[Magedark]

Of course, some people may want flavor in their amp as well :wink_face:.

I'm liking my O2 though. Really brings power to the K501s, and allows me to actually listen to it efficiently. Now as to the fact the K501s reveal every bad recording on my setup, that's another issue .

 

[estreeter]

Quote:

 
I set the gain at 3.1, which has proved to be incredibly excessive, as I can't get the volume knob past 9 o'clock without blowing my ears off - and this with quietly mastered stuff! As for the amplifier's sound, it balances out my AKG's with the amount of bass they should have when given enough power and an amplifier with a low output impedance. I can't really say much else about liquid mids or airy highs without feeling incredibly stupid, so I'll just say it sounds nice. Like my Clip+, but with more bass and without the soft clipping.
 
 

This. Damn it, I am going to email Oliver and ask if he will reconsider lowering the gain setting for low gain. The problem you describe is very similar to what I have atm with my uHA-120 : Justin had the gain too high on the initial batch, and only fixed it after a few IEM owners complained. Live and learn, I guess, and so many here seem to want to be able to drive big cans from small(ish) amps.
 

 

[bcg27]

Quote:

This. Damn it, I am going to email Oliver and ask if he will reconsider lowering the gain setting for low gain. The problem you describe is very similar to what I have atm with my uHA-120 : Justin had the gain too high on the initial batch, and only fixed it after a few IEM owners complained. Live and learn, I guess, and so many here seem to want to be able to drive big cans from small(ish) amps.
 

Your volume depends a lot on your source so unless you have the same source output voltage you may or may not be ok. Honestly I don't understand why people are always so confused about volume/power requirements, it is really a straightforward calculation. I think nwavguy may even have a blog post detailing it.

 

[Satellite_6]

Quote:

Your volume depends a lot on your source so unless you have the same source output voltage you may or may not be ok. Honestly I don't understand why people are always so confused about volume/power requirements, it is really a straightforward calculation. I think nwavguy may even have a blog post detailing it.

I'm still confused. THE MATH IT BURNS.

 

[mikeaj]

I think I mentioned this earlier, but if you want 1x gain, all you need to do is read the instructions, find a couple of resistors on the board, and do a snip snip to remove them.  Channel tracking seems to be okay with the volume pot turned down, at least as far as analog volume controls go.  It should be okay.
 
But Oliver probably has not gotten any of the amps made, so it's probably a good idea to message him about it anyway.

 

[limpidglitch]

Quote:

I'm still confused. THE MATH IT BURNS.

 
Fortuneately, someone has done the math already (not me, although I've done some amendments).
 
Linky
 
But remember that on AC power the Maximum Gain = 7 / Vin_(max) and on (low) batteries it’s 4.5 / Vin_(max).

 

[bcg27]

All you need to know to calculate maximum volume are your headphones sensitivity and impedance, the RMS voltage output of your source, and the gain of your amplifier. Sensitivities are generally quoted in dB @ 1mW of power. To go from 1 mW of power for your headphone to volts use Power=Volts^2/Impedance. Solving for volts yields volts=sqrt(power*impedance). So, now take the voltage output of your source and multiply it by the gain of your amplifier. This yields the RMS voltage output from your amp. The maximum loudness your headphones will reach is then the quoted sensitivity of your headphones added to 20*log(voltage out of amp/volts), where the volts is what you calculated from the headphone sensitivity and impedance.
 
Here is an example using some of my gear. My source is a gamma 2 which has an output of 1.4 Vrms. My amp is a beta 22 with a gain of 5, and my headphones are lcd2s with sensitivity of 91 dB @ 1 mW and impedance of 60 ohms. Using the steps from above I want to find out how many volts put 1 mW of power into the headphones, so 1 mW=Volts^2/60, Volts=.245. The output of my beta 22 with input of 1.4 Vrms and gain of 5 is 1.4*5=7 volts. Thus the maximum volume I can get is 91 dB + 20*log(7/.245)=91+29=120 dB. 
 
The steps above can be repeated with any headphone/amp/source combination as long as the specs I mention are available. And if they aren't I would probably stay away from those products. 

 

[svyr]

ordered one from oliver. looks like I might even use it as a portable amp, depending on the size

rechargeables included, right ?

 

[Magedark]

As for size, don't think portable, think transportable.

 

[svyr]

As for size, don't think portable, think transportable.

109X30X80MM; for 'B2-080 portable case' ... is that the right one? (*tries to suss out the dimensions considering the battery(ies?)

 

[cheapskateaudio]

Wow, the O2 has made me hate the uDac 2 with a passion. I think I understand the unnamed one's vitriol a little better. The uDac 2 is probably a purposefully hobbled component that sounds pretty nice until you put it in a proper system such as O2 + HD650. uDac 2 is not just bad with the O2, it's pain inducing. Preferring low volume I tend to respond to fatigue by dumping volume to the point my laptop fan sounds loud next to the music, but even whisper quiet levels are fatigue inducing over time with the uDac 2...
 

 

[Willakan]

Just to fill in the details of my previous comment, the source I'm using (DACMagic) has a 2.1V output.
Channel balance seems O.K. even at low volumes, so I'll probably leave it as it is.

 

[upstateguy]

Quote:

 
You'll never guess what my O2 is driving!
 
I set the gain at 3.1, which has proved to be incredibly excessive, as I can't get the volume knob past 9 o'clock without blowing my ears off - and this with quietly mastered stuff! As for the amplifier's sound, it balances out my AKG's with the amount of bass they should have when given enough power and an amplifier with a low output impedance. I can't really say much else about liquid mids or airy highs without feeling incredibly stupid, so I'll just say it sounds nice. Like my Clip+, but with more bass and without the soft clipping.
 
 

 
That it sounds like a Clip + is not very impressive.

 

[cheapskateaudio]

 
Quote:

 
That it sounds like a Clip + is not very impressive.

It sounds pretty good overall. I haven't heard the Clip+ but it's a clear as day improvement over the uDac 2's headphone out which I found decent despite all the rage it inspired.
 
It's not without faults. It's analytical to the bone. There is no turd polishing here. If the source is the bottleneck the amp will sound like everything else, ie the source. 
 
What I'm hearing right now is that the sound is a little bass light and a little dry/analytical sounding as a result. EQ'ing fixes that, I'm not a big fan of doing that though. Since I'm using the computer line out which is a little thin compared to the uDac 2, I have to reserve judgment on that quality for the time being. I should probably try it with my DVD player...
 
Overall it's good, great detail, lots of inner detail in instruments, still a fairly smooth sounding amp though. I'd love to do a side by side with a top notch SS amp like the ß22.

 

[cheapskateaudio]

Ok, I checked the sound with the DVD player, right off the bat the sound is a lot more full. The DVD player actually sounds pretty good which is amazing considering how cheap it is. The computer line out is simply flat sounding. Again, I'm feeling that the amp is completely transparent to the source. It's not so much dry sounding as extremely revealing. I think thats a good quality in an amp.
 
It's probably just this DVD player, but the O2's gain is way too high with it, basically it's almost too loud at the 7 oclock position on the volume control.