[Mullet]

I'm not sure why people put down the O2 as a suitable amp for the ADs. Mine gets plenty loud at 2.5x gain. Perhaps, it's because I've recently added AGDRs booster board to my O2. http://agdraudio.com/Page2.html
 
It provides the ability for current to peak at 250mA per channel vs. the 120mA with the stock O2. It adds a nice snappiness to the O2 in conjunction with the ADs. If you're DIY inclined don't hesitate to do it @ $25 for a bare board. AGDR also sells completed boards for $85, which seems like a decent price for an upgrade.
 
One thing to note, I never thought the stock O2 was lacking with the ADs. It's just that this upgrade steps it up a notch.

 

[skeptic]

  I'm not sure why people put down the O2 as a suitable amp for the ADs. Mine gets plenty loud at 2.5x gain. Perhaps, it's because I've recently added AGDRs booster board to my O2. http://agdraudio.com/Page2.html
 
It provides the ability for current to peak at 250mA per channel vs. the 120mA with the stock O2. It adds a nice snappiness to the O2 in conjunction with the ADs. If you're DIY inclined don't hesitate to do it @ $25 for a bare board. AGDR also sells completed boards for $85, which seems like a decent price for an upgrade.
 
One thing to note, I never thought the stock O2 was lacking with the ADs. It's just that this upgrade steps it up a notch.

 
Ditto that!  The combination of more current for transients, 150x less less DC offset, and 10x the stock slew rate (if you also drop a dual lme4990 in place of the stock gain opamp - http://www.ebay.com/itm/2PCS-LME49990-SINGLE-DIP8-ADAPTERS-/191313077452?pt=US_Amplifier_Parts_Components&hash=item2c8b25e4cc ), makes for a really nice little amp that sounds great with the AD's.  To me, while retaining the ulta clean sounding signature of the o2, the agdr mod seems to subtly smooth out the sound and eliminate the occasional hint of treble glare that I sometimes perceived in the stock build.    
 
I'm pretty sure the parts for my booster, including shipping, cost me more than $85, so it is a great deal if agdr is actually selling the completed board for that price now.  Once assembled, the board is fairly easy to install and only requires you to solder in three wires connecting it to the main board (for grounding purposes and to eliminate all turn on/off thump).
 
As Mullet indicated though, I also really liked my AD's with my stock O2.  Contrary to certain posts in this thread, AD's are not power hungry phones, and even at unity gain, you will make your ears bleed if you turn the volume up past 10-11:00 on the O2.  
 
Many listeners may prefer some tube warmth in their chain, and I certainly get that as a big fan and owner of multiple bottlehead amps.  But within the realm of opamp based SS designs (which have to use global negative feedback to keep the opamps in a linear mode), the O2 is certainly a very good one. 

 

[Wildcatsare1]

Ditto that!  The combination of more current for transients, 150x less less DC offset, and 10x the stock slew rate (if you also drop a dual lme4990 in place of the stock gain opamp - http://www.ebay.com/itm/2PCS-LME49990-SINGLE-DIP8-ADAPTERS-/191313077452?pt=US_Amplifier_Parts_Components&hash=item2c8b25e4cc ), makes for a really nice little amp that sounds great with the AD's.  To me, while retaining the ulta clean sounding signature of the o2, the agdr mod seems to subtly smooth out the sound and eliminate the occasional hint of treble glare that I sometimes perceived in the stock build.    

I'm pretty sure the parts for my booster, including shipping, cost me more than $85, so it is a great deal if agdr is actually selling the completed board for that price now.  Once assembled, the board is fairly easy to install and only requires you to solder in three wires connecting it to the main board (for grounding purposes and to eliminate all turn on/off thump).

As Mullet indicated though, I also really liked my AD's with my stock O2.  Contrary to certain posts in this thread, AD's are not power hungry phones, and even at unity gain, you will make your ears bleed if you turn the volume up past 10-11:00 on the O2.  

Many listeners may prefer some tube warmth in their chain, and I certainly get that as a big fan and owner of multiple bottlehead amps.  But within the realm of opamp based SS designs (which have to use global negative feedback to keep the opamps in a linear mode), the O2 is certainly a very good one. 

There is "loud" and there is beautiful, the O2 can play loud, but it will never be beautiful, both tubes and class A no op-amp based SS amps can, when well executed, pass the "soul" of the music from the artist to the listener.

 

[skeptic]

There is "loud" and there is beautiful, the O2 can play loud, but it will never be beautiful, both tubes and class A no op-amp based SS amps can, when well executed, pass the "soul" of the music from the artist to the listener.

That's a pretty extremist view. I agree that the best amps (to my ears) are non feedback designs, and in particular well executed parafeed tube designs. But they don't come cheap (or small in stature), and there is certainly plenty of beauty to be found in the o2, wire and other well designed opamp based amps. My mainline hd800 rig is all of 25 steps away from my bedside agdr o2 AD setup, and I greatly enjoy both on a daily basis.

Qusp, an mot and long time industry insider, preferred his wire to his dynahi, and LFF widely recommended the o2 as his go to for the paradox. So let's cool it with the o2 bashing.

 

[goldenSHK]

There is "loud" and there is beautiful, the O2 can play loud, but it will never be beautiful, both tubes and class A no op-amp based SS amps can, when well executed, pass the "soul" of the music from the artist to the listener.

Not to steal your thunder, but that just sounds fancy talk for you preferring the sound signature outputted by tube and class A amps over the O2...

 

[Wildcatsare1]

That's a pretty extremist view. I agree that the best amps (to my ears) are non feedback designs, and in particular well executed parafeed tube designs. But they don't come cheap (or small in stature), and there is certainly plenty of beauty to be found in the o2, wire and other well designed opamp based amps. My mainline hd800 rig is all of 25 steps away from my bedside agdr o2 AD setup, and I greatly enjoy both on a daily basis.

Qusp, an mot and long time industry insider, preferred his wire to his dynahi, and LFF widely recommended the o2 as his go to for the paradox. So let's cool it with the o2 bashing.

OK, I do really like the iFi iDSD Micto, it is warmish and tuned to sound like tubes....neither it or the O2 have the juice I like, but yes are serviceable semi-portable solutions.

 

[Dixter]

There is "loud" and there is beautiful, the O2 can play loud, but it will never be beautiful, both tubes and class A no op-amp based SS amps can, when well executed, pass the "soul" of the music from the artist to the listener.

The best way to play any high powered amp is at normal listening levels....  then if and when the amp is tasked to handle dynamic music then the power in the amp should be able to handle the high powered passages as well as the low powered passages....    don't play a high powered amp just to be loud please... your ears will thank you for it years later...
and you will enjoy that kind of music so much better....  
 
Tube and class A no op-amp SS included 

 

[Wildcatsare1]

Not to steal your thunder, but that just sounds fancy talk for you preferring the sound signature outputted by tube and class A amps over the O2...

You are on too me Bro', do prefer things just slightly on the warm side of neutral, but ever so slightly. Would like to check out the iDSD Micro with my Alpha Dogs, for a semi-portable rig.

 

[goldenSHK]

You are on too me Bro', do prefer things just slightly on the warm side of neutral, but ever so slightly. Would like to check out the iDSD Micro with my Alpha Dogs, for a semi-portable rig.

Haha, I just thought that if a headphone is already ear splitting loud through an amp, but people claim that other amps still "sound better" that just means at that point that it's well driven, but the sound signature isn't the preference of the person. I am personally interested in checking out the Schiit Fulla myself. Sounds like a real winner. The AD/AP/other Fostex mods + Schiit Fulla (just $79 new!!!) sounds like it could be the audiophile deal of the decade in terms of sound quality and portability. 

 

[Lillee]

  Haha, I just thought that if a headphone is already ear splitting loud through an amp, but people claim that other amps still "sound better" 

 
It's something to do it "grip and control". Loudness doesn't mean that that the amp has wads of power to grab the earphones and wring every last drop from them. Especially true with magnetic planar. I noticed a big difference between about 500mW per channel and 2W per channel. Both were ear piercingly loud, but only one had the grip and control to really make the bass go wow.

 

[goldenSHK]

   
It's something to do it "grip and control". Loudness doesn't mean that that the amp has wads of power to grab the earphones and wring every last drop from them. Especially true with magnetic planar. I noticed a big difference between about 500mW per channel and 2W per channel. Both were ear piercingly loud, but only one had the grip and control to really make the bass go wow.

