[Alex Kitic]

Zitat:Original geschrieben von Rumgucker


Für die Anodenspannung ist es völlig egal, ob Du vor dem Wandler oder nach dem Wandler mit einem großen Kondensator siebst. ICH wollte keine direkt geheizte Röhre betreiben (ich besitze gar keine direkt geheizten Röhren). Das willst DU. Dadurch hast Du eine andere Lösung gefunden: nämlich den Siebkondensator primär zu setzen.

I had to straighten this out:
- if we rectify the electronic transformer output, we get 200Hz ripple instead of 100Hz, and we can fight it with caps, regulators, etc. But it is DC, which means the two ends of the filamentary cathode (direct heated) are at different potential, i.e. bias. This is the main problem with DC on direct heated cathode.
- if we add the cap before the half wave circuit, we improve 100Hz ripple that will be thus dramatically reduced (virtually irrelevant) in the output of the electronic transformer. This leaves us with a "pure" 40-60kHz AC that we can use to heat the direct heated cathode. 40-60kHz "hum" is something that we cannot hear, and once nulled across a humdinger pot, we are left with the residual 2nd harmonic which is 80-120kHz that is so high that even intermodulation distortion is not audible.
The cathode is all at the same potential, because it is heated with AC, which becomes a major plus if hum is not audible.

I hope you are getting the huge difference now.

If we apply your inverse additional transformer, we are going to get high voltage B+, like 300V, without 100 or 200Hz ripple. The rectification ripple is going to be, if with full wave doubler, at 80-120Hz, thus not audible. And you can save on the caps.
This arrangement I am going to try for a preamp (with phono) to check the sound quality: simple and cheap solution, but the resulting sound is the most important issue, otherwise it is just an exercise.

I hope you got it now, since I am not going to repeat.