Digital is more tolerant of noise than analogue.
D+ and D- are LVDS and have to be in close proximity to each other and length matched to within 1mm, if you don't length match you are going to cause more damage to the signal, but you will all know this cos you'll have read the relevant USB specs and numerous design guides available on the internet before you started playing?
Oh I forgot the 90 diff impedance requirement...
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Hi thank you and very interesting ! Good to know !
I ask this because i remember it was one of the most popular modification on stock cd players.
I remember even a batteries based PS for that purpose
Actually now that i have discovered that my dac does not rely on usb power i can cut the wire and stop with the problems.
Thanks a lot again
Kind regards,
gino
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Marce
I cannot explain it, 😕 but I can experience it. Not subtle. No mystery.
With a little searching I could point you to Peter Daniel thread where he experimented with this and found minimum cable length was best by far. He rearranged boards to allow for about 1/2" cable. He created quite a following with his shigaclone cd player and chip amp kits. Most parts chosen for sound.
I have not tried galvanic isolation which I suspect is better, it is worth the small effort to try a short unshielded usb cable. Simple catv teflon twisted pair!! Investment, $0. Just chop any usb cable lying around the house.
By the way i wonder why it is so difficult to get a usb data only cable
Why ?
How much is the max current available on the 5V wire of the USB ? 0,5 A ? 1 A ?
Which is that peripheral that can work consuming only 5 W ????
This power line is useless.
Just look at the video connections ... no one has ever dreamed to power a monitor from the DVI cable
Crazy ...
Why ?
How much is the max current available on the 5V wire of the USB ? 0,5 A ? 1 A ?
Which is that peripheral that can work consuming only 5 W ????
This power line is useless.
Just look at the video connections ... no one has ever dreamed to power a monitor from the DVI cable
Crazy ...
If a USB device needs more power or different one (cleaner, different voltage, etc.), it is designed with independent power supply. No need to use internally the power coming over the cable. But I would not want to have to check I am using a correct USB cable, the one with power leads properly connected.
The best way to avoid these problems is to simply chop off an existing USB plug and replace it with a solder type worth just over $2, without terminating the red wire. (This IS DIY Audio ! )
You can then use a piece of heatshrink over the new plug. White heatshrink is easy to label with a ball point pen, and doesn't smudge too easily.
This is the basis of the kit, i just built a custom enclosure with Neutrik sockets to go around it. You have a few options for power so i dont recomend using the power supply circuit on this board, instead buy the kit without it and then connect your own 5v supply. Even if your device dosent need 5v the output side of the isolator still needs the power to operate. All the details can be found in the site.. USB Interfaces « Circuits@Home
In the case of the ODAC it has its own 12mhz crystal on board to generate the USB clock rate.
Norm these days for pc's is 500ma, some boards can output 1amp to charge iPhones at full speed. AFAIK the ODAC uses something like 120ma max.
Actually Apple did exactly that by adding two 25v power lines, google ADC connector. For such a "revolutionary" concept it is a wonder it never caught on 😛
Thanks a lot for the advice
I will do it ! what about the screen ? connected only on one side ?
which ? pc or dac ?
I feel that i am quite close to an happy ending
Kind regards,
gino
Thank you ! this is exactly what i was looking for
I will email to the European reseller immediately
This is exactly what i need.
i have already two dacs to try ... but there are so many kits extremely interesting of usb dac. Also the ODAC is extremely interesting.
But what i really needed was that isolator. Badly needed.
I am sure it will give a decisive boost to performances. I am completely sure because of the extremely bad reputation of the usb power line.
Replacing it with a nice linear PS the result cannot be worse. I have great expectations indeed.
I wonder why the nice solutions seem to come all from Apple
They seem the only ones who thinks !
there is indeed everything
Great cable
Thank you very much for the advice on the isolator
Kind regards,
gino
Are you serious? Or is this the "ignorance" thread?
What about all the flash sticks, external keyboard & mice wired/wireless interfaces, external hard/ssd drives, 3g modems?
It is not like the USB interface has been designed with the idea of low-jitter dacs in mind.
And of course there are commercial cables without the +5v line, or even with an optional battery pack
Elijah Audio - Products
I think you have nailed the problem
Exactly my conclusion
And thank you for your suggestion
I think i will look at the usb isolator instead
It seeme really serious
Kind regards,
gino
Universal Serial Bus
The name pretty much defines what sort of interface it is, those into computing and electronics will be aware of the history of computer interfaces from parallel, RS-232 RS-485 etc. and through to USB these days. Info on the interface and specifications etc. can be found here:
USB.org - Welcome
If you are going to use the USB interface to transmit audio then a separate USB card, with that USB used exclusively for the audio would be my first thought...
