Measuring THD with Tektronix SG505 and DA4084

You have a 505 with the balanced output option. It has a floating/grounded selection. The easiest way to avoid ground loops is to select floating on the 505 and connect the RCA input to the amp to the + and - connections of the 505. It may be described in the manual but Tektronix had a separate book on audio measurements that's more helpful: http://lcweb2.loc.gov/master/mbrs/r...ektronix Cookbook of Standard Audio Tests.pdf
 
Make a loop test. Balanced out of generator to balanced in of analyzer. If it passed, insert the amplifier but turn off the generator. No hum should be measured (400 Hz filter on or off shold not make any difference in residual noise reading).
 
Thanks for the link, Demian. From a quick look at the manual, it seems it only shows connections for the styandart 505 with a single bayonet out. I couldn't find a manual that describes the balanced option. So you are saying, I should use "-" port on both 505 and 4084 as a reference point, leaving 505 floating. What is CT port then? Do you have a manual for the balanced output version?
 
Sorry-no manual. I found this closeup SG505 - TekWiki on Tek wiki. You have option 2. Yes. tie the - to the DUT's ground for both the source and the analyzer. The CT is used when you need a balanced connection with a center tap.

That's a very high performance combination. it should not be limiting for pretty much any audio testing.
 
I hope it will help
 

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