistor to conduct the negative portion of the waveform. 99% of all audio amplifiers today are Class B. Class B amplifier can be built today so that its distortions are well below what the human ear can detect and nearly to the point where it is unmeasurable.

Many amplifiers call themselves Class A/B. In reality, very few are. Early Class B amplifiers had a problem known as switching delay. In a class B design, a transistor works 50% of the cycle while another transistor works 50% of the cycle. In early class B amplifiers, there was a distortion created between the time the devices were switching back and forth. Some people referred to this distortion as notch distortion because there was a notch appearance on an oscilloscope between the two waveforms.

Class A/B was created to leave the transistor conducting while the second transistor was conducting. This created an overlap between the two signals. The problem with this approach is that it created its own distortion called gumming. This means that the signal would get a little fatter where the two devices were both conduction.

Today, if you look at a properly designed Class B amplifier on a scope, you will see no switching distortion.

Class D amps are sometimes called digital amplifiers. There is really no such thing today as a digital amplifier. A Class D amplifier uses transistors that are either switched on or off to represent positive or negative values. The transistors are either on or off. The advantage of such a system is that it is highly efficient and generates very little heat. The disadvantage is that there can be a distortion caused between the switching of the positive and negative transistors as the positive and negative transistors can not be on at the same time.

Many Class D amplifiers are finding their way into Subwoofers. They are inexpensive to build and the logic is that the switching distortion is not important in a subwoofer.

Class T amps are a more refined switching amplifier developed by Tripath. It uses signal processing to eliminate the switching distortion of Class D. nOrh is currently working with parts from Tripath to determine the sonic merits using the Tripath parts. Our current view is that advantage to using Class T and Class D amps is not to achieve better sound than can currently be achieved with standard A or A/B amplifiers. Rather it is an attempt to create a lower priced amplifier that offers good performance.

Probably 90% of the amplifiers on the market are designed to get a particular RMS rating and little consideration is provided to provide any extra power from the power supply. A properly designed power supply requires three times the output from the power supply than required to drive the amplifier to its maximum RMS rating. Buying and shipping large transformers is very expensive. Manufacturers are looking for ways to cut these costs.

Copied from here : (http://www.norh.com/docs/amps/)

There are more classes of amps but this should give you a little bit of insight on amp classes.

 

Hey thanks alot

 

Pollax-
Great link- Thanks! The esoteric audio there is pretty interestng. Ever heard any of this hardware?

 

sony

 

What does anyone know about the MTX 81000D amp. My neighbor installed one and it pounds hard. I'm seriously thinking of getting one to run my 12" kicker comps. What do you think?

 

From looking at the amp its sounds like a knock off of the Xtant X1001, MTX and Xtant both being owned my Mitek corp. This amps seems to favor DB setups though in that it has very little damping only >100 where the Xtant had >200 and in comparision the new JLs have >500.

It is also way to much power for 1 Kicker comp. THis amp would be better powering 2 solobarics at a 2 ohm load. You could use it but the gain would stay so low that you'd basicly be unusing power. Also for this beast you'll need 1/0 since its recomanded fuse is 150 amps, also like the Xtant.

The amp doesn't sound bad but just overpowered for you aplication.

What kicker comp do you have and can you gat another?
With 2 kicker comp VRs I would say that it would be fine. You would still have some wasted power but not alot. with regular comps don't bother they simply are not constructed to take that much power. I not saying there a bad sub, I always liked kicker but they aren't capable of taking that amp.

For one regular comp the MTX 4250D is enough and with a kicker comp VR a 6500D is enough.

NOw some people will love to tell you its good to over power subs. This is bullshit! When you have a drasticly more powerful amp then the subs can handle you don't actualy use the power. the intention behind an overpowering amps is that you can keep the gains very low thus keeping down distortion and keeping up control and head room. However unless you saturate an amp you won't get distortion and you pay a hell of alot more for no real gains even headroom isn't realy effected. Unless your in a competition where everyone is trying like hell to get an edge over the other compeditors.

 

to continue the discussion...

A class D amplifier is called a switching amplifier because the output transistors are set to full output for the positive and negative outputs. This means that the output from a sinusoidal input will be a square wave. When ever the input is positive (even a very small amount) the output is full positive, same with the negative.

This is also why the amplifier is called a digital amplifier, the output is a square wave.

So.... why class D for an audio amplifier? aren't audio amps supposed to be high fidelity (i.e. the output tracks the input perfectly, or as closely as possible). Sure! that is the case, when you are dealing with a wide range of frequencies and amplitudes. But when you are dealing with thumping kidney punching bass, then it does not matter as much. You only have one speaker and that speaker does not have a very wide response range, so it smooths the square input (due to the dynamics of the system) into a sine wave at the output (audio). In this case the speaker is just going from max deflection one way to max deflection the other way... and for low low hard bass that is OK. A cheap way to get lots of thump. If you want anything else, then a class D is not the way to go.

 

1st MP3 in NH

I do have two Kicker Comp vr 12"s. I am currently running a hi-fonics zeus Z700 amp and I know it's underpowered. Here is what I have so far:

Kenwood kdc-mp819
2 12" kicker comp vr's
stock door speakers
Hi-Fonics Zeus Z700 five channel amp
1 farad cap
kenwood crossover

I want to get the MTX 81000D for the subs and use the Hi-Fonics Zeus to run the door speakers, which I will replace with component speakers when I get the money. I was also thinking of getting an Epicenter bass control thing.

Will I be able to run both amps with a one farad cap?
Will it be a strain on my electrical system?

What do you all think?

 

The MTX will definitly be a strain on your electrical system. I have the Xtant X1001 that i mentioned was similair and I have 2 1 farad caps and 200 Amp alternator and my lights still can dim. I would never get a 1200 watt sub amp before running good front speakers and amps but I'm not you. You can use that MTX with your subs but like I mentioned its overkill. Get the 6500 instaed, its cheaper will be just as loud and won't strain the electrical system that much. I would also add another 1 farad cap for the 6500, 2 for the 8500.

 

1/0 or 2 4 guages.

 

So has anyone here actually run the sony mono amp? Is it good or does it give problems? I am just planning on using it for my two 12s and someone is getting it for me for $100. I have another a person who is willing to sell me a 3 channel xtant amp but based on what he says it will not give enough power to the subs. Any help is appreciated.

 

I have run Sony amps, I used to install them before Tweeter finaly made the right desicion and stopped selling them. They are no where near as powerful as they claim to be. Just look at their fuses. BY them alone it would be impossible for them to produce the powers they claim becuse the fuse would blow. If you are refering to the Xtant 603 3 channel it is more then enough power to run most 12s and out powers most Sony amps with its mono channel alone. THe 603 puts out 100 x 2 + 400 x 1 rms at any voltage and 4 ohms.

I have seen numerous returned Sony amps, can't say its all sony fault most customers that came in looking for Sony were idiots. Most of the amps came back in with the gains peaked and the crossovers unset.