[diamondears]

Assuming your target maximum volume loudness is 115dB and a 3dB headroom. To drive HE-6 to 118dB requires around 12Vrms

How about 110dB?

 

[chimmycham]

I've heard from numerous sources that the O2/ODAC is very neurtral and "cold" sounding compared to a combo like the magni2/modi2 or the vali/modi2.
 
Can anyone attest to this?

 

[adydula]

The ODA offers several benefits over the O2 for desktop use, including:

* Three times the output current capability at 300mA per channel
* Super quiet 2 stage power supply with regulators heat sinked to the case
* Input power CRC filter to remove power line noise
* Lower noise and THD LME49990 (optional FET LME4988) gain stage chips
* 1K volume control and 4.99K ground return resistors for lower Johnson noise
* Lower distortion and higher S/N ratio with 6 paralleled op amps per channel
* Rear RCA in, from 3.5mm in, input select, 4 position gain switch, front 3.5mm & 1/4" out, front pre-am out, damping factor adjust.

Also one of the things that the O2 has issues with is those hard to drive headphones like HE500 and HE6.
 
It has a pre-amp option I use to drive a network Onkyo receiver for listening and gaming.
Clipping LEDS to see when your clipping at various gains.
 
 
 A fellow in the O2/ODAC thread was asking about the ODA powering the HE500 and notoriously hard-to-drive HE6. Turns out the answer is no problem at all for the ODA. AGDR has added a folder to the V2.0 ODA Google Drive link called "Headphones vs. the ODA" with the spreadsheets and a README with all the details.
https://drive.google.com/folderview?...28&usp=sharing
 
http://www.bing.com/videos/search?q=oda+amp+youtube&FORM=VIRE1#view=detail&mid=90789AE352B2C205664E90789AE352B2C205664E
 
http://www.head-fi.org/t/719611/objective-desktop-amp-a-version-from-agdr
 
I have an ODA and its very, very good.
Alex

 

[headwhacker]

How about 110dB?

 
Antilog ((110 - 83.5) / 10) = 0.446 W
 
sqrt (0.446 * 50 ) =  4.7 Vrms

 

[adydula]

From AGDR at Diyaudio:
 
So here is your answer about the HE500 and HE6. The ODA will not only power both perfectly with the standard +/-12.5Vdc power rails, they will do so all the way up to 118dB and 113dB, respectively. And those were just the power levels that broke the spreadsheet. Nobody should be listening to headphones at those levels anyway! See the hearing damage chart at the bottom of the fellow's spreadsheet. 

I have created a new folder at the V2.0 ODA Google Drive link called "Headphones vs. the ODA". Here is a direct link to it:

https://drive.google.com/folderview?...28&usp=sharing

In there I have used a nice power calculation spreadsheet that was posted on Head-Fi back in December. See the README file in that folder. It has a link to that post with the sheet and links to the specification pages for the HE500 and HE6. They are 38 ohm at 89dB/mW sensitivity, and 50 ohm at 83.5dB/mW respectively. Note that per mW is assumed, both by the fellow who created the spreadsheet and by me, since the manufacturer does not say whether per mW or per V. Per mW is the older and more standard measure so its a good bet.

For more normal levels I have also included sheets for both at 95dB.

Only the 113dB power level with the HE6 is coming near the using the full 7.25V(rms) swing of the ODA with the +/-12.5Vdc rails, at 6.67V(rms). The current is still a no-brainer for the ODA, divided by 6 for the 6 output chips.

So.. these kind of headphones are exactly what the ODA eats for lunch. 

Also please note that the +/-15Vdc power rails should not be used with either headphone. +/-12.5Vdc does the job as per the charts. The output chips could overheat at the higher voltages. Those are only for 300R and 600R cans.  
 
FYI
Alex

 

[MrMateoHead]

  I've heard from numerous sources that the O2/ODAC is very neurtral and "cold" sounding compared to a combo like the magni2/modi2 or the vali/modi2.
 
Can anyone attest to this?

By definition neutral is neutral. It can't be hot or cold. My Odac does run cool however and I hear the Schiit stuff can run pretty hot

 

 

[raoultrifan]

Thanks adydula for your very fast answer! I've read your posts from audiocircle and diyaudio while ago and I respect your work done there. I've also read all of agdr's posts, since he was talking with nwavguy on how to better design the O2.
 
My O2 is modded a little bit by myself: 2 headphone front jacks (1 big and 1 small), back jack and RCA input pugs, back power plug, changed 2 small capacitors on PSU, changed NJM2068 with LM4562 (can be no improvements on audio spectrum...ofc, but at least I might be able to use high gains in the future) etc. I will try myself the 15V mod presented by agdr, also the electrolytic caps mode and maybe some other mods too. All I need is a bit more time for that.
 
I strongly recommend the agdr's ODA to anyone trying a decent upgrade from O2, because ODA has the same neutral sound signature like O2, but is more powerful and technically is having less distortions. I am thinking of getting one ODA myself, in case I'll buy some planars or 600 ohms headphones, mostly because now I'm using the O2 at 1x gain for K550 and SR60i, at 2.5X gain for K701 and I don't have a 3-way push button to select a higher gain value like 4X or 5X. So having 2 decent headphones amplifier will better pair with all of my headphones.
 
