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O2 AMP + ODAC - Page 23

post #331 of 3453
Quote:
Originally Posted by Smoke Signals View Post

Hmm, so it falls very short in delivering 1 W per channel, man I'm getting a lot of mixed message about the O2 + HE-500.  Some are saying the O2 won't power it and it gives poor dynamics and others are saying it works fine and delivers plenty of power.  This is pretty frustrating.


See my other post. Lets pretend you have headphone which can do 90 dB @ 1 mW. You have to double the power each time to gain another 3 dBs. By the time you apply a half a watt (500 mWs), you are theoretically hitting 117 dB. You should be in pain at that point, or otherwise unwilling to listen very long. At that point, 1 W is only taking you to 120 dB. 2Ws to 123 dB, and so on.

 

So, "falling very short of 1 W" is NOT a problem, unless your source is utterly "quiet" or has ridiculously high dynamic range. In that case, you will need a lot of power just to supply the peak bursts of sound that are there.

 

That said, even listening to Chopin, I don't need more than half a dial to experience the raging crescendos and baby-to-sleep key strokes. Trust me, I sweated the numbers myself. Then I got over it. The O2 provides a ton of power compared to the USB devices, you will have to spend a lot more to get to 1W and beyond.


Edited by MrMateoHead - 11/14/12 at 6:20pm
post #332 of 3453
Quote:
Originally Posted by MHOE View Post

 

Go to his blog, find "O2 summary" article and search for "LCD-2" or "Hifiman"...

 

O2 is powerful enough to drive LCD-2, HE-500 and even HE-6 (according to nwavguy). Especially if you use SIPs that allow you to change gain resistors to fit your needs better. Of course DO NOT USE BATTERIES FOR POWERING HERE...


In his article he only says "Hifiman planars", so I can't be certain he is including HE-500s in that.

 

Edit: Ok thanks Mrmateohead, that's some good info.


Edited by Smoke Signals - 11/14/12 at 6:25pm
post #333 of 3453
Quote:
Originally Posted by sling5s View Post

Quote:
Originally Posted by Smoke Signals View Post

Hmm, so it falls very short in delivering 1 W per channel, man I'm getting a lot of mixed message about the O2 + HE-500.  Some are saying the O2 won't power it and it gives poor dynamics and others are saying it works fine and delivers plenty of power.  This is pretty frustrating.

I think the mixed message comes from that: the O2 has enough power to give it all the volume you need.  But it does not have the power to give it the headroom and dynamics.

 

Of course it does. The mixed message is due to misunderstandings of how amplifiers work.  It delivers clean power, headroom, dynamics, soundstage, you name it.

post #334 of 3453

If you're using the ODAC its better because the ODAC itself provides 2V RMS. 

I use the combo with my HD650, and I don't even need to use the gain. 

post #335 of 3453
Quote:
Originally Posted by proton007 View Post

If you're using the ODAC its better because the ODAC itself provides 2V RMS. 

I use the combo with my HD650, and I don't even need to use the gain. 


Speaking of gain, new ODAC/O2 user here, what gain settings do people have?

Customer support of JDS Labs recommended the 2.5/1.0x gain settings for a K 701 if I want to listen to music at low levels. I did the modification myself and still have the resistors in case I need to change it.

post #336 of 3453
Quote:
Originally Posted by miceblue View Post


Speaking of gain, new ODAC/O2 user here, what gain settings do people have?

Customer support of JDS Labs recommended the 2.5/1.0x gain settings for a K 701 if I want to listen to music at low levels. I did the modification myself and still have the resistors in case I need to change it.

 

I made mine myself, I think I have the 1.0x and 10x. I used the sockets in order to change the resistors, but haven't really used the gain.

post #337 of 3453
Quote:
Originally Posted by miceblue View Post


Speaking of gain, new ODAC/O2 user here, what gain settings do people have?

Customer support of JDS Labs recommended the 2.5/1.0x gain settings for a K 701 if I want to listen to music at low levels. I did the modification myself and still have the resistors in case I need to change it.

 

Use SIPs, you can have whatever gain you want up to 12x... Enough for powering pretty much everything. You can change gain resistors anytime this way to let the amp work for you the best. But I would get WAU 16-400 transformer instead of WAU12-200 that is normally supplied by JDS Labs, especially for Hifimans, Audeze and other low impedance phones etc.

 

If you want more info about how to find out the most suitable gain, read author's blog... There are hints as well as mathematic formulas. If you do not want to calculate anything, I suggest "THE GAIN RESISTORS" section of O2 details article and/or All about gain article ("A rough guideline" section).


Edited by MHOE - 11/14/12 at 7:24pm
post #338 of 3453
Quote:
Originally Posted by miceblue View Post

Quote:
Originally Posted by proton007 View Post

If you're using the ODAC its better because the ODAC itself provides 2V RMS. 

I use the combo with my HD650, and I don't even need to use the gain. 


Speaking of gain, new ODAC/O2 user here, what gain settings do people have?

Customer support of JDS Labs recommended the 2.5/1.0x gain settings for a K 701 if I want to listen to music at low levels. I did the modification myself and still have the resistors in case I need to change it.

