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RTL-SDR destabilizes USB sound card?

Posted: Sun Mar 29, 2020 6:09 am
by bjornhallberg
Just got my RTL-SDR and installed the drivers and SDR# but found an annoying sound problem that kept cropping up after a few seconds to a minute of listening. It sound like the sound is breaking up, heavily distorted until the output from the sound card cuts off completely. After a while the sound comes back and then the cycle begins again. It also affects sound from other applications should they be playing at the same time so it is not just the audio coming out of SDR#.

So far I've tried decreasing the gain and the usb sampling rate or whatever it's called in SDR# with no apparent effect.

Like a lot of people I suspect I have too many USB devices hanging off my PC. I've recently moved to a USB sound card as well (Sound Blaster G6) plus I have a Røde NT USB microphone. Plus the usual stuff people also have, keyboard, mouse, pen digitizer, external hard drives, printer and so on.

Would a USB PCI-E expansion card solve my issues do you think as it would separate devices and if so do you have any recommendations for a USB card that performs well for this type of application?

Re: RTL-SDR destabilizes USB sound card?

Posted: Mon Mar 30, 2020 6:01 pm
by Username
Do you activate AGC -> [X] User AGC ?

Re: RTL-SDR destabilizes USB sound card?

Posted: Mon Apr 27, 2020 10:08 am
by bjornhallberg
I added a separate PCI USB expansion card so I could separate the sound card from the RTL-SDR. I also Changed the output in SDR Sharp to Windows Directsound. It seems to work better but from time to time the sound coming out of the speakers becomes really distorted and crackling. Still affects other applications as well, and just like before the sound keeps deteriorating until it cuts of completely only to come back in a few minutes. It's like the sound driver or sound card crashes.

Maybe decreasing the sample rate helped some? It does seem to work a little better now ... but idk ...

2020-04-27 11_54_34-SDR# v1.0.0.1732 - RTL-SDR (USB).png
2020-04-27 11_54_34-SDR# v1.0.0.1732 - RTL-SDR (USB).png (264.62 KiB) Viewed 2154 times
I'm considering moving the RTL-SDR away from the PC using an extension cable to rule out other forms of interference.

Obviously I don't intend to use the RTL-SDR for listening to FM radio on my PC, but I thought it would be a good starting point to see if the hardware and software was working as intended.

Re: RTL-SDR destabilizes USB sound card?

Posted: Sun May 03, 2020 12:17 am
by rtlsdrblog
The RTL-SDR and USB sound card might be fighting for USB bandwidth. Try plugging the RTL-SDR into a different USB port that is hopefully on a separate USB controller on your PC.

Reducing the RTL-SDR sample rate will also help reduce the amount of bandwidth it needs.