The possible reason they might want software control over headphones/speakers, is that the user can select software filtering schemes in the driver, which optimize for headphones versus big speakers versus tiny speakers. If the jack tells the computer that a headphone is plugged in, then the software can auto-insert a different dsp software driver module to 'optimize' for headphone output rather than speaker output.

Dollars to donuts that the actual power amp is the same for the headphone feed versus the tiny laptop speakers. The voltage drive is nearly identical for headphones versus tiny speakers, except that the lower impedance of the speakers delivers more power from the same volts when the speakers are connected. Inexpensive commercial 'home-studio' headphone driver boxes often use the same class of little half-watt or one-watt amplifier chips that are used in low-volume portable shortwave receivers or clock-radios or cheapie desktop computer speakers or whatever.

It strains credibility that a manufacturer would include two 25 cent amplifier chips on a laptop motherboard, if one amplifier chip could be used for both headphones and speakers. That is just wild guessing of course. No telling what a manufacturer would choose to do.

One innovative headphone driver was used in early-generation Mackie mixers. Maybe Mackie still uses the same scheme, dunno. Rather than using a possibly-lo-fidelity tiny amplifier chip, or an opamp with current-booster transistors, the Mackie mixers would wire several ordinary opamps in parallel to get sufficient current drive to push headphones. That circuit sounded pretty good IMO.

Which has nothing to do with your friend's problem. Just free-association chain-of-consciousness rambling <g>.

Last edited by JamesChandlerJr; 04/23/10 09:42 PM.
James Chandler Jr
http://www.errnum.com/