 

I have the standard 2.5/6.5 dB gain. If I bought another, I'd get the 1.0/2.5 dB option. I tend to listen at low volumes and 6.5 dB gain is WAY more than I need.

post #339 of 3453
Quote:
Originally Posted by miceblue View Post


Speaking of gain, new ODAC/O2 user here, what gain settings do people have?

Customer support of JDS Labs recommended the 2.5/1.0x gain settings for a K 701 if I want to listen to music at low levels. I did the modification myself and still have the resistors in case I need to change it.


I think those settings would work well. I am at 2.5x and 6.5x, but my understanding is that the amp shouldn't clip unless you feed it 2Vrms and crank it @ 6.5X gain. Can anyone confirm?

 

With more efficient headphones, 1X should be ideal. For less efficient phones like mine (94dB) the 2.5X is working great, though I could probably get by on 1X. I've only used 6.5X so far on a movie screening test, and in that case it was useful. Chances are, 1X - 2.5X is going to cover a very wide range of phones'. 10X sounds too high to me for practical purposes, but 6.5X is about right to cover all my "non music" needs.

post #340 of 3453
Quote:
Originally Posted by MrMateoHead View Post


I think those settings would work well. I am at 2.5x and 6.5x, but my understanding is that the amp shouldn't clip unless you feed it 2Vrms and crank it @ 6.5X gain. Can anyone confirm?

 

With more efficient headphones, 1X should be ideal. For less efficient phones like mine (94dB) the 2.5X is working great, though I could probably get by on 1X. I've only used 6.5X so far on a movie screening test, and in that case it was useful. Chances are, 1X - 2.5X is going to cover a very wide range of phones'. 10X sounds too high to me for practical purposes, but 6.5X is about right to cover all my "non music" needs.

 

It can possibly clip when using the amp on battery power under certain conditions... Not skilled enough technically to answer though. I think the best source for answering your question is the blog :-)

post #341 of 3453
Quote:
Originally Posted by MrMateoHead View Post


I think those settings would work well. I am at 2.5x and 6.5x, but my understanding is that the amp shouldn't clip unless you feed it 2Vrms and crank it @ 6.5X gain. Can anyone confirm?

 

With more efficient headphones, 1X should be ideal. For less efficient phones like mine (94dB) the 2.5X is working great, though I could probably get by on 1X. I've only used 6.5X so far on a movie screening test, and in that case it was useful. Chances are, 1X - 2.5X is going to cover a very wide range of phones'. 10X sounds too high to me for practical purposes, but 6.5X is about right to cover all my "non music" needs.

 

With 2V RMS I haven't felt the need to use the gain at all. I don't even max out the 1x. I think I'd kept 10x for sources that don't have a line out. Then I felt I should change it, but now I don't really use it anyways.

post #342 of 3453

Ah, mmk thanks for the feedback guys. :) I'm still new to the whole O2/ODAC objective stuff.

With the 2.5/1.0 gain option, I do notice a background hiss, or some high frequency noise with the 2.5 gain (while using an AC adaptor). Is this normal, because I recall seeing many people say that this amp has a very "black background" sort to speak?

post #343 of 3453
Quote:
Originally Posted by miceblue View Post

Ah, mmk thanks for the feedback guys. :) I'm still new to the whole O2/ODAC objective stuff.

With the 2.5/1.0 gain option, I do notice a background hiss, or some high frequency noise with the 2.5 gain (while using an AC adaptor). Is this normal, because I recall seeing many people say that this amp has a very "black background" sort to speak?


There shouldn't be any noise.

Is it present without the audio signal as well?

post #344 of 3453
Quote:
Originally Posted by proton007 View Post


There shouldn't be any noise.

Is it present without the audio signal as well?

Yeah that's what I thought. Yes I hear it even with no audio signal.

On 1.0x gain, I hear nothing, which is what I expect. On the 2.5x gain, I get that kind of background hiss that one would hear with a portable media player and IEM's. It's subtle, but I can definitely tell the difference between the 1.0x and the 2.5x gains.

 

I don't think it was my desoldering job...the circuit looked pretty clean when I took out the resistors.

 

 

This happens on multiple computers. And actually, with the O2/ODAC, I discovered that one of my USB ports on my MacBook is dying because the audio produced from that particular port is all distorted like one would find in a horror movie. Switching USB ports fixes this issue. XD


Edited by miceblue - 11/14/12 at 8:46pm
post #345 of 3453
Quote:
Originally Posted by mikeaj View Post

I don't know, is "output straight from the DA chip" kind of misleading?  Or more relevantly, I'm not so sure about dependence on the amp input stage.

 

Specs on ES9023 are not publicly available, but the literature that's out there calls it a "24-bit stereo audio DAC with integrated 2Vrms op-amp driver."  If there's a trick involved, it's Sabre putting op amps in the DAC IC package.  Do you really consider it to be different than a DAC with an op amp line driver in a separate package?  Lots of ICs these days have many integrated components and functionality though.  That's the name of the game now.

 

Ahh, thanks for that. I hadn't read the info for that particular chip. Makes a lot of sense now. 

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