Originally Posted by VinnieD
How limiting is the 5v source? I don't know to be honest. They are using OP Amps somehow to amplify the signal before it reaches the TI headphone amp. What this does exactly I'm not sure. I can tell you the card will play my HD595s so loudly I could use them as speakers or blow them out.
I just looked at the datasheet for the TPA6120A2 and something makes me scratch my head. The TPA6120A2 requires a minimum of a 10v(-5,+5) supply. PCI is 5V and PCIe is 3.3 volts.
So I went and looked at this page
for the PCI pin specification. It has a +12v and a -12v. Then I went and looked a the PCIe spec. It has two 12 volt pins as well. PCI also has 5 and 3.3 volt pins, whereas PCIe does not have 5 volt pins.
Assuming the 12 volt pins are not used, this would explain why the Asus needs an external power connector. The Halo could use two 5 volt pins whereas the Asus is stuck with two 3.3 volt pins. But then I have to ask the question, if the 12 volt pins are there in the spec, why does it seem like nobody ever uses them?
Regardless of my rambings, the TPA6120A2 requires a 10 volt supply to work. Unless this statement by TI is false, any sound card using this chip, in a minimum supply voltage design, is within 4 volts of the 14 volt VHP-2.Vinnie
-To answer your original question, all this voltage stuff is just speculation and curiosity on my part. It's also more of an issue with high impedance phones rather than your HD595. I've tried to find an engineering answer as to what is voltage is required for high impedance headphones during very dynamic music with large voltage swings, but have never got a definitive answer.
Unless there is something wrong with the implementation of the Halo, I doubt 5v, 10v, 12v, 24v, is going to make any difference to low impedance headphones.