[jinschoi]

I would like to explore suitable battery power options for portable headphone amps, relying on AAs. I threw together a boost converter using a MAX761 to provide 12V from four AAs to power a Cmoy amp. It works, but I can hear some high frequency switching noise when driving low impedance ear buds. I can't hear any noise with Sennheiser HD-650s (why?). I used a 33 uH inductor and 100 uF output capacitors in parallel with a .1uF ceramic capacitor for noise rejection. The Cmoy has 220 uF input capacitors as well.

Are there any battery voltage boost solutions that would be suitable for quality audio circuits? Would it be possible to condition the output of a switching boost converter enough to reduce the ripple to inaudible levels?

Two other possibilities come to mind: charge pumps, which from my brief investigation seem to be used more for space considerations than line quality, and maybe some sort of battery-powered inverter/transformer/rectifier/regulator circuit.

Just looking for some feedback, thanks.

 

[cobaltmute]

I about to use one for the first time, but some charge pumps can be used to double your + rail or you could use it to create a negative rail (which doubles your total voltage range) For example, I'm going to use this

 

[error401]

You'll probably need to post-regulate the boosted supply (though mind that most integrated regs don't reject high frequency very well) or add a multistage filter. Try adding a simple CRC (or CLC) filter to the output and see if that helps.

 

[jinschoi]

I can go to 220 uF or higher on the output cap. Would it help or hurt to go to 1uF from .1uF for the high frequency capacitor?

I think post-regulation is the right answer. What I'd want is a 12V to 12V regulator with good high frequency ripple rejection and low dropout voltage. Does any such thing exist?