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I often see class D and digital amp together in the same article. It's not surprising. Dequals digital for most people. But in this case D doesn't stand for digital. D is just a letter that comes after C which describes another amplification format.
What probably adds to the confusion is that the normal input signal is encoded, amplified and then decoded. But the encoding is an analog format, not a digital one. The signal is converted into variable length square waves and then decoded the same way a CD digital signal is, with a low pass filter.
In many ways this is just a detail since for most of us the thing that matters is the performance, not how it gets there. But I do think it is important to keep the record straight.
Follow Ups:
The signal to the output transistors is binary, not analog. To me, that seems like it is more digital than analog.
Edits: 02/02/16
Digital amplifiers use the PCM signal, and convert it to a form (PWM) suitable to switch output transistors on and off quick enough to modulate a power supply connected to a speaker load.
The analog conversion is done at the output stage were the carrier frequency is stripped off the signal via a low pass filter.
The TACT Millenium, NAD C390DD, Devialet, and Nuprime amps are examples of this type of amplification. Wadia had a digital amp about a decade ago.
All of them convert analog sources to digital format prior to amplification.
I don't even know if it's theoretically possible?
I remember hearing about "Class T" at one time. Not sure what that was about.
Cheers!
Jonesy
"I know just enough to get into trouble. But not enough to get out of it."
Yes, some class D amplifiers are fully digital, performing feedback and feed forward computations in digital domain. Others are not.
First category includes NAD 390 and Lyngdorf and others.
Second category includes Hypex, which are entirely analog: it is a switching system but one designed as an analog nonlinear dynamical system. I think ice is also in this category but I'm not sure.
i have a NAD M22 which I enjoy quite a bit (Hypex Ncore) so at least NAD is not taking sides in this.
.
Aren't power dacs just an integrated dac and amplifier? And the amp usually class D.
I guess I'm wondering if amplification can be done entirely in the digital domain. Maybe the power dac meets those requirements by definition and may be called a digital amp.
We'll, here's to the future!
Cheers!
Jonesy
"I know just enough to get into trouble. But not enough to get out of it."
Aren't power dacs just an integrated dac and amplifier?
Not units like the NAD C-390 :
"Like the M2, the C 390DD has no analogue stages in the signal path, keeping music in the digital domain right up to the speaker outputs"
Another advantage is they do not require using a high sampling rate and its attendant high frequency noise that must be filtered from the output.
And looks like Nad has been using that technology for some time now. I've obviously been spending too much time in the tube forum.
Thanks for the info!
Jonesy
"I know just enough to get into trouble. But not enough to get out of it."
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Have Fun and Enjoy the Music
"Still Working the Problem"
I guess if it also has a DAC included, they are allowed to call Class D a 'Digital Amplifier'.
the Infinity SWAMP in the pre digital era of the 70s.
They're still as inherently non-linear today as they were then. :)
The Infinity was class D, not digital.
I'm glad you got the part about it arriving in the pre digital era. :)
...sounds like you've summoned the monster.
that such designs rely upon massive amounts of "correction" to address non linearity - with a power ratio of a million to one!
The debate lies as to whether or not you can hear all the fixin' going on with musical content. :)
Most of all posters have known this for many years, have you been asleep, or maybe you should lay off the scotch.
Regards,
Mike.
Well I keep reading articles that use digital and class D in the same paragraphs.And I'll be damned if I'm going to lay off the Lagavulin.
Edits: 01/28/16
In that case I strongly suggest trying LAPHROAIG :-)
They're just a few minutes down the road in Islay anyway. :)
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