Audiophile CMOY Headphone Amplifier USA Made with Parts-Penguin Tin

Great little headphone amp, but wish the designer had put a power indicator lamp on the outside of the metal case. There's one inside, but you need to crack the case to see whether the device is still on (and sucking battery). Even a hole punched into the cover would help with this, but a more elegant solution would be to have the LED mounted into the side of the case. But for under $40, you do get a great sounding little headphone amp. That is undeniable.

Before I say anything else - this is just my subjective opinion about headphone amps in general and this amplifier in particular.Granted - for approx. 90% of all people a portable headphone amp might be somewhat useless since the money would better be spend in different headphones, and another 5% are better off by just purchasing a Fiio E6 (which I also own, and a Fiio E7/E9 combo). This is for the remaining 5%.What you get (I ordered from stevovee85):A very well assembled CMOY amplifier including an (exchangable) OPA2134 (op) amplifier chip. You will need a 9V battery and a 3.5mm cable to hook it up to your source.You can probably stop reading here. The OPA2134 will serve most people very well (yes, it would serve me). I tried it 'as is' in several combinations and it always sounded good to me. I listened to it using Sennheiser HD590, AKG K701, AKG K61 (blu tak modded), Shure SRH940, Shure SE535, Yuin PK1, Monoprice 109927, Ultimate Ears Triple.Fi 10 phones. Sources were mainly a Sandisk Sansa Clip Zip (rockboxed), Marantz 1060, and - I admit it - ipod Shuffle 3rd gen.tl;dr:There is no 'one serves all' superb perfect solution for everyone in every condition. However, this amp is awesome as it is, comparably cheap, and I also enjoy the analog volume knob a lot! If you want to modify it, you can.If you still want to read further:The only thing that made me think about changing the OPA2134 to a different model was the curiosity.If you look deeper into internet boards and reviews about changing the amplifier you will encounter almost a 'this is the best amplifier' vs. 'the other one is still better' vs. 'in a blind test nobody will find a difference' war going on. In addition - 'just changing the amplifier without adjusting the other components accordingly is stupid'. Though I agree here in principle, my idea is that if you can change it and it suits you better - why not? Also, most 'best amplifier' opinions seem to ignore the source as well as the headphones, the latter still being the part with the most impact on sound quality. They also usually do not state the kind of music they would like to play with that.Since my main application for the amplifier is to sit between my Sansa Clip Zip and my Yuin PK1, I tried to optimize for this. The kinds of music I like range from medieval (Gregorio Paniagua) via Bach, Beethoven, Mendelssohn, Bruckner, Mahler to Pink Floyd, Kansas, Pearl Jam, Diana Krall,...So I just ordered some other op amps, namely OPA2107, LM6172, LME49720 (aka LM4562) which are the same DIP design as the 2134 so changing is easy and the circuit worked with all of those. I also ordered the AD8620 and the AD8066 with a SOIC to DIP8 adapter so I had to solder a little bit. At first, after soldering, they did not work. Turned out the soldering temperature was too low so I 'burned' it again. The AD8066 was then stable in the circuit, the AD8620 seems still unstable (maybe need to try again?).However, here my conclusion for my application: The OPA2107 sounds similar to the OPA2134 but with a better separation of instruments and overall fuller sound. Would prefer it over the OPA2134 (although it is operating at its limit with a 9V battery and apparently needs at least 12V to sound awesome - I do not know). Both LM chips sound similar, I personally would prefer the LME49720, very open, very fast, very analytical. Does not pair well with my Yuin PK1 earphones, however, maybe better for a Sennheiser kind of phones. The AD8620 (when it worked) is very detailed with a wide stage but I do not like the midbass which is overly present to my ears while the heights were somewhat missing. In the end, the AD8066 stays in for now. Very open highs, still good deep bass - it sounds awesome with the Yuin PK1 (it sounds e.g. awful with the AKG K701, this was better with OPA2107).Hope, that helps. Thanks for reading ;-).

Random loud distracting noise from this thing since I turned it on the first time. No response from the seller on why. Trash.

Good power which enhance my listening experience very much. I am using Beyerdynamic DT-1350-80, iPod Classic playing AIFF format. Bring more details, even better than many apm costing over USD200.The only setback is using 9V battery, i.e. not using rechargeable battery. It will cost user more.

Just what I needed for a weak volume level on ipod to hi-end headphones. Plus it looks amazing. Thank you!

Best amp I have bought

I gave this as a gift and he said it works great, he loves it

Handsome amp build providing solid and clear sound.