89 dB/mW, which presents a rather tough job for most regular headphone amplifiers. 5V won't cut it.
Your average onboard audio out will deliver about 1 Vrms max, often with some extra series resistance, so yes, you should be just fine there. (You can also measure output levels with a mini to mini cable and at least half-decent multimeter that has a low-level Vac range. Doesn't need to be a TrueRMS job, just stick with 50-60 Hz otherwise. If you have a splitter cable, you can also do loaded measurements to determine output impedance, preferably at 1 kHz though. With Windows versions from Vista onwards, you can also get relative level readings in dB, though the function is well-hidden: Go to output device properties, Level tab, and right-click in some level display field. Note that WASAPI output in exclusive mode may be required for maximum output levels, else they may stay 3 dB short.)
As luck would have it, there are InnerFidelity measurements for both your cans. Or at least memory claims that the Koss Tony Bennett was a celebrity version of the DJ100. 39 ohms, 50 mV for 90 dB --> easy as pie. Ye olde K240 Sextett needs a whopping 893 mV for 90 dB, but at least it won't be pushing any current limits at 630 ohms.
If the output from 5 V alone won't cut it, you could still use a chip with integrated charge pump negative power supply, à la TI TPA6130. The FiiO E11 gets up to about 2.75 V out of what's probably an internal 5V supply this way.
What exactly you need will depend on your level requirements. I'd probably be fine with the 800 mV of a Clip+ even with the 600 ohm oldie most of the time, though Ravel's Bolero may be pushing it. That being said, I'm not a loud listener in general, with average levels at home often ending up in 55-60 dB SPL territory, so peak levels of 80-85 dB would be fine.
As luck would have it, there are InnerFidelity measurements for both your cans. Or at least memory claims that the Koss Tony Bennett was a celebrity version of the DJ100. 39 ohms, 50 mV for 90 dB --> easy as pie. Ye olde K240 Sextett needs a whopping 893 mV for 90 dB, but at least it won't be pushing any current limits at 630 ohms.
If the output from 5 V alone won't cut it, you could still use a chip with integrated charge pump negative power supply, à la TI TPA6130. The FiiO E11 gets up to about 2.75 V out of what's probably an internal 5V supply this way.
What exactly you need will depend on your level requirements. I'd probably be fine with the 800 mV of a Clip+ even with the 600 ohm oldie most of the time, though Ravel's Bolero may be pushing it. That being said, I'm not a loud listener in general, with average levels at home often ending up in 55-60 dB SPL territory, so peak levels of 80-85 dB would be fine.
I built a small USB powered amp to boost the output from my iphone. 5V in to inverter which produces -8V and used a neg LDO to get -5V. I wanted to avoid coupling caps on input and output. Audio Tech AT-M35 are 65 ohms so peak currents are only 50mA or so.
http://www.diyaudio.com/forums/headphone-systems/249084-8-10v-5v-usb-power-converter.html
Hope this helps.
http://www.diyaudio.com/forums/headphone-systems/249084-8-10v-5v-usb-power-converter.html
Hope this helps.
Thanks for all the replies.
I found TDA2822 in my parts bin and few days ago finished putting a small headphone amplifier using this chip. Works fine on 5V though I have not tested it with the headphones yet. Just with some speakers I had laying around.
I also have parts for Starving Student amplifier on the way (that's not 5V, I know). So I think, I am all set for now.
I found TDA2822 in my parts bin and few days ago finished putting a small headphone amplifier using this chip. Works fine on 5V though I have not tested it with the headphones yet. Just with some speakers I had laying around.
I also have parts for Starving Student amplifier on the way (that's not 5V, I know). So I think, I am all set for now.
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