OK, that did not take too long. I only ran L-R crosstalk this time. THe result is better this time but still about 10dB less than the expochrip & manual method, which I will post here for just 20khz.
This shows pk dbv at 30khz after running the crosstalk test:
Here is the manual measurement at 20khz with the right input shorted, which shows about 37dB. The level of the right channel does fluctuate a few dB, so there is not as much difference with the routine’s measurement:
Looks better than yesterday’s measurement. Just for grins I will see if it makes any difference selecting it to measure the R-L crosstalk as well, which I did yesterday…
Not sure what is going on, but further testing today and things look pretty good- no change in the amp or setup… Here is the automated plot with both L-R &R-L:
which shows 37dB at 20khz. I should point out that the Right channel was stable. Then I ran the expochirp, which shows about 38dB at 20khz- I am not going to worry about 3dB of crosstalk between today’s readings, but yesterday I got 43dB at 20khz using the expochirp…strange stuff
Hi @Var, thanks for the plots. In the sine spectrum, the left peak is 15.47 and the right is -24.88, which suggests 40.35 dB of crosstalk. But the plot showed -35 dB???
That is correct, Matt. I did not pick that up, but at 20khz that would be the case- Note that I have the freq range set for 10hz-30khz for the manual method and 20hz-20khz for the expochirp method. It is interesting that the delta Y shows ~37dB, and I used the marker “peak” function to position the cursors, which is about what the expochrip method shows.
Ahh, probably the band edge explains it. Assuming 20 kHz is your measurement limit, if you are at the band edge with FLAT TOP, then the window is wide enough to pick up most all of the energy:
Matt- much of my life revolves audio these days with the QA402 being a large part of it, so it is not too difficult to fit this into my schedule. I have been using Hann with most of my normal measurements- some RECT. With the expochirp I think it has to be RECT. I never use FLAT TOP. Once I finish “transplanting” parts between a pair of receiver I will hook up the power amp and try the Crosstalk routine with Flat Top from 10hz-30khz, as well as the manual measurement with the limit set at 21khz and report back. Thanks!
So I did several measurements and I think everything is looking good now. I set the windowing to FLAT TOP and went from 10hz-21khz. Here is my standard expochirp measurement with the right input shorted, showing about 37dB @ 21khz:
I can certainly live with the difference between the two methods. I did not see much of a difference when I removed the Right input and used a termination on it and re-ran the Automated cross talk test. I now have an instrument state setting for crosstalk that uses the FLAT TOP windowing and 10hz-21khz with the setting showing in these examples. The Gen1 level will vary as I set that such that I get 5w/8ohms- at least for amplifiers…