Regards!

 

[headwhacker]

  From AGDR at Diyaudio:
 
So here is your answer about the HE500 and HE6. The ODA will not only power both perfectly with the standard +/-12.5Vdc power rails, they will do so all the way up to 118dB and 113dB, respectively. And those were just the power levels that broke the spreadsheet. Nobody should be listening to headphones at those levels anyway! See the hearing damage chart at the bottom of the fellow's spreadsheet. 

I have created a new folder at the V2.0 ODA Google Drive link called "Headphones vs. the ODA". Here is a direct link to it:

https://drive.google.com/folderview?...28&usp=sharing

In there I have used a nice power calculation spreadsheet that was posted on Head-Fi back in December. See the README file in that folder. It has a link to that post with the sheet and links to the specification pages for the HE500 and HE6. They are 38 ohm at 89dB/mW sensitivity, and 50 ohm at 83.5dB/mW respectively. Note that per mW is assumed, both by the fellow who created the spreadsheet and by me, since the manufacturer does not say whether per mW or per V. Per mW is the older and more standard measure so its a good bet.

For more normal levels I have also included sheets for both at 95dB.

Only the 113dB power level with the HE6 is coming near the using the full 7.25V(rms) swing of the ODA with the +/-12.5Vdc rails, at 6.67V(rms). The current is still a no-brainer for the ODA, divided by 6 for the 6 output chips.

So.. these kind of headphones are exactly what the ODA eats for lunch. 

Also please note that the +/-15Vdc power rails should not be used with either headphone. +/-12.5Vdc does the job as per the charts. The output chips could overheat at the higher voltages. Those are only for 300R and 600R cans.  
 
FYI
Alex

 
It should be dB/mW as their spec for the newer cans is specified in dB/mW.
 
That power estimate is conservative imo. I'm pretty sure some will argue you need more headroom if you are listening to some rare wide DR recordings. And granted we want to keep an anolog volume control between 11 to  3 o'clock position. Many wants to see an amp be capable of driving a can at 118 dB to 120dB to be on the safe side.
 
Nwavguy even recommends a 1 to 3dB headroom at a target SPL. 115 dB being the loudest level that majority of people can tolerate. Thus 118dB should be a good target SPL for an amp on a given load.

 

[Peti]

 
My O2 is modded a little bit by myself: 2 headphone front jacks (1 big and 1 small), back jack and RCA input pugs, back power plug, changed 2 small capacitors on PSU, changed NJM2068 with LM4562 (can be no improvements on audio spectrum...ofc, but at least I might be able to use high gains in the future) etc. I will try myself the 15V mod presented by agdr, also the electrolytic caps mode and maybe some other mods too. All I need is a bit more time for that.

Would love to see a pic/pics of your O2!!

 

[raoultrifan]

No time for quality photos...sorry, so please check the photos I just did quickly with my phone right about now.
 
The back plate is upside down (2mm not aligning on the vertical, upper side), because of my mistake when I did the holes drilling for RCA and power plugs.
 
The front plate is still having the power plug, which is still operational, so you can charge the O2 from the front plug or from the backside plug. On the right side you can see that the small jack for input signal is missing and it was replaced by the big Neutrik headphones jack.
 
Headphones output cables for Neutrik plug and power cables from front to back panel are all shielded, just in case of any possible interferences.
 
Just hope in the summer to have some time to move on with the 15V mod and put some small radiators onto opamps.
 

 

 

[Peti]

Nice job pal! I do like it. Especially the knob, is it home-made as well? Looks bigger than the stock one.

 

[luiztfc]

Hi. Due to unforeseen events, I'll have to settle with a cheaper amp+dac for my LCD 2s. What would be better, Magni Modi combo or O2+Odac? 

 

[raoultrifan]

  Nice job pal! I do like it. Especially the knob, is it home-made as well? Looks bigger than the stock one.

Thanks man. It's the default knob from Head'n'HiFi online store (Swiss).
 
@luiztfc, optimal power requirement for LCD2 would be 1 – 4W, so...you might want to try something else maybe. Or at least go for an Asgard or Magni2, but try it out first before buying.

 

[diamondears]

It should be dB/mW as their spec for the newer cans is specified in dB/mW.

That power estimate is conservative imo. I'm pretty sure some will argue you need more headroom if you are listening to some rare wide DR recordings. And granted we want to keep an anolog volume control between 11 to  3 o'clock position. Many wants to see an amp be capable of driving a can at 118 dB to 120dB to be on the safe side.

Nwavguy even recommends a 1 to 3dB headroom at a target SPL. 115 dB being the loudest level that majority of people can tolerate. Thus 118dB should be a good target SPL for an amp on a given load.

Why would one want to listen at more than 110dB is beyond me. Even 90dB is irritating already. DSD music format prolly needs more than 110dB though.

 

[diamondears]

Hi. Due to unforeseen events, I'll have to settle with a cheaper amp+dac for my LCD 2s. What would be better, Magni Modi combo or O2+Odac? 

You're in an O2-ODAC thread...