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Benchmark DAC1 now available with USB - Page 43

post #631 of 3034
Is there any advantage to having the computer and drive in the living room, other than the user interface?

A bit OT, hope that's OK...
post #632 of 3034
Quote:
Originally Posted by Regnad View Post
Is there any advantage to having the computer and drive in the living room, other than the user interface?

A bit OT, hope that's OK...
The extra distance in cable (we assume) will increase the possibility of introducing rogue signals into your cable. Also, it dampens the signal a bit (not that much) and could introduce extra jitter. Additionally, if you are using grounded equipment you could create a bad earth loop which essentially means you introduce hum
post #633 of 3034
Quote:
Originally Posted by Regnad View Post
Is there any advantage to having the computer and drive in the living room, other than the user interface?

A bit OT, hope that's OK...
Hello Regnad.

I'm not sure I completely understand your question. Which user interface are you referring to?

Thanks,
Elias
post #634 of 3034
Regnad, having the computer in the living room works for me as it's on my desk, and that's where I do my listening. My furniture and arrangement are atypical. For those with a real living room, access to the computer would be different. Some PCs come with a remote control for music access. You could use Apple's Airtunes and their remote, or you could have a Squeezebox in your living room connected to a computer elsewhere. The Squeezebox remote would give you full control.
post #635 of 3034
dont think it worth $300 extra
post #636 of 3034
Very long USB cable could cause increased error rate on some systems. Don't forget USB Audio doesn't use error correction.
post #637 of 3034
Quote:
Originally Posted by little-endian View Post
Interesting statement, Elias.
I already asked myself why Benchmark doesn't list the dynamic range of the DAC1. Although this value is often used equally to the signal to noise ratio, some seem to distinguish between them. For example, according to the mastering engineer Bob Katz, one can hear details below the noise level, thus the dynamik range can be greater than the SNR, especially in conjunction with dithering (as far as I remember he gave 91 dB SNR and ~ 116 dB dynamik range for properly dithered 16 bit material).

Now it would be interesting to know how great the dynamic range (!) of the DAC1 actually is. If it should be really able to resolve the 24th bit, it would have to exceed 140 dB. Is this the case?

I'm confused also why more than 20 Bit of wordlength are used, at all if no converter is actually able to reach such a huge SNR and dynamic range. Many devices don't even match 20 bit performance (by pure math).

I'm sure you can clarify this. Again this would be worth an own thread.

little-endian
Little-endian mentioned that I missed this question, so I'll try to address it here.

The DAC1 has a S-to-N and Dynamic Range that is very close to the D-to-A chip used in the DAC1 - the AD1853. Therefore, the DAC1 has an S-to-N of ~ 117 dB and a Dynamic Range of ~ 116 dB. This, however, does not indicate that the 24th bit cannot be accurately realized. Conversely, the 24th bit can absolutely be realized, but it will be almost 30 dB below the noise floor. The human ear can discern tones more then 30 dB below the noise floor, so the 24 th bit is audible in the DAC1. We have confirmed this using an FFT and with listening tests.

The human-hearing threshold is not dependent on bit-depth. If the 32nd bit of a 32-bit audio word is accurately reproduced, and the noise floor is sufficiently low (<160 dB), the tone will be audible (if there is enough clean amplification).

Therefore, even if a system doesn't have a noise floor as low as the theoretical limit (-144 dB for 24-bit), the 24-th bit is still audible, and therefore valuable. (However, global-system limitations say if you have noisy analog electonics (including amplifier), then the 20-24 bits may be inaudible).

Thanks,
Elias
post #638 of 3034
Quote:
Originally Posted by EliasGwinn View Post
The human-hearing threshold is not dependent on bit-depth.
I think this statement is unintentionally misleading, since if you have sufficient bit depth, then depending on levels, you will hit either hearing threshold, pain threshold (and above it, deafness threshold), or both. The human hearing dynamic range is what's at issue here. Levels should be matched to cover the full usable range, so that the lowest quantization code is at hearing threshold, and highest one below pain threshold for good safety margin (damage starts occuring below that threshold) -- that is, 120 dB is plenty. Within that, increasing bit depth beyond a certain limit will be inefficient since differences between nearest codes would be imperceptible (I'm simplifying here by assuming detectable differences are equal throughout the hearing range; they are not). If you have a 32 bit word as in your example, and the highest PCM code doesn't cause immediate hearing damage, then the lowest one will be far below the threshold of audibility. Hex 00000001 that is audible would mean an even momentary hex FFFFFFFF will cause instant hearing loss.
post #639 of 3034
usb has a specified length limit. i think it is 15' or there about. you can increase this to about 45' with amplification. you will run into errors with an amplified signal. for data this is not a huge problem for casual computing. we would never use usb over 6' in pro audio. neither would users of mission critical bussiness applications. for music enjoyment it is up to you what level of error you can deal with. at the point of dropouts i would pass.

