Well. . . . .
Typical headphones don't need that much current to drive them--typically ~10mA max unless you have an especially difficult pair of headphones. If you have a specific pair of headphones in mind that you want to drive, then it will be easier to make a suggestion. Remember too that headphones look like a capacitive load to the opamp, so that could frustrate the stability question. I glanced at the LME49713 data sheet, and I don't think stability should be a problem, but I simply don't know how this chip will behave.
Furthermore, since the LME49713 appears to only be available in SOIC-8 surface mount packages, then you would be hard pressed to build the amp without a DIP-8 adapter or a printed circuit board. Also, since this chip is a single opamp package, it won't be pin-compatible with either the LM4562 or the OPA2134 if you need to swap out the chip if stability problems arise.
All in all, I would stick with either the LM4562 or the OPA2134 since I know those chips work well for this application, and they are pin compatible with any DIP-8 parts.
If you want to get into surface mount parts, I would go straight to the TPA6120a, quite honestly. If you haven't looked at that chip, I would highly recommend you glance at its data sheet before using the LME49713. The power requirements are similar, and the 6120 is purpose built to drive headphones, so you shouldn't run into any unexpected issues. Also, there is pretty extensive documentation and example circuits that you can draw from.
Again, if you give us the headphones you are trying to drive, we may be able to make some better suggestions!
Typical headphones don't need that much current to drive them--typically ~10mA max unless you have an especially difficult pair of headphones. If you have a specific pair of headphones in mind that you want to drive, then it will be easier to make a suggestion. Remember too that headphones look like a capacitive load to the opamp, so that could frustrate the stability question. I glanced at the LME49713 data sheet, and I don't think stability should be a problem, but I simply don't know how this chip will behave.
Furthermore, since the LME49713 appears to only be available in SOIC-8 surface mount packages, then you would be hard pressed to build the amp without a DIP-8 adapter or a printed circuit board. Also, since this chip is a single opamp package, it won't be pin-compatible with either the LM4562 or the OPA2134 if you need to swap out the chip if stability problems arise.
All in all, I would stick with either the LM4562 or the OPA2134 since I know those chips work well for this application, and they are pin compatible with any DIP-8 parts.
If you want to get into surface mount parts, I would go straight to the TPA6120a, quite honestly. If you haven't looked at that chip, I would highly recommend you glance at its data sheet before using the LME49713. The power requirements are similar, and the 6120 is purpose built to drive headphones, so you shouldn't run into any unexpected issues. Also, there is pretty extensive documentation and example circuits that you can draw from.
Again, if you give us the headphones you are trying to drive, we may be able to make some better suggestions!
Quickly looking over the specs for those, it appears as though the Senn's are VERY efficient and have a pretty normal load at 70 ohms. The Grados also fall fall in the "normal" range, but they aren't nearly as efficient and have a lower impedance at 32 ohms. I was more concerned that you had a pair of Sennheiser HD650's (300 ohm load!) or something goofy like that.umut1001 said:
Both of the sets of headphones you mentioned should be fine with any of the options we have been discussing, even (I believe) the LME49713's if you put an output series resistor in the circuit.
As a reference point, I have a pair of Audio Technica ATH-A900's that are 40 ohm and are fairly efficient. I drive them with a TPA6120 and have never had any issues with the chip keeping up. The TPA6120 is rated at 80mW, but I doubt I ever get anywhere close to that!
Good luck!
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