In article ,
Arny Krueger wrote:
"Paul Stamler" wrote in message


Nope, testing a commercial product. At -1.1dBFS and below it's
unbelievably clean, but from -1.0dBFS on up it produces surprising
levels of HF IM distortion, especially on a 3-tone test..

IME not all that unusual.

Probable cause - clipping in the converter's digital filter.

Look at the bit stream out of the sample rate chip going into the converter
chip. A bitscope would be nice, but you should be able to see what is going
on even with just an oscilloscope. If you put a signal at 1.0 dBFS into the
input, are you seeing FFFF anywhere in the data stream? You shouldn't, you
know.
--scott
--
"C'est un Nagra. C'est suisse, et tres, tres precis."