[willmax]

Hi everyone, since I got my ODAC a month or so ago, I'm finding that I don't really need to use an amp anymore to get the volume that I want from my headphones, actually I have to turn the volume down a lot of times. I know that all my current headphones are low impedance - Grados and Denons - but still my initial impression was that to get the best out of my listening experience I was going to need to amp the signal from my ODAC, however I'm quite satisfied with the quality and volume of the ODAC output for my current circumstance. 
That poses the question - Do I really need an amp with the ODAC?
 
For instance when I have the computer volume maxed out I can listen to Foobar at around 10 o'clock and it is plenty, and if I put Foobar volume beyond 12 it is too much. Let me know if anyone has had a similar experience and whether I should still try to use a amp or not.
 
Thanks.

 

[NiceCans]

OK, so it is loud enough . . . . but perhaps the question you should be asking is: how is the tonality, are you getting all the source and the headphone have to offer?

 

[MomijiTMO]

Someone is losing bits......

 

[proton007]

You really need an amp with a DAC.
The output of a DAC is line out, which means its pretty high output impedance, and fixed in Voltage. While it may work for *some* very high impedance headphones, most will suffer some problems depending on their frequency-impedance relationship. You plug in a low impedance source, something like 22 or 32 ohms, and you have a setup that won't supply enough power because your DAC becomes the limiting factor.

 

[mikeaj]

First of all, make sure you're using 24-bit output.
 
An amp is recommended because the device isn't designed or intended to be driving headphones directly, so it probably doesn't do such a good job at it.  You can think of it as the wrong tool for the job.
 
However, publicly-available information on the Sabre ES9023 DAC+op amp driver chip used is scant.  Maybe it has some secret superpowers (yeah right).  I'd suspect that the sound quality would rapidly deteriorate if you cranked the volume up higher, but it's not so surprising with those headphones that the sound may seem to be okay at lower levels.

 

[tzjin]

Does the ODAC have an analog pot inside of it like the Dragonfly does?
 
Echoing the comments above. I would not recommend using the lineout of the ODAC with headphones directly.

 

[proton007]

No, the ODAC is fixed line level.

 

[tzjin]

Then how exactly does it make an amp redundant? You still require one to use the ODAC.

The OP says it increases volume to the point where it becomes too loud, but an amplifier's main function isn't just volume boost; it is to provide the power needed to drive less efficient headphones.

 

[Kayk]

When used with active speakers and an active sub, a standalone amp is not necessary.

 

[sachu]

what's a ODAC??..OOO....DAC!?

 

[tzjin]

The ObjectiveDAC (ODAC) is a budget DAC that supposedly measure the same as one many times its price. It's a bit controversial, though most agree it is very good for its price.
 
 
Quote:

When used with active speakers and an active sub, a standalone amp is not necessary.

 
That is correct. Not sure what your point is though?

 

[Radio_head]

Quote:

what's a ODAC??..OOO....DAC!?

 

[willmax]

Quote:

OK, so it is loud enough . . . . but perhaps the question you should be asking is: how is the tonality, are you getting all the source and the headphone have to offer?

Ok I get it that the amp will give me better tonality and improve sound quality, however what I'm saying is that when the master volume from the computer is maxed out - in order to get the full bit rate from the ODAC - the sound coming out of my low impedance headphones is already too loud leaving no room for volume control when I connect the ODAC to an amp like the O2 for instance at standard 2.5 gain.
Quote:

You really need an amp with a DAC.
The output of a DAC is line out, which means its pretty high output impedance, and fixed in Voltage. While it may work for *some* very high impedance headphones, most will suffer some problems depending on their frequency-impedance relationship. You plug in a low impedance source, something like 22 or 32 ohms, and you have a setup that won't supply enough power because your DAC becomes the limiting factor.

I thought it would work better with a lower impedance headphone as opposed with a higher impedance one, isn't that the case?
Quote:

Then how exactly does it make an amp redundant? You still require one to use the ODAC.

The OP says it increases volume to the point where it becomes too loud, but an amplifier's main function isn't just volume boost; it is to provide the power needed to drive less efficient headphones.

That is my point, my headphones have very low impedance therefore very easy to drive.

 

[proton007]

Well, not really. Its not about the impedance alone. For the same power, a low impedance setup will require higher current, which your DAC may not have, as its not an ideal voltage source. Its limited in power because of the USB port.
Secondly, its just not an efficient setup from an electrical point of view. Your DAC and headphone impedances are so close (10 Ohms vs 30 Ohms) that the DAC is limiting the amount of potential drop that can occur at the headphone, thus reducing the power transfer to the headphones.
In case of portable use, with iPod and such, it works because batteries have lower potential but can produce a higher current to compensate. Still, the output impedance is not as high, its something in 2-5 Ohms range.
Also, you have damping considerations when dealing with impedances this close. While being a power dissipation device, a headphone is also an EMF generator. This reverse current needs to be dealt with, and having the lowest impedance possible on the source/amp side helps in creating a low resistance path for the current to flow back.
Plus, impedance itself is a complex variable, consisting of resistance and reactance. This affects the phase relationship between AC voltage and current, and so, the actual power used by the circuit will be different(higher) than a simple V.I product.
 
Quote:

I thought it would work better with a lower impedance headphone as opposed with a higher impedance one, isn't that the case?

 

[tzjin]

Quote:

That is my point, my headphones have very low impedance therefore very easy to drive.

 
Yes, but at the same time the ODAC allows you to get a more accurate signal than what your computer's DAC can produce.
 
Back to your original question. Yes you probably want to use an amplifier with the ODAC because headphones aren't optimized for line-level output.