Do We Really Need a DAC?

[wireburn]

In this age of digital everything at the source and digital amps at the endpoint, do we really need a DAC? I'm no newbie to audio and electronics, having completed many successful projects, amps, pre-amps, speakers, python, arduino, etc. and it seems to me that there would be a way to circumvent the amplifier's gain stage and skip the DAC. You would then have a device in the amp that takes PCM and translates it through the SMPS directly to a high gain signal for the speakers. I realize that device is technically a DAC but we'd get to at least skip the analog interconnects and gain stage.

So, to the many here with much more EE cred than I, what say you?

 

[M00ndancer]

In my opinion, there will always be a DAC present as well as a ADC. You still have to convert the bit based information to a wave that moves a transducer. Moving the air so our small hairs in our ears can detect the movement.

You would then have a device in the amp that takes PCM and translates it through the SMPS directly to a high gain signal

Secondly, there is no such things a "digital" amp. A D-class amplifier is not digital.

How Class D audio amplifiers work - Link removed. Not making any sense. Thanks for the feedback.

 

[solderdude]

I realize that device is technically a DAC but we'd get to at least skip the analog interconnects and gain stage.

What's the problem with interconnects ?

 

[julian_hughes]

Skipping the DAC is already being done. There are more & more PWM amplifiers. They don't require a DAC at the digital input stage and nor do they require a preamp. I have a couple of cheap ones from aliexpress, I.AM.D V200s. They work great but don't have a good headphone output. If you're feeling rich you can try something like the NAD M32.

 

[wireburn]

Thank you for the link. Decent read! From that article: "Class D amplifiers take on many different forms, some can have digital inputs and some can have analog inputs."

Maybe I'm not actually "on to something". Where are these digital input class D amps?

 

[wireburn]

Ha, too slow. Thanks to all who replied!

 

[M00ndancer]

Skipping the DAC is already being done.
If you're feeling rich you can try something like the NAD M32.

Where are these digital input class D amps?

The M32 is a DAC with a D class amp. A "digital" amp... also called marketing fluff....
There is no skipping anything.

 

[NTK]

Thank you for the link. Decent read! From that article: "Class D amplifiers take on many different forms, some can have digital inputs and some can have analog inputs."

Maybe I'm not actually "on to something". Where are these digital input class D amps?

An article by Bruno Putzeys.
https://www.audioholics.com/audio-amplifier/the-truth-about-digital-class-d-amplifiers

Quote from the article:

One should ask the question: would any D/A converter designer in his right mind build a DAC using power components? Probably not.

 

[julian_hughes]

The M32 is a DAC with a D class amp. A "digital" amp... also called marketing fluff....
There is no skipping anything.

I suggest you read up on PWM amplification. A DAC is not needed. In reference to NTK's post, it's important not to conflate Class D with PWM amplification.

 

[M00ndancer]

A DAC is not needed

Define a DAC. Is it the process or the chip?

 

[M00ndancer]

They don't require a DAC at the digital input stage and nor do they require a preamp. I have a couple of cheap ones from aliexpress, I.AM.D V200s.

Care to explain this? I'm confused.

"Amplifier Class D TAS5614LA,I.AM.D V200B integrates a 24bit / 192kHz analog digital converter with an S / PDIF interface as standard. This amplifier has the characteristic of being " Full Digital", ie the S / PDIF signal is converted to I2S and then directly amplified by the TAS5614LA. " from https://www.audiophonics.fr/en/inte...led-class-d-tas5614la-2x65w-8ohm-p-11039.html

 

[Killingbeans]

Yeah, since SMPSs, Class-D amps and the current output of many DAC chips have a pair of switching transistors in common, the idea of combining all of the functionality in a single pair is not new.

There's the "digital" amps that combine DAC and Class-D (well, strictly speaking it's not Class-D, but you get the picture), and there's "ampliverters" that combine SMPS and Class-D (only experimental?). Don't think I've ever seen all three combined?

 

[julian_hughes]

A DAC is an object, a device, a Digital to Analog Converter. It performs conversion.

Alternatively define a way to say "That's interesting. I hadn't heard of PWM amplification before."

