Yes most are in that range, 25-35 ohms. However some higher-end ones are much more - 300 to 600 ohms. Quite a different thing to drive these without clipping, you need +-15V or more. (AKG 242, for example, are 600R and used in studios). J Josh Koffman wrote: > On 9/4/06, Mario Mendes wrote: > >>Does anyone know what is the typical output impedance of a laptop's >>headphone jack? The only usefull info I have found is that the majority >>of these jacks will put out 1v rms. Also, not being knowledgeable in >>analog electronics (I do fine in with digital electronics though), can >>anyone help me out with coming up with an opamp circuit that would take >>care of this impedance matching? Since this is for home use, I thought >>that a couple of opamps (1 left and 1 right) could take care of it with >>either a 9v battery or a simple power supply. This would plug into the >>pc headphone jack and the fm transmitter would plug into it. > > > I seem to recall that most headphones are around 32 Ohms impedance. I > can't remember where I read that though, and that's sort of assuming > that the laptop manufacturers are actually designing for average > headphones. > > Josh -- http://www.piclist.com PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist