From: skybuckflying@gmail.com   
      
   OK,   
      
   Mystery solved. The 100% volume low frequency sinus wave/signal causes the   
   protection circuit of the denon 1909 receiver to be activated !   
      
   This can happen with HDMI and ANALOG connections/signals as well.   
      
   The culprit is more or less the ASIO4ALL driver I think... it has no volume   
   control, it will simply output the signal at 100% volume ?!?   
   (But the wave is so slow, it cannot be heard without a subwoofer)   
      
   Though I am not entirely sure about ASIO4ALL volume level... but that is my   
   hypothesis for now...    
      
   Dave Platt wrote a nice explanation on the sci.electronics.design newsgroup !   
   Check it out there !   
      
   I will copy & paste it here just in case you don't have that newsgroup:   
      
   "   
   This is unsurprising. The receiver is not "crashing" - it is behaving   
   as it was designed to behave, It has nothing directly to do with your   
   ASIO or other software. It's all about the (low) frequency you are   
   trying to play.   
      
   Your receiver is designed to reproduce music and normal theater-   
   type sound effects (typically 20 - 20,000 Hz). What you're   
   playing isn't "in its scope".   
      
   What you are seeing, is the "ASO / DC protection" feature operating   
   normally. You should find this described in the owner's manual   
   (the only one I could find on-line is the Japanese version) and the   
   feature and the error blinking patterns are described in the   
   receiver's service manual.   
      
   This receiver is designed to protect your loudspeakers from being   
   accidentally overdriven with DC or sub-sonic power which could damage   
   them. Many modern audio speakers are of a "ported" or "vented"   
   design, and it's possible to damage these by driving them with   
   high-level signals which fall below the resonant frequency of their   
   woofer. You can actually drive the woofer so far forwards or   
   backwards that the voice coil pops out of the gap (in the front) or   
   hits the magnet (in the back). THWAP... permanent damage.   
      
   Speakers can also be damaged by a fault in the amplifier itself...   
   e.g. a shorted output transistor. Such short circuits can cause the   
   output voltage to "slam against the rails" (maximum positive or   
   negative), and this will both pop the woofer out to its maximum   
   excursion limit (as above) and turn the small voice coil into a   
   hundreds-of-watts heater. In his book on audio amplifiers, Doug Self   
   reports that deliberately DC-faulting an audio amplifier in this   
   general power range can destroy a loudspeaker system within a second   
   or so - the voice coil and cone literally caught fire!   
      
   So, many audio amplifiers and receivers (and yours is one such) have a   
   DC fault protection circuit. They monitor the average voltage level   
   at the output, and if it moves far enough away from 0 volts for long   
   enough, the protection circuit kicks into action and turns off the   
   outputs (and sometimes even the power supply) to protect the   
   loudspeakers. Think of it as a sophisticated electronic "fuse" of   
   sorts.   
      
   Apparently, a 7 Hz signal (at the level you're trying for) is   
   low enough in frequency to be interpreted as either "DC fault"   
   or "sub-sonic power capable of damaging loudspeakers" and the   
   protection circuit is operating. That's probably a more   
   conservative limit than you'd find in a high-end amplifier, but   
   it seems reasonable for a home-theatre amplifier and it allows   
   the circuit to react rapidly in case of a fault.   
      
   The analog input to the receiver (or the analog output of your sound   
   card) probably has a high-pass filter which blocks signals as low as 7   
   Hz. HDMI, being digital, doesn't have a simple passive filter like   
   this, and so it's capable of passing very-low-frequency signals.   
      
   If you want to generate subsonics like this, and want to risk your   
   loudspeakers by playing them, you'll need a different amplifier - one   
   which was designed for that purpose (or, at least, one which doesn't   
   have a "protect the owner's expensive loudspeaker from expensive   
   accidents" safeguard).    
   "   
      
   He was probably slightly mislead by my previous analog experiment where the   
   protection did not trigger (tests was not at 100% volume), but my recent   
   experiment (with 100% volume) showed that the protection is also there on   
   analog signals ! ;)   
      
   See below for more details, I know this text below is fuzzy but wth, see below   
   for links to videos proving it:   
      
   I just tested it on analog connections and the same thing happens eventually,   
   the receiver goes into "protection" mode.   
      
   Old stinky DreamPC from 2006 situation:   
      
   The reason why it did not happen the other day was because the volume was not   
   at 100%.    
      
   (The Creative X-Fi Elite Pro soundblaster has control over volume as well as   
   the web browser/tone generator)   
      
   Both must be at 100% to mimic the situation which occurs on the other system:   
      
   The toshiba L670 laptop which uses HDMI and ASIO4ALL driver.   
      
   With the laptop situation the volume is always at 100% because the ASIO4ALL   
   driver does not seem to have any control over volume.   
      
   So I think I now understand what happens:   
      
   The sinus wave is very slow at 1 to 5 Hertz or so... so it's not or barely   
   hearable... at least on speakers, on a subwoofer it might be different, but I   
   have no subwoofer currently.   
      
   Because the membrane of the speakers move so slowly it cannot be heard.... but   
   because the volume is set to 100% to membranes of the speakers are pushed to   
   their outer limitations... and this could cause maybe damage on some speakers,   
   like described by    
   the other two persons, they might fall out, or touch something.   
      
   Perhaps with my speakers this is not an issue because as far as I know/can   
   tell there is no damage, or at least I think so lol.   
      
   Since the sinus wave is moving rather slowly... 5 times per second or 7 times   
   per second, the risk of damage is maybe low.... or maybe not... depends on how   
   hard the membrane vibrations, 5x or 7x per second can still be quite fast....   
      
   So setting the volume to 100% has no effect on hearability of the wave,   
   because it's moving so slow... it's not hearably... even at 100%.   
      
   Perhaps not enough air is being moved around at this frequency... at least   
   from these little speakers.   
      
   I could do further testing and remove the foam on the front of the speakers to   
   verify that they are indeed vibrating, but I am not going to do that, because   
   I have seen enough.   
      
      
   [continued in next message]   
      
   --- SoupGate-Win32 v1.05   
    * Origin: you cannot sedate... all the things you hate (1:229/2)