W dniu wtorek, 16 kwietnia 2019 15:57:35 UTC+2 użytkownik johnk napisał: > > Well, how do I say this Thomas? > > It is NOT to be called Watts RMS ! > > They left the vital word out – it is Watts [RMS derived]. They left out > “derived”. > > > > The RMS volts and RMS amps that you mention when multiplied together > produce Watts. Just plain Watts. > > These Watts are actually the average power of the power waveform that > resulted from your two sinewaves. > > Remember too, that the RMS value of the voltage waveform gives the DC > voltage that provides the same heating effect. And that is average power. > > Gee, I didn’t say that well. I have just spent a while fighting with Win > 10 and drivers for CH340 on Arduino clone boards – I haven’t recovered ! > > > > You might think that I am nit picking. However you did say this, “RMS > power of a sine wave is 0,5 times peak power.” > > And the power waveform isn’t really a sinewave in the way we mean it. The > values of interest here lie in the area under the curve (notice it is twice > the frequency too?]. In a sine wave [like the Voltage one] the areas of > interest are the equal sized ‘lobes’ above and below the zero line. > > I invite you to draw out the two sinewaves [Volts and Current] and the > resulting power waveform and perform an actual root-mean-square calculation > on it to prove your statement. [Graphically is more reliable because it > shows the workings J ] > > Spoiler: you will NOT get 0.5 x pk as the answer. > > > > The VERY rough sketch that I sent Charles shows what I mean about the > average value [the green bit tipped over into the trough]. > > (Rough because I was on a new touch screen laptop and NOT in tablet mode. > I was experimenting; made it tricky to draw with the pen. ) > > > > I know that you know what you mean when you refer to amplifiers this way, > but you could add the extra word and be ‘more right’ J > > Thanks for nibbling on the hook. But, I really do wish that someone had > been willing to do the graphical maths thing. Someone must want to prove me > wrong, surely. > > > > John Kaesehagen > > Australia > > > > > OK, I see your point. The right way to spell power is just watts (V RMS * I RMS = W) I've ran a little excel excercise - I calculated voltage and current with peak value equal to sqrt(2) for 360 points of a sine wave. If I run RMS calculation (from definition) on voltage or current, it is equal to 1 (so one times the other is 1W), but running it on voltage*current gives a value of about 1,22W RMS. I admit this is a mistake to use W RMS.
When it comes to Loudness War - I am also for dynamic range, but mostly, I am for consistent loudness between digital files, so I don't have to change volume for each track. Fortunately, loudness war is being actively fought against - as far as I know, Spotify attenuates a track if it is too loud, which eliminates the whole reason songs were overcompressed. So now those tracks are left with their poor dynamic range, but being no louder than slightly compressed or not compressed at all songs. I'm currently building a vacuum tube amplifier, which works greatly with uncompressed tracks - it compresses them itself via soft clipping! That's the reason 15-20W tube amp can sound like 50W solid state, vocals and most instruments can stay at the same SPL, but vacuum tube amp will compress the short spikes from percussion or other instrument instead of grossly distorting them. Solid state needs that power headroom to prevent going into clipping, because you can easily hear it and it isn't pleasurable. Of course, I could also just build a simple Gainclone amp with higher output power for more headroom... but high voltage is fun! Coming back on topic of audio signal level - I think that if I worked in proffesional audio, all the different standards would make more sense to me. But being a hobbyist who just wants to build an amp, it is straight up annoying. By the way - you can keep calling me Thomas. It is practically the same name. Also when I was a kid I used to live in USA for over a year, so I was called Thomas a lot in my life :) -- You received this message because you are subscribed to the Google Groups "neonixie-l" group. To unsubscribe from this group and stop receiving emails from it, send an email to neonixie-l+unsubscr...@googlegroups.com. To post to this group, send an email to neonixie-l@googlegroups.com. To view this discussion on the web, visit https://groups.google.com/d/msgid/neonixie-l/029027cb-4ef1-47cd-b915-cdbaf837f5ca%40googlegroups.com. For more options, visit https://groups.google.com/d/optout.
