I remember a customer from very early on in my 3.5-year career working in the build your own PC department at Micro Center who insisted that he had to have an AMD video card because his computer has an AMD CPU. When I explained to him that this was inaccurate, he told me another sales associate had said otherwise. “He was wrong,” I said flatly. It went on like this for some time until I told him that it really didn’t matter to me whether he bought an AMD video card or an Nvidia video card and it was true: I couldn’t possibly have cared less. I remember it clearly because it was one of countless interactions to come in which the customer would question my expertise, which always came as a slap in the face because I prided myself as a guru. When I went home for the day, I sat down and researched computer components. I lived it and I breathed it. I ate it for breakfast, lunch, and dinner.
This customer wasn’t the first person in the world who thought that pairing products by the same brand would somehow make things more compatible. In most cases, it’s nonsense, which is exactly what I used to think when headphone manufacturers like Beyerdynamic and Sennheiser release headphone amplifiers. The Beyerdynamic A20 was no exception. I had been aware of its existence for years, but I had never really paid it any heed. It didn’t help the A20’s case that it was a standalone headphone amp without a DAC when, for the majority of my four years in this hobby, I had been using DAC/amp combos like the JDS Labs Element (piece of garbage, by the way), the Oppo HA-1, and the Schiit Jotunheim with balanced DAC module. It had always just seemed cleaner and less cluttered until I realized only earlier this year that it was really limiting my gear selection and I finally pulled the trigger on an endgame standalone DAC, the Schiit Gungnir Multibit (aka Gumby), that I could plug into any amp I pleased, whether single-ended or balanced.
I believe the A20 has been out since 2014 and it only eventually caught my eye in the latter half of 2017 because I read somewhere that it had a high output impedance; in fact, at 100 Ω, its output impedance exceeds that of most output transformerless tube amplifiers. Suddenly, it all made sense. High-end Beyerdynamic headphones typically have high impedances of between 250 Ω and 600 Ω, so they benefit from a high output impedance amplifier. This relates to a “rule of eighths” that suggests an ideal amp output impedance should be an eighth that of the headphone it is driving, and, in turn, this relates to a concept in audio called damping, which I will not attempt to explain here because I lack confidence in my knowledge.
Actually, if we adhere to the rule of eighths, the output impedance of the A20 is overkill even for the 600 Ω Beyerdynamic T1. The rule of eighths would put the ideal output impedance at 75 Ω for that headphone or 31.25 Ω for my DT 1990 Pro; that said, now that I saw there might be something to matching the brand of the amp with the brand of the headphone, I decided to give Beyerdynamic the benefit of a doubt. Presumably, their electrical engineers know more than I do about this topic, so I went ahead and pulled the trigger on an A20, skipping the much pricier A2 that only seems to betray the glorious simplicity of the A20 by adding unnecessary features.
The A20 can be had for $300 if you get a good deal or, if you’re smarter than me, you can often get bundle deals through Beach Camera on Amazon with various Beyerdynamic headphones that make the A20 either $100 or free. I seem to recall that being an option when I got my DT 1990 Pro and I didn’t want to spend the extra $100 because I’m an idiot.
The A20 is a simple unit. You get a pair of RCA inputs, a pair of RCA outputs, and a pair of 6.35mm headphone jacks. The build feels extremely solid, though it could be improved upon. The unit is wrapped in brushed aluminum, but the bottom appears to be steel and the top is a high quality plastic. I would have preferred a full aluminum chassis, but, to my surprise, I would later find that the A20 generates absolutely no heat, which, now having a Schiit Valhalla 2 in my amp collection, comes as a huge relief. I could never place the Valhalla 2 under my monitor because I feared it would melt the monitor. With any tube amp, you generally don’t want to leave it unattended for more than an hour at a time. The Valhalla 2 could literally burn my hand if I held it on top of the unit for more than a couple of seconds.
I’ve had hot solid-state units, too. The Schiit Jotunheim doesn’t exactly run cool to the touch and the Oppo HA-1, with its class-A power, runs hot as hell. The A20 is the coolest running amp I’ve had since the JDS Labs Element, with which I have long since parted due to its extreme sensitivity to EMI.
Going back to build, the power button was very loose in its housing upon first removing the A20 from its packaging, but, after a few presses, it seems to have resolved itself and the looseness has gone. I really like the green illumination when the unit is powered on and the red illumination when the unit is powered off. Its ALPS potentiometer is buttery smooth and the headphone jacks are the nicest and tightest I’ve encountered. This was one of my nitpicks with the Feliks-Audio Euforia, which has probably the loosest headphone jack I’ve encountered, especially given its price tag.
I quickly found the A20’s preamp outs to be fixed, which can be either a good thing or a bad thing, depending on your use case. If you want to hook up some passive speakers and connect a separate speaker amp, it’s great. If you wan to connect some powered monitors, it kind of sucks. The only piece of gear I have owned that allows one to switch between a fixed and variable preamp output was the HA-1. I really like my Miccas. I like them enough that I have both the passive (MB42X) and powered (PB42X) versions, as well as Micca’s new OriGain A250 speaker amp, so I was prepared for either situation, but, because the Gumby has two sets or RCA outputs, I am not using the A20’s preamp outputs at all. A weird quirk with the Euforia was that it somehow disabled the second set of RCA outputs on the Gumby whenever the Euforia was powered off, which proved incredibly frustrating. The A20 does not cause this same issue.
The most important aspect of any amp, whether it’s a speaker amp or a headphone amp, is whether it can drive your gear to satisfactory listening levels without distorting in the process. Another reason for my hesitation with the A20 was that it only has a maximum output power of 170mW into a 250 Ω load, which doesn’t sound like a lot, especially compared to the Valhalla 2’s 800mW into 300 Ω. Even at 600 Ω, the Valhalla 2 can supposedly deliver 450mW RMS per channel. I’m not an electrical engineer. All I can report is that the A20 has far more power on tap than the Valhalla 2 at high gain. I was actually stunned by the ease with which the A20 drove my DT 1990 Pro. I had laughed at the idea that the A20 would be able to drive two high impedance pairs of headphones simultaneously through its dual 6.35mm outputs and now I have no doubt that it can.
It’s well constructed, it’s incredibly powerful, and it runs cool, but how does it sound? Good. It sounds good.
Okay, to answer this question with a hair more detail, the A20 has a very full, meaty sound. I’d call it a warmish amp and, as such, it pairs well with Beyerdynamic headphones, which are often quite bright. It sounds as good as the Valhalla 2 without the background hiss of an output transformerless tube amp. The Euforia may have a slight amount more punch to it, a dash more bass slam, but I can’t be certain. That a $300 amp can sound so close to a €2,000 amp says it all though.
The A20 seems too good to be true. I hate writing a review without more negative bullet points because it makes me seem like a shill, especially in the deceitful world of personal audio, but the A20 is just that good. I’m quickly becoming a Beyerdynamic fanboy because the last two Beyerdynamic products I have purchased, the DT 1990 Pro and the A20, have been nearly flawless products that thrash the competition but also don’t get nearly as much recognition as they deserve.
As a final note, I would not recommend the A20 for low impedance headphones. If your headphones are 250 Ω and up, I cannot recommend the A20 enough. All others would do well to look elsewhere. Always choose an amp that complements the headphone.