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Old 24th October 2011, 12:19 PM   #551
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Pardon if I'm dropping in, I’d like to parallel two separate O2 amps to the headphone output jack of my bus-powered DAC and attempt to have each amp drive a set of high impedance (600 ohm) low sensitivity (88 db SPL at 1mW) headphones. Will it work? Gain, power, impedance, where do I start? I guess it’ll either be loud enough or - it won’t!
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Old 24th October 2011, 01:56 PM   #552
wuffer is offline wuffer  Denmark
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Im going to order parts at mouser next month, but is there a shared bom i can use at mouser so i dont have to type every part in??

And what about upgrading parts instead of stock parts??
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Old 24th October 2011, 03:30 PM   #553
MrSlim is offline MrSlim  Canada
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Quote:
Originally Posted by diyhifishop View Post
Agree with this:If you are genuinely interested in the O2 as a DIY project, then it's up to you to set the output level of your source correctly or in lieu of being able to do so, then set the input gain of the O2 correctly
Dumbears isn't talking about input levels, he's talking about using a higher power supply voltage.
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Old 24th October 2011, 03:55 PM   #554
MrSlim is offline MrSlim  Canada
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Quote:
Originally Posted by wuffer View Post
Im going to order parts at mouser next month, but is there a shared bom i can use at mouser so i dont have to type every part in??
If you download the BOM from NwAvGuy's(RocketScientist) website, you can copy the parts list and upload it to Mouser with their Import BOM tool that's under the Services & Tools Tab. No typing required..

Quote:
And what about upgrading parts instead of stock parts??
What parts do you want to upgrade? It's unlikely to buy you anything, and NwAvGuy has already explained why he chose the Opamps that he did, and has been very thorough in his testing and design.

See BionicSniper's opinion here: O2 Headphone Amplifier GB

Last edited by MrSlim; 24th October 2011 at 04:09 PM.
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Old 24th October 2011, 04:03 PM   #555
MrSlim is offline MrSlim  Canada
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Quote:
Originally Posted by richardpp View Post
Pardon if I'm dropping in, I’d like to parallel two separate O2 amps to the headphone output jack of my bus-powered DAC and attempt to have each amp drive a set of high impedance (600 ohm) low sensitivity (88 db SPL at 1mW) headphones. Will it work? Gain, power, impedance, where do I start? I guess it’ll either be loud enough or - it won’t!
This has been discussed earlier in the thread(sorry you'll have to dig for it).
The headphones you are talking about are outside the operating parameters of the O2 and trying to do what you want to do is unlikely to work very well.

You'll need something more powerful, like the previously mentioned "The Wire" or the Twisted Pear Ventus (unfortunately out of stock at this time) which both use the LME49600 buffer.
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Old 24th October 2011, 05:02 PM   #556
wuffer is offline wuffer  Denmark
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Quote:
Originally Posted by MrSlim View Post
If you download the BOM from NwAvGuy's(RocketScientist) website, you can copy the parts list and upload it to Mouser with their Import BOM tool that's under the Services & Tools Tab. No typing required..



What parts do you want to upgrade? It's unlikely to buy you anything, and NwAvGuy has already explained why he chose the Opamps that he did, and has been very thorough in his testing and design.

See BionicSniper's opinion here: O2 Headphone Amplifier GB
Thanks i have missed that.
Just better caps and non magnetic resistors
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Old 24th October 2011, 05:18 PM   #557
jcx is offline jcx  United States
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if you have symmetric V drive, balanced source then the 2 channels of one amp could be bridged for 600 Ohm cans, 2 amps to drive one headphone, requires custom cabling

2 @ 600 Ohms in parallel would only look like a 300 Ohm load, bridging doubles current demand again - so 150 Ohm equivalent load - still fine for O2

you will always get some sound, the question is how much

with bridged operation you would be able to go over 100 dB into 600 Ohm, 88 dB re 1 mW

not "Rock Out" or "Audiophile" levels - but adequate for listening at levels safe for all day use (80 dB ave, very few recordings have 20+ dB peak-to-ave)

Last edited by jcx; 24th October 2011 at 05:31 PM.
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Old 24th October 2011, 08:25 PM   #558
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Quote:
Originally Posted by diyhifishop View Post
Agree with this:If you are genuinely interested in the O2 as a DIY project, then it's up to you to set the output level of your source correctly or in lieu of being able to do so, then set the input gain of the O2 correctly
Just curious, what would be a "correct" output level of the source?
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Old 24th October 2011, 08:43 PM   #559
MrSlim is offline MrSlim  Canada
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Quote:
Originally Posted by dewasiuk View Post
Just curious, what would be a "correct" output level of the source?
under 2.0V, which is generally what most sources output..

Actually, his comment is out of context I think, since the discussion at the time was about power supply voltages, not source voltages..
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Old 25th October 2011, 01:58 AM   #560
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Quote:
Originally Posted by MrSlim View Post
This has been discussed earlier in the thread(sorry you'll have to dig for it).
The headphones you are talking about are outside the operating parameters of the O2 and trying to do what you want to do is unlikely to work very well.

You'll need something more powerful, like the previously mentioned "The Wire" or the Twisted Pear Ventus (unfortunately out of stock at this time) which both use the LME49600 buffer.
I appreciate the alternative suggestions. I’ll look into them.

Yes, mention of this was made in post #135 along the lines of duplicating everything after the input stage or, more simply - and reluctantly, (without independent volume control), using parallel output jacks from a single O2 with maybe an NE5532 in the gain stage to handle the extra load.

After reading this forum as well as NwAvGuy’s blog articles, I didn’t really pick up that these headphones would be incompatible with the O2, in fact I rather thought the opposite. Although I was kind of wary given my headphone’s atypical specs and I do have quite limited understanding of these things. Would you mind explaining a little more how you’ve determined this?
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