[SSassen]

Okay, I'll put it in English to avoid any confusion due to my horrible use of the German language.

I've measured the carrier-frequency (taktfrequenz) of both my SODFA design, a UcD180 and my UcD400 to check for anomalies (HF-swingungen) with a muted input (eingang kurzgeschlossen) and either a resistive load (widerstand am ausgang) or a reactive load (lautsprecher am ausgang). In all these amplifiers I measured across the output terminals of the amplifier with a 10x 100MHz probe (calibrated prior to measuring) on a 100MHz scope.

UcD400 measurement setup
[Bild: 11684.jpg]

I see these anomalies (HF-swingungen) with all amplifiers, but only the UcD400 allows me to minimize them with a potentio meter, but they're never really gone. Attached below is the output of the UcD400 with the anomalies minimized using the potentio meter, which is a THD adjustment according to Hypex.

UcD400 amplifier carrier frequency
[Bild: 11683.jpg]

So the question is not why these anomalies occur, as they obviously also do in commercial designs, but why is my SODFA design showing far worse behaviour?

Mit fruendlichem gruBen,

Sander Sassen
http://www.hardwareanalysis.com