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pilgrum

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  1. USB Interface Jitter Measurement (16 bits) We have a keen interest in measuring the jitter of the USB interface because its level of jitter is typically much worse than the SPDIF interface. If left untreated, the degradation in sonic quality is readily audible. So we wanted to see if our multi-stage jitter reduction circuit would be effective on the USB interface. The FFT plot of the D1 DAC output (16-bit, 11.025 KHz signal) shows that there are no jitter sidebands visible above the noise floor, around -135 dB, which means that if they exist, they are buried under the 16-bit quantization noise. If there were a single jitter-induced tone at -135dB, the corresponding jitter would be 4 ps rms. http://www.anedio.com/images/anedio/art_jittUSB1.png Here is the same measurement, zoomed in along the frequency axis. Notice the slight spreading around the signal, about +/-20Hz. This spreading is a characteristic sign of low-frequency jitter. As mentioned above, such a low frequency jitter is masked by the presence of the strong nearby tone and is well below the threshold of audibility. http://www.anedio.com/images/anedio/art_jittUSB2.png
  2. And to add if your spending thousands of dollars on audio equipment chances are you have a quality line conditioner somewhere on your rack. I understand and totally agree that 1. a better cable can reduce noise but is it audible and how common is it. 2. now knowing that error correction is part of usb how many times in your life have you heard bit errors? 3. a better made cable is going to have a higher rate of success and integrity. So how come no one can post something that shows its common and noticeable to microphones, sound editing software or spectrum analyzers? I would say the most important part of an over engineered cable is the shielding being in the audio business for 15 years I have had issues with audible interference less than 1% of my entire career but that is just my exposure. As far as crosstalk on communication lines out of the 60,000 cat6 lines i ran last year we re ran 3 due to cross talk and this was on a military base with more bicsi violations than the world combined.
  3. I never found the specs, graphs or dyno testing sheets. Can someone post the link for them thanks. I would never trust 50-80 year old ears in any hearing test of audio equipment i believe in science.
  4. it's very common for complete designs (computer, program ROM, data RAM, and interface logic) to be inside one chip. often these are FPGAs (field-programmable gate arrays), essentially hardware that can become whatever you want it to be. the designer works as if he's drawing a normal schematic (or uses a logic language like verilog), and the design tool spits out data that goes into a little PROM, which is loaded into the FPGA at power up. Error detection is embedded in the data stream and corrections applied one block at a time. The format of the data stream determines how robust the detection and correction can be. Data file transfers can be guaranteed error free. Media streaming assumes that the transfer will continue even if there are uncorrectable errors. They are filled in fro the before and after parts of the stream. Then there's the business of jitter. A great DAC will have it's own clock and will reconstruct the waveform before converting it to analog. you MUST have a memory buffer to stream anything from USB. it has nothing to do with error correction. USB is bursty (sends small packets at high speed, with pauses in between), and the DAC wants one sample per sample clock tick.
  5. it's very common for complete designs (computer, program ROM, data RAM, and interface logic) to be inside one chip. often these are FPGAs (field-programmable gate arrays), essentially hardware that can become whatever you want it to be. the designer works as if he's drawing a normal schematic (or uses a logic language like verilog), and the design tool spits out data that goes into a little PROM, which is loaded into the FPGA at power up. Error detection is embedded in the data stream and corrections applied one block at a time. The format of the data stream determines how robust the detection and correction can be. Data file transfers can be guaranteed error free. Media streaming assumes that the transfer will continue even if there are uncorrectable errors. They are filled in fro the before and after parts of the stream. Then there's the business of jitter. A great DAC will have it's own clock and will reconstruct the waveform before converting it to analog. you MUST have a memory buffer to stream anything from USB. it has nothing to do with error correction. USB is bursty (sends small packets at high speed, with pauses in between), and the DAC wants one sample per sample clock tick.
  6. From what I asked the tech at the jazz society it seemed like the phonograph components/vinyl purity was the key element in getting a high quality transfer. I am interested in hearing what is said about this. I remember he did also mention they switched from dat to HDD based on cost and clutter not drastic quality improvements. This was in 2007. I my friend has some vinyl that was never released in a digital format so I am hoping to get back to him he is going to use a digi-2 or HD i think.
  7. I would like to know how you can have error correction with out a memory buffer and whats the delay involved when using a dac with bi directional talk and error correction? I was wondering because several dac's state they do this but by looking at one or two of the boards i don't see any memory modules that would hold the data and analyse it. I am not an computer or electrical engineer but it struck me as odd. I was under the assumption that in order to compare the data you would need 2 file locations. Is there memory built into the a dac chip itself or the usb controller? Or is this a false statement?
  8. I would like to know how you can have error correction with out a memory buffer and whats the delay involved when using a dac with bi directional talk and error correction? I was wondering because several dac's state they do this but by looking at the boards i don't see any memory modules that would hold the data and analyse it. I am not an computer or electrical engineer but it struck me as odd.
  9. show me results on a graph not "is on record saying". How many people on this forum have recording equipment and a usb dac with a decent cable and a generic one? Its easy hook up a usb dac to rca in of a pc record it with a shit cable and a good one. post the screenshot. even just record silence maybe.
  10. from what you are saying you want to do i am assuming you have tons of money? We are talking about isolating and redistributing digital signals to 3 separate DAC's and 3 seperate preamps? (at this point i would have custom DAC's built with the op stages made for the specific freq range) tri amping or 6 monoblocks? with class A audio correct?Do you already have the audio equipment short of the dac's, digital cross and the custom speakers made or production tri ampable speakers? I think these guys make upgrade blades with digital crossovers that can isolate the digital frequencies and reroute them to separate DAC's. Get a check book and HAVE ABOUT 20,000-100,000+ USD READY TO KILL. http://www.msbtech.com/products/platinumHome.php
  11. lets see some results! dynos? tests? or i am filing this under sugar pill cures cancer! Let's be honest the reason why any of us like how a certain DAC sounds its mostly due to the output stage coloring so imho anything before that is not as important. I am personally more interested on whats after the DAC not before it as long as the files are on par with redbook of course. I would say I'd even buy a chinese tube preamp before a hifi usb cable. And I would hear the difference right away or at least after i got the bias calibrated ;p
  12. The unit costs how much retail? $1800 divide that by 4 and that is probably in the range of what the production cost is to make it (not including marketing and dev costs). Audioquest's dealer prices are anywhere from 50-80% less than retail so that cinnamon cable is about 15-25 dollars and the other one was not stated. It is a nice gesture to include a cable with a product and I would like to see the difference on paper. IMHO its like this are you going to put $5 wiper blades on a bentley? No. So why would you plug in a generic chinese $1 cable into a $1800 DAC? Because you have no taste aesthetically. The Wavelength Brick claims to have error correction and a buffer with two way communication built into the USB controller on the board so I would say it is 99% aesthetics 1% theoretical chance. And if your worried about ground noise and these other things then a high quality custom PC with a platinum grade PSU(not available on stock mac) hardwired power cord, pole pig/line conditioner would be on the list before the $300 usb cable wouldn't it? As far as I know the DAC and clock are going to have the biggest impact on the sound. the cable is out for argument but I have yet to see evidence of it. Trade secret companies demo stuff with tracks that are mastered differently to enhance results so a "well i heard it at a trade show" doesn't fly .
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