I'm not saying you're dead wrong, but I'd like to see some concrete numbers/equations as to what correlates to "grip and control" and "making the bass go wow." To my knowledge (and I'm not claiming I know everything there is to audio engineering, that's why I asked for proof and didn't just outright say you're wrong), the only discernible difference between two amps at identical volume with all other things equal up the audio chain is the differences in their sound signature. Whether to you that correlates to describing the sound signature as having "grip and control" vs. wildcatsare1 describing it as "soul of the music" is all descriptive style of language for talking about the same thing - just different sound signature of the amp. 

 

[Ableza]

You simply cannot attribute all these non-engineering terms to engineered phenomenon with any accuracy or certainty.  "Grip" and "Soul" and "wow" and "air" and "PRAT" and anything else are all purely subjective descriptions and are unique to the listener.  What "grips" me may leave your opinion covered in "veils." 
 
This is why I dislike the whole audiophile hype world.  It's nonsense to everyone except the listener (and those who convince themselves they understand the listener, but unless you share that person's head you are fooling yourself.)
 
Use what you like.   Make up your own mind.  If you wish, pay attention to others who like A more than B and try it yourself  Describe your reaction by saying "I like A more then B too" (or not) and leave it at that.  Nothing else matters (cue Metallica)

 

[sonitus mirus]

The O2 amp was specifically designed to be audibly transparent and to accommodate the power requirements for a wide variety of headphones.  I have no issues with my Mad Dogs and the O2.  I don't see any major differences in the specifications for the Alpha Dog.  The O2 should be a good SS amp to use with the Alpha Dog.

 

[Alphanewb]

The O2 amp was specifically designed to be audibly transparent and to accommodate the power requirements for a wide variety of headphones.  I have no issues with my Mad Dogs and the O2.  I don't see any major differences in the specifications for the Alpha Dog.  The O2 should be a good SS amp to use with the Alpha Dog.

I think one of my posts started this tangent and I'm thankful for all the various perspectives of the experienced posters here. Your first sentence above was pretty much the reason I chose the O2 as my first headphone amp to go with my first $500+ headphones (most I'd ever spent was about $100 in the mid 90s which has to be in the range of $200 in today's dollars).

I do think I'll be picking up a tube or hybrid amp at some point along with a higher end open orthodynamic headphone. I do prefer to listen at lower volumes, with that being the case will my ADs likely sound better with a lyr2? I guess what I'd like to better understand is whether there is any support/evidence that it could be more than just a preference for a warmer sound signature that drives some of the glowing reviews for the lyr2 and AD combo?

 

[Lillee]

  I'm not saying you're dead wrong, but I'd like to see some concrete numbers/equations as to what correlates to "grip and control" and "making the bass go wow." To my knowledge (and I'm not claiming I know everything there is to audio engineering, that's why I asked for proof and didn't just outright say you're wrong), the only discernible difference between two amps at identical volume with all other things equal up the audio chain is the differences in their sound signature. Whether to you that correlates to describing the sound signature as having "grip and control" vs. wildcatsare1 describing it as "soul of the music" is all descriptive style of language for talking about the same thing - just different sound signature of the amp. 

 
I wasn't referring to sound signature at all. Simply put, if your amp cannot at least output 750mW (give or take) bare minimum at the ohms for your magnetic planar earphones (50 Ohm for Alpha Dogs) then there isn't enough power to sufficiently drive them.
 
Here's what Audeze has to say, they recommend 1W
https://audeze.zendesk.com/entries/20866002-Selecting-an-amp- 
 
It's not just about loudness, as some amps with small wattage can play music loudly @ 50ohms but a 350mW amp being pushed to 95% volume and experiencing clipping is not going to the same as a 2W amp at 30% volume and no were near max. Both are playing music at 85db but one is significantly distorted when reaching dynamic peaks (complex passages of music) and hence "wow" bass just isn't there. The "grip" and "control" needs power. Without power there is no "grip" or "control". Never mind how warm/dark/textured the amp is, that is separate.
 
Here is another great, short read and although its talking about hifi amps, it's still relevant
http://www.gcaudio.com/resources/howtos/voltageloudness.html
 

 As you can see, clean, undistorted power is the key. A 25 watt amplifier, constantly driven to clipping, is more dangerous than a 250 watt amplifier that is never taxed

 
Have a nice day everyone!