I built a rough test version of the above circuit, it is intended as a bridged (i.e 'balanced') unity gain buffer for headphones. The test circuit seems to work, as in there is sound and it is not blatantly distorted .
The op amp outputs in the circuits are from the balanced XLR output from my DAC, therefore the op amp circuit is internal to the DAC and can not be modified, it's just there for clarity.
If possible my aim is to have distortion no worse than a typical emitter follower (e.g single supply, ac coupled, dc biased) with this circuit, but with a reduced number of parts.
Would this behave like a typical emitter follower or is there any obvious issue?
There are 2 things I'm most interested to know and will be do my best to describe them:
1. The load 'floats' between the 2 outputs it seems, how does the NPN handle negative voltage swings from the op amp?
For example, If the negative side of the load (300 ohm headphone) were connected to -12V supply instead of the output of the negative half as it's shown in circuit then the NPN would be able to source current even during negative voltage swings on the op amp output. So what happens during negative swing when it is connected 'floating' between the negative and postive halves? can the NPN still source current during negative voltage swings from the op amp?
2. The -12V supply is treated as ground for the NPNs, this means Re is connected to the output of the negative voltage regulator, does this matter?
Would it be better/worse to instead connect Re before the regulator, to the negative output of bridge rectifier? This would resemble a more 'normal' single ended supply for the NPN... you would never see a negative regulator on ground for a single supply.
To be clear I am not looking for a 'better' alternative to this circuit, I want to know the problems with this circuit and, if they exist, solutions. If problems exist without solutions then my alternative will simply be to build the standard single supply, AC coupled emitter follower