[KenB]

Problem: Intermittent RF-like interference with USB audio streaming
Equipment: Galaxy Note2 (SGH-I317) connected via USB (OTG cable) to iBasso D-Zero
Carrier: AT&T
ROM: Stock (not rooted)

When streaming music (esp. Pandora), intermittently, annoying static will be introduced for a period which can vary from 5-30+ seconds. Sometimes, it will stop on its own and return to normal. Other times, I have to unplug the USB cable and reconnect. That will usually give me several minutes of clear music, but eventually, the interference/static problem recurs. When I have my headphones on, occasionally, the static jumps from one channel to the other! It reminds me of high-pitched radio interference; but, after much troubleshooting on my part, including Internet research, I have not been able to pinpoint a cause. If I connect the D-Zero to my laptop via standard USB cable, I can listen to streaming audio with no static. Similarly, if I plug my headphones directly into the Note2’s mini-jack, the music streams without incident. I also tried connecting the D-Zero to my wife's Galaxy S3 - no static or other interference problems at all! 

I wrote to iBasso asking if there could be a shielding problem with the USB audio cable, but they believe that the interference is most likely being generated by the phone itself. After my own testing, it seems likely that the Note2 is the culprit, but what could be causing the interference? An app? I have tried shutting down Bluetooth, GPS, Power Saving, Tasker, AVAST, and pretty much every other app that seemed a potential candidate. One post I read suggested that the pen stylus could be causing electromagnetic interference. Hmmm... I don't think that the problem is being caused by any other devices in my house (e.g., cordless phone, router, Roku), but I can't be certain. I have tried disconnecting everything I can think of; but, thus far, the only antidote I have found is to unplug the USB audio cable and reconnect it. 

I should mention that I have a ZeroLemon battery installed in this Note2, but it seems unlikely that it could be generating RF-like interference and only to the USB audio output stream. 

I am at wits end and would sure would appreciate help from this forum's experts. Any ideas or suggestions as to possible causes? 

Thanks, Ken

 

[jasonb]

It's probably EMI from the wifi and cellular radios. Try it with wifi off and in airplane mode. 
 
My E17 makes a tiny little bit of noise when wifi is on on my GS4. With wifi off and connected to 3G or 4G it is dead silent. Maybe the D-Zero is not shielded very well against EMI. Some amps will block all or most, and some will be pretty noisy with cell phones. 
 
I always wonder if most people put their phones in airplane mode when they use them with amps and DAC's or if most peoples amps are shielded well, or if people just deal with the EMI. I see a lot of people using amps with phones in the portable gear picture thread.

 

[KenB]

Quote:

It's probably EMI from the wifi and cellular radios. Try it with wifi off and in airplane mode. 
 
My E17 makes a tiny little bit of noise when wifi is on on my GS4. With wifi off and connected to 3G or 4G it is dead silent. Maybe the D-Zero is not shielded very well against EMI. Some amps will block all or most, and some will be pretty noisy with cell phones. 
 
I always wonder if most people put their phones in airplane mode when they use them with amps and DAC's or if most peoples amps are shielded well, or if people just deal with the EMI. I see a lot of people using amps with phones in the portable gear picture thread.

I turned off WiFi and ran Pandora with the D-Zero attached via USB OTG cable and the interference occurred after a short period. I then disabled Mobile Data, which I hope isolates the WiFi and the same thing happened. If the distortion is being caused by the phone, and I have no reason to disbelieve it at this stage, I cannot figure out the culprit. Could it be the digitizer pen? I tried taking it out and reinserting it, but it appears to have no impact on the audio. 
 
It would be of little benefit to stream audio if I cannot do it via WiFi because I am on a 10GB family data plan with AT&T. WiFi lets me play music over the Internet with no impact on our data usage. 
 
At the moment, it looks like, if I want to use my Note2 to stream audio, it will have to be sans D-Zero or, at least, sans USB audio since I don't yet know whether it's the USB connection or the amp itself that is being affected. 
 
These kinds of intermittent problems are maddening, but what is even more curious is that no other Note2 owners seem to be experiencing this interference. Could I be the only Note2 guy streaming audio using an iBasso D-Zero?! 
 
I wonder if other Note2 owners stream audio using other DACs. That would be helpful to know. I didn't pay that much for the D-Zero and would gladly substitute another device if I reasonably certain it would work. 
 
Do you think that a better shielded USB OTB cable might make a difference? I saw one on EBAY and it wasn't too expensive. 
 
Ken

 

[KenB]

I may have discovered a solution after searching "airplane mode" on Google. There is an app in the Play Store called "Airplane Mode Wi-Fi" (Free) that allows an Android phone to be placed in Airplane Mode while still being able to utilize Wi-Fi services. 
 
