The biggest challenge for us (FiiO) is to choose what kind of power for E12, below are some kinds of power:
1, 2 X 9V battery, it is used in most high end portable headphone amp, simple and the power voltage is high enough, and you can also buy rechargeable 9V battery to keep the cost,
but the problem is that you can not control the thickness, also, we don't want to make a FiiO SR71A, lol, should be something new.
2, one Li-on battery, the problem is the power supply will become very complex , you need to boost the voltage from 3.7V to 12- 20 V or even higher, and separate the single power to +/- power,
the whole power circuit will be very complex, and hard to control the hiss because you have to use DC/DC to boost the voltage or convert to negative,
There are one word, the simple the better in SQ, lol. maybe we should just a resistor inside the amp.
3, 3 or 4 li-on battery, the power voltage will be high enough ( but not as high as 2 9V batteries), and convert the single power to +/- power, this is used in some portable amp, but the problem is
that hard to control the charging circuit and make sure that each batteries is fully charged. of course, it is big challenge to FiiO but maybe other company can solve it, who know?
Consider we will sell to so many customers, it is not safe for us to use this power although it can control the size at the same time and make the power simple.
So, This time we decide to be the first company ( please share with us if you found any similar headphone amp use the same design ) who use 6 X AAA li-on battery , the only problem is you have
to charge the battery with a extra charger, but the good news is , we can control the thickness to 15mm, and make the power circuit very simple, not need any DC-DC , and will have very high
power supply , means +/- 10V(min) to +/- 12.6V( max), it will good for the SQ. I don't find any portable amp use such high power supply voltage.