The Objective2 (O2) Headphone Amp DIY Project

[richardpp]

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!

[wuffer]

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??

[MrSlim]

Originally Posted by diyhifishop

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.

[MrSlim]

Originally Posted by wuffer

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..

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

[MrSlim]

Originally Posted by richardpp

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.

[wuffer]

Originally Posted by MrSlim

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

[jcx]

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)

[dewasiuk]

Originally Posted by diyhifishop

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?

[MrSlim]

Originally Posted by dewasiuk

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..

[richardpp]

Originally Posted by MrSlim

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?