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OPA1612: Using as headphone driver

David D
Prodigy 230 points
Part Number: OPA1612
Other Parts Discussed in Thread: OPA1622, OPA1688

Hello,

I am considering the OPA1612 as a headphone driver replacement for JRC2114.

In note slyt630.pdf (sorry, pasting the address makes a huge link) you use a ~50 ohm isolation resistor.  Is this necessary when using the 1612 as a headphone driver? The headphone output section of my DAC has a 220R in series with the output.  Should I leave it as is or is it a good idea to bridge it?  I would like to be able to drive any impedance headphones.

Thanks!

David

  • 0
    TI__Genius 12345 points

    A 220R series resistor is fine for the output, it doesn't need to be reduced to 50 ohms. The purpose of this resistor is to isolate the capacitance of the headphones (from the cable) from the amplifier output to maintain stability. 

    The OPA1622 was designed to be stable into headphones without any series resistance and will deliver significantly more power into headphones (and at lower distortion) than an OPA1612. OPA1688 will also deliver more output power than the OPA1612 if price is a concern in the system.