Hi guys, I'm glad to be part of this great community!
Anyway as the thread title, I have a question for you. After my SMSL Sap II died, I remained without an headphones amp. My friends decided to buy for my birthday an O2, but my bigger question is: with wich gain should I buy it?
I have the dt990 pro 250 ohm as main headphones, and an xonar u7 as audio card. The xonar has a low end integrated amp that can bring maximum 64ohm, so, if I'll the u7 with the o2 + dt990 pro, which gain settings should I use? Standard 2,5 / 6,5 is too much? Someone recommended me 2,5 / 4.

With such gain settings , can I also use "less difficultous" phones? (HD681 evo, Ostry kc06a in ear etc. ).

Thanks in advance for the help.

fooook92 said:

I have the dt990 pro 250 ohm as main headphones, and an xonar u7 as audio card. The xonar has a low end integrated amp that can bring maximum 64ohm, so, if I'll the u7 with the o2 + dt990 pro, which gain settings should I use? Standard 2,5 / 6,5 is too much? Someone recommended me 2,5 / 4.

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With such gain settings , can I also use "less difficultous" phones? (HD681 evo, Ostry kc06a in ear etc. ).
 

Click to expand...

protegemaniac said:

That "64ohm" doesn't tell us anything about what gain setting the O2 should probably be at when using the U7 as a source. You need to look up what the line output voltage is. CD standard is 2volts, most DACs go up to around 2.5volts, iPods and many DAPs are at the 1.0v to 1.3v range.

If it outputs less than 1.8volts you might want the 6x high gain setting for the DT990 but you'd need the lowest available gain setting to be able to use it with lower impedance, high sensitivity IEMs or headphones. Yes, lower than 2.5. If you can get 1x and 3.3x that's still probably not going to be too bad for the DT990.

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Thanks for your answer.

This what asus report about the u7:

Output/Input Full-Scale Voltage: Rear output (Speaker) 1Vrms (2.828 Vp-p)
(Headphone) 1.3Vrms (3.677 Vp-p).

I really don't know what to do, even if I can change the gain settings later. 1x / 3.3 I honestly have the fear it's "low" for the dt990 pro.

fooook92 said:

Thanks for your answer.

This what asus report about the u7:

Output/Input Full-Scale Voltage: Rear output (Speaker) 1Vrms (2.828 Vp-p)
(Headphone) 1.3Vrms (3.677 Vp-p).

I really don't know what to do, even if I can change the gain settings later. 1x / 3.3 I honestly have the fear it's "low" for the dt990 pro.

Click to expand...

 
With a 1v line output it's basically got the same signal strength as an iPod. If you can get it in 1x and 6x, I'd get that - 6x for headphones and 1x for IEMs.

protegemaniac said:

   
With a 1v line output it's basically got the same signal strength as an iPod. If you can get it in 1x and 6x, I'd get that - 6x for headphones and 1x for IEMs.

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Well, I then thought, I'll never use IEM with PC, so I think I'll go with a 2/2,5 and 5. I think 6 it's a little bit "exaggerated" or no? On headphones output U7 seems can push 1.3vrms, so maybe 6 will too much? 
I read of people with Xonar DX (barely the same card as U7 without built in AMP) that have distorsion with stock high gain (6,5). I don't know what to do ^^

fooook92 said:

  Well, I then thought, I'll never use IEM with PC, so I think I'll go with a 2/2,5 and 5. I think 6 it's a little bit "exaggerated" or no? On headphones output U7 seems can push 1.3vrms, so maybe 6 will too much? 

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I had my Meier Cantate.2 at the +4dB high gain setting (it uses -10dB for low gain on IEMs and Grados, etc; either way it has a 30v peak to peak voltage output I think) and a D-Zero MkII (1.2volts output) and my HD600 are still well past 9:00 on the dial.
 
5x and 6x aren't too far apart though and that's likely enough.

protegemaniac said:

   
I had my Meier Cantate.2 at the +4dB high gain setting (it uses -10dB for low gain on IEMs and Grados, etc; either way it has a 30v peak to peak voltage output I think) and a D-Zero MkII (1.2volts output) and my HD600 are still well past 9:00 on the dial.
 
5x and 6x aren't too far apart though and that's likely enough.

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I think I'll go for 2x/5x. Then, I'll always have the possibility to change the resistance without problems ^^.
Thanks for your answers