Stereodude
Not really a
I wanted better audio from my laptop at work, so after reading a lot of reviews on head-fi.org and other places on the web I decided to dip my toe into the pool of USB DAC & Headphone amps. At first I had grandiose visions of spending a lot of money on a supposed really high quality setup, but later I came to my senses and decided to buy something more reasonably priced to start. This was mainly driven by my belief that the vast majority of the people posting on head-fi like most "audiophiles" are delusional consumers of snake oil hearing what they want to hear. ;-) So, I settled on a Aune Mini USB DAC / Headphone Amp MkII SE. It's solid state (no tubes to wear out or color the sound), does USB audio, drives a set of headphones, had good reviews, and didn't cost an arm and a leg.
Note: Mine did not come with the red MX500 earbuds show in the pictures or in the product listing.
I bought it from an ebay seller in China for $130 w/ free shipping (ebay listing). It arrived on my front porch in the US 12 days after I bought it.
One of my concerns was background hiss from the unit since my Shure E4 IEMs have a high sensitivity and low impedance which makes them both hard to drive typically suffering from low frequency roll-off and prone to exposing background noises in the headphone outputs of gear (buzzes, hums, hisses, etc). My work Lenovo T410 has rather audible low frequency rolloff with the E4's, but the background noise level was better than I expected. It suffered mostly from hiss. It's about on par with my Sansa Fuze in terms background noise. As a point of reference the Fuze doesn't have low frequency roll off which was somewhat rare in a PMP a few years ago (not sure about now). And, unless you're listening in a dead silent environment the background hiss from the Fuze gets lost in the small amount of ambient noise that sneaks past the isolating characteristics of the E4's.
So before purchasing the Aune I read every review I could find and didn't find anyone complaining of hiss so I hoped it would be safe. So, when I got it I was a little surprised to find a rather obvious background hiss with the Shure's. The Aune was much worse than the Lenovo T410 or the Sansa Fuze. The unit also had way too much output gain becoming too loud after about 20 degrees of rotation from the minimum position of the volume knob. So, I grabbed the inline volume control that came with the Shure's and used it to decrease the volume hiss until it was inaudible. Listening to the Aune with the inline volume control in the output path I was happy with the sound quality of the Aune over USB, so I decided to modify the unit to put some series output resistance inline with the headphone output internally to kill the hiss. I opened it up and found these 3.01ohm 1% 1/2 watt resistors already in series with the headphone output.
So the modification will be easy, just replace them with a larger value. I measured the resistance of the inline volume control when the hiss had been completely suppressed and found it was about 200 ohms. I then confirmed with my Sony MDR-V6's (the only other pair of headphones I might use with the Aune) that the extra 200 ohms in series with the output didn't prevent the Aune from still generating more than enough listening volume. Even with the extra 200 ohms inline the less sensitive MDR-V6's was unbearably loud with the volume 1/2 way up in the 12 o'clock position.
One other thing I found in the reviews was that some of the Head-Fi crowd thought the Aune sounded better with a 18V DC input than the 12V DC input it shipped with in the past. :skepo: Mine came with a wall wart labelled for 220V / 50Hz input 15VDC / 1A output. I measured an open circuit voltage of 24.43V from it.
The Aune is labelled as accepting 12-18V on the case, but a seller of it posted on Head-Fi that it could really take up to 24V. So I broke out a benchtop linear DC power supply and connected to the Aune to test the theory and found that starting at 12V the output volume increased slightly until about 13V and then held steady all the way up to 20V where I stopped testing. Unsurprisingly I didn't notice any sound quality differences. Current consumption increased as the voltage increased from .1A at 12V to .12A at 18V. Cranking the volume to the max with the Sony MDR-V6's connected (and not on my head) increased the current draw to .13A at 18V.
So, I decided to replaced the piece of crap wall wart that came with the unit with one that is actually properly regulated. I settled on a 15VDC / .8A unit from Mouser since there was no point in needless consuming more power at higher input voltages and 15V was past the point of increasing volume. Add in a few 200 ohm .1% tolerance 1/2W resistors and hopefully audio bliss awaits.
Note: Mine did not come with the red MX500 earbuds show in the pictures or in the product listing.
I bought it from an ebay seller in China for $130 w/ free shipping (ebay listing). It arrived on my front porch in the US 12 days after I bought it.
One of my concerns was background hiss from the unit since my Shure E4 IEMs have a high sensitivity and low impedance which makes them both hard to drive typically suffering from low frequency roll-off and prone to exposing background noises in the headphone outputs of gear (buzzes, hums, hisses, etc). My work Lenovo T410 has rather audible low frequency rolloff with the E4's, but the background noise level was better than I expected. It suffered mostly from hiss. It's about on par with my Sansa Fuze in terms background noise. As a point of reference the Fuze doesn't have low frequency roll off which was somewhat rare in a PMP a few years ago (not sure about now). And, unless you're listening in a dead silent environment the background hiss from the Fuze gets lost in the small amount of ambient noise that sneaks past the isolating characteristics of the E4's.
So before purchasing the Aune I read every review I could find and didn't find anyone complaining of hiss so I hoped it would be safe. So, when I got it I was a little surprised to find a rather obvious background hiss with the Shure's. The Aune was much worse than the Lenovo T410 or the Sansa Fuze. The unit also had way too much output gain becoming too loud after about 20 degrees of rotation from the minimum position of the volume knob. So, I grabbed the inline volume control that came with the Shure's and used it to decrease the volume hiss until it was inaudible. Listening to the Aune with the inline volume control in the output path I was happy with the sound quality of the Aune over USB, so I decided to modify the unit to put some series output resistance inline with the headphone output internally to kill the hiss. I opened it up and found these 3.01ohm 1% 1/2 watt resistors already in series with the headphone output.
So the modification will be easy, just replace them with a larger value. I measured the resistance of the inline volume control when the hiss had been completely suppressed and found it was about 200 ohms. I then confirmed with my Sony MDR-V6's (the only other pair of headphones I might use with the Aune) that the extra 200 ohms in series with the output didn't prevent the Aune from still generating more than enough listening volume. Even with the extra 200 ohms inline the less sensitive MDR-V6's was unbearably loud with the volume 1/2 way up in the 12 o'clock position.
One other thing I found in the reviews was that some of the Head-Fi crowd thought the Aune sounded better with a 18V DC input than the 12V DC input it shipped with in the past. :skepo: Mine came with a wall wart labelled for 220V / 50Hz input 15VDC / 1A output. I measured an open circuit voltage of 24.43V from it.
The Aune is labelled as accepting 12-18V on the case, but a seller of it posted on Head-Fi that it could really take up to 24V. So I broke out a benchtop linear DC power supply and connected to the Aune to test the theory and found that starting at 12V the output volume increased slightly until about 13V and then held steady all the way up to 20V where I stopped testing. Unsurprisingly I didn't notice any sound quality differences. Current consumption increased as the voltage increased from .1A at 12V to .12A at 18V. Cranking the volume to the max with the Sony MDR-V6's connected (and not on my head) increased the current draw to .13A at 18V.So, I decided to replaced the piece of crap wall wart that came with the unit with one that is actually properly regulated. I settled on a 15VDC / .8A unit from Mouser since there was no point in needless consuming more power at higher input voltages and 15V was past the point of increasing volume. Add in a few 200 ohm .1% tolerance 1/2W resistors and hopefully audio bliss awaits.
