Got it setup, played around with the settings, and it is driving the HE-400i quite well. Initial impressions is there is a little harshness in the treble which I found with the other amps offered by s.m.s.l.
Using optic it took me less than 1 minute to set it up. No driver installation needed non-DSD files.
Will get the review up a few days after it comes in
SMSL M8 USB DAC + VMV VA2 Headphone Amplifier + P1 Linear Power + W6 Cable Kit
Brainwavz is always up for innovation and their new M100 earphone ( IEM ) adds to a long list of products. This IEM is built around amping so it will be very interesting how it performs with the various headphone amps I have at my desk including the beyerdynamic A20, s.m.s.l. SD-793ii, Grace m903, and the HeadRoom BUDA.
Check in soon for updates…
The next major review going up will be that of the s.m.s.l. SD-793II which is a desktop DAC/amp. For the price this thing rocks! Stay tuned.
SPECS: ( from Beyerdynamic North America )
Dimensions 164 x 212 x 55 mm
Frequency range 10 Hz – 100 kHz (-1 dB)
T.H.D. 0.01 % at 170 mW / 250 Ω
Maximum output power 170 mW / 250 Ω
Unweighted signal-to-noise ratio > 100 dB (unweighted)
Channel separation > 80 dB at 1 kHz / 250 Ω
Headphone outputs 2 stereo jack outputs 6.35 mm (1/4″) in parallel
Analog inputs 1 pair RCA
Analog outputs 1 pair RCA
Net weight without packaging 1640 g
OVERVIEW
I am constantly looking for equipment under $500 that beats out my end-game setup. The A20 headphone amp caught my eye for two reasons. It has great reviews and beyerdynamic is known releasing great audio equipment. They are not afraid to tailor the sound for a particular need. I hope that the A20 can drive the finicky HiFiMAN HE-400i and Audio Technica ATH_R70x that I plan on testing it with and will it keep me into the music and less focused on the flaws of the amp?
AESTHETICS
This amp is simple. The front panel has a power button, two ¼ inch headphone jacks, and a volume knob. The back has RCA in/outs and a 3-pin power supply jack. The power button on the front will glow red with the unit is powered down and green when it is ready for use. The brightness level is just right and will not leave your pupils permanently the size of pinholes. The headphone jacks are identical. I would have liked to see one of them used for high-gain and the other low. The volume knob is solid, but I feel it is part of the design that was used to cut costs as it feels cheap compared to the rest of the unit. The A20 weighs more than 1.5 kilograms making it heft amp for its size. It is a beefy unit when you unpack it so why not include a stellar-feeling volume knob. I will say it is made of very fine brushed aluminum or stainless steel and never gets hot to the touch. Well done on that beyerdynamic.
You can rest assured the A20 looks and feels high-end. The weight, brushed chassis, and finishes are all top of the line.
ACOUSTICS
The headphone output on the A20 has an impedance of 100 Ohms. The lower the output impedance on a headphone amp the better the amp can dampen the harmonic resonance of the driver. You can read more about that here. Unwanted resonance will lead to distortion not originally found in the signal path. I was curious how a 100 Ohm output impedance headphone amp would sound compared to the other gear I have with output impedances of < 10 Ohms.
It is recommended that damping ratios be greater than 5 and some engineers prefer 8 or 10. For you more visual people:
For the HE-400i has an impedance of 35 Ohms and the A20 has an output impedance of 100 Ohms. Doing the arithmetic yields:
As you can see the damping ration for the A20 driving the HE-400i is not ideal.
Enough about damping. Back to how it drives headphones. What are some of the strengths of the A20 and how about the weaknesses?
First, the A20 can drive the HE-400i with no volume problems. The 400i has an efficiency of just 93dB which is pretty low for a headphone. A value under 100dB is a sign that a good amp will make the headphone sound its best. This is certainly true for the 400i. The A20 drives this headphone into sonic harmony by providing enough power for the bass, clarity for the midrange, and does not diminish the treble. Even for some of the classical pieces I tested I found the A20 to have enough power.
