[mbd2884]

I prefer USB. Why? The entire point of having an external DAC is to skip the whatever processing that may happen in the sound card. As stated before if you use optical, whether people say or not, the data is being processed in the soundcard. Impossible not to do so. With USB, doesn't go to soundcard, skips it entirely. The computer sends pure bit rate data out of the USB and its processed in your external DAC.

As someone mentioned before, designers of these DAC have already taken consideration of the USB deficiencies and already address the issue of jitter. Personally for me, don't care, as I have accepted that my ears are biological and I am only human. So whenever someone claims to have such golden ears, I call bullcrap and take anything they say from that point on at entertainment value from then on, usually.

Would add though, I would prefer to use Firewire over USB though. But no such luck at my price range so far.

The other thing I would add, we are talking about 16 bit 44.1khz sound data. So who cares if optical can go up to 24 bit 192khz. As far as I'm concerned if the data has to be resampled, well its no longer bit perfect. Its been processed, degraded, and that defeated the entire point of having bit perfect sound output from an external DAC. USB is the way to go for me, or Firewire.

 

[forsberg]

Both sounds the same to me.

 

[Quaddy]

Quote:

Originally Posted by tacitapproval /img/forum/go_quote.gif I discovered a potential problem with USB that has nothing to do with how the information is processed. My USB powered DAC (IBasso D3) picks up noise from the laptop's ac input. This can only be heard clearly at a high degree of amplification (beyond listening level), but it is there. So grounding issues are something to consider with USB.

try using another USB port, some are better than others, like on some macs, their can be a 'hot' one on some makes and models, on my latitude x300 from dell, i would sometimes run into issues with the USB with ticks and pops, even with it configured optimally, i simply used an add in PCMCIA (stands for People Cannot Memorize Computer Industry Acronyms - ironic but easy way to remember it

) usb card, and that worked a treat, and was actually great way of cutting through the onboard interrupts and the onboard usb bus. thats probably the cleanest way you can connect USB on a laptop.

@mbd2884 - i agree, resampling is instantly degrading the original stream and is a false economy to try and build on top of resampling with all other fancy means. - i hear what you are saying about firewire, i actually think USB is the superior protocol right now, over and above firewire even, for a whole host of technical reasons, i guess we dont like to think that though with the USB protocol being so old, its almost to simple for it to be the accepted and preferred method for audio.

 

[kbug]

I also had problem when using USB from my laptop. I can hear pops when I move mouse over menus. I searched around and found out it is due to graphics card contending for resource. I turned off hardware acceleration and the problem is gone.

 

[Quaddy]

nice solution, you can also use PCI latency tool, which as the name suggests, not just for PCI devices, but you can tweak how long devices/ports contend for resources also, a lot of gamers use this.

 

[I3eyond]

Quote:

Originally Posted by Quaddy /img/forum/go_quote.gif nice solution, you can also use PCI latency tool, which as the name suggests, not just for PCI devices, but you can tweak how long devices/ports contend for resources also, a lot of gamers use this.

Vinyl > Digital

We all know optical cables provide us a digital sound. 0s and 1s, off and on. But, as I've said before, DACs CAN be imperfect, but that depends on your definition of imperfection, of course.

iPod Direct > Headphone .. (For example), is an analog signal. A wave. Sin waves, cosine waves. Oscillation.

Digitalization, however, is either on or off (Binary, 0s and 1s)

Picture included:

 

[dmashta]

you're aware that ipod is a digital source and the analog signal you speak of is the result of internal dac conversion?

Quote:

Originally Posted by I3eyond /img/forum/go_quote.gif Vinyl > Digital We all know optical cables provide us a digital sound. 0s and 1s, off and on. But, as I've said before, DACs CAN be imperfect, but that depends on your definition of imperfection, of course. iPod Direct > Headphone .. (For example), is an analog signal. A wave. Sin waves, cosine waves. Oscillation. Digitalization, however, is either on or off (Binary, 0s and 1s) Picture included:

 

[AzN1337c0d3r]

USB is digital.
Optical is digital.

The conversion from digital -> analogue is done on your DAC (hence, Digital to Analogue Converter)

Digital is bit perfect. Barring any design flaws in your USB/Optical connection, the bitstream should be identical for both methods.

I don't buy this jitter claim either. USB and Optical both do not transfer a clock along with their signals. Being that there is no clock transferred along with the data, all the bit edges are resynchronized to the clock of the slave device. Any jitter should be in the extreme low range of picoseconds, if not femtoseconds.

