[Falconetti]

  The Essence STX will perform just as well as any of the amps and DACs mentioned in their thread with the HD600 and HD650. Stereophile tested the original STX with loads of 300 and 600 ohms (the Senns are 300 ohms) and it measures excellently. Everything is well below audible.
 
It has several issues, but none of them mean much with these headphones:

1. Output impedance is 10 ohms, but this is no issue at all with the 300 ohm Senns. It can cause problems with headphones that have impedances of about 80 ohms or lower, however.
2. Volume control is digital, which will lower the SNR as you turn it down. This is only problem with sensitive headphones, however; the card's SNR is high enough to be inaudible with the Senns at any reasonable volume setting. It also offers 3 analog gain settings to choose from; low or medium gains will be plenty and will minimize the amount of digital volume control you need to use.

 
The biggest one, that's not mitigated by the headphones, is its lack of portability. If this is a concern, then obviously you shouldn't be looking at internal cards

 
I used the card with my LCD-2 for three years. Low impedance headphones, not ideal, but no audible difference between it and the O2 (or, by extension, any other transparent amp or DAC). The HD600/650 are a better match to begin with.
 
The Magni/Modi and O2/ODAC are excellent options as well if you plan on taking the amp/DAC somewhere, using it with other sources, or low impedance headphones. But if the sound card works in your situation, it'll work just as well. Don't let everyone scare you.
 
Oh yeah, another negative and the reason I got the O2: As an internal soundcard, it lacks #swag
 

 
Stop ruining it for me 

Im about to pull the trigger on a NFB-11, and you say there is no audible difference paired with high impedence headphones

 

 

[lucassaint]

Is the NFB-11 better than O2 + ODAC?

 

[jodgey4]

The NFB-11 has more digital inputs, no analog inputs, but plenty of power... I couldn't say much beyond that. They are both detailed and neutral and versatile. It really comes down to budget and inputs at that point.

 

[SSSN]

  I used the card with my LCD-2 for three years. Low impedance headphones, not ideal, but no audible difference between it and the O2 (or, by extension, any other transparent amp or DAC).

That's mainly because the LCD-2 are planar magnetic headphones and these are unaffected by output impedance mismatches, AFAIK

 

[lucassaint]

No analog inputs? Is it important to have?

 

[PurpleAngel]

No analog inputs? Is it important to have?

 
I'm guessing people who buy the NFB-11/NFB-15 buy them for their USB, optical; coaxial digital audio inputs and great DAC.
So an analog input would just bypass those nice DAC setups.
Audio-GD does offer DAC/Amps that also come with analog inputs (Audio-GD Compass 2), but your paying more money ($400-$500).

 

[lucassaint]

NFB-11 is at $355. Hmmm Compass 2 is 100 more.

 

[lucassaint]

confused now. any point to go for the Compass 2 instead of NFB-11? please help me out. thanks.

 

[jodgey4]

The Compass 2 should sound darn near the exact same, except the analog inputs might be nice to have if you wanna hook up another DAC or analog source like a turntable. Plus, you can swap DAC chips if you really want to.

 

[lucassaint]

does Compass-2 contain all the 3 chips or default just with Sabre and rest needs to purchase separately? Is paying another $100 worth it?

 

[PurpleAngel]

  does Compass-2 contain all the 3 chips or default just with Sabre and rest needs to purchase separately? Is paying another $100 worth it?

 
I would say to get the cheaper NFB-11.
If down the line you find you have a need for an analog input on an amplifier, you should be able to find a decent headphone amplifier for $100.
Like a new Schiit Magni or a used Objective 2.

 

[jodgey4]

The chips are bought separately. I'd only pay extra if you have need for analog inputs.

 

[lucassaint]

thinking of getting O2 + ODAC at around $279 (exclude shipping). Have to pay like $400 (include shipping) for NFB-11. hmm... will i regret if i get O2+ODAC from JDS? how long do they ship?

 

[jodgey4]

They probably sound pretty similar (especially for the differences in price) if you don't need the extra inputs and power. Just buy the one that suits your input desires, and call it good . Either one should ship pretty quick, and you can always look used for either item.

 

[jazzwave]

Bottlehead crack with small upgrade (tube and caps) is soulmate for HD600. Put DAC (Audio-GD or Resonessence Labs) in between....you will able to listen angel sing..