Headphone Amp | OpAMP mods

Headphone Amp

The Home Theater HD 7.1 marks the second X-fi equipped soundcard from Auzentech to sport a discrete component based headphones amplifier.  Other cards that features headphone amplifier usually have a chip cased solution. Auzentechs audio team designed a proprietary amplification circuit.

This amplifier circuit puts out about 100mw per channel, giving it enough power to handle everything from your generic mp3 player headphone to high needs audiophile grade headphones.   Let have a look at this circuit:

On the right hand side we see the JRC4580 signal buffer; to the left we see the two lines of 4 transistors.  There are various types of configurations for amplifiers.  Class A, Class B, AB, Class D.  These transistors for the power amplifier section are utilized in a class AB configuration which offers a more linear signal response over normal Class B amplifiers and is more efficient the normal class A.

Modification Options

Opamps - The front opamp can be changed out for a new model of higher quality or a unit more to the end users personal preference.  There are many units you can test out; we will suggest a few that will work well within the existing circuit.  The stock opamp is the LME49720NA and is similar in the LM4562NA. 

We are always building new custom opamps to test in the Guru3D audio lab, one of our favorite new test models is the dual LME49710HA module.  Many would consider this unit one of the best in the LM/LME series of opamps.  Based on testing in this card, it tightens up the lower bass and widens the forward soundstage.

You could also use a higher quality LME49720 model such as the LME49720HA which is the metal can TO-99 version of the chip.

We would also suggest swapping out the 4580s for a unit of higher quality such as LME49720MA SOIC8 surface mount opamps.