Scope: stitching atrifact?

[Magnus741]

I'm new to REW. When using the Scope, it seems to me the sampling frames are stitched together artificially and creating jumps not present on my otherwise continuous signal. Is there a setting to avoid the stitching? Highlighted the concern, I'm using the latest REW with UMC202HD.

 

[John Mulcahy]

Looks like part of the signal to me, particularly given the ringing before and after the discontinuity. If you are using ASIO drivers make sure the buffer is set large enough to avoid dropouts.

 

[Magnus741]

Signal is clean on a regular TEK oscilloscope. The ringing seems tone created by the interpolation.

REW runs on a Mac, buffer was set to 32K or 64K.

 

[John Mulcahy]

What sample rate? A discontinuity would require either a dropout or buffer overrun, if that were happening it should also be evident if looking at signals on the RTA.

 

[Magnus741]

What sample rate? A discontinuity would require either a dropout or buffer overrun, if that were happening it should also be evident if looking at signals on the RTA.

Sample rate is at 192KHz

 

[John Mulcahy]

Might depend on the Mac. My old (late 2012) Mac mini ran OK at 192 kHz but failed at anything higher. My current M1 mac mini runs without issues at 768 kHz with an ADI-2 Pro. What's the signal source?

 

[Magnus741]

Signal source is an AD9833. Happens on sine and triangle, as well on an MCU PWM generated square exactly the same way. All signals are clear of the jump on a TDS-1012 scope.

 

[John Mulcahy]

There's nothing inherent in the scope to generate that, which suggest the issue is between the OS and JavaSound on that particular platform. Background apps, network activity etc are possible contributors, per the usual lists of optimising computers for audio.

 

[Magnus741]

As far as REW’s spectrum analysis go, it works as expected.