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O2 AMP + ODAC - Page 178

post #2656 of 3572

Flat impedance line means only as much as no strange FR humps resulting from low damping factor/high amp output imedance. With dynamic headphones that usually have some sorts of impedance peaks you get a boost, or a null if the amp is running out of voltage headroom.  Driver resonance is a whole other matter (by this I mean resonances of the membrane itself, not the suspension).


Edited by MaciekN - 4/18/14 at 3:01am
post #2657 of 3572
Quote:
Originally Posted by SilverEars View Post
 

Well if you look at a resonance on an impedance vs frequency graph, it's the point where impedance is the lowest.  If the impedance is low everywhere, the damping is still low at any frequency.  If the there is only resonance dip at certain frequency, that means at certain frequency it is not damped well.  This makes sense to me, I still don't get how orthos explanation logically go with that example.


Resonance frequency is assumed to be the frequency at which impedance is at it's HIGHEST and it does not usually correspond to driver break-up modes which are the peaks in the frequency response (not impedance).

 

Orthos work in a different way than dynamics, the coil is moving differently relative to magnets, that is why they are seen as a resistive load in contrast to reactive load presented by dynamic headphones. If you take a look at some pictures presenting internals of both types of headphones and read a bit how amp is actually damping the headphone you'll see wherein lies the difference.

 

Saying that "damping is low when impedance is low" is generally true, but please consider that if you have an output imedance of, say 1 Ohm, then you are fine damping-wise at 8 Ohms and up, and there are no headphones reaching 8 Ohms in their impedance. Thats speakers territory.

post #2658 of 3572
Quote:
Originally Posted by Xenophon View Post
 

No.  I own a HE-6.  Tried it at the time with O2/ODAC.  It most definitely, empathically does not  work for them.  I don't care what numbers get pulled out of hats but this I know for sure, it's plain and simple to anyone simply trying it.  Not even a question of volume, it sounds like fried crap.

What is the AC adapter you are using?
I heard that the 110v ones out there arent enough for high gain mode.

post #2659 of 3572
Quote:
Originally Posted by anthk View Post
 

What is the AC adapter you are using?
I heard that the 110v ones out there arent enough for high gain mode.

No, no....been there, tried that.  I'm on 220V and already tried a more powerful than stock adapter.  It's very simple:  while it might work ok with most headphones, the O2 is simply not the tool for cans like the HE-6.  In high gain even with cans like the HE-500 you push it into clipping, btw.  This is one of the issues that adgr's setup addresses.

 

But it's not an issue to me, I use it in standard gain, low/mid volume in my office setup and am happy enough with it.  Though I have to say I'm more impressed with the DAC than the amp part.

post #2660 of 3572

If you like agdr booster board's then take a look at his ODA V2 that he just got working at DIY.

 

More power.

 

A.

post #2661 of 3572
Just a message to let you guys know that whilst I only understand half of what you speak, nonetheless this is a fascinating thread.

Kudos to the engineers of this world.

smily_headphones1.gifsmily_headphones1.gifsmily_headphones1.gif
post #2662 of 3572

I replaced the op-amps in the O2 a few days ago with the OPA2227. Expected it to sound mostly the same, but I don't think I like it.

It actually now sounds too warm, almost muddy sounding with my HD-650 and DJ100. The OPA2134 I seem to love (in my other amps) and I should have went with that.

Seems impossible. It's actually hard to believe this is an O2.

 

I will instead try the LM4652 and see how that goes. OPA627 sounded like a fun experiment, but too much trouble and they cost way too much.

 

I guess there must be a reason why most amps use the OPA2134 instead of the 2227. Don't think it has to do with price..

 

I don't use the O2 much and kind of wanted to try some things to make it sound very slightly different with my Q701.

post #2663 of 3572
Quote:
Originally Posted by Xenophon View Post
 

No.  I own a HE-6.  Tried it at the time with O2/ODAC.  It most definitely, empathically does not  work for them.  I don't care what numbers get pulled out of hats but this I know for sure, it's plain and simple to anyone simply trying it.  Not even a question of volume, it sounds like fried crap.


Not to be challenging you in a hostile way or anything, I am simply curious and I hope someone could shred some light on this problem. You see, theoretically, there should be sufficient power for the headphone. Yet, you find the power lacking.
What might be the possible reasons behind this discrepancy ?

post #2664 of 3572
Quote:
Originally Posted by Xenophon View Post
 

No.  I own a HE-6.  Tried it at the time with O2/ODAC.  It most definitely, empathically does not  work for them.  I don't care what numbers get pulled out of hats but this I know for sure, it's plain and simple to anyone simply trying it.  Not even a question of volume, it sounds like fried crap.

