- Thread Starter
- #21
What's the tweeter inductance?That goes a long way toward reducing the current.
Of course I was waiting for this reasoning
What's the tweeter inductance?That goes a long way toward reducing the current.
The only source of such a high frequency I can think of just now would be the noise shaped stuff coming out of an SACD player or a DSD DAC.
No - as I wrote I remember having seen plots somewhere at ASR.Are you sure?
Since I don't have an SACD player I cannot measure its noise. I'm sure though that someone else with more knowledge than me will correct me.Did you make some research and measurements on this?
What Im saying is can you demonstrate this is a real world problem?
All it needs is a catchy name. Audiophiles will lap them up by the thousand, others will deconstruct and make their own, but it will become an essential add-on.
Let the running gag begin.The Hypex module needs an aditional RF / EMI filter (if mains is noisy, usually in urban concentrations). And two stages filter work without problems. They are economical
this seems like a very reasonable approach to see whether this affects a given cd design, and if i am not wrong, something we have people around can do, to know whether there is any fire correspomding to this smokeAt first thought it's interesting. Then you have to think about it.
A better approach is to use pink spectrum NID multitone input signals to test this. First limit the bandwidth to 20khz then increase to 35khz, 45khz,80khz to see at what point it starts to affect the spectrum under 20khz.
One thing to point out, instead of using sampling as analogy, it's actually more like AM signal. That's how you get to see the signal being "demodulated" into audio band.
Rod Elliott talked about this before, directing the actual rf interference present in the environment. http://sound-au.com/amp_design.htm#s12
At first thought it's interesting. Then you have to think about it.
A better approach is to use pink spectrum NID multitone input signals to test this. First limit the bandwidth to 20khz then increase to 35khz, 45khz,80khz to see at what point it starts to affect the spectrum under 20khz.
In other words, do the real world device gain controls affect the out of auditory range signals proportionally relative to the auditory range as measuring instruments would? I don’t know the technology enough to answer this.
Pink spectrum is to mimic the spectrum of music. You cannot have a white spectrum in any way. So pink is a good option. As pink spectrum decreases along the frequency increase, it shows how much effect there will be with music playing.Thinking about this, I am not sure pink noise at some reference level across the band would necessarily prove or disprove anything about the real world. If the out of listening band signal is not necessarily controlled by the gain setting in the real world and hence uncorrelated with the reference level used within the audible region, the level of any perturbation induced by it might be significant or not depending on the gain setting.
What I am trying to get at is that there are 3 possibilities to eliminate to relate to real world
(1) eliminate any possibility that any induced or leaking out of band signal does not create audible noise when there is no signal in the audible range (like audible hiss or hum when no content is playing), which is what I think OP covers. So don’t have any signal in the audible range but keep increasing the band above it until you see any effect in the auditory range.
(2) eliminate any possibility that even if there is any audible effect in (1) above that it is not masked by audible band signals at reference level.
(3) eliminate any possibility that any audible effect is not masked at low levels of signal as may happen when listening at low levels. This would require a sweep across gain levels.
In other words, do the real world device gain controls affect the out of auditory range signals proportionally relative to the auditory range as measuring instruments would? I don’t know the technology enough to answer this.
Oh, this is the perfect audiophile silver bullet solution! Introduce doubt as to whether instruments can measure something the golden-ears claim to be able to hear, and then present the solution.
Ok, I'll stop now.![]()
Pink spectrum is to mimic the spectrum of music. You cannot have a white spectrum in any way. So pink is a good option. As pink spectrum decreases along the frequency increase, it shows how much effect there will be with music playing.
In design we think about worst possible case. So varying gain is not helping.
If you are talking about the rf interference not coming from the source, it can be filtered out and mostly they are not strong enough to push enough current in a low impedance input terminal.
The most possible case is when playing hires audio music. Otherwise there shouldn't be any issue.
I do not understand why usual measurements are almost always restricted to audio band measurements, 20Hz-20kHz, maybe 50kHz. SINAD, THD vs. amplitude, THD vs. frequency. Is that enough, really? Isn't it pointless? Above some level of parameters, like SINAD = 80dB, do we find differences by listening? Why do we concentrate our efforts at those standard measurements only? Because they are easy to make? Why do not we try to find broader consequences? In the age where we are surrounded by EMI pollution, digital sources having MHz and tens of MHz rubbish at the output? Isn't it the key to perceived differences, these out of audio band interferences transformed as intermodulations and aliases into audio band? Why do we resist to investigate something else than a conventional, decades old audio band measurements?
The only source of such a high frequency I can think of just now would be the noise shaped stuff coming out of an SACD player or a DSD DAC. I seem to remember having seen worst case levels up to -30dBFS ( I may be wrong though) which could lead to spurious signals within the audible range.
Yep, that should be done always and fixes many potential problems.
Another thing - is it OK if the power amp sends 460kHz rubbish like this into the tweeter? Are there any possible nonlinear effects in the tweeter driver? Or we just keep saying the only issue is negligible amount of added heat? Any serious explorations on this?
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I'd ask the question the other way- if there's nothing significant being introduced into the audio band, why would I be interested in RF stuff?