[faffi]

Hey All,
 
Just bought a pair of HD650's and I'm set on an O2/ODAC combo, seem to be a safe bet. Last time I did research, there was only a single option for the JDSLabs O2/ODAC combo, now they have customizable gain options of standard (2.5x, 6.5x), medium (1x, 3.5x) and low (1x, 2.5x).
 
Which would pair 'best' with the 650's? I'd assume a 1x option is kinda just like passthrough since it wouldn't really be amplifying? Would they ever require 6.5x gain?
 
Thanks!

 

[Cankin]

Unless you use source with low output, or you will be using O2 with battery or very inefficient headphone(HE-6) or combination of above, you don't need 6.5x

Medium(1x, 3.5x) or low(1x, 2x) will be more than sufficient.

I use my HD800 with 1x only and almost never of over 11 o'clock on volume knob even with quiet classical recording.

 

[faffi]

Unless you use source with low output, or you will be using O2 with battery or very inefficient headphone(HE-6) or combination of above, you don't need 6.5x

Medium(1x, 3.5x) or low(1x, 2x) will be more than sufficient.

I use my HD800 with 1x only and almost never of over 11 o'clock on volume knob even with quiet classical recording.

 
Thanks for the reply, am I right in assuming that 1x doesn't amplify at all? Or is it an "arbitrary" 1x amplification as per the standard of the O2?
 
Just received the headphones and I need to crank volume on my MBP to max in order to get it loud enough, which I kind of expected.

 

[Cankin]

http://www.sengpielaudio.com/calculator-FactorRatioLevelDecibel.htm

 

[faffi]

http://www.sengpielaudio.com/calculator-FactorRatioLevelDecibel.htm

 
So the latter. Thanks, makes more sense

 

[Claritas]

The lowest gain setting can be used with IEMs too. The highest I've ever had to go with comparable phones is 11-12 o'clock on "high" 2.5 gain. But I listen at very low volumes. So I think the medium gain option would be your best choice, unless you listen at very low or very high volumes. That's what it really comes down to. Best luck!