Edit: Well I kind of lied. SPDIF does carry a word clock embedded into the signal to assist in recovery of the data rate, but ultimately, all the signals are clocked using the slave's internal clock.

 

[olblueyez]

Quote:

Originally Posted by mbd2884 /img/forum/go_quote.gif I prefer USB. Why? The entire point of having an external DAC is to skip the whatever processing that may happen in the sound card. As stated before if you use optical, whether people say or not, the data is being processed in the soundcard. Impossible not to do so. With USB, doesn't go to soundcard, skips it entirely. The computer sends pure bit rate data out of the USB and its processed in your external DAC. As someone mentioned before, designers of these DAC have already taken consideration of the USB deficiencies and already address the issue of jitter. Personally for me, don't care, as I have accepted that my ears are biological and I am only human. So whenever someone claims to have such golden ears, I call bullcrap and take anything they say from that point on at entertainment value from then on, usually. Would add though, I would prefer to use Firewire over USB though. But no such luck at my price range so far. The other thing I would add, we are talking about 16 bit 44.1khz sound data. So who cares if optical can go up to 24 bit 192khz. As far as I'm concerned if the data has to be resampled, well its no longer bit perfect. Its been processed, degraded, and that defeated the entire point of having bit perfect sound output from an external DAC. USB is the way to go for me, or Firewire.

You do realize 99 percent of USB dac implementations convert the USB stream to SPDIF before the information is sent to the dac meaning the music is still suffering some kind of conversion. This type of conversion is also thought of as an after thought so a manufacturer can claim USB compatibility in the list of features. If you have a DAC1, Pico, Empirical Audio Device, Wavelength, or Scott Nixon then your USB dac will have a direct USB to Dac configuration but if your dac is not on the short list then there is no point assuming USB is superior for any reason.

 

[mbd2884]

Yeah I wouldn't go as far as to say USB is superior, but say that is my preference since I still like the idea of bypassing my soundcard completely regardless of what happens in the DAC. But good to know Blueyez.

 

[I3eyond]

Quote:

Originally Posted by dmashta /img/forum/go_quote.gif you're aware that ipod is a digital source and the analog signal you speak of is the result of internal dac conversion?

Therefore, vinyl is greater than digital; however, see picture.

 

[dmashta]

as far as which is technically superior, usb is. when implemented properly, usb can utilize methods such as async transfer (which slaves the computer to the dac instead of the other way round) and direct I2S conversion (as olblueyez mentioned), both of which greatly benefit jitter performance. however dacs currently implementing these are still rare and until they become more common, your ears will be the best judge as to which is better.

 

[olblueyez]

Quote:

Originally Posted by mbd2884 /img/forum/go_quote.gif Yeah I wouldn't go as far as to say USB is superior, but say that is my preference since I still like the idea of bypassing my soundcard completely regardless of what happens in the DAC. But good to know Blueyez.

I don't know why but quality USB implementations in D/A converters is slow in progressing. What sounds better, Optical or USB, is different from dac to dac as well, I see a lot of people buying dac's with 3 or 4 different types of input and never trying each type to see what input sounds best. Moral of the story is try them all of you have more than one input and decide for yourself. I do notice a tendency for people to gravitate toward USB when using a computer for transport, I felt that way too when considering dac's, but if you have optical or coax available on your computer then think less of USB and more of the over all quality of the dac when shopping. There are a lot of good opt/coax dac's out there being ignored unnecessarily.

 

[Bones13]

As with all gear, better stuff is better stuff.

Some things that I take into account.

Optical cables are not affected by other equipment in your system, and runs a longer distance without picking up interference.

In the PC world, you end up with some software driver to produce bitperfect audio. This tends to be pretty easy with most sound card versions of SPDIF optical. I am not sure if the motherboard audio systems will output 44.1, they could not last time I looked. USB ASIO drivers are a good bit more tricky in my hands.

In the Mac world, you have both USB and Optical out of the desktops and laptops with built in bit perfect.

I really like using a USB based system when traveling with my laptop. The Predator works fine for even a week trip with a full charge. No chargers or other paraphanalia, just the USB cord. One cannot by definition have a DAC/AMP powered by an optical cord. Either batteries, or an adapter would be needed.

On both of my stationary systems, I use optical cables to plugged in DACs. Both runs are 8 feet, and the cables run thru a maze of computer and audio wiring. That being said, I am not sure I can tell a difference between the USB and optical inputs on my UltraMicroDAC when run from an iMac, with 3 foot cords for either.

 

[mbd2884]

Yeah my Compass uses direct I2S from the PCM2707 to the AD1852