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REW issues - popping, static in frequency sweep output.

Hi All,

I'm using an HP Win 10 Pro, headphone jack out via RCA adapter to the amp and a MiniDSP calibrated mic.

I've read all the help files and adjusted the sound card output to 16 bit which helped but did not eliminate the popping/static noise in the test sound. In my set up the sound card cannot be calibrated and I've adjusted everything I can find. 

Has anyone experienced the same problem and solved it?

 

Thank you. 

 

macg19
jsalerno277
509 posts
 

+1 @erik_squires My first guess is also clipping.  Correct me if wrong but it appears your setup is a PC source to a DSP to a headphone amp.  The problem occurs during a frequency sweep output.  A frequency sweep is a dense signal of high output.  I did not see you indicate this happens during normal playback. I would start with input-output tolerance stacking to manufacturer’s specifications and adjust if necessary to be within the mV range specified.  You need to tolerance stack the following:

  • PC output to DAC input
  • DAC output to amp input.  

If your equipment does not have adjustable output input settings but rather gain controls, lower the gain.
 

If that is not the root cause, then check any or all of the following until you hit the cause:

  • amp capacitors or tubes
  • cleanliness of contacts  (use contact cleaner and enhancer)
  • cables

Good luck.  Let us know what you find.  

erik_squires
17,594 posts
 

If it's not clipping, then @jsalerno277   identified my other thought, a missing/bad DC coupling capacitor. 

The 95% chance of fixing this is to use a cheap-o USB DAC instead.  And by cheap I mean $20 or so. 

macg19 OP
1,435 posts
 

@jsalerno277 @erik_squires 

Thanks. I am not using a headphone amp or DAC.

I am connecting my PC directly to my integrated amp using the 3.5 mm headphone/earbud audio outlet using a 3.5mm to stereo RCA adapter cable. 

If I plug my ear buds into the PC, the "static" is audible. If I play a PC system tone through my stereo, it is crystal clear.

So my thought is, I have a setting in REW set incorrectly or my PC’s sound card just can’t play the sweep without distorting.

PS. I played the sweep on the PC using earbuds and the PCs built in mic without any distortion (so with the MiniDSP mic unplugged) and sample rate set to above 48kHz so there is come sort of conflict with the USB mic. 

erik_squires
17,594 posts
 

Wait, are you driving loudspeakers directly?  Dont do that

macg19 OP
1,435 posts
 

@erik_squires are you driving loudspeakers directly?

I don’t understand. How else would I get a sweep test tone from REW installed on my PC to play through my speakers but via my integrated amp? 

btw the popping noises have nothing to do with connecting to my integrated. The popping is present on my laptop speakers/ear buds when USB mic is connected and goes away when I unplug the mic.

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