Recording - August 2010 - 22

BY SCOTT DORSEY

AEA A840
Powered Ribbon Microphone
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 highfrequency 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.]
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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 offaxis 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

Recording - August 2010

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