I have just noticed your avatar48kHz Sampling rate? (22kHz BW) What happened to 192kHz?
I have just noticed your avatar48kHz Sampling rate? (22kHz BW) What happened to 192kHz?
I have just noticed your avatar
Isn't "official" Hi-Res 96 kHz SR, thus 48kHz BW ?48kHz Sampling rate? (~22kHz BW) What happened to 192kHz?
Yes, pleaseYep. I'm stirring the pot a touch. Shall I go back to electrocuted guy?
howz about with the amplifier not connected ?Just for info (and fun), this is what I get from speaker cable connected to both amplifier and speaker, in the place where I live. I know that it is individual and location dependent .
View attachment 39211
Why limiting this test to class D? Demodulating out of band noise in audible band can be done in many ways.
Moreover, I believe the issue highlighted here is not general to class D, but associated to self oscillating amplifiers.
For me testing should be agnostic.
Only if you can show that many dacs output a sufficient level of RF garbage to create a problem. I would suggest that is the first place to start. Take a look at the output of a bunch of dacs to see whats coming out and if there is something to be concerned about or if you are chasing ghosts.
WoW!!!Lucille Ball hearing strong radio signals via her temporary lead dental fillings has never been confirmed or disproven, but one thing that she did is appreciated by me and millions of other science fiction fans - and she had no idea what the show was about. A very "strange but true" tale.
Were you chasing ghosts when you decided to put a RF input filter in your amps?
Not sure why that is a condition since we can never guarantee there is no DAC or a SACD player or whatever source in the future might do without testing all of them. Seems like given the potential behavior and that you think it important enough to put a RF filter, we should expect this of any Class D amp and should ensure that such filters do what they do by a measurement. To give it a clean bill of health, so to speak.
Just for info (and fun), this is what I get from speaker cable connected to both amplifier and speaker, in the place where I live. I know that it is individual and location dependent .
View attachment 39211
TBH really yes. I did it as good design practice to try and account for all eventualities. It wasn't actually because I had experienced a problem with external RF or created a problem by attaching any dac I had available.
That isn't to say there are no dacs out there that could spew out enough crap to create a problem, but it hasn't happened with anything I have tried.
RF filters are good design practice on any class of amp. This is not about class d. I would do exactly the same on a class A or A/B
Yes. All classes can be affected by RF, demodulating, dc offsets etc.Is there any other class of amp where audible effects are known to happen IF such an RF input came in at sufficient levels as shown by the OP test? This is not a rhetorical question. I really don’t know.
If not, then it would be a documented Class D peculiarity and so worth making sure that it was protected against it. If there is, then it would be worth establishing the outcome in the same way OP did. And if that is done, then they can be tested as well. I don’t really see a problem with doing such a test. But if I was worried about the optics of such a test on a class of amp I was selling, I would be. It could lead to people with vested opposing interests making it a talking point in their narrative.
Adcom amps always had a bad rap for not having speaker protection although getting a reliable report of an Adcom amp failure actually taking out a speaker were hard to come by and it wasn’t because the amps never failed, just didn’t fail in a mode that would fry the speakers while theoretically possible. They just didn’t realize how insecure people would feel with even a suggestion that their expensive speakers could be taken out by an amp failure.
So, I always thought Adcom messed up by not putting some protection as a precautionary measure rather than letting that narrative grow from a marketing point of view while trying to dismiss such concerns. And making that protection circuitry a matter-of-fact bullet in their brochures.
Seems to me, from a marketing point of view, Class D amp manufacturers would be better off just owning this possibility and simply saying it is a non-issue given the RF filters as you did (and making the effectiveness of the filter a talking point) but not protest so much about whether it is chasing ghosts because it cannot happen. Don’t need the latter. It does feel like it is over-defensive even if technically correct and that can create the kernel of doubt that lets opposing narratives grow.
the faster amplifier
Yep. I'm stirring the pot a touch. Shall I go back to electrocuted guy?
+10Yes, please
Spreading FUD is rife in audio. You won't counter it with a few tests on ASR. Non technical audiophiles will continue beleive what they want.
Yes. All classes can be affected by RF, demodulating, dc offsets etc.
I am not in the slightest bit concerned about doing some tests. I have suggested Amir does exactly this.
Did you not notice?