Artist: Katarzyna Mycka
Album: Marimba Classica (feat. Franz Bach)
Track: Libertango (feat. Franz Bach)
The volume knob, at zero volume rests at 7 o’clock and creeps up above 2 o’clock with this track indicating the A20 could use a little more power/voltage with inefficient headphone like the HE-400i, but no track I own was underpowered. It came down to where I prefer the volume knob. Even though the damping factor was low in the HE-400i / A20 combo I heard no signs of distortion even at high volumes.
How does the A20 sound with high impedance headphones like the Audio Technica ATH-R70x? Because the damping factor increases as the impedance of the headphone increases the distortion caused by improper damping will lower. In the case of the R70x which has a peak impedance over 1000 Ohms the damping factor becomes > 100. In this regard the listening experience will improve. One would expect, because the impedance is so high, that the A20 would have difficulty driving this headphone, but this is the common problem with people trying to use impedance instead of sensitivity when talking about how loud a headphone can get. The sensitivity ( efficiency ) should be looked at first and not the impedance ( Ohms ).The sensitivity tells you how easy the headphone is to get loud. At 99dB the R70x is actually easier to drive than the HE-400i because the HE-400i is rated at just 93dB. These measurements should actually include another value as in 99dB / mW instead of a raw dB number. Companies often supply either a per mW or per mV value which tells how much loudness in dB the headphone will get per that mW or mV rating. The larger the value the easier the headphone is to drive. So if you have a 99dB / mW headphone then at 1 mW the headphone will be 99dB loud which is almost deafening. It is the fact that the sensitivity is more important to the average consumer and not the impedance.
The general sound signature of the R70x leans towards detail rather than bass. It is one of the most open headphones by design and really cannot deliver low bass due to its severe sound leakage. The R70x is also a bright-sounding headphone causing my ears to fatigue after just a few minutes of listening with most amps. The soundstage is also spectacular and will be noted when paired with the A20 amp.
When Hush by Angus and Julia Stone from the Down the Way album started up I was expecting this track to deter me from long listening because it can sound bright and fatiguing with bright headphones. Normally the R70x would have too much treble for me to enjoy this track, but this track sounded smooth and relaxing through the A20. It sounds like the high output impedance of the A20 is really helping the harshness of the R70x. If you are looking for an amp to tame some of the troublesome brightness on headphones like the R70x and HD800 then the A20 is a great place to start.
If you are looking for an amp / headphone combo that delivers some serious detail without becoming fatiguing the A20/R70x is awesome!
What are the A20’s strengths?
What are the A20’s faults?
Favorite Test Tracks
Artist: Global Trancemission
Album: Pier ‘o’ Heaven (The Assorted Divine Chillout Music)
Track: The Secret Path (Variation 2 Mins Ending)
Global Trancemission has really done a spectacular job in recording this track. It has everything from hard-hitting bass to shakers and chimes. Nothing sounds harsh or too-bright and the bass certainly thumps nicely.
Artist: Days of Funk
Album: Berlin – Monday Morning Hours, Vol. 2
Track: Water
Another great track to test your setup. This track should sound engaging, have tons of attack to draw you right in, and the clarity should remain resolving enough to let you enjoy each section of the track. Listing with the A20 reveals no distortion, no shortfalls in clarity or attach, and the track draws me in as is found with my high-end setup.
No major issues with soundstage were heard testing the A20.
CONCLUSION
If you are looking for a standalone amp that can deliver some serious bass, clarity, and attack then the beyerdynamic A20 is a great place to start. It is easy to setup and use, feels like a German tank when you unpack it, and drives my cans well. Perhaps a bit weak it could use a little more gain, but it gets you 99% of the way there for and still sounds great. Due to the high output impedance and noise floor I cannot recommend the A20 for IEM listening as the noise is clearly audible, but in all other aspects of the sound with other headphones the A20 receives high marks. Perhaps most importantly it draws me into my music more than the more expensive Grace Design m903 and I find myself wanting to come home after work and give it another listen.
Headphone Reviews by NA Blur 