[Tympanum_Plan]

Hey guys,

A couple hours ago I received my Pico amp/DAC in the mail. I plugged the DAC in and started listening to AKG K702s through Media Player Classic. All filters disabled and playing uncompressed audio FLACs. At first there was an intermittent hissing in one ear and then the other. Now everything has gotten worse and there is distortion across the board. Pops, hisses, etc. I have tried adjusting all the various volume controls (Windows, Media Player and the actual DAC), switching from high to low gain, to no avail. I restarted my computer, hoping it was some software/hardware issue that would work itself out and it played undistorted for a bit and then degraded back to its distorted state.

This being my first amp/DAC, am I doing something obvious wrong? Are there settings I am missing that could be causing this distortion? Any help would be greatly appreciated

Thanks,
- Tom

 

[GreatDane]

Do you have another computer to test the Pico with?

With my laptop PC I needed to use a cheater plug for the power supply. This eliminates the ground. Your description may not match what my noise problem was.

 

[tjumper78]

i had a similar problem with 3move a while ago.
turned out that i had the bad usb cable.
btw, (this might be a stupid/useless question but) is your pico fully charged or being charged? i've heard lots of distortion and hisses from amps with low battery.

 

[Tympanum_Plan]

Quote:

Originally Posted by GreatDane /img/forum/go_quote.gif Do you have another computer to test the Pico with? With my laptop PC I needed to use a cheater plug for the power supply. This eliminates the ground. Your description may not match what my noise problem was.

Just tried it with my desktop computer (initially I was using a laptop) and it was beautifully clear. Interesting... Time to look up "cheater plugs".

Quote:

Originally Posted by tjumper78 /img/forum/go_quote.gif i had a similar problem with 3move a while ago. turned out that i had the bad usb cable. btw, (this might be a stupid/useless question but) is your pico fully charged or being charged? i've heard lots of distortion and hisses from amps with low battery.

I tried it both plugged in charging and unplugged, but I still have distortion. Oddly, after I changed about a billion sound settings (including a manual altering of the resampling rate to 96 khz, which I would think would be automatic) the heaviest distortion is gone. I am still getting clicks and pops like I am playing bad vinyl though. (Oh, and I tried a couple different USB cables as well so it most likely isn't a cable issue)

 

[Tympanum_Plan]

Update: Back to being horrible, with pops, hissing and actual blank-outs in the sound. After playing for a while (not just being turned on, but actually playing music) some of the distortion goes away, oddly.

I feel stupid because I realize I should have posted this in "computer audio" instead as it seems to be a DAC issue.

Anyone know what I can do or have heard of a similar problem? The cheater plug seems to be unsafe from what I am reading.

Thanks!
- Tom

 

[GreatDane]

Quote:

Originally Posted by Tympanum_Plan /img/forum/go_quote.gif Update: Back to being horrible, with pops, hissing and actual blank-outs in the sound. After playing for a while (not just being turned on, but actually playing music) some of the distortion goes away, oddly. I feel stupid because I realize I should have posted this in "computer audio" instead as it seems to be a DAC issue. Anyone know what I can do or have heard of a similar problem? The cheater plug seems to be unsafe from what I am reading. Thanks! - Tom

You can send the Pico to me to test...I miss having one.

But seriously, when I had a noise problem with my Pico, I believe it was Justin who suggested using a cheater plug. I was previously using a Meier Porta Corda (portable amp/USB DAC) and I don't recall having a problem with my laptop being grounded. If that's true, I don't have a clue why that was the case.

Good luck. Have you contacted Justin for advice?

 

[justin w.]

Is this Pico new or used? First thing you should do is try a different computer, maybe on a different operating system.

 

[Tympanum_Plan]

Quote:

Originally Posted by GreatDane /img/forum/go_quote.gif You can send the Pico to me to test...I miss having one. But seriously, when I had a noise problem with my Pico, I believe it was Justin who suggested using a cheater plug. I was previously using a Meier Porta Corda (portable amp/USB DAC) and I don't recall having a problem with my laptop being grounded. If that's true, I don't have a clue why that was the case. Good luck. Have you contacted Justin for advice?

