Digital amplification

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goodguy

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Hello and thanks for taking the time to read this post.

Can anyone advise on a good digital amp. I searched google for " digital amplifier versus analogue amplifier " to gain a good knowledge of the subject, I like the idea of being able to insert a digital signal and have it amplified without the need for digital to analogue conversion, essentially keeping it within the digital domain but cannot really find any specific lists of who the best manufacturers are or any model numbers.

I saw the name Tripath and also a few Tripath items on ebay, how do they rank.

Finally I purchased a digital amp out of curiosity (for the car) it did sound different but not particularly better when compared with my Audison lrx 4.300 which is analogue.

For home use i have a analogue quad 405-3, what kind of digital amp should i be looking at as a replacement for this.

Many thanks in advance. John.
 
What are you plugging into this amp (instruments, CD player ...)? What are you planning on driving with it (speakers, other digital equipment)? If you plan on listening to the sound at some point, it has to be converted from digital to analog. It's best to have a good converter (interface) then use an amp that shapes the sound according to your needs.
 
I may have missed something....but most "digital" amps I know of are only "digital" in regards to voltage switching and amplifier internal workings, but don't have anything to do with the audio which stays analogue the entire pathway through the amp.
There may be digital line amps for transferring digital signals long distance...but this has nothing to do with speakers and cars.

In regards to "digital" amps in the studio...you may be a little on guard, because the one I had reaked havoc on guitarists and other pickup based instruments because it caused a horrible amount of inducted noise.
 
Digital amps or Class D amps are switching amplifiers ...... they take the analogue signal and put it through a PMW (Pulse Width modulator) which converts the audio to pulses which get amplified and move the speaker cone , the more pulses the more the speaker cone moves .....

The advantage of Class D amps are that they are very efficient (75%-95% +) so they require a lot less Power to use and also put off a lot less heat than regular Class A/B amps which are at best 50% efficient .....

In the past the problems with Class D amps were that they didn"t have very good noise specs but they have evolved over the years to be quite good especially for bass or subwoofer duty ......

Cheers
 
Hi. Thanks for the reply.

Sorry guess i didn't explain properly. I was referring to pure-path amplifers sometimes known as ddx amplifiers, not class-d amplifiers. Has anyone had any experience of these, what is the sound quality like, would be interesting to hear from an experienced perspective.

Many thanks. John.
 
PurePath and DDX are both Class D amplifiers .....

DDX amps can actually handle a Digital signal like the digital out on a Soundcard ...... most class D amps start off in the analogue domain because most all music is analogue and even digital music starts off and ends up Analogue at some point.....

The DDX amp still converts the Digital signal to pulses useing a PWM ..... The only advantage is that if you are working with digital signals the DDX amp doesn"t convert them to analogue before being converted too Pulses by the PWM .......
DDX are developed by Apogee are are fairly expensive .....

As far as audio quality goes Class D amps still have higher THD and noise specs than a good Class A/B design but efficiency is so much better .....

PurePath is a simular technology accept developed by texas Instruments .....
 
Another way of looking at these amplifiers (assuming they take a digital input) is as high power output D/A converters. While this sounds attractive in that it seems to eliminate a step in the process, it's a net loser in terms of fidelity. You don't gain enough by eliminating/combining the traditional D/A converter and analog amplifier to make up for what you lose in terms of the performance of the Class D amplifier topology. The reason is because of what the amplifier is trying to do. It's basically a switching power supply that tries to follow the input signal with its power supply voltage. It's very efficient because there's no power lost in the difference between the output voltage and the power supply voltage, but making a power supply move around at high frequency is no small feat. In theory it can be done with as much fidelity as you wish, but when you have to actually build one, the limitations of real world components creeps in. You need to have the switching frequency very high compared with the audio you are trying to pass so that you can filter out all of the switching aritifacts without affecting the frequency response of the output signal. When you want 20khz to pass unaffected that puts the necessary switching frequency quite high indeed which causes many problems for anything other than theoretical components. As someone else has pointed out already, for low frequency purposes like subwoofer amplifiers, this problem goes away and Class D amps work quite well, delivering huge power output from an unbelievable small and lightweight amplifier. Usually these have a normal audio input signal that is digitized in the amplifier.

J
 
Hi. Many thanks for all the replies, very informative.
 
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