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The A840 is a modern active ribbon design.
The A840 is a modern active ribbon design.

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AEA A840 Powered Ribbon Microphone
By Scott Dorsey
Date: August 2010

This is how AEA (Audio Engineering Associates) introduced the A840 microphone at last year's AES convention in New York: "...a powered version of the acclaimed R84 microphone. The A840 gives you the same award-winning sound, but with the hotter signal of an active microphone that yields a lot more versatility both in usage and choice of mic pre."

A closer look

I spent about 20 hours in the studio with this microphone, and having reviewed the R84 in our November 2003 issue I can say that the A840 sounded better to me than the R84.

One of the first things that come to mind when you hear the A840 is the classic RCA 77DX ribbon microphone, and this is in great part probably due to the grille design. The grille of the A840 is cylindrical, much like that of the 77DX. What is interesting is that a lot of the characteristic sound of the 77DX comes from that cylindrical grille, because any sound that is reflected from the grille inside is immediately focussed toward the center of the mic where the ribbon is, and this creates high-frequency standing waves at some frequencies. The AEA grille is more acoustically transparent than the perforated metal that the 77DX uses, and so this effect is greatly reduced because there is less reflecting going on. But still, the 77DX instantly comes to mind.

The A840 is a figure-8 mic, and it has a very deep and solid null. When I checked the null, just by moving the mic around in front of a sound source, it seemed pretty good. The front and rear lobes don't have quite the same frequency response, much like on the R84. This degrades the null a little bit, and makes it harder to use the mic for things like putting ten backup singers around a single mic, and impossible to use as a side mic for M-S miking. That's a shame because the good top end on this mic would otherwise make it a good choice for M-S. [AEA recommends the R88 mk2 as a better choice for M-S work.-Ed.]

The off-axis response is not wonderful, but for a ribbon mic where there is a lot of mechanical stuff up close around the ribbon it is quite respectable and certainly better than that of the 77DX. It sounds good up front, and it still keeps sounding good when you pull it back, unlike the current generation of cheap Chinese ribbon mics that have some internal acoustical issues. You can't pull it back as far as you can pull back a BK-11 or a Schoeps, but again that's a very high standard to meet. [AEA notes that the long, narrow ribbon in the A840 causes them to have good off-axis response in the horizontal plane, but for there to be a notable high-frequency loss off-axis in the vertical plane. Users can actually "eq" the A840 just by tipping it up or down!-Ed.]

The electronics inside are very effective and have a nice low output impedance. I didn't measure it (the timing of the loan period prevented me from opening the mic and doing test-bench evaluations), but I ran it into a thousand feet of cable and the high end didn't disappear as it would with conventional ribbon mics. The JFET buffer electronics are designed so that while there is not much voltage gain because the output is not super-hot, yet it seems impossible to make the A840 clip, even up close to a Marshall guitar cabinet at full volume. But it's hot enough that you can use it with quiet instruments into a Mackie preamp. I guessed that there's a Lundahl transformer in there from the sound, and AEA confirms this.

In use

The overall sound of the A840 is like that of a classic ribbon mic, but it's definitely more extended and less ragged on top. The more extended and much less colored top end makes the A840 a more versatile mic.

The first thing I tried it on was an electric guitar, and it sounded great. This isn't really very meaningful because even the worst of ribbon mics sound great on electric guitar. However, when I started pulling it back from the cabinet and getting more and more room tone, the quality of the room tone remained good.  It wasn't as good as with some of the higher-end condenser mics, but it was better than with an old RCA 77DX.

I used the A840 on acoustic guitar and it sounded good. Not a lot of bite on the strings, but a clean acoustic sound without losing all of the bite.

On fiddle the A840 was very smooth but maintained a lot more of the bite on the strings than typical ribbon mics do. In the end, I decided to pull the A840 out and put an old Oktava ribbon in for this application; I wanted a more colored mic to kill some of the screech from being so close in on a fiddle... Likewise on mandolin, the A840 was too accurate on top and I wanted something to settle the top-end clang down.

On flute and recorder, the A840 was a great choice. It had a good and clean sound, without any shriek on the top end; the mellowing effect was pleasant and more subtle than with an older RCA design. It was present but not harsh. Same thing on concertina... it made for a very forward sound without exaggerting the noise of the keys.

On vocals, the A840 didn't make everyone who used it sound like Gary Owens (the classic deep-voiced radio announcer); it was more versatile than that and handled a very wide range of vocals. It was a great choice on a soprano, mellowing on top without losing the top register. It did have a little bit of an odd constricted sound that made things a little more nasal, but it had much less of that than the R84 I had tried before.

I would have liked to try the A840 on piano, which was one application where the earlier R84 had some midrange problems, but I never did get a chance to do that. (Well, I tried it on an upright piano that sounded awful, and got a recording that sounded like an upright piano that sounded awful. "This piano belongs in a church!" complained the performer. It's all part of the music festival experience, so I don't blame the mic...)

It did fairly respectably as a drum overhead, and as a general room mic on a string section, although I will say that it didn't do as well as the BK-11 or as the better condenser mics. I put this down to the off-axis response on the A840 not being quite as good as the on-axis response; in that regard it seems to be a whole lot better than a 77DX in figure-8 or a 44B, but not quite up to the standards of the BK-11. There is no shame in that, as the old RCA BK-11 is a very hard act to follow.

As a PA mic, the A840 had quite good gain before feedback. A lot of folks are afraid to use figure-8 microphones for PA because they are worried about pickup from the rear lobe. It can take some moving around to get things right, but the very deep null of the figure-8 mic means you can set it to get far better monitor rejection than a conventional cardioid. When I used the A840 on a massed group of fiddle players, the gain before feedback was not as good as that of a BK-11 but better than that of a 77DX, probably for the same reason I mention above with room miking.


The A840 is promoted to be an R84 with added phantom powered electronics, but to my ears it sounded better than that; I did not hear much of the midrange issues that I heard with the R84. The added phantom-powered electronics do what they are supposed to do and they don't get in the way, and the resulting mic has a very good and usable sound.

Price: $1725 ($1552.50 street)

More from: Audio Engineering Associates,

Scott Dorsey ( knows and loves ribbon mics.


Kef America

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