I have both the Denon d2000 and HD650, and the O2 does an excellent job driving them. I do not have the urge to try any other headphoneamplifier after having listened to the O2. And i have owned more than 20 headphoneamplifiers from various well known  manufacturers. For my ears it fullfills all...

re upstateguy   My source is a desktop computer paired with a Cambridge DacMagic,

re upstateguy   My O2 is not clipping. headphones I use are Sennheiser HD650 and AKG K601.

I just love my Objective O2 amp. I have used it for several hours each day since I got it from Mr.Slim. It is paired with a Cambridge Dacmagic and a desktop computer. I like it more than my Decware CSP2 and Stax Srm-1/Mk2 with Stax lambda Pro. My Decware is for sale, and the Stax system was sold...

I have, and have had a lot of headphone amps. With this objective O2 I feel that it fulfills all that I need in a headphoneamp. I will now sell all my other headphoneamps which consist of Stax, Decware Audio, Meier audio, Ibasso, and other companies. I will make one more heaphoneamp buy, and...

I received an Objective O2 from Mr.Slim yesterday. I find it to be an amazing amplifier for a very cheap price. The build quality from Mr.Slim is excellent, and the O2 is now my main headphone amplifier. Headphones used; Sennheiser HD650.

Yeah! I know NwAvguy is the inventor, but I thought I was not allowed to mention his name here :) 

I think Mr.Slim offers the O2 for a very good price! And it is great to be of the first people getting a completely new design from the very educated inventor of the O2.

Great review! I have allready ordered one from Mr. Slim. And later I will buy the desktop version.

Same here. I want this headphone amplifier as fast as possible!

I just found this: "Trade In We will give you credit for your old headphone amplifier toward the purchase of any new Headstage amp. Please notice that the upgrade price must be $80 or more and we can only upgrade one old amp to one new order. The old amp may be faulty and can be damaged...

I tried the Arrow with a pair of Etymotic ER-4P. There were no hiss!

I received my "Arrow" 29 days ago, and I have fallen asleep with it every single night after that! I am so satisfied with it that my RSA Tomahawk, iBasso D10, iBasso P3+ and my Corda 3Move has been forgotten in the drawer! I use it with several hadphones I got: Sennheiser HD595, 600, 650, Denon...

http://www.head-fi.org/forums/f105/w...-arrow-461344/

9,8cm x 5,4cm x 0,8cm!