if you need long runs i'd go with a bit perfect wireless solution or usb>cat5, coaxial etc.

music_man
post #640 of 3034
Quote:
Originally Posted by EliasGwinn View Post
Conversely, the 24th bit can absolutely be realized, but it will be almost 30 dB below the noise floor. The human ear can discern tones more then 30 dB below the noise floor, so the 24 th bit is audible in the DAC1. We have confirmed this using an FFT and with listening tests.
This may be correct empirically, but the reasons stated are not. When you say noise floor, you mean the SNR over the entire measured bandwidth. When humans hear or when you use an FFT to pick up your 24th bit, that's done over the bandwidth of the ear's critical band at that frequency or the bin width of the FFT. If noise is white, and the signal fits within that bandwidth (bin or critical band), then the amount of noise will be reduced proportionally to the bin or critical bandwidth. For example, if your SNR measurement bandwidth is 20 kHz, and your bin width is 100 Hz, there will be 100/20000= 1/200 or 23 dB lower noise floor in your bin than the full 20 kHz SNR measurement.

Bandwidth considerations aside, I think experiments have shown that humans will hear something like 10+ dB below the noise for the same bandwidth. But this all depends on the kind of signal you have. If you have a very pure tone (narrow spectral line), and if you measure long enough, you'll find it since you are essentially making a very narrow passband filter to reduce the noise floor to the level where you can detect the tone. But if you have a broadband signal, like a lot of music, then things get very complicated.

--Andre
post #641 of 3034
The AD1853 is simply not linear to 24 bits. There's significant offset at -110 dB as shown in the datasheet, and that makes the resolution of signals below that largely irrelevant since they're smaller in magnitude. Indeed, it would've been better for ADI to do what they did with the 1955 and shape it as noise, which is better than distortion.
post #642 of 3034
Quote:
Originally Posted by music_man View Post
usb has a specified length limit. i think it is 15' or there about. you can increase this to about 45' with amplification. you will run into errors with an amplified signal. for data this is not a huge problem for casual computing. we would never use usb over 6' in pro audio. neither would users of mission critical bussiness applications. for music enjoyment it is up to you what level of error you can deal with. at the point of dropouts i would pass.

if you need long runs i'd go with a bit perfect wireless solution or usb>cat5, coaxial etc.
The official max USB cable length is 5m.

Wether or not a specific device can tolerate 10 or 15m depends on its design. 10m is usually safe but don't hurt me if you run into trouble.
post #643 of 3034
I would like to share an experiment which we just conducted here. I took a classical piano recording and loaded it into Nuendo. Using a Lynx AES16, I piped the digital output to a DAC1, then sent the analog output of the DAC1 to an ADC1 (our A-to-D converter). I recorded the digital output of the ADC1 back into Nuendo. I then sent this 2nd generation recording through the same signal chain to record a 3rd generation. I did this 20 times, so that the final recording had been converted in and out of the analog domain 20 times.

We then streamed the original recording and the 20th generation recording via AES XLR's to our listening room (acoustically treated 12'w x 14'l x 9'h with Klein and Hummel 4-way system). We put both the original recording and the 20th generation into an ABX switcher and conducted listening tests with the monitors and with Sennheiser HD600 headphones. After several tests by several people, the results averaged to 50% accuracy. In other words, no one could reliably discern the difference between the original and the 20th generation!! As hard as I tried to listen to differences in things such as noise floor, recorded room noise, mechanical (pedal, hammer, etc) noise, attacks, decays, reverb tails, etc.... I simply could not find any differences!!

We are currently requesting the permission by the artist and label to post these recordings on our website to let users experience this test. I will keep you posted.

Thanks,
Elias
post #644 of 3034
Quote:
Originally Posted by EliasGwinn View Post
In other words, no one could reliably discern the difference between the original and the 20th generation!!
Very impressive. I appreciete the rigor with which you conducted your testing. It seems to me that if your test has been described in theorital terms as a "what-if", many many people would have contended that they could very easily hear the difference.

Very, very impressive! My friend's DAC1 is due to arrive any day now, I am eager to hear what it adds to his system.
post #645 of 3034
I find this fascinating. Here we are discussing equipment that can actually give a usable signal at -116dB. If I'd had that when I was recording in the 1970s, I'd have considered it magic. I thought a 60dB dynamic range was pretty neat.

I was listening last night to one of my LP transfers on my usual system (computer, squeezebox, DAC1, HD25) and the sound was just delightful. Better than I've heard, which reinforces my growing belief that the main difference I have heard between analog and digital sources comes from the final digital-to-analog conversion. I wouldn't stake my life's savings on a bet, bu this is the way my thoughts are running. Dynamic range is just part of the story.
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