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O2 AMP + ODAC
May 20, 2014 at 7:05 AM Post #2,941 of 5,671
Xenophon,,,,
 
Agdr posted this:
ODA works perfectly with HE500 and HE6 up to 118dB and 113dB
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.

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

Note that 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 with 70mA available each for powering the load.

So.. these kind of headphones are exactly what the ODA eats for lunch.
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Also note that the +/-15Vdc power rails should not be used with either headphone. +/-12.5Vdc does the job as per the charts, and the output chips could overheat at the higher voltages. Those are only for 300R and 600R cans.

--> I'm going to post this PM contents in the thread becasue it is an excellent question and really shows what the ODA is useful for. More good work, Alex! Thanks.
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May 20, 2014 at 7:10 AM Post #2,942 of 5,671
Just another aside, the cost of the panels in the completed and tested ODA is about $100 more if I got he panels done by Front Panel Express. Seeing how I just retired I am on a fixed income and wanted to keep the costs down as much as possible.
 
If your handy with mecahanical tools and stuff you could look at maybe buying the board and mount it in a box and drill holes etc...not that hard but again time consuming etc..
 
Alex
 
May 20, 2014 at 8:15 AM Post #2,943 of 5,671
Thanks a lot Alex!  
 
I'm not listening at anything near those levels, no problem, don't want a peak in a classical record to wipe out some nerve endings :)  Hearing still extends to >15kHz at age 41, not too shabby for a guy who listens to music wearing headphones for hours/day.
 
I'm sorely tempted...only the power supply left to consider but that's a small thing and easily fixed.  If I order it I'll go with the Front Panel enclosure, you're absolutely right that everything could be built from scratch but as you say, it's a tradeoff between money and time...and with all the business trips and time away my wife would appreciate it if I'd pick spending some cash over spending hours in the basement tinkering away.  Hmm, gonna do some re-reading at DIY-audio I guess.  Decisions, decisions....  But it'll take up less desk space than the vintage Pioneer SX-1980 I managed to find (FedEx guy still gives me the fisheye over its 40 kg) 
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Next project here will be a self built 45 or 300B tube amp....crunching the numbers.
 
May 20, 2014 at 5:51 PM Post #2,945 of 5,671
Is it normal that O2 distorts bass very badly at 6.5x gain (even at volumes much lower than I listen on 2.5x, which sound clean)? I have only low impedance headphones (18 and 35 ohm), if that matters.
 
May 20, 2014 at 6:47 PM Post #2,946 of 5,671
ieee754 said:
Is it normal that O2 distorts bass very badly at 6.5x gain (even at volumes much lower than I listen on 2.5x, which sound clean)? I have only low impedance headphones (18 and 35 ohm), if that matters.
Click to expand...


What is the Vrms level of your source? At 6.5x your source voltage must be less than 1Vrms.
 
May 20, 2014 at 6:58 PM Post #2,947 of 5,671
headwhacker said:
What is the Vrms level of your source? At 6.5x your source voltage must be less than 1Vrms.
Click to expand...

I have JDSLabs integrated O2/ODAC combo, so it is probably at proper level. I have read somewhere that higher gain equals to lower output power, and since I use current driven headphones maybe it should clip? But I don't have to listen very loudly to get these distortions so I'm not sure.
 
May 20, 2014 at 7:20 PM Post #2,948 of 5,671
ieee754 said:
  I have JDSLabs integrated O2/ODAC combo, so it is probably at proper level. I have read somewhere that higher gain equals to lower output power, and since I use current driven headphones maybe it should clip? But I don't have to listen very loudly to get these distortions so I'm not sure.
Click to expand...

 
Yes, with the ODAC the O2 at 6.5x gain will clip regardless of the volume pot setting. This is because the 6.5x gain option is for low output devices like mobile players. The ODAC delivers a 2V redbook compatible signal and thus 3.5x gain is the possible maximum.
 
Joachim
 
May 20, 2014 at 7:36 PM Post #2,949 of 5,671
jring said:
   
Yes, with the ODAC the O2 at 6.5x gain will clip regardless of the volume pot setting. This is because the 6.5x gain option is for low output devices like mobile players. The ODAC delivers a 2V redbook compatible signal and thus 3.5x gain is the possible maximum.
 
Joachim
Click to expand...

You're right, when I set volume in Windows to 80%, the clipping disappears. Now I know that there is nothing wrong with my O2. So 6.5x is only useful for amping external sources, I thought it's for high impedance headphones, which require higher voltage.
 
Thanks guys!
 
May 20, 2014 at 7:36 PM Post #2,950 of 5,671
Not very many people really understand what gain is and how it differs to volume etc....The 6.5 gain setting is seldom used.many folks, and your correct with the ODAC its not needed...it will distort.
 
The ODA has a clipping indictor and it doesn't take much to clip..
 
A. 
 
May 20, 2014 at 7:44 PM Post #2,951 of 5,671
adydula said:
  Not very many people really understand what gain is and how it differs to volume etc....The 6.5 gain setting is seldom used.many folks, and your correct with the ODAC its not needed...it will distort.
 
The ODA has a clipping indictor and it doesn't take much to clip..
 
A. 
Click to expand...

ODA looks very interesting. Do you think that upgrading from O2 to ODA would make a difference for amping HE-560 (it has about the same efficiency and impedance as HE-500)?
 
May 26, 2014 at 12:46 PM Post #2,954 of 5,671
Has anyone noticed the highs are a bit emphasized on many jazz and rock albums. At first I thought it was the O2, but since the O2 has a flat frequency response, I am thinking it is the recordings. This particularly shows up with guitar work.

Bob
 
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