Is it normal (tolerance of the specifications)?
Where do the peaks below 1 kHz come from?
For the asymmetrical measurement, the lower, unused inputs were terminated with 50 ohms.
The inputs and outputs were connected with 15 cm BNC RG58 cables.
Best regards from Germany
Dear Forum,
now I have read, some posts in this forum about “the left and right problem”……It seems to be a known hardware issue.
But it’s still a shame.
I’m otherwise very satisfied with the performance of the QA403.
Couldn’t there theoretically be a solution in the software (adjusting the individual channels)?
Hallo Diskus
the peaks below 1kHz are mains noise (“Brumm”, n x 50Hz). At such low levels, there is always a risk that you pick up some hum. Sometimes it helps to move the QA403 and the device you want to measure to another location on your desk. Good BNC cables can also make a difference. Differential measurements usually have lower hum.
Please note that the differences between the channals of your QA403 are not very big. THD+N measures the same on both channels. THD of the left channel is 5.2dB better … but we are talking about less than 1uVrms. Same for the hum, 50Hz and 150Hz are at -120dBV (1uVrms).
If you want anything better, I’m afraid you need to look for Audio Precision.
Have fun with this amazing tool.
Beste Grüsse
AVO
Hi @Diskus, from your plot you might have some contamination from the power line in your THD measurements. See if you can re-orient nearby mains powered equipment to improve the levels at 50 Hz. At 50 Hz, these levels you are seeing are about 1 uVrms, and very likely it’s nearby equipment radiating into the front-end of the QA403. Also, note your 3 kHz on the left channel is really good: about -130. Would you be happier if both channels worked as the right channel did?
PS. The THD imbalance is inherent in the chipset. If you look at QA403 production data, there’s a very clear difference between left and right channels, with left always being better. And since the circuity and layout around the left and right channels is the same, that makes it pretty clear the imbalance comes from the silicon. So, there’s not much that can be done there because the chipset performance is so good in most every other area and dumping the current chipset for an inferior chipset that was perfectly matched would be waste IMO.
Hello AVO, Hello Matt,
Thank you very much for your expert answers.
It’s true that other manufacturers, such as Audio Precision, are in a completely different price range.
Before I ordered the QA403 four weeks ago, I was interested in older, used audio analyzers from Rohde & Schwartz (UPL, UPV, etc.). However, the age of these devices (more than 20 years old) and the still relatively high price deterred me.
Here in this forum, a successor, the QA404, is mentioned from time to time.
When will this analyzer be launched on the market and what improvements/changes can be expected?
Best regards from Darmstadt
When will this analyzer be launched on the market and what improvements/changes can be expected?
Hi @Diskus, it’s not yet clear when it will be ready. But for sure not this year.