How this works was discussed earlier in the thread. There some patents related to this if you want to read more. It's using sigma delta modulation, but without a low pass filter so they're able to say 'direct digital drive'. The innovation is to use multiple voice coils and drive them in parallel which reduces the needed drive voltage and increases efficiency. Having 4 voice coils also gives them some very coarse direct digital control of the driver. The primary motivation is power efficiency, which is why it was first used in car stereo systems, and now if bluetooth headphones. They aspirationally state that it can open possibilities for better audio quality in the future.Well, my 1Z is supporting AptX HD, and the only worthy headphones for this feature is ......
Anyways, it is interesting to see the digital audio world being evolving. Direct digital drive ? Very interesting. Apparently there is no Digital to Analog conversion with the D-Note chips. I cam across their website, and it appear that the Dnotes are utilizing “multiple voice coil configuration” to Directly move the Dynamic driver which in turn will generate sound. Therefore, the more voice coil count, the better. The differences from 9BT vs 7BT is 4 Wires voice coil Vs 1 Single wire voice coil. It seems to me that the way this chip is working is that it invert and feed the digital signals directly into the different voice coil all at the same time, and in return it can move the voice-coil so fast that utilize this mechanical movements to resemble the original “sinwaves” , where as conventionally the digital needs to be converted into Analog signals and then being amplified by the amplifier. By going conventional, the analog conversion and amplification will color the sound in the end.
Sony had been using S-Master as a tool of calling Direct Digital as well, but instead of driving the Voice Coil mechanically like this, Sony put it through Pulses Modulation Coding Which in turn converted it into Analog signals, and then feed this signals into Class D amplification to drive Headphones.
The D-Notes, I think is using something similar, but instead of having some switching mechanism of semiconductors and clocking mechanism, it uses the different phases inversions and feed them all at the same time into the “multiple voice coil winding”. So the Pulses generated by the Digital is totally “Direct” and in turn it resemble the movements up and down of a complete Sin waves, so the Analog is the Voice-Coil itself, and the diagrams are making music.
Now, the question is how did the D-Note get enough power to move the multiple voice coil ? Well, I would say that the received Digital Signals gets Amplified, but since the Digital signals are DC signals, to amplify the DC signals using DC signals, the task is easier than having DC powersource (battery) and then all that conversion to in the end amplifying an analog signals. I guess this is where the ultimate result of pure amplification, pure digital drive, and efficiency come into play.
Genius ideas ! I am very interested into this Headphones and so I have bit the bullet to try and see if this is the Bluetooth evolution that I had been waiting for.
If I understand this technology properly, it is best applied into Bluetooth technology, and not yet DAP or DAC. Because each Chip can only be specially tuned for the physique of each unique voice-coil only and alone. Interchanging voice-coil seems not possible as this block is showing 4 voice coils from 1 Driver. Unless any other interchangeable Headphones driver also have 4 voice-coils or 8 Wires to become possible. I don’t think the market is ready for it yet.
The diversity is real ! Direct digital from S-master for interchangeable headphones or loads! And Direct Digital drive for Bluetooth from Dnotes! The good thing is that D-Notes is not patented by ATH, so we will be more likely seeing a huge market of High-End Bluetooth Headphones very soon in the future
https://www.trigence.com/digital-speaker-module
ATH-DSR9BT !!
In the marketing material they say 'The Pure Digital Drive system also enables the ATH-DSR9BT to overcome the sonic limitations of conventional Bluetooth wireless transmissions by supporting the 24-bit/48kHz Qualcomm® aptX™ HD codec'. They're really conflating aptX HD and the 'direct digital' drive of the transducer. As they state, it's the aptX HD codec which enables better audio quality over bluetooth.
Audio Technica haven't patented this because the ipr belongs to Trigence.
sad