I'm not responsible for French retail outlets making errors in their product descriptions! You can get an accurate description including photos of the boards from the manufacturer's own retail store at https://www.aliexpress.com/item/32417096558.html?spm=a2g0s.9042311.0.0.27424c4dp2QNtv

If you'd like to see another NAD amp built on the same tech, again you can investigate at the manufacturer's own outlet: https://nadelectronics.com/product/d-3045-hybrid-digital-dac-amplifier/

 

[Killingbeans]

https://www.audiosciencereview.com/...-ddfa-direct-digital-feedback-amplifier.9413/
https://bits-chips.nl/artikel/axign-chips-at-the-heart-of-harman-kardons-beat/
https://media.flixcar.com/f360cdn/Harman_Kardon-75965644-Digital_Loop_Amplifier_White_Paper.pdf

 

[NTK]

A DAC is an object, a device, a Digital to Analog Converter. It performs conversion.

Alternatively define a way to say "That's interesting. I hadn't heard of PWM amplification before."

I'm not responsible for French retail outlets making errors in their product descriptions! You can get an accurate description including photos of the boards from the manufacturer's own retail store at https://www.aliexpress.com/item/32417096558.html?spm=a2g0s.9042311.0.0.27424c4dp2QNtv

If you'd like to see another NAD amp built on the same tech, again you can investigate at the manufacturer's own outlet: https://nadelectronics.com/product/d-3045-hybrid-digital-dac-amplifier/

NAD's M32 "direct digital amplifier" is based on technology from Cambridge Silicon Radio (CSR was acquired by Qualcomm). The technology is named Direct Digital Feedback Amplifier, which means it incorporates feedback error control.

Again, quote from Bruno's article:

2. Digitally controlled class D. Amplifiers with a digitally generated control that switches a power stage. No error control is present. Those that do have an error control can be shown to be topologically equivalent to an analog-controlled class D with a DAC in front.

[Edit] Diagram of the DDFA architecture from Qualcomm. Notice the DAC and ADC?

 

[Beershaun]

There is a company Trigence that has a patented technology using digital signal to drive speaker using multiple voice coils.
https://www.trigence.com/dnote

This was implemented in some Clarion car audio speakers and the audio Technica DSR7BT and DSR9BT bluetooth headphones. I would love to see this measured to see how it performs compared to conventional headphones. I have the DSR9BTs I can give to Amir when he has capacity.

 

[M00ndancer]

A DAC is an object, a device, a Digital to Analog Converter.

Yeah, since SMPSs, Class-D amps and the current output of many DAC chips have a pair of switching transistors in common, the idea of combining all of the functionality in a single pair is not new.

Thanks, makes things easier to discuss. My opinon is that it's the process of going from a digital data stream to an analog out, that is a DAC. If you can amplify it and integrate into one unit, it still serves the same function. Language is hard and I'm no language expert. So the answer to OPs question is that it depends on how you define the parts that do the work.

 

[M00ndancer]

There is a company Trigence that has a patented technology using digital signal to drive speaker using multiple voice coils.

Please, send it in. Would be interesting how it performs. I wonder how they amplify the on and off bits...

 

[Beershaun]

Please, send it in. Would be interesting how it performs. I wonder how they amplify the on and off bits...

I've offered it to Amir. It will depend on his capacity and priorities. There are likely many more popular headphones he has to get through first. I am super interested to see how it measures. Also, since it can take USB audio or bluetooth LDAC, APTx-HD it's a good candidate to perform an "apples to apples" comparison of the top bluetooth codecs vs. a wired digital connection and see how they compare at the speaker output level, with the bluetooth codecs being the only variables.

 

[Beershaun]

Please, send it in. Would be interesting how it performs. I wonder how they amplify the on and off bits...

Regarding amplifying the on/off bits. I interpret the Dnote marketing material as the bits are used to somehow "energize" multiple voice coils to create a potential difference as a way to "tell" the transducer a position to move to. I am not sure how it eventually becomes a final voltage output or how each voice coil is energized. I guess that's where the underpants gnomes get involved.