Class D

Is that the same NC500 you bypassed the buffer clearly violating the recommendations of the app note that the amplifier stage be driven by a low impedance source to maintain performance?

2.5.1 Audio input


The INH/INC inputs form a differential pair. Note that the input impedance is fairly low meaning that
minimalist discrete circuits or valve input stages won’t work. All op amps commonly used in audio can handle
them though. See section 9 for suggested circuits and connections.


Do not drive the input with fully floating sources, be it electrically floating ones like line driver IC’s intended for driving XLR outputs or transformers. Using a floating source will always result in a common mode
component that will exceed the common mode input range and will manifest itself as gross distortion.

Make sure to set the outputs of your distortion analyser to grounded, not floating.

There is also capacitance in that input which means that a high impedance input will cause phase shift and a non flat frequency response.

Admin, Is there a way for me to ignore a member? I am so tired of trying to read a thread without georgehifi crapping all over it. Thank you

Is that the same NC500 you bypassed the buffer clearly violating the recommendations of the app note that the amplifier stage be driven by a low impedance source to maintain performance?

You buy them without buffers get a life!!
Just yet another furphy of yours, that you can’t remember to see the forest for the trees??
Yes as I told you once before (is your memory shot) because my MSB dac has twice the output voltage needed from it’s very low output 10ohm impedance balance direct coupled outputs to drive the NC500 balanced input direct, so NO!! buffer board is needed!!

Woosh right over your head ....

Over your head that's for sure.