The CD uses a photodetector to read the laser's reflection off of the disc. At that point and thereafter it's electrical. There is some work to get that electrical signal converted into a bitstream but all that is well established technology. Unless the medium is damaged in some way, a cheap transport should be just as capable of reading the bitstream as an expensive one.
At least you’re admitting it now.
Not to be splitting air, but I don't know any DAC chip that will take a USB signal directly, SPDIF yes, altough not always desirable.. Let's just say that there is more similarities between a IIS signal and SPDIF, than a USB Packet stream... Yes it's still just pushing samples, but USB needs hand shaking, needs reclocking to work... You'll need some sort of USB receiver in between, typically a XMOS chip.
A USB interface is asynchronous. It has the data for each sample in order, but no clock information. The clock is in the DAC. So you feed it with a buffer to keep the data flowing without running out or filling up and the DAC clocks it out. Generally internally an I2S interface does this. If a DAC only has SPDIF, then the DAC has to synch the clock to the incoming data rate. There are various ways to do this, and most increase jitter even if only slightly. The result of synching to that SPDIF clocked data stream then goes over an I2S interface to the DAC chip itself. It is the SPDIF connection which is more complex. You have it backwards in regards to conversions and complexity.
USB signals have no clock related to the playback of digital audio. SPDIF does. DAC chips don't take SPDIF directly, they have to synch clocks to it before using the signal. The I2S interface has separate clock and data signals. You have to peel the data from the clock with SPDIF to feed it to the I2s connection. With USB you get the data and let the DAC clock be the master and clock it out without regard to outside timing sources.
How do you know is the same DAC? For this price/size there could be 10 DACs inside it. I mean, do we assume something about how the device is build and works internally or not? The manufacturer sells this device mainly to play CD/SACD, and I believe users than can be seriously interested in buying this kind of device will be interested in that too. Besides, so there is no need for any assumption if the device is tested with a CD. Testing only the USB input and not the other functionalities, as digital output or headphone jack is the result of a biased approach, ASR biased I mean. Not the end of the world of course, and it can be justified by saying that there is not enough time or that such details are of no importance here, but it makes no sense, it's simply wrong, to say is not necessary because we know the result in advance. No big deal, but let's not fool ourselves.
I understand that well, but well, as you said USB is Asynchronous, DACS aren't, so yes USB will need some sort of "processing" Sure most DAC will use a SPDIF receiver for clock recovery, at least lately, but it's not obligatory, yes many DAC chips have SPDIF inputs.
I don't know how people can argue CD data isn't read into a buffer. A buffer is some storage - usually ram but it could be anything - used temporarily. A CD player reads light into bits, stores that in ram, does a bunch of error detection/correction (which is part of how it can play scratched disks without audible artefacts), then sends that data on for further processing (D->A, or encoding it into packets for USB output). Some have just enough ram to handle decoding; others, such as a little £30 "diskman" I had once, have more and read a few seconds ahead so if you knock it about when walking/running the music can play on uninterrupted (up to a point). Anything which operates on bits IS a computer, essentially. There's a data, which is operated on, and there's the computer, doing the operating. Apart from quantum machines, all computers are turing machines which means they are all 100% identical in terms of what they can do. Some can do a given piece of work in a few microseconds which would take another machine days because of architecture, scale etc but they are in theory all capable of doing the same thing. The archetypal turing machine is simply a long piece of tape which can be played backwards and forwards and there's a machine which operates on data on the tape, reading and writing a bit at a time. Everything else - ram, caching, USB, lasers, buffers, parallel computing, etc etc are just meaningless abstractions.
Sure yes, but the discussion was about Asynchronous USB, It was assumed by me UAC2 what you are referring to is obsolete.
Because there is no indication otherwise: The marketing does not mention it, the specs don’t show it, and the inside pictures seem to point at just one DAC implementation.
Largely yes. It will show the same crappy filter response, especially bad for Redbook. The rest is then immaterial. Playing SACD does probably not use the magical upsampling, so there’s that.
Yes sure, I’d like to see some test on the CD drive part, just to make sure it performs equally. But we can also deduce a lot from the data we already have.
Got any sources for the SACD upconversion? To do that, one would first need to convert to PCM. That’s basically sacrilege
Just the spiel on the Marantz product page linked above.Got any sources for the SACD upconversion? To do that, one would first need to convert to PCM. That’s basically sacrilege
It's digital in both cases.....not sure what your point is.
Seems. like many "hifinuts", not to know much about how it actually works
Just keep wondering what he's understood in the past of the process and why it matters here. Then again we're talking about a pretty silly cd player.
I used a Marantz CD94 for about 10 years. Any decent CD player has wooden side-panels.