I installed the app successfully under JB 4.1.2 and put the phone in Airplane Mode with Wi-Fi enabled (radio is OFF). I have been streaming Pandora on my Note2 for over 30 minutes and, while there is still a tiny bit of hiss; so far, the previous disruptive and annoying RF-like interference has not recurred. 
 
If I want to check email or perform any other data function, I simply click "Landed" on the app and the phone is restored to its normal state. 
 
Court is still out on this solution, but I am becoming optimistic that I may have found a satisfactory workaround... 
 
Ken
 
P.S. I read a review from someone that this app does not work in JB 4.2. If it continues to perform successfully, I will write to the developer and ask if it is still being supported. 
 
P.P.S. I added a profile state in Tasker to run this app as soon as the USB Audio is connected. 

 

[KenB]

Drat! No sooner did I hit the SUBMIT button on my latest post than the cursed interference returned!!! 

 The first time only for a few seconds before it stopped abruptly; then, a 2nd time where it persisted until I unplugged and reconnected the USB cable! 
 
At least I have ruled out the 4G radio as the primary culprit. The annoying static/interference must be triggered by the wireless transmitter in the phone. As a another test, I turned off Wi-Fi, walked outside and far away from my wireless router so that it would not auto-connect. I then played Pandora for about 15 minutes and I did not encounter the interference. That test is inconclusive because the darned problem is intermittent. If I had sit out there another 30 minutes, it might have happened. 
 
Looks like I'm back to the drawing board... 
 
In any event, I am going to keep this Airplane Mode Wi-Fi app because, if nothing else, it should significantly reduce battery consumption while streaming music. Most of the time when I am listening to Pandora or other Internet radio, it's nighttime or during the weekend and I don't need to be constantly monitoring email, text messaging, et al. 
 
Ken

 

[KenB]

UPDATE:
 
I just discovered that there is a setting in the Galaxy Note2's Advanced Wi-Fi to check for Wi-Fi availability when connected to Airplane Mode.
 
So, there is no need any more for that Airplane Mode Wi-Fi app -- uninstalled! 
 
Ken

 

[KenB]

Further Updates and Bizarre Occurrences:
 
I recently decided to upgrade my iBasso D-Zero (For Sale) to a Leckerton UHA-6S.MKII primarily because of its better internal shielding design against interference of all types. I purchased a HakShop micro-to-micro USB cable to use with the Leckerton ([size=11pt]http://hakshop.myshopify.com/products/micro-to-micro-otg[/size]). 
 
I have now isolated two different types of noise that I experience when streaming audio via USB from my Galaxy Note2 through a DAC/AMP: 
P1: Whine-Squeal Noise
P2: Static-White Noise
 
The Leckerton has basically eliminated P1 which, according to Nick, is most likely GSM interference. I can make it absolutely dead silent by using Airplane Mode with Wi-Fi enabled, but it is normally fine even with that mode disabled.
 
Now for P2... As I am listening to Pandora, for example, I will intermittently hear a slight click-pop (almost like a switch is flipped) and a high-pitched static begins -- a constant "ssssshhhhhh" noise that is persistent. Sometimes it is more noticeable in one channel than the other and, occasionally, it flits from one to the other! I have noticed that, if I pause the music, wait 5 seconds or so, and resume, the noise will subside, but it will inevitably recur after a short while. This noise happens even in Airplane Mode, so it is not GSM-related.
 
In my quest to hunt down this annoyance, I installed an Android app called "OS Monitor," which dynamically lists all of the processes running based upon CPU usage. I then started Pandora streaming, switched to the monitor app and watched for any sign of a process that might launch coincident with the P2 noise. I waited and waited and waited... In fact, throughout my repeated attempts to catch the P2 problem in action (many hours at a time), it has NEVER occurred while the OS Monitor app was running.
 
If that weren't weird enough, if I switch back so that the Pandora screen is visible, then P2 will recur after some period although it seems random to me. I thought it might be triggered by the battery indicator percentage changing on the home screen, but that does not appear to be the case.
 
I cannot explain this behavior, but an uneducated guess is that there is some intermittent interference caused by the Note2's graphics processor which only activates when the Pandora screen is active. I have tried just turning off the display (and letting it time out), but that alone does not stop the problem if the last active screen was Pandora. I literally have to switch apps to the OS Monitor, then all is quiet and stays that way. It is almost as though the monitor app is keeping the graphics processor "busy" so that it doesn't have an opportunity to do whatever is causing P2 to start.
 
I now have a workaround (so far) that eliminates P1 and P2 using the combination of Galaxy Note2 and Leckerton UHA-6S.MKII, but if anyone has a theory about what may be happening under the covers, I would appreciate hearing it. I would be gratified if someone else can even duplicate this problem on a Note2 phone. 
 
Ken