When the 1 kHz has kicked in, it is massively present when listening in AM to what is supposed to be a clean carrier; it appears fully modulated with an unclean 1 kHz. Listening with ssb or cw filtering there is a plethora of spikes at 1 kHz intervals because clearly the 1 kHz modulation is not a sine wave but something wit a squarish envelope and many overtones. There are times when the modulation is absent (after trying ptt on / off multiple times) , present all the time, and sort of randomly crackling between present and not. None of it under influence of what one does to the Peaberry board in terms of touching circuits or even exerting some force on the board. The RF path appears stable in itself; the heatsink of the BS170s gets warm but it just amplifies an unclean signal that emanates already from the DA stage but is not unstable in terms of tendencies to oscillate.
The PC motherboard is a modern Asus P8H67-I Pro board with an i7-3770 CPU @ 3.40GHz × 8, 8 GB DRAM, and running Ubuntu 12.04. Am wondering whether perhaps the PCM3060 has an internal problem. Just not looking forward to redoing the ssop soldering ... Or that perhaps the usb clock gets a spread spectrum treatment that unsettles this audio sync ??? But then I do not understand how reception could be fine. It is really only TX that gives problems.