@Matt, @Dan Just looking at the graph on levels after running the test, you can see changes of say 5db when using different attenuation( this is SE so Balanced unchecked). Also there is a pic of 3 graphs results for dut resistance using different Atten levels( correct is 10k).
Better pic
Hi @Moto, determining impedances requires math on larger numbers (voltages) and smaller numbers (currents). That’s why I was asking for tone, not a sweep. We should be able to see the voltage peak of a tone, and the current peak of a tone in your setup, and manually calculate the resistance from that. And then, switch to a different attenuator, note the levels, and manually calculate the resistance from that.
So, can you keep the setup the same, use a 1 kHz tone, and then note the levels measured for L and R using both Pk Vrms and Pk dBV at the different attenuator settings?
@dan, @matt I know you are sick of me beating this poor dead horse. Let me try to put it to rest. After a lot of testing, with a 10k Rdut, any atten works perfectly if you keep the Rs above say 100 ohms.
I then tested at 27k, 50k, 100k. If you don’t want to be concerned about atten level, then it’s best to keep Rs in the 5-10% of Rdut range.
The nonlinearity at those very high Rdut levels when you are measuring past 1khz is pretty bad.
I might play with some preamps with around 50k input impedance but I don’t think the results would be meaningful.
All this testing was SE. I have not been able to get balanced working accurately. Don’t know what to say there. At 50k Rdut I get 40k measurement at most of the atten levels and tried a few Rs levels as well.
