Interface NI USB-6281 to an audio output

[DavidDLC]

I need to connect a NI USB-6821 card to a line audio output of an amplifier, I need to use single ended input on the card

Can I make a direct connection straight from the audio line level output to the card, or am I need to match impedances ?

Please comment and thanks for any help.

David.

[Henrik_Volkers]

Two points came to my mind:

Output level:  DAQunit usually up to 10 V , line in usually 1 V to 0.7 V RMS

Ground loop: Nice to catch hum and other spiky noise (swichted power supply from DAQ) 

Impedances are not that important in this case.

[Henrik_Volkers]

Sorry, you want to measure....

Channel crosstalk might be an issue.

I would think about a INA217 as an input buffer ....  the INA out ref.s  to DAQ-AI-GND ....  buffer and ground loop breaker 🙂

Could be done with a low noise OP , but the INA has matched resistors already build in 😉

[DavidDLC]

Thanks for you answer, we are trying to measure signal level, frequency, THD and SINAD.

I need to check if we want to put something on the middle chain as the INA217,  because then we are going to be measuring it as well as the DUT.

David.