[Uriel41]

Dear Head-Fiers
 
I've got a minor issue with my Fidelio X2s, O2 ODAC and the inbuilt amp section of my PC's motherboard (chain: PC > O2 ODAC > X2). I'll try to explain the problem as best I can:
 
So after extensive testing, I figured that I get the best sound out of my system if I maximize windows volume and leave the O2 ODAC knob at a fraction past 6 o'clock (minimization). However, due to high sensitivity and low impedance of my X2s, I can now no longer control the volume with the amp's knob the way i'd like to if I maximize windows volume. The knob is now too sensitive, even pushing towards 7 o'clock might be too lound, depending on my mood.
Thus in a nutshell, I would like to maximize sound quality by maximizing windows volume and still be able to control the volume properly with the knob on my O2 ODAC. Any advice on the matter is greatly appreciated. I thought of somehow disabling the amp section of my PC's motherboard, so that the only amp is the O2. Is that possible and would that help?
 
Cheers,
Uriel

 

[MindsMirror]

Are you bypassing the ODAC and using the motherboard's sound/DAC? If you use the ODAC, the motherboard sound or amp wouldn't have anything to do with it.
 
You can modify the gain of the O2, it's just a mater of removing or changing some resistors.

 

[Uriel41]

hmm, no, i'm quite sure i'm NOT bypassing the ODAC using the motherboard's DAC, it's the other way round... right?. But then what am I adjusting when i change the volume in windows? When I click the little icon at the bottom right corner, it tells me that i'm adjusting the volume of the ODAC device. So I can adjust the ODAC's volume both virtually and physically, how does that make any sense? I thought that adjusting volume in windows has to do with the onboard sound. Or does that mean that when I turn the knob, I'm changing how much the amp amplifies the signal and when I adjust the volume in windows, I control/change/affect the DAC? Since I've got no knowledge in that area, I'm pretty confused now ^^
 
If there's no other way, then I'll try modifying the gain. Do I need to be good at this or can a layman like me do this?

 

[MindsMirror]

I asked if you were bypassing the ODAC because you mentioned the motherboards built in amp and asked about disabling it. If you're using the ODAC, the motherboard's onboard sound including it's DAC and amp are automatically bypassed.
 
When you use the ODAC, the windows volume will adjust the volume digitally, modifying the digital audio data that is sent to the DAC. The volume control on the O2/ODAC is part of the O2 amp, and adjusts the volume in analog, changing the amount of amplification.
 
I haven't done it myself, I don't have an O2, but it seems all you have to do is desolder two resistors. Here it shows which ones:
http://www.jdslabs.com/pdf/O2_LowGain.pdf
You can clip one leg of each resistor if you don't have a soldering iron. You'll need to solder them back on if you want to change it back though.

 

[Uriel41]

Thank you so much for the explanations and suggestion! I understand it now and I will clip. The only question I still have is: What do you mean by "modifying the digital audio data"... does that mean you increase or decrease the amount of digital data sent to the O2 ODAC or...? I mean, it adjusts the volume somehow.
 
Also, why do I merely clip one leg if i don't have a soldering iron? In the pic it says "remove"

 

[MindsMirror]

Say you have some digital audio data and the values of the samples are 10, 14, 8, 2, -6. If you use windows volume to half the volume, it would simply send 5, 7, 4, 1, -3 instead. In a way, it does reduce the amount of data sent, because the smaller numbers have less precision, and because it can't send fractions so if there is a fraction, that information will be lost. You are right in saying that 100% volume in windows is best for sound quality.
 
You don't have to completely remove the resistor. With one leg clipped, the resistor makes an incomplete or open circuit. There is no way for any current to flow through the resistor, so it is as if the resistor is not even there.

 

[Uriel41]

Perfect, now I know everything I wanted to know. Have a few thumbs up! Thanks a lot.
I'll let you know how things go with the clipping. 
Cheers

 

[Uriel41]

It's worked out perfectly! The odd thing is that now, the amp is set to low gain if the gain button is pushed in. Before the modification, it was 2.5/6.5 gain and now it's 2.5/1.0 gain and not 1.0/2.5. That's not reason for concern, right? I mean, I'll just keep the button pushed in.

 

[MindsMirror]

One of the sets of resistors must be for when the button is pressed and the other is when it's not, so you changed button pressed gain from 6.5 to 1.0.

 

[Uriel41]

I see, that's not a problem in any way, is it? I can't see why it would be well, either way, thanks again. You've been a great help!!!