On Thu, 2005-10-06 at 12:53 -0400, Pat Farrell wrote: > On Thu, 2005-10-06 at 09:30 -0700, bjackson wrote: > > I would be suprised if you got any decent output out of the SB2 into a > > HD600/650 load which are 300 ohms. > > > > The standard headphone is 16-32-64 ohms, and the SB2 produces decent > > power into them, but I don't think it has the voltage needed to > > properly drive 600/650's, which are 10 x the impedance. > > I'm pretty sure you have it backwards. A source produces voltage for the > signal, and the driven impedance determines how much current is > required. And the current times the impedance is the definition of > power.
Errr,,, how I do I say this, my math is right, but I forgot a fundamental concept, so what I wrote is at least insufficient. > A high impedance driver is easier to drive. It takes lots less power. But, and this is the part I messed up on, is that there usually is some correlation between sound loudness and amplifier power. It is not enough to drive the load with a voltage, it needs power. Or as Tim says on Hometime, More Power. So, it is easy to put one volt into a high impedance load, that part was correct, but most of the high impedance loads still take nearly the same power to make the same loudness. (plus or minus the efficiency of the speaker/headphone) As one of my smarter friends explained it to me, the source can't supply enough volts to make the watts you want, then it will appear to be working hard (volume control wide open) and not making much music. The waveform may clip if the amp runs out of volts. Of course, it isn't really working as hard because it isn't supplying the watts. In the case of a SqueezeBox, it isn't going to put out many watts of power. Which is why you need a amp to drive anything that isn't highly efficient. Sorry if my mistake confused anyone besides myself. -- Pat http://www.pfarrell.com/music/slimserver/slimsoftware.html _______________________________________________ audiophiles mailing list [email protected] http://lists.slimdevices.com/lists/listinfo/audiophiles
