As the thread starter I feel coerced to give my "OK" to this.
I have no problem with this (still very interesting and informative) discussion being carried on in English.
Due to the fact I have your okay and that all people here seem to understand English as well as German I will try to stick to that language as far as my abilities allow that.
man begibt sich in der Tat auf vermintes Gelände, will man das eine ohne das andere beschreiben. Die Zusammenhänge sind sehr komplex und deswegen funktioniert eben auch oftmals "nur" ein Ampnachbau nicht so, wie ein Original. Besonders, wenn dieses in seinem Lastverhalten nie explizit dahingehend dimensioniert wurde, sondern früher eher empirisch oder aus Kostendenken erschaffen wurde, die Musiker es über die Zeit immer mehr aufdrehten und übers An- und Zerrverhalten begeistert waren - und heute ist es vintage.
Absolutely correct!
There are two sides:
SIDE ONE:
The amp "designer" who often does not know much about electronics and builds something that sounds good rather by "accident" or by continuous trying to find the sound he wants to achive. After long times of designing amplifiers they know what they have to do in order to make their amps sound the way they want them to but many of them never know WHY the amp sounds the way it does. Of course there are people who consider themselve being amp designers and they know about the electric and physic background of all the parts involved but that is only a very small part.
SIDE TWO:
The engineer who knows about electronics, physics, circuit analysis and network theory. Many of these people do not know much about sound because they are not interested in it but they CERTAINLY know what happens when you change some part values and they see problems in circuits which can cause malfunction or other problems.
This discussion shows the differences quite well:
Das kommt auf die Betrachtungsweise bzw. den Vereinfachungsgrad an.
Wenn du eine ideale Spannungsquelle annimmst, dann ist sie im Kleinsignal Ersatzschaltbild nicht vorhanden. Aber das ist eben nur eine Vereinfachungsform.
Wenn man jetzt ein Netzteil hat was einbricht wenn man zuviel Strom zieht dann ist das Kleinsignalersatzschaltbild schlicht und einfach nicht mehr gültig bzw. ungenau. Und deswegen ist halt eben alles im Signalpfad was einen signifikanten Einfluss auf das Signal hat.
Of course it is a correct statement that a power supply unit can be removed from the signal chain
if it is a true voltage source. But this is a feature most guitar amplifier PSUs do not have because they of course have some series resistance which is often well above 100 ohms - especially when tube rectifiers and chokes are being used in the plate voltage rails.
Although it is a rather hard thing to develop such a PSU, it is possible to make this series resistance - which is often frequency dependent and increases the lower frequencies go which leads towards "muddy bass" and such problems - very small by installing regulated power supplies at least for the screen grids and preamp circuits. Doing so one can treat the PSUs for these rails as ideal voltage sources and then one can say that the PSU is NOT part of the signal chain. In any (!) other configuration it is - even in Class A when the amplifier stages are driven into non-linear parts of the load-line.
These statements are - of course - only correct if the anode voltage rails have a constant value (DC!) independent of the frequencies the amplifier stages are driven with. In any other environment the amplifier will behave differently from what one would expect by calculations in which the PSU has not been thought about.
And as you already mentioned: You threw in the term "Kleinsignalersatzschaltbild" which I would call "small signal system analysis" in english. For those who do not know about this topic: The point here is to approximate all parts/devices in the circuit to rather linear equivalents which means that many non-linear elements - for example the bendings in tube characteristics are replaced by straight lines and so on - are replaced by straight lines in order to make calculations easier. These calculations are correct as long as we talk about SMALL signals but in a guitar tube amplifiers many tubes are driven into heavy distortion or at least non-linear parts of these characteristics because this produces the "sound". Having that in mind it is of course nonsense to try some small signal analysis at all because in most cases one will get results that are not of any interest
Mein Ansatz bei einem Ampbau wäre allerdings eher die Kompression in der Vorstufe unterzubringen und eine saubere Endstufe mit harten Netzteil zu konstruieren. Dann hat man den Effekt schön schaltbar und bei jeder Lautstärke.
That statement could have come from my fingers. I use regulated supplies in some amplifiers I have built so far and I think about using set impedances at the output of the PSU in order to be independent from rectifier tubes and other parts that do rather unpredictable things or do these things depending on their lifetime...
Auch der Netzstrom kann ja den Klang beeinflussen (siehe Eddie Van Halens Experimente mit Dimmern), eine schwache Batterie in einem batteriebetriebenem Amp kann ebenfalls das Klangergebnis beeinflussen.
Dennoch käme niemand auf die Idee, Batterie oder Stromnetz als Teil des Signalweges eines Amps zu bezeichnen (ausser du vielleicht).
Fakten bleiben Fakten, und da sollte man auch nicht dran herumbiegen, finde ich.
Yes there are facts and these facts are based on models which are abstract models of real components/circuits. The question is how far one can think and how far one wants to think and how far it makes sense to think about the models, their problems and limitations and so on.
And I would like you not to deflect from the "second topic" in this thread which was a discussion about power supplies. When you discuss about such a topic a constant mains voltage is obligatory - else you cannot say anything about the differences in PSU design and what those differences lead to ("sound like"). The mains voltage changes the sound - of course - but when we start to discuss about that we can also discuss about tubes that are 30 years old and completely burnt out and their "tonal differences" to newer ones...
You should see that it is not the problem that we do not know the facts but instead it is your problem that you do not take certain things into consideration - maybe because somebody told you that those things are irrelevant or simply because you do not think in a way abstract enough to cover those effects.
This should not be considered being an insult! It is simply my point of view on this topic - backed by lots of books....
Regards
Stephan
