Why can't computers have BNC ouput?

[audiophail]

My dac doesn't accept usb.. I also wonder how could I connect it. I'm kind of new to High Fedelity.

[anatech]

Hi audiophall,
Because the USB is a straight data connection standard and the BNC is one type of digital audio transmission standard. You would need some type of digital out, as available in some sound cards. Otherwise a device that creates a device the computer can recognize as an audio device. It then receives the full USB type data flow and converts that to a digital audio format. I don't know if this exists. The sound card would be less expensive, but make sure it has a digital audio port output that is compatible with your DAC.

Some sound cards have better performance than after market DAC units. That's even if that DAC is terribly expensive (no guarantee it's any good).

-Chris

[wwenze]

Why not?

[anatech]

Hi wwenze,

Why not?

Your statement is not precise enough to understand what you are talking about.

Looking at this sound card, it is not representative of every card out there. The main audio chip may or may not be a good one, Os-Con capacitors are not worth mentioning, but they are good for the switching power supply. The oscillators shown there are not necessarily what I would call "High Precision", and the short term jitter spec is what matters in this case. So you would want to see quartz crystal oscillators instead. In fact, it is possible to buy oven controlled, GPS discipled oscillators at the frequency you need. All that does is increase the long term accuracy, although the oven may reduce phase noise some.

I'm not that familiar with the HDMI specifications, but that port would seem to be of no interest. The BNC exists on the rear of the card. If the interface is designed properly, it is driven through a transformer, which breaks the connection with the computer chassis ground.

-Chris

[phofman]

Originally Posted by anatech

The main audio chip may or may not be a good one

It is Envy24 Tremor, bit-perfect 192/24 PCI audio controller with no DSP. There is nothing this chip could do wrong.

Originally Posted by anatech

Os-Con capacitors are not worth mentioning, but they are good for the switching power supply.

It is most likely a standard linear regulator ADJ713, found on other inexpensive Tremor cards (one of which I hold in my hands now)

Originally Posted by anatech

The oscillators shown there are not necessarily what I would call "High Precision", and the short term jitter spec is what matters in this case. So you would want to see quartz crystal oscillators instead.

There are two quartz crystals on the board - each for 44.1Hz and 48Hz fs families. Unlike vast majority of other audio chips, Envy24 uses no jittery PLL for clock generation, only dividers from two crystal clocks.

Originally Posted by anatech

I'm not that familiar with the HDMI specifications, but that port would seem to be of no interest.

It is a regular SPDIF output on header pins, used to feed the HDMI output of older graphic cards without built-in Intel HDA soundcards. The HDMI specification has no relation to this output.

Originally Posted by anatech

The BNC exists on the rear of the card. If the interface is designed properly, it is driven through a transformer, which breaks the connection with the computer chassis ground.

Each SPDIF output has its own transformer - see the two black cubes on the card:



In fact, I would consider this card a rather decent SPDIF interface.

[qusp]

Originally Posted by phofman

In fact, I would consider this card a rather decent SPDIF interface.

indeed so would I, even if the regulator section isnt quite up to snuff (not saying it isnt) this is something that can be overcome by modders, I might have to have a look into this one for a second set of outputs, I wonder if the i2s is easily tapped also?

one thing that might stop me, as I already use an RME card for spdif/aes duties and its a better card, would be if I was looking to upgrade I would probably be looking at higher bandwidth than 24/192

[phofman]

Originally Posted by qusp

I wonder if the i2s is easily tapped also?

The chip has 6 output streams (i.e. 3 x I2S pins) VIA Vinyl Tremor PCI Audio Controller - VIA Technologies, Inc. . All I2S channels are easily available in linux, only minor mods to open source drivers are needed. However, unlike for its bigger brother Envy24HT-S, a datasheet for Tremor is not available anywhere on internet, at least I have not been able to locate it. It means the pinout is generally unknown. It may be similar to Envy24HT-S though.

Originally Posted by qusp

one thing that might stop me, as I already use an RME card for spdif/aes duties and its a better card, would be if I was looking to upgrade I would probably be looking at higher bandwidth than 24/192

:-) Wow, how much is higher for you? :-)