i'm very confused still, is there any way to explain it in very simple terms? how is it any different to normal double amping?
Here is one way to look at it:
It may be simpler to understand if I use the definition of Double Amp to mean: Analog amp1 output to Analog amp2 input. This is a double amp (2 analog amps) configuration.
- A typical double amp config is: DAP Digital signal ->
D/A -> analog signal -> internal
analog amp1 -> DAP Phone out -> External
analog amp2 -> IEM . This is a double amp configuration. In this configuration, there is distortion from the D/A conversion, the first Amp stage, and also the 2nd Amp stage. This is considered undesirable, and people try to avoid it. Though if it sounds OK, because each stage is done very carefully, then it is still usable. Just theoretically not desirable
The Sony does not have any analog amp.
- Sony direct digital pulse stream -> low pass filter -> IEM is a signal that is very close to the original Digital signal. So if you amplify this signal(double amp it), it does not have the same negative effects as a typical double amp configuration. There are theoretical negatives still, but much, much less than a typical 2 analog amp config. Effectively, you can look at it as the equivalent of a single amp configuration, as there is only the single external analog amp in play.
- Sony direct digital does not have a D/A conversion stage, nor an analog amp stage (as there is no analog signal involved). The digital signal stays digital all the way, from input to output, and is never converted to Analog. Except at the output, where the LPF does a simple convert by filtering out the non audible frequencies.
SONY DAP digital signal -> reclocked/shaped for more accurate timing/dither -> High current Digital Pulse Stream - > LPF(Low Pass Filter) ->IEM.
There is no Analog amp involved. It uses a high current digital pulse stream to create the high current output to drive the IEM (after Low Pass filtering). The digital stream is passed from input to output. Thus the Sony Phone out is not like the output from a typical DAP.
In fact, it is simpler than a normal DAP single analog amp configuration, as there is no analog amp involved. If you double amp this, on paper, it is a double Amp configuration, but internally, it does not have the same drawbacks as a regular DAP that is double amped. This is the advantage of Sony's Direct Digital implementation.
Another way to look at it is that it is very true to the digital signal and is very R2R like in how direct it is in processing the digital signal, with the added advantage that it does not have an analog amp stage like a typical R2R DAP(or any DAP) would have. Of course a direct digital amp is not a simple/perfect solution either, and it takes a lot of work and engineering knowhow to make a good one. Otherwise, if it were easy to do, there would be a lot more DAPs using a direct digital configuration, and simplifying the hardware parts count.
EDIT: The Sony direct digital configuration is simple, but understanding it and explaining it simply is a challenge!