DAT-Heads Digest #711, Volume #2 Tue, 16 Apr 96 02:12:04 EDT ---------------------------------------------------------------------------- From: PBM%mimi@magic.itg.ti.com subject: DAT tapers: BEWARE of brickwalling while taping live!! date: Mon, 15 Apr 96 10:31:28 CDT To: message to internet M2I From: Mark Powers PBM Subj: DAT tapers: BEWARE of brickwalling while taping live!! Hi all - I've been seeing more and more tapes with this problem lately, and am convinced that it is probably one of the main causes of people's "auds suck" gripes. The problem is known as "brickwalling", and can induce distortion to a recording that can range from mild to horrendous. Apologies to those of you that know about it, but there are obviously growing numbers of tapers that don't, and it's important. Brickwalling occurs when the output of your microphones is too hot for the preamp you are using (either the deck's input or an outboard mic-line amp), which results in the preamp being overloaded. Most of the better condenser mics out there (AKG's B&K's, etc) are capable of output voltages higher than the mic inputs on, say, a D7 are equipped to handle. This will turn what could have been a terrific recording into a mudbath in a big hurry. Fortunately, brickwalling is both easy to spot *and* easy to prevent: the name "brickwalling" stems from the fact that when this phenomenon occurs, the levels on the DAT deck will typically go right up to but never beyond a certain point, as if they're running into a "brick wall". Note that IT CAN AND WILL OCCUR WITH THE LEVELS SET *ANYWHERE*, this has NOTHING to do with going over zero, which is *digital* distortion; brickwalling is *analog* distortion, the same thing you get when you turn a cheap AM radio up too loud. You can get it with the levels set at -12, and it has nothing to do with where the record level knob is set!! So, for example, if you're recording a show and see that the levels are always hovering right at or around -6dB and never go beyond it, no matter how intensly the band is playing, it's a pretty safe bet that the mic preamp of your deck isn't happy with what it's seeing. In the worst case, the recording will be unlistenable; in cases where the overloading is bad but not severe, the recording will sound really good during the quiet parts but will tend to get muddy-sounding during the louder stuff. So, for example, Fee will sound great, but the finale of Bowie will sound muddy, garbled, trashy, etc. As I said, I have been seeing this on a *lot* of the recordings I've been getting lately, so I figured a word to the wise oughtta make a lot of people happy. :-) So how do you stop it? Simple. Most of the good condensor mics out there also have attenuation pads, which will drop the output signal level of the of the mics down to where your mic preamp will be much happier (as will all of the people that listen to your tapes, including you! :-) So if you see this happening, all you've gotta do is switch the attenuator pads on your mics to the "-10dB" position (make sure you don't hit the rolloff switch by mistake!). Note: this will require you to set the record level knob up significantly higher to get good levels, but your recording will sound *tons* better. If you do this *and* maks sure that the levels don't go above zero, you'll be rewarded with much-better sounding tapes! FYI, if you want to see what to look out for, play some of the less-than-perfect sounding tapes in your collection while watching the levels. Assuming that good gear was used to record it, there's a pretty good chance you'll see the brickwalling effect. Living up to my name again, PickyBastardMan ---------------------------------------------------------------------------- DAT-Heads Digest #715, Volume #2 Wed, 17 Apr 96 13:12:06 EDT ---------------------------------------------------------------------------- From: "Michael J. Shaw" Subject: SB brickwalling Date: Wed, 17 Apr 1996 01:59:36 -0400 (EDT) That little note from a digest or two ago about mic-input brick walling can also occur when one is patched from a soundboard. All of the same "syptoms" pretty much apply. The signal in this case is overloading the line input as opposed to the mic-input. It will be fine in soft parts, but come loud parts it get ugly. The problem mainly occurs when a deck with consumer level line inputs of -10dBV is hooked up to a pro console that had +4dBu line level outs. This has happened to me once before. I had to learn the hard way. There was a bit of talk a while back about using attenuators and such, and that can help with this. I don't think that brickwalling was mentioned, though. If you are taking RCA outs of a board, those are a pretty safe bet, but be wary of 1/4" outs and esp. XLR outs. 99% of XLR outs are going to have a nominal level of +4. If you're coming out of a board with multi-matrices, you might be able to get the sound person to back off on your send, but always ask when in doubt. If you've got a deck with XLR in's, you should be fine as they will likely have a nominal input level of +4 (or swithable). Learn from my mistake and don't let any more recording get ruined. happy taping, Michael ------------------------------ From: Gary Davis Subject: RE: "Brickwalling" Reply-to: gdavis@loop.com Date: Tue, 16 Apr 1996 23:14:09 +0000 A much simpler way to avoid mike-pre-amp distortion is to avoid the mike pre-amp. If your mikes have their own power supply, and the music is loud, you can probably go right into the "Line" input on most decks and avoid this problem...