[technology] Qualcomm DDFA: Direct Digital Feedback Amplifier

[miero]

Chips with DDFA technology allows to build "amplifiers without analog input". It was developed by CSR company:

The DDFA architecture employs a fast and highly accurate digital feedback loop to create a Class-D audio switching amplifier that sets new standards in digital amplifier sound quality. Even when used with an inexpensive, unregulated power supply, including switching power supplies, digital amplifiers based on DDFA technology can achieve THD+N performance levels of less than 0.004% and a dynamic range of 120dB, according to our internal studies.
...
Unlike more traditional linear amplifier solutions, the DDFA architecture integrates the functions of DAC, DSP, pre-amp and power amp...

Source: https://www.businesswire.com/news/h...engthens-Audio-Platform-High-Fidelity-Class-D

Here are expected performance stated by the current owner Qualcomm:

- SNR and Dynamic range > 113dB (A-weighted, 20Hz to 20KHz)
- THD+N < 0.005% (20Hz to 20KHz)

Source: https://www.qualcomm.com/products/features/ddfa-amplifier-technology

... and these chips are used in several products we already "know":

BlueSound PowerNode 1 speaker
Denon DA-310USB
Denon DNP-2500NE amplifier
Denon DRA-100 amplifier
Denon PMA-50 amplifier - https://www.audiosciencereview.com/...-measurements-of-denon-pma-50-amplifier.7940/
Denon PMA-60
NAD C 390DD amplifier
NAD D 7050 amplifier - https://www.audiosciencereview.com/...-measurements-of-nad-7050-streaming-amp.6983/
NAD M2 amplifier - https://www.stereophile.com/content/nad-m2-direct-digital-integrated-amplifier-measurements
NAD M51 DAC - https://www.stereophile.com/content/nad-m51-direct-digital-da-converter-measurements
NAD Viso 1 Speaker
Sonos Amp - https://www.audiosciencereview.com/...ds/review-and-measurements-of-sonos-amp.6957/
Yamaha MusicCast BAR 400

Source of this product list: https://www.qualcomm.com/media/docu...mm-ddfa-amplifier-technology-presentation.pdf

 

[bunkbail]

IIRC @IVX wanted to use one of these chips in his upcoming integrated amplifier but for some reason he was unable to acquire the datasheets from Qualcomm.

 

[restorer-john]

These numbers are good, but hardly exceptional. I own plenty of 30+ year old amplifiers with considerably better numbers than that.

Consider the 113dB S/N is referenced to full power...

 

[boXem]

From memory, TI and ST also have chips taking I2S as input and outputing some watts.
Difference here is that it seems to work in closed loop. Don't know if the feedback is pre or post output filter. Their product brief is frankly poor there is not even a system block diagram.

 

[John76]

I have been trying to figure this out for the longest time and joined the forum in hopes of an answer. Does the Qualcomm chip in a digital amplifier do the AD processing when the amp has an analog line input?

 

[NTK]

I have been trying to figure this out for the longest time and joined the forum in hopes of an answer. Does the Qualcomm chip in a digital amplifier do the AD processing when the amp has an analog line input?

The two current Qualcomm chips only support digital audio inputs. Analog inputs will need to be converted to digital first.

 

[John76]

Thank you! Any idea what AD chip is used in the new Sonos Amp?

 

[NTK]

Thank you! Any idea what AD chip is used in the new Sonos Amp?

Sorry. I have no idea.