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| Thanks every1 for the help, apparently bad/complicated idea. |
not a bad idea at all,a good thread.
Complicated ? Can be if you are trying to get beyong just powering the device from the buss to creating something that sounds as good as a non USB-buss powered amp.
You can get there by using a "slow" op-amp with a DC-DC converter but that converter needs to be good at audio frequencies,needs proper decoupling plus would be best served by having a shunt reg following it or you can use one of the new single supply low power op-amps,easily sounding as good as a better chip done with an improper power source,or if all you need is current drive for low impedance cans one of the drivers that operate down in the low voltage region.
comes down to what you need to drive and then you look at what voltages you have available.If a single +5VDC meant for driving voltage hungry headphones you are limiting yourself if you try to split it into two voltages unless you increase the voltage so it is better to go with a singe polarity op-amp or the DC converter.You may get volume but no way you get any headroom for peaks so you kill the dynamics or you use the "trick" of Fake Dynamics which is an improperly filtered DC-DC converter tossing artifacts into the sound that when the amp runs out out headroom sounds like upper octave detail hence the appearance the music is "exciting" so considered dynamic.
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| i mean, headroom bitheads are USB powered amps AND dacs |
DACs are another audio device that respond well to "feeding" but being already low voltage devices having their own internal single polarity CMOS Op-amp stages I sometimes wonder if it wouldn't just be better to tap the signal at the DAC output itself and couple it directly to the output jacks through a DC blocking cap and call it a day rather than screw around adding ANOTHER op-amp (op-amp to op-amp) unless you need the current drive and then why not shoot right to a low power buffer ? If you need more voltage then yes,you are stuck with it but if not then just another useless addition mucking things up.
I have zero clue what Headroom uses or how they go about it but would be very surprised if the buss powered portables sounded as good as the battery operated versions.
if there are other ways to get from A-to-B I don't think I know them and would be REAL intersted in someone explaining the "this is how you do it rick" part
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| Otherwise, the schematic from the hpdac is online so you can copy the dc-dc converter from there. PCB layout is important to keeping it stable, however. |
anything that operates in the Mhz range (digital,DC Converters,High Speed Analog) is a pain in the ass because you are no longer dealing with audio frequencies but RF so to get up to speed better reading material would be antenna theory and radio theory not audio primers and definately NOT the manufacturer data sheets which are mostly meant to tell a manufacturer using the parts how to best save a buck rather than how best to do it......