Cure the problem at source rather than try to treat the symptoms is the best way of engineering a solution to sound reproduction problems IMO.
The name pretty much defines what sort of interface it is, those into computing and electronics will be aware of the history of computer interfaces from parallel, RS-232 RS-485 etc. and through to USB these days. Info on the interface and specifications etc. can be found here:
USB.org - Welcome
If you are going to use the USB interface to transmit audio then a separate USB card, with that USB used exclusively for the audio would be my first thought...
Cure the problem at source rather than try to treat the symptoms is the best way of engineering a solution to sound reproduction problems IMO.
Dear Gentlemen,
please let me elaborate a little because i do not want to sound like a mad man
I am sincerely interested in PC Based audio system because it is a very efficient and convenient way to manage all these audio files.
So i started reading, trying to learn a little.
I have read hundreds of messages, pages talking about the best OS, the best RAM, the best CPU, the best SSD ... for music
While the real bottleneck is this bloody usb port
There is a commercial product particularly well designed and built ... it is a usb to spdif converter
The digital out is of a very high quality ... maybe the current best in the market
During the review it was quite apparent that the type of pc and OS upstream was not influencing the overall sound.
This for me is a revolution
I would expect that all the efforts would be put in this interface
Instead i see again discussions on mini/micro pc ... android based pc ... ssd ...
Maybe this interface is not enough intriguing ... i do not know
Any decent pc with a rightly designed and built interface could be an extremely good digital source
This is not little of a conclusion at least for me
And this should not extremely expensive to do, i think
A good isolation ... a good clocking circuit ...
Sorry for the outburst and have a nice day
I have finished my ramblings
Thanks and kind regards,
gino
please let me elaborate a little because i do not want to sound like a mad man
I am sincerely interested in PC Based audio system because it is a very efficient and convenient way to manage all these audio files.
So i started reading, trying to learn a little.
I have read hundreds of messages, pages talking about the best OS, the best RAM, the best CPU, the best SSD ... for music
While the real bottleneck is this bloody usb port
There is a commercial product particularly well designed and built ... it is a usb to spdif converter
The digital out is of a very high quality ... maybe the current best in the market
During the review it was quite apparent that the type of pc and OS upstream was not influencing the overall sound.
This for me is a revolution
I would expect that all the efforts would be put in this interface
Instead i see again discussions on mini/micro pc ... android based pc ... ssd ...
Maybe this interface is not enough intriguing ... i do not know
Any decent pc with a rightly designed and built interface could be an extremely good digital source
This is not little of a conclusion at least for me
And this should not extremely expensive to do, i think
A good isolation ... a good clocking circuit ...
Sorry for the outburst and have a nice day
I have finished my ramblings
Thanks and kind regards,
gino
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Do you actually have a problem, and if so do you have some metrics (measurements) of the problem, this is the only way to find a solution...
And why use a USB to SPDIF! why not just get one interface working.
And why use a USB to SPDIF! why not just get one interface working.
Having tried most of what you mention my conclusions are entirely different.
First, converting USB/SPDIF is generally counterproductive. Spdif is severely compromised in 99% of the implementations and practically always when PLL receivers are involved. Why do such devices exist? Only to allow owners of old, expensive dacs to still use them with PCs. It puts the responsibility of dealing with jitter squarely on the shoulders of the dac.
Second, USB isolation is only easy and cheap for USB full-speed devices. For USB hi-speed, or anything hi-res you are looking at a very limited number of expensive isolators.
Not to mention that ground isolation is by far not solving all the problems. In fact, bypassing the isolation is not even audible in a lot of systems. All it does is isolate ground or common mode noise.
After a lot of experiments i haven't been able to assemble a system where the OS, bios and PC software/hardware have no dramatic effect on sound. And i doubt such a system exists, unless it is of very low transparency.
USB was designed for transferring data. Ask it to transfer data, only data and nothing but data (plus perhaps a little power) and it will be fine. Ask it to transfer timing too and you are on your own - PCs don't do timing very well anyway as they too are intended for handling data.
I certainly have no timing expectations from USB
USB > I2S > galvanic isolation > reclock > new timing domain (basically another reclock only time delayed by FIFO) > dac in asynchronous mode - everything gets reclocked again
And what? Everything listed above is still plainly audible. USB cable quality as well.
USB > I2S > galvanic isolation > reclock > new timing domain (basically another reclock only time delayed by FIFO) > dac in asynchronous mode - everything gets reclocked again
And what? Everything listed above is still plainly audible. USB cable quality as well.
Thank you very much again
I am sure your chain above is very well optimized
And you still hear when you change pc ? this was my doubt/question.
I still feel that a very good usb dac should be quite insensitive to different transport ( i.e. pc i mean)
Thanks again and kind regards
gino
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