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Author Topic: How to get clean audio from the PC to a USB powered Dac?  (Read 24443 times)

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AstralStorm

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Re: How to get clean audio from the PC to a USB powered Dac?
« Reply #40 on: December 27, 2012, 01:36:04 PM »
What source do you have for that 1ns jitter being audible?
The stringest sources say 10ns.

EDIT: Of note, the perfect 16-bit jitter @ 20kHz is something on the order of 120 ps. No device is capable of that regardless of clock source. You'd need an atomic clock.

EDIT2: I made a mistake, there are people insane enough to put an atomic clock in an ADC/DAC. Rubicon series.
« Last Edit: December 27, 2012, 02:21:02 PM by AstralStorm »
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DaveBSC

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Re: How to get clean audio from the PC to a USB powered Dac?
« Reply #41 on: December 27, 2012, 02:38:57 PM »
Talk to AR-T. They are using femto second range clocks as are a number of other manufacturers. 1ns is garbage, even the worst of the adaptive mode converters are not THAT bad.
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AstralStorm

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Re: How to get clean audio from the PC to a USB powered Dac?
« Reply #42 on: December 27, 2012, 05:34:16 PM »
Exactly, but the end result can be worse, the jitter is one of these kind of distortion that doesn't add linearly.
So, 0.5 ns + 0.5 ns is better than 0.2 ns + 0.8 ns. Maximum jitter is what matters most.

Prove rigorously that 1ns jitter is garbage. Or rather, *sounds* garbage if you still have a lock.
(I know that typically everything now is <0.5 ns, even in budget solutions.)

Femto clocks might be necessary as internal clock reference in highly oversampled class D and F 1-bit DAC to keep jitter low, as there jitter directly translates to SNR. Not in more standard multi-bit converters with lower ratio.
For reference, typical I2S has single digit picoseconds jitter.
« Last Edit: December 28, 2012, 11:26:57 PM by AstralStorm »
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munch

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Re: How to get clean audio from the PC to a USB powered Dac?
« Reply #43 on: December 31, 2012, 09:28:33 AM »
is there any cheaper USB hub solution available for a laptop user? sub 50 and would prefer 4 ports as I'd like to use external HDD too if that isn't going to affect the sound too much. and I want to use it with an iPad too if there are any limitations to that. cheets!
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DaveBSC

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Re: How to get clean audio from the PC to a USB powered Dac?
« Reply #44 on: December 31, 2012, 11:21:48 AM »
Quote from: munch on December 31, 2012, 09:28:33 AM
is there any cheaper USB hub solution available for a laptop user? sub 50 and would prefer 4 ports as I'd like to use external HDD too if that isn't going to affect the sound too much. and I want to use it with an iPad too if there are any limitations to that. cheets!

If you just want to add USB ports you can use anything, $10 hubs will do that. External HDDs will negatively affect the sound - you're much better off using NAS. If you want something that's actually going to improve anything, you've gotta spend more than $50.
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munch

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Re: How to get clean audio from the PC to a USB powered Dac?
« Reply #45 on: December 31, 2012, 12:35:47 PM »
hmm yeah, okay... well I did kind of expect it. I was just thinking if there is anything that might be better in the price range or if it is all about the same. 200 for the vaunix or ifi is your lowest recommended then? I only have an ODAC so it feels a bit excessive to spend a lot more on just the usb connection.
thanks!
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DaveBSC

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Re: How to get clean audio from the PC to a USB powered Dac?
« Reply #46 on: December 31, 2012, 03:03:04 PM »
The only real difference between most low cost hubs is whether they are wall-wart powered or they just draw from the VBus. If you want one to be able to power an iPad, your gonna want one that is wall-wart powered.

For hubs, the $200 Vaunix and iFI are pretty much the lowest you can go. There are a number of low cost isolators you can try, just keep in mind that none will pass 24/192. If that's not a problem, they may be worth a go.

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kkl10

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Re: How to get clean audio from the PC to a USB powered Dac?
« Reply #47 on: December 31, 2012, 05:54:37 PM »
Quote from: munch on December 31, 2012, 09:28:33 AM
is there any cheaper USB hub solution available for a laptop user? sub 50 and would prefer 4 ports as I'd like to use external HDD too if that isn't going to affect the sound too much. and I want to use it with an iPad too if there are any limitations to that. cheets!

You might want to checkout "portable battery pack" on Amazon...
I think it's a shame that still no manufacturer has moved forward with the idea of a battery powered USB Hub...
I guess is just a matter of time as the mobile/portable battery pack market is booming and there are already a lot of high capacity Lithium batteries at very reasonable prices.
Today 40$ will buy you a battery pack of the size of an Iphone, with 5V USB outputs and with enough capacity to charge any smartphone up to 5x or even to fully charge a netbook with either 9 or 12V output... and with enough current, up to 3Ah to power an external HDD or up to three devices at the same time...

This is more than enough power for an ODAC and could be an interesting alternative to the Vaunix and iFi hubs.
These batteries could actually power a small 3-4 ports USB hub providing more and cleaner power than the VBus, this could be something to explore.
Whatever the USB DAC I'm going to buy, I'm pretty set on also acquiring a portable battery pack along with an Y USB cable. I'm going to rip off the +5V pin on the PC head and power my Dac with the battery.

By the way I have added some more links for documenta and related discussions on the first post, there's an interesting paper with noise measurements of several types of batteries dating from 1995.
Might be worth a read.
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munch

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Re: How to get clean audio from the PC to a USB powered Dac?
« Reply #48 on: January 01, 2013, 02:11:07 AM »
DaveBSC: cool, I saw those in the thread posted in the OP. https://www.olimex.com/Products/Modules/Interface/USB-ISO/ right? is there any use making my own PSU for it? can I use it WITH a hub? or does that not make any sense? if there are any good DIY schematics for stuff I would love to try that :p I am just trying to cut costs though. not sure if I even have any noise but I kind of want to try things to optimize my computer audio. I have had big issues with my laptops usb ports... and do need a hub.

kkl10: hmm that is indeed a cool idea, but I am a bit unsure about using an iPad with that and well... battery life. I am not too keen on the idea of constantly charging the pack even if performance might be be great :( I will take a closer look soon though.
happy new year guys
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DaveBSC

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Re: How to get clean audio from the PC to a USB powered Dac?
« Reply #49 on: January 01, 2013, 01:18:34 PM »
Quote from: munch on January 01, 2013, 02:11:07 AM
DaveBSC: cool, I saw those in the thread posted in the OP. https://www.olimex.com/Products/Modules/Interface/USB-ISO/ right? is there any use making my own PSU for it? can I use it WITH a hub? or does that not make any sense? if there are any good DIY schematics for stuff I would love to try that :p I am just trying to cut costs though. not sure if I even have any noise but I kind of want to try things to optimize my computer audio. I have had big issues with my laptops usb ports... and do need a hub.

By far the lowest cost solution would be to roll your own battery power supply for it. Wall-warts are cheap but they are very noisy, linear supplies and custom battery supplies are far more expensive than either the Vaunix or the iFI. I don't see why you couldn't use an isolator with a regular USB hub if you wanted to.
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