I discussed this issue via email with one of the HiJack designers. I’d be delighted if he jumps in, but I won’t post names without his permission.
His suspicion was that some change in the iPad’s hardware or software (perhaps as a result of the concern over hearing loss from ear buds?) might have lowered the power output so much that HiJack does’t get enough power on some devices. Checking this, the voltage drop across VCC to GND was the expected 2.75V on my iPhone 4, but only 0.87V on my iPad 3.
(Of course, I did turn the sound volume all the way up. That’s necessary to get the most power through the headphone. Be sure and try that first!)
I asked if I could supply power externally, and was told that might work, but I was strongly cautioned not to exceed the 2.75V design limit for the voltage. I used a couple of resistors to drop the voltage from 2 AA batteries to 2.7V and applied this across VCC-GND in a potentiometer based circuit. Success!
Here’s a photo:
So, it appears that many of the problems may be related to lack of power. Supplying external power to the circuit corrects the issue–but I have not exceeded 2.75V, and again, was sternly cautioned not to go much above this.
Please share your experiences, I’d like to hear if other people have success, too.