FF_CCSa1F
New Member
- Joined
- Feb 6, 2021
- Messages
- 2
- Likes
- 3
Hello, I'm a power amp guy so you'll have to excuse my ignorance about these digital gremlins!
Just for fun, I decided to do a bit of contrast and compare between my various audio devices by hooking them up to my HP 339A distortion meter, and I stumbled upon something that baffles my analogue brain:
The only difference between those pictures is the sample rate sent to the UR22mkII (using WASAPI or ASIO through Foobar2000), and the difference is huge! -74.8 dB THD+N at 44.1 kHz vs. 86.4 dB at 192 kHz. To make matters worse, the 30 kHz low-pass filter was enabled on the 339A, so it's not even particularly high-frequency noise. I did the same test on a Yamaha AG03 which uses the same Cirrus Logic CS4270 CODEC, with very similar results. If I do the same test on the Xonar DX sound card installed in the same PC, it performs much better, landing at somewhere around -95 dB THD+N, so I don't think I have a problem with my testing set-up.
Can anyone shed some light on what I'm seeing here? The frequency of the distortion seems to be roughly 43 kHz by just counting the peaks between the 1 kHz cycles. That's not an exact science though, so it could be off by a few kHz. The 30 kHz LPF is down about 8 dB at 40 kHz, so there really needs to be quite a bit of noise up there to show up on the measurement.
...and here's a what the frequency is according to a DSO (16 sample average, ignore the bottom frequency counter, it tells only lies):
Thanks,
FF
Just for fun, I decided to do a bit of contrast and compare between my various audio devices by hooking them up to my HP 339A distortion meter, and I stumbled upon something that baffles my analogue brain:
The only difference between those pictures is the sample rate sent to the UR22mkII (using WASAPI or ASIO through Foobar2000), and the difference is huge! -74.8 dB THD+N at 44.1 kHz vs. 86.4 dB at 192 kHz. To make matters worse, the 30 kHz low-pass filter was enabled on the 339A, so it's not even particularly high-frequency noise. I did the same test on a Yamaha AG03 which uses the same Cirrus Logic CS4270 CODEC, with very similar results. If I do the same test on the Xonar DX sound card installed in the same PC, it performs much better, landing at somewhere around -95 dB THD+N, so I don't think I have a problem with my testing set-up.
Can anyone shed some light on what I'm seeing here? The frequency of the distortion seems to be roughly 43 kHz by just counting the peaks between the 1 kHz cycles. That's not an exact science though, so it could be off by a few kHz. The 30 kHz LPF is down about 8 dB at 40 kHz, so there really needs to be quite a bit of noise up there to show up on the measurement.
...and here's a what the frequency is according to a DSO (16 sample average, ignore the bottom frequency counter, it tells only lies):
Thanks,
FF
Last edited: