2. amps-preamps
  3. 186312-183932

Digital input amp

I see a few coming on market.  Previous threads were quite old.

They take a USB or other input. No DAC on the front end. Just the DSP engine to do volume, eq, etc, then whatever conversion to PCM to feed the class D output. So the only "DAC" is the output stage.   This makes sense as it further reduces the functions in the chain.  I have not seen objective testing or any reliable subjective testing. The ones I have seen are Infineon processer based. No idea if the output filtering or feedback implementation is up to the Purify quality.   I guess the next innovation is the GaNFET output.  One has a DAC to feed a sub out. Easy as any old $5 DAC will wo there. 

I was browsing and came across the Sajab A30a. ( quite inexpensive)  Peachtree has the old Gan-1 but coax PCM only.  That would be fine if it managed buffering and clocks internally. Unfortunately my all-in-one only has USB out. 

I suspect there is a lot to be learned here but it makes sense to me for the future. 

tvrgeek

Showing 3 responses by erik_squires

erik_squires
15,925 posts
 

I didn't eat a donut, I am the donut.

erik_squires
15,925 posts
 

Want to add a little:

 

Class D is a switched output amp but the switching is completely controlled in the analog domain.

Modern amps like Technics may be called a digital amplifier in the sense that it is a digital process controlling the switching of the output duty cycle, but it IS a DAC. Further, these digital amplifiers (as I define here) have challenges in properly implementing a feedback circuit.  Technics famously gets around their issues with a calibration cycle.

erik_squires
15,925 posts
 

OP:

Exactly how are you defining a DAC? From your description, the amp IS A DAC.

Simply put, a DAC stands for digital to analog converter. You don’t listen to PWM. You listen to, must listen to, music as an analog event.

So that PWM signal must go somewhere, and the moment it becomes an analog signal you have a DAC.

I should also point out that Class D is an analog, but switched system. A purely PWM driven amplifier has complications of it’s own, especially how the lack of feedback is a challenge.

To borrow a term from marketters, this is a powerDAC.

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