Upsampling/MultiDAC technology works!

Julian,

A digital amp with analogue inputs is essentially an ADC + 1-bit DAC both working at a very high frequency rate (typically 500kHz to 1MHz).

If you bypass the ADC stage (I think Wm does it) and feeds the bitstream DAC directly with the data from the CD transport output, what do you have?

You have an upsampled bitstream signal with a changed sample rate of 44.1 kHz to 500 kHz! The ADC stage doesn't change this... unless you already have an upsampled signal of say 192kHz from which you upsample again to 500kHz.

But what about the analogue signal, you ask?

Well, in this case the difference between the analogue signal (prior to the amp) and the digital one is the staircase shape of the latter which is smoothed out in the former. Now, just imagine the staircase-shape signal (with the smoothing line designed over it - the analogue signal) and then think about what sampling at a much higher frequecy (which is not an integer multiple of the former) will do to it... nothing more, nothing less than interpolate new samples between the already existent samples forming the staircase-shape signal. THAT IS UPSAMPLING!!!

Sampling vinyl is absolutely stupid... you'll necessarily loose information even further and you loose what is for many regarded as its intrinsic advantage over digital media.

 

bd,
i don;t think wm bypasses the analogue in's on his amp. even so i'm not talking about this type of digital amp. unlike some i try not to comment on things unless i have personal experience of them - and if i do i try to make that clear.

also go and read up on sampling theory and you'll realise just why you are wrong. sure 22.05 khz is not enough but at 250 to 500 hkz maximum frequency i doubt even the most rabid vinylista would claim that there is anything missing and if they did they'd be rightly branded a luddite/ anachrophile.
cheers


julian

 

Completely false. I suggest you do your research, you don't know what you're talking about here.

-- Ian

 

Damn you, Julian... In essence, there is only one type of digital amps, and within it those with analogue, digital or both inputs...

Do you really understand what is in stake here? Do you really believe you can have higher sampling rate than studios have for recording live music, that you buy?

Do you understand why SACD (which was born as a cheap way of digitally archiving old music) have inferior resolution than PCM, although its sampling rate is 2.8224Mhz? And what about it, for the same token wouldn't you be loosing great deal of information with only 1MHz digital amps?

 

If you have anything to add I would be grateful...

 

bd,
as tripath are cagey about their amps internals i can't really argue with you any further however i suspect that the sampling of the analogue signal is done in a multibit manner rather than as a bitstream and then converted to a bitstream later in the process for feeding to the output transistors. i suspect this as dsping a bitstream is a nightmare whilst dsping pcm is relatively simple.
that really leaves noise shaping as the only 'evil' going on and i suspect that by varying the input sample rate as they claim they are making things easier for themselves in this respect.
in the end i'll always buy with my ears rather than with my head if you understand what i mean. that's why the dac i very nearly bought was a 24/96 upsampling delta sigma c.e.c. dx 71. as i said earlier i believe psu's and output stages to have just as big - if not a bigger - influence on the sound of a dac then the chipset used.
let's just leave it as 'you say pataytah and i say pohtaytoe'
cheers


julian

 

Julian,

I am NOT argueing with you, I am just talking with you, after all you were of the few that always showed some respect for other people opinions... and I respect you for that.

Now we are getting somewhere... That's just it Julian, SAMPLING OF THE ANALOGUE SIGNAL IS NOT DONE IN A MULTIBIT MANNER (surely, not at a sampling rate superior to 44.1kHz).

And even if it were, you'd loose this advantage immediately, as soon as the bitstream conversion would take place.

I couldn't agree more with you. However, I also hope you can understand that in the end of the day a multibit system with equally cared psu's and output stages will always sound better than any bitstream system with sampling frequency inferior to 2.89GHz.

I would be the first to buy a digital amp with a switching frequency of 2.89GHz+, because my ears don't lie to me, never did and never will.

Till then, my ears and my head are just telling me that they like a good analogue amp better.

No Julian, we always can do better than that... as long as we respect each other opinions.