[sonitus mirus]

Thanks mikeaj,
 
Yep, Asgard has a few relatively large electrolytic capacitors that I can see through the cooling grates.  I'm certain these caps explain the 4-5 second wait between flipping the power switch on and the alarmingly loud "bump" I hear 4-5 seconds later in my headphones, even with the volume turned all the way down.  I believe any potential damage or wear on my headphones is significantly less than what I would experience by unplugging my headphones before shutting off my amp every time.  My headphone drivers will probably be able to handle the transients far longer than my amp's connectors will be able to handle frequent insertions and extractions.

 

[Bogatyr]

 
Back panel of Xonar DG is indeed without noise as long as its set to speakers mode. This solution however creates another problem, switching between headphones and speakers. If I were to get a DAC + Amp I could dedicate them to my headphones and dedicate Xonar DG to speakers, otherwise I'd have to unplug and replug each time I wish to go from one to other. From what I understand splitters aren't all that great.
Quote:

Well then get an O2 and use it through the DG.  If there's still noise (I think a combination of attenuation through the O2 and some of the RF filtering will clean it up, so I don't think it will be necessary), then you can look at some relatively cheap DAC or sound card that has lower noise.  You aren't by any chance using the DG via the front panel connection, right?  edit: sorry, I can't read.  Try the back panel connection.  The cable from the card to the front panel often picks up a lot of stray EMI from noisy computer internals.  By the way, the noise is much more likely to be from stray radiation and so on, maybe all sorts of components dirtying the power in between the power supply and audio card, than the power supply itself.
 
Yes it's possible for one amp to do better than another, at any volume.  Voldemort's blog has reviews where there are graphs of different headphone amplifiers, showing THD+N vs. output voltage.  This is just one metric, but look at the value at say 0.1V for different amps, at a given load.  There's just usually less of a difference at lower volumes because (1) most headphone amps won't be stressed so badly by such modest power draws and (2) small differences in sound quality are harder to detect when the sound level is lower.  More of the slightly bad crud may just be lost in the noise.

 

 

[palmfish]

I removed the 6.5X gain resistors tonight (wow, resistors are a lot smaller than I remember them being back when I used to work with electronics) . Now at 1X gain I can turn the volume knob all the way up to 9:00 before it starts getting too loud. I never realized how much gain 2.5X already was. I'm glad I've been keeping up with this discussion and learned about this.

 

[JRoyen]

Auditioned the O2 the other day, and it blew me away. I have been waiting many years for a headphone amp this powerful, revealing, quiet and neutral. Actually got me excited about audio again in the longest time. Now my only decision is whether to wait for the ODA/ODAC, for a neater all-in-one package.

 

[uelover]

Quote:

Auditioned the O2 the other day, and it blew me away. I have been waiting many years for a headphone amp this powerful, revealing, quiet and neutral. Actually got me excited about audio again in the longest time. Now my only decision is whether to wait for the ODA/ODAC, for a neater all-in-one package.

I would think that the O2 is affordable enough for you to keep it even after you have gotten the ODA/ODAC.
 
Its portability is a plus for traveling use =)

 

[turokrocks]

Quote:

I would think that the O2 is affordable enough for you to keep it even after you have gotten the ODA/ODAC.
 
Its portability is a plus for traveling use =)

I have a lost twin, who reads my mind!
 

 

[a_recording]

Quote:

I would think that the O2 is affordable enough for you to keep it even after you have gotten the ODA/ODAC.
 
Its portability is a plus for traveling use =)

That's my plan exactly. :3 I'm thinking that this: http://www.headstage.com/USB-DAC-Cable/USB-DAC-Cable-with-35mm-Mini-Plug-75cm-30::10134.html?XTCsid=ef7d80bbc2f318d5c52b1a5a010badee would be a wonderful companion for the O2's 3.5mm input and a laptop. I'm a little discouraged when the website hasn't even bothered to update the images with the latest version of the cable though. Anyone got any opinion on these or can suggest a similar alternative?

 

[turokrocks]

I never used my O2 with Batteries, I directly removed the batteries and connected it to my DAC LX,  I think I should see how it sounds.

 

[shotgunshane]

That's my plan exactly. :3 I'm thinking that this: http://www.headstage.com/USB-DAC-Cable/USB-DAC-Cable-with-35mm-Mini-Plug-75cm-30::10134.html?XTCsid=ef7d80bbc2f318d5c52b1a5a010badee would be a wonderful companion for the O2's 3.5mm input and a laptop. I'm a little discouraged when the website hasn't even bothered to update the images with the latest version of the cable though. Anyone got any opinion on these or can suggest a similar alternative?

I'm using the dac cable with my O2 and laptop. Works very well. I have the previous version of the cable with the components in the middle.

 

[wje]

I was reading someone's for sale thread on the O2 (possibly in another forum) and they indicated that their O2 amp was properly grounded to the case.  I suspect mine is suffering from a grounding issue because I bumped it with my metal iPod classic and I noticed a slight spark.  Apparently, this was more than just static, but suspect since the PCB was just inserted into the slots on the case and the front / rear covers were put on, the PCB itself isn't, or may not be properly grounded to the case.  Thoughts?  If this should be done, I was wondering at which point would be best to attach my ground wire on PCB and then I'll locate an area on the case to secure it to.
 
Thanks,
 

 

[uelover]

Quote:

I have a lost twin, who reads my mind!

 

 
Quote:

I never used my O2 with Batteries, I directly removed the batteries and connected it to my DAC LX,  I think I should see how it sounds.

I would think that the batteries, in addition of serving its primary purpose, works also to ensure that the power supply is as clean as possible. Something like the JKenny MK3.
 

 

[stv014]

Quote:

Originally Posted by uelover /img/forum/go_quote.gif
 
I would think that the batteries, in addition of serving its primary purpose, works also to ensure that the power supply is as clean as possible. Something like the JKenny MK3.

Not really, the power supply voltage (which is regulated) should never drop to such a low level that the amplifier becomes battery powered.
 

 

[uelover]

Quote:

Not really, the power supply voltage (which is regulated) should never drop to such a low level that the amplifier becomes battery powered.

 
Not sure what you mean really. You mean that amps like the RWA Corvina, SR71B and etc should never have used battery in the first place?
 
Anyway, arguing about what voltage level is appropriate is not my point. I am just stating the fact that a battery powered amp also helps to ensure that the power is as clean as possible.
 

 

[stv014]

Quote:

Not sure what you mean really. You mean that amps like the RWA Corvina, SR71B and etc should never have used battery in the first place?
 
Anyway, arguing about what voltage level is appropriate is not my point. I am just stating the fact that a battery powered amp also helps to ensure that the power is as clean as possible.

I do not know about those other amplifiers, but from the schematics of the O2, it seems the batteries do not really make the power "cleaner" under AC operation. That purpose is served by the capacitors C2 to C10, C17, and C18, as well as the two voltage regulator ICs. The batteries are effectively only in the circuit through the 220 Ohm resistors (R1 and R2), and they are actually being charged, rather than providing any power.
 

 

[uelover]

Quote:

I do not know about those other amplifiers, but from the schematics of the O2, it seems the batteries do not really make the power "cleaner" under AC operation. That purpose is served by the capacitors C2 to C10, C17, and C18, as well as the two voltage regulator ICs. The batteries are effectively only in the circuit through the 220 Ohm resistors (R1 and R2), and they are actually being charged, rather than providing any power.

I wasn't referring to the O2 when being powered by the AC power, for that will make it no different from ODA.
 
My comment is on the fact that the availability of battery power (when disconnected from the AC) allows the O2 to benefit from a clean power source.