On Thu, 2005-10-06 at 22:14 -0400, Pat Farrell wrote: > 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.
Ignoring the maths, the SB (1&2) works perfectly well with my Sennheiser HD580's, which are also 300ohms. The amount of power you typically need to drive headphones to high volumes is effectively tiny, and everything I have tried with a headphone socket has worked perfectly well with the high impedance Sennheisers. -- "The biggest problem encountered while trying to design a system that was completely foolproof, was, that people tended to underestimate the ingenuity of complete fools." (Douglas Adams) _______________________________________________ audiophiles mailing list audiophiles@lists.slimdevices.com http://lists.slimdevices.com/lists/listinfo/audiophiles