Yes I emailed him a couple days back... Oh, here he is!

Quote:

Originally Posted by justin w. /img/forum/go_quote.gif Is this Pico new or used? First thing you should do is try a different computer, maybe on a different operating system.

The Pico is used. I just got it from another Headfi member. It works on the desktop computer I tried it on (running Windows Vista Home Premium like me) beautifully with no signs of distortion. Same settings, programs, everything.

At this point I am virtually certain that it must be an electrical interference issue. The distortion and static vary so much from time to time on the same device, and seem to change depending on how long they have been plugged into the computer and how long the laptop has been turned on.

For instance, I just played a song through the device on the problem laptop with virtually no distortion or static, then hit "replay" on the same song and it sounded as it if was being put through an underwater meatgrinder. All this is after I shut the laptop down for the first time in weeks.

About the cheater plug: I understand that removing the ground can sometimes lead to you becoming the ground.

Any insight Justin? Anyone?

 

[qusp]

hyeah I cant see an issue in floating the ground on a device that is designed to be run on batteries. in fact many audio enthusiasts do it with their home gear as a tweak anyway.

also, do not use 96khz, the pico does not accept 96khz (that is why it isnt set to that by default funnily enough

, well it does, but it is downsampled to 48khz by the USB receiver, then upsampled to 96khz by the DAC. the pico is a 96khz UPSAMPLING dac, not a 96khz capable dac. in fact the dac used in the pico is capable of 192khz, but the USB receiver is only capable of 48, so all signals great and small are sampled at ≤48khz and all upped to 96khz for playback.

suppose it could be a ground loop, or some other problem with your USB interface. I doubt very much it has anything to do with the pico

 

[Tympanum_Plan]

Quote:

Originally Posted by qusp /img/forum/go_quote.gif hyeah I cant see an issue in floating the ground on a device that is designed to be run on batteries. in fact many audio enthusiasts do it with their home gear as a tweak anyway. also, do not use 96khz, the pico does not accept 96khz (that is why it isnt set to that by default funnily enough , well it does, but it is downsampled to 48khz by the USB receiver, then upsampled to 96khz by the DAC. the pico is a 96khz UPSAMPLING dac, not a 96khz capable dac. in fact the dac used in the pico is capable of 192khz, but the USB receiver is only capable of 48, so all signals great and small are sampled at ≤48khz and all upped to 96khz for playback. suppose it could be a ground loop, or some other problem with your USB interface. I doubt very much it has anything to do with the pico

I think the ground would have to be floated on the laptop power source and not the DAC, though I'm sure I could try floating just the DAC as long as it was plugged in.

Thanks for the info on the sampling brother. I still have a lot to learn about audio.

I have an HDMI, VGA and eSATA ports on my laptop. If I can find some way to output audio through one of these alternate ports with a USB conversion then perhaps I run that through the DAC without interference. Looking into it, though I haven't seen others talking about anything like that on here so far.

 

[qusp]

errmm where do yo think the DAC ground comes from? both of these things are portable devices, so must be able to generate their own ground reference and in general the power supply (most often the ground side of the main supply cap) is a good place for a star ground where everything is eventually routed and this is connected to the DC plug ground possibly through a loop breaker. so this way when its plugged into the wall, it will use the power plug ground to drain, when running portable tho, there is no ground, its generated by any number of means, but in general by in some way splitting the rails so taking a mid point between say +5v and -5v as 0 and using that as ground. the dac chip itself may even just use its own floating internal ground reference as VREF, which it generates in a similar manner; instead of being fed a split rail ground reference to the VREF pin. even something as simple as pulling a passive ground reference from the middle of a battery, so if you have a collection of cells in series, there is a positive end and negative end of the battery, in the middle of the series is the point in the middle of +5 and -5, so 0 (voltages arbitrary)

its highly doubtful you will find a device like you want. mostly they are designed to go the other way and produce an SPDIF signal from usb, because USB is convenient because of the included power supply.