[Arm3nian]

   
That is about right. At 3.5x gain and ODAC as source, max power around that value (163mW) for 300ohm load. At unity gain (1x) O2 acts like a buffer and output is 2Vrms for max power of 13mW for 300ohm load.

 
 

   
Voltage gain occurs in any stage of amplification (either as attenuation, unity gain, or amplification). An amplifier can have any number of stages. In O2, voltage gain occurs in the pre-amplification stage, followed by analog attenuation, then a current buffer output stage.
 
Someone posted a longer mathematical explanation in this thread a few weeks ago, so I will not repeat the exercise.

Yeah updated my post. I was picturing a completely different design. Thanks

 

[Solrighal]

So 3.5x is better than 3.0x but not as good as 1.0x?

 

[headwhacker]

So 3.5x is better than 3.0x but not as good as 1.0x?

better at what? 3.5x can supply more power than 3x and 1x. But in return noise/distortion is higher than 3x and more so than 1x.
 
If your headphone is loud enough at 1x then you don't need to raise the gain and is technically better than higher gain. But for harder to drive phones which need more power than 1x can provide then the higher gain is better.

 

[diamondears]

So 3.5x is better than 3.0x but not as good as 1.0x?

I think John's point is just that since you have a free choice of a 2nd gain in an O2 (in addition to unity), might as well get the 3.5x to maximize possible gain without any clipping.

 

[Solrighal]

I think John's point is just that since you have a free choice of a 2nd gain in an O2 (in addition to unity), might as well get the 3.5x to maximize possible gain without any clipping.

 
 

  better at what? 3.5x can supply more power than 3x and 1x. But in return noise/distortion is higher than 3x and more so than 1x.
 
If your headphone is loud enough at 1x then you don't need to raise the gain and is technically better than higher gain. But for harder to drive phones which need more power than 1x can provide then the higher gain is better.

 
OK, I think I understand. I only listem to HD 650's and unity is fine for me.

 

[diamondears]

I have another question...let's say my HP doesn't sound loud enough to my liking using unity gain on O2 and I'd like to increase volume, which is better, (a) increase Vrms output on the DAC (my DAC can be increased from default 2Vrms up to 2.8Vrms), or (b) use the 3.5x gain on the O2?

 

[headwhacker]

I have another question...let's say my HP doesn't sound loud enough to my liking using unity gain on O2 and I'd like to increase volume, which is better, (a) increase Vrms output on the DAC (my DAC can be increased from default 2Vrms up to 2.8Vrms), or (b) use the 3.5x gain on the O2?

 
increase the DAC output and stay at 1x on O2.

 

[diamondears]

increase the DAC output and stay at 1x on O2.

Why? To avoid additional noise? What else?

 

[Solrighal]

Happy new year everyone!

 

[Peti]

+1
 
Let me wish to all of you an abundant New Year in superb music, headphones and amps. I have ordered my O2/ODAC for Christmas and LOVING it!

 

[WilliamLeonhart]

Guys I have this strange issue on my DIY O2/ODAC (boards made by JDS): sometimes when I click on another song on foobar it gives a small (but clearly audible) crackling sound. It does not happen everytime but sometimes it's louder than the others. I'm a bit worried. This does not happen on my integrated Realtek, and on the O2/ODAC it happens to every cans I own (all of them Grados).
 
Have you ever had this issue? It happens to me both on low gains and high gains.

 

[WilliamLeonhart]

After further checking I found that foobar often makes a small "tsk" sound when I was switching songs (on both my Realtek and the O2/ODAC), but the crackling sound only happens on the O2/ODAC. Quite audible.

 

[headwhacker]

Why? To avoid additional noise? What else?

 
I only realize this while reading through the sound science forum. 
 
Since the O2's volume control is between the gain and the output stage, O2 will apply the gain first on the signal before it is attenuated by the volume control. This means that if the gain ratio is too high for the input voltage, the signal clips even if the volume knob is far from the it's max level.
 
I think this make sense but not 100% sure. Can anybody else can confirm this? 

 

[diamondears]

I only realize this while reading through the sound science forum. 

Since the O2's volume control is between the gain and the output stage, O2 will apply the gain first on the signal before it is attenuated by the volume control. This means that if the gain ratio is too high for the input voltage, the signal clips even if the volume knob is far from the it's max level.

I think this make sense but not 100% sure. Can anybody else can confirm this? 

2.0Vrms x 3.5 gain won't clip. That's the limit before clipping. Otherwise, I would have not asked the question and just preferred increasing the Vrms out of the DAC. But I think yeah, if gaining rads to clipping, that means something is being done on the SQ?

 

[Jakkal]

   
I only realize this while reading through the sound science forum. 
 
Since the O2's volume control is between the gain and the output stage, O2 will apply the gain first on the signal before it is attenuated by the volume control. This means that if the gain ratio is too high for the input voltage, the signal clips even if the volume knob is far from the it's max level.
 
I think this make sense but not 100% sure. Can anybody else can confirm this? 

That is correct, it was explained earlier in this tread.