| Originally Posted by bangraman Try sticking a pair of headphones in to the Line Out port. (PS. wear earplugs
The Line Out isn't unpowered. The output simply conforms to a level which is accepted as a Line Out. |
| Originally Posted by recephasan Line out is a certain voltage level driven for the high impedance inputs of the amplifier. The idea is to maintain the output signal around a certain voltage level. There is not much current being supplied, since this is taken care of by the amp. The headphone output is driving the headphones, which is a load that requires high current. The loudness of the phones is actually dependent on the match between the jack impedance and the headphones' impedance (thevenin). Largest power output occurs when the source and load impedances are equal. An example: I have a CDP with headphone and lineout jacks. The volume setting affects the headphone jack and not the lineout. When I use my Grados, and adjust the headphone volume so that the volume I get from the headphone jack is same as the one I get by connecting the cans to the lineout (NO AMP, just lineout), the volume is set quite low. It is the opposite with the HD-600. The lineout is quite loud with them and the volume setting of the headphone jack needs to be high to match that loudness. The reason for this is the difference in the impedances. The Grados are 32ohms. They will sound loudest when the source impedance is also 32ohms. The Senns are 300 ohms. They will sound loudest with a source impedance of 300 ohms. The headphone out jack has a low impedance (dunno exactly but surely lower than 50ohms) whereas the lineout impedance is high (because the inputs of the amplifier are also high impedance and the signal is not driving a big load like the headphones, but is supplying a signal to be further amplified). This translates to the lineout being a better match for the HD-600 with its high impedance than the Grados with their low impedance. Your amp is high impedance, and the power output of the system (player + amp) is greater when connected to the high impedance lineout than the low impedance headphone jack. Hope I am clear enough and am actually answering your question. |
| Originally Posted by recephasan Hope I am clear enough and am actually answering your question. |
| Originally Posted by recephasan The reason for this is the difference in the impedances. The Grados are 32ohms. They will sound loudest when the source impedance is also 32ohms. The Senns are 300 ohms. They will sound loudest with a source impedance of 300 ohms. |
| Originally Posted by antonik This is incorrect. Loudness of the sound from headphones is proportional to the voltage across them. For that reason if you increase the ouput impedance of the amp the loudness will always go down, as the voltage across the headphones is reduced. The rule works other way round - for a GIVEN output impedance, maximum output POWER achieved if the load impedance is equal to the output impedance. This does not mean that by increasing the ouput impedance we can increase the volume - it is exactly opposite
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| Originally Posted by antonik How loud the headphones sound from a particular output depends on 3 things - output voltage without load, output impedance and headphone impedance. If the combination of these 3 parameters is such that the voltage across connected headphones is higher, than the sound will be louder. |
| Originally Posted by antonik Answering the first post: simply the output voltage on the headphone output is lower than that on the line out and that is what counts for the high impedance load - i.e. amplifier. |
| Originally Posted by delenda est Sony perfect explanation and crystal clear! Thanks for your help on this. My next question: for a portable device, would use of a headphone jack drain more, less, or equal amounts of battery power as compared to line out usage? des |
| Originally Posted by recephasan That is, assuming the circuitry that drives the output stage remains the same? And since max P is achieved with Zo=Zi and P=V^2/Z and Z is constant, max P is max V, and hence, the loudest. |
| Originally Posted by recephasan You mean headphone out vs line out to drive an amp (not headphones)? Let's see, if the amp impedance is assumed to be constant and high, the power output will be higher with the lineout. Power is voltage squared divided by impedance. Therefore the voltage drop across the imputs of the amp will be higher, and hence, louder. Am I correct, antonik? |
| Originally Posted by antonik For an amplifier with high input impedance the important bit is not the power but the input voltage. For most audio application it is best if the load impedance is much higher than the output impedance, as it minimises the voltage drop. Alex |
| Originally Posted by recephasan You're talking about signal transmission (interconnects), right, not transducers (speakers and headphones)? AND imperfect sources, as in sources that drop max voltage with increasing load? |
| Originally Posted by recephasan Whatabout headamps suited for high impedance cans vs. low? They have high o/p Z, don't they? You realize I'm asking to learn, not to argue, right? |