I agree. I tried ODAC\O2 with Hifiman HE-4... Well, the bass was weak, the sound was lifeless, constrained and harsh in treble region (though super detailed). Actually, even if the amp can drive Hifiman HE-4\HE-6\LCD-2 to high volume levels it doesn't mean the amp drives them well. In case of O2 and most other amps there might be power supply and current limitations. According to russian audiophile community Doctorhead, Beta 22 is a different story - dynamic, smooth in treble, punchy, spacious! It's no surprise - serious power supply does its job well. Beta 22 really helps to get the best out of HE-4\HE-6\LCD-2 and any other HPs. Using speaker amps to drive power-hungry headphones doesn't give the same performance as Beta 22 (speaker amps are designed to work optimally with very low impedance - 4-8 Ohms) but it's still better for orthos than typical HP amps. 

 

To sum up, O2 is a nice little amp for the price. But using it with orthos - please, no. :)

post #2665 of 3572
Gigart - if you haven't heard it with fostex, ADs etc, you're really not in a position to judge orthos across the board. Recall that the O2 was, for a very long time, LFF's (creator of the paradox etc.) amp of choice for his orthos. He recommended it frequently for fostex drivers and many of us enjoy the combo.

Audeze and Hifiman are hardly the only game in town. I'd wager fostex has sold 100x as many orthos as the boutique brands combined.
post #2666 of 3572

Sure, I forgot about T50RPs - they are significantly easier to drive. But I decided to try Fostex TH600 with my ODAC\O2. O2 is more than enough for TH600. Though LFF Paradox will be my next HP if I won't like TH600.

post #2667 of 3572
Quote:
Originally Posted by GigArt View Post
 

Sure, I forgot about T50RPs - they are significantly easier to drive. But I decided to try Fostex TH600 with my ODAC\O2. O2 is more than enough for TH600. Though LFF Paradox will be my next HP if I won't like TH600.

 

 

Cool.  I'd be curious to read about your take on the combo with the th600's once you have them on hand.  I have yet to hear a paradox, but LFF's ears are pretty darn golden, and I have no doubt they sound great.  Several of his past off the cuff recommendations as to well recorded music have become favorites in my collection.  

 

Quote:

Originally Posted by adydula View Post
 

If you like agdr booster board's then take a look at his ODA V2 that he just got working at DIY.

 

More power.

 

A.

 

Definitely on my short list along with trying my hand at a pupdac!  Given how much I like agdr's booster, I can only imagine how good the high powered version might be.  I have to finish my wire se-se off first though and figure out how the hell one actually wires up a case - the only thing building kits and pocket amps simply doesn't prepare you for.  Then building an ODA to compare to the Wire sounds like a lot of fun. 

post #2668 of 3572
Quote:
Originally Posted by anthk View Post
 


Not to be challenging you in a hostile way or anything, I am simply curious and I hope someone could shred some light on this problem. You see, theoretically, there should be sufficient power for the headphone. Yet, you find the power lacking.
What might be the possible reasons behind this discrepancy ?

You run into voltage/current limitations of the design at the HE-6's impedance, given its 83.5 dB sensitivity.  See the 'more power?' article on the designer's blog which gives a good overview, in particular, take a look at the output graphs listing Vmax and current at 1% THD+N into various impedances.  Simply put:  you'll drive it into clipping at anything approaching normal levels, even when not taking into account headroom or dynamic music etc.  This is assuming that there's no more current limitations at 50 Ohm loads (at 33 Ohm it's limited to 4.5V/613 mW).

 

Nothing against the O2 (been getting some hate mail from people who seem to think I have something against the design which, for the record, is not the case) but it's not the right tool for the HE-6.

post #2669 of 3572

The O2 drives the LCD2's with AUTHORITY.

 

This means with clarity, loud, soft, anywhere in between.

 

Totally in command.

 

For anyone that's interested in an ODA check out www.agdraudio.com

 

You can get one all built and tested.

 

The parts with a case and AC adapter costs $250+ easily and you do all the work.

 

A fully assembled one tested will cost a bit more....more than ample power to drive most anything.

 

A.

 

oh...NOTE: the O2 was not meant to drive HE6's.....its one of those 2% cans that are well....just hard to drive due to their inefficiency.

post #2670 of 3572

Too bad it's not good with the HD800 from what i read here, i wanted a budget rig if i ever get the HD800 in the future,it would have been perfect:frown: 

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