Q. Should I hire a U47 valve or a U47 FET mic?

I've been looking for a vocal mic for a particularly 'old-time' sounding project — something to give some classy warmth. I've decided I may as well go ahead and rent the real deal — a vintage Neumann U47. However, I'm also thinking I should try to get the most out of it and pop it in front of the kick drum for the drum tracking stage, or indeed use it for anything else that I can manage to squeeze out of it! But which model is best? I've heard that the U47 FET is the standard front-of-kick mic, but does it also deliver a good vocal? Alternatively, should I be looking to hire a valve U47?

SOS Forum Post

 
The U47 FET (left) may be the industry standard for miking a kick drum, and a well-respected vocal mic, but with possibly 30 years of high-SPL recording behind it, a hired model's performance could be compromised, especially for vocals. The U47 valve model (right) is one of the best vocal mics out there, but its SPL-handling capacity may be lacking for kick recording. The moral of the story is that one U47 probably won't do both jobs!  

SOS contributor Mike Senior replies: While the U47 FET has been cited as a vocal mic by top-name producers such as Steve Churchyard, Bob Clearmountain and Alan Parsons, its fame is easily eclipsed by the U47 valve model, which can lay a good claim to being the king of vocal mics — having appeared on hundreds of classic records by The Beatles, Michael Jackson, Mick Jagger, David Bowie, Jim Morrison and many more besides. So if you're after a vocal mic, I would personally choose the valve over the FET for that reason.

But there's another reason I'd steer clear of the U47 FET, too. Although it's not the most celebrated vocal mic, you're right in saying that it's far and away the first-call professional choice for kick drum close-miking. This means that any rental U47 may have spent more than 30 years sitting inside kick drums. Despite this mic's prodigious ability to cope with extremely high levels (as long as you switch in the pad), any condenser mic is still a piece of delicate precision engineering, so regular exposure to that kind of punishment has got to take its toll. I've come into contact with a handful of U47 FETs, including a number of rental models, and not only do most of them look like they've been through the wars, I've also had bad luck with them going intermittent on me mid-session for no apparent reason. (The Electrovoice RE20 is another kick-drum favourite that I find tends to suffer the same fate after that kind of sustained abuse.) More of a concern for vocal work, though, is that the extreme pressure levels may have stretched the mic's diaphragm, thereby compromising its performance when recording anything more delicate than a kick drum — our technical editor Hugh Robjohns is not the only engineer who keeps specific dedicated mics for kick-drum use for this reason.

The problem with the U47 valve, though, is that judging by the specifications given for it on the Rycote Microphone Data web site (www.microphone-data.com), it simply won't handle the kind of level a kick drum puts out without distorting to hell. To put things in perspective, I recently tried a KM84 on the batter side of a kick drum (not even inside), and it was noticeably struggling. On paper, that mic can take a maximum SPL of 130dB with its pad switched in, whereas the U47 is rated at 120dB maximum SPL, and has no pad switch. Even if you were happy to put up with the distortion you'd get out of a U47 valve on kick drum, I reckon you'd still be unwise to try it, simply because of the vintage status of the mic. It's possible your model could have been in service for more than 50 years, and I would personally treat any high-end audio equipment of that age with the softest of kid gloves.

Published July 2008