The question we’re using for today’s Tech Tip walks a fine line between a question and a complaint, but it’s an issue many of us have noticed and wrestled with.
“Good info on the analog/digital meter difference and relative zero (see inSync 4/4/00). How ’bout going a bit further though. Here’s my question. I’m running a +4 analog console into a +4 DAT. When I record onto DAT I’m just below 0 (over), but when I play this back the meters on the console peg HARD, clipping more than they ought to. I can understand the difference in digital and analog metering, but what’s strange is how are you supposed to control the amount of level coming into the console? The DAT doesn’t have an output level and it’s just coming into the console thru one of the fixed (nominal +4) 2-track inputs. It seems silly to have to add an external pad to the line before it hits the console. And it seems silly that the DAT doesn’t do it’s own compensation on the +4 outs to give you what 0db on the meters is expected to sound like (and look like). What else would you be hooking that +4 analog output to? It sure isn’t going to get plug into something digital, it’s an analog out!”
So what you really want to say is, “AAAAAAAAHHHHH,” isn’t it?
First, understand that if your DAT machine is set up and working properly it isn’t going to spit out any more level than you hit it with in the first place. Therefore you should be returning the same signal to your console that you sent out of it to the DAT to begin with. You didn’t say what the console’s meters were doing when you recorded to the DAT, but if everything is set up properly they should have been pegging hard then too. Of course, if you have another gain stage, such as a compressor or level control, between the console and the DAT machine then all bets are off.
Here’s a quick test. Route the cables from your console’s main output (the one you use to drive the DAT) right back to its two track inputs. Verify that the meters read the same between the two. If not, you’ve found one problem right there. Assuming they read the same just reconnect the whole signal path between your console’s outputs, the DAT, and the 2-track returns. If everything is set up properly all the way through you should see identical levels returning to the mixer. Again, be aware of what things like compressors and equalizers can do in line. A big variable for a lot of folks here is the input level control on the DAT. If you turn it way up to get the recording levels you want on the DAT then who knows what the output of your console really is (I suspect this is your main problem). It is possible to have a somewhat low level coming out of the mixer and then just make up that gain with a boost at the input of the DAT. This is not ideal because it doesn’t maximize the dynamic range and signal to noise ratio of your mixer. What do you do? You find out what unity gain is for those input level controls on the DAT and you set them there. The manual should tell you this. Hopefully your mixer can muster enough output to drive it. If not, then that’s what those controls are for. You’ll have to turn it up at the DAT and then live with the levels coming back in to the mixer, pad them down somehow, or get a DAT that has an output level control. If your mixer can handle the full level without distortion then I would consider leaving things as they are and just using the 2-track level control to lower the volume (yes, I know this will still leave the meters pegged).
It’s also possible that your meters on your mixer just don’t have enough resolution at their top range. This is the case with many old analog mixers because they weren’t originally designed with the levels we use in today’s digital recording in mind. Let’s look quickly at this.
Last week (inSync 4/4/00) we showed that meters in digital gear are designed to always read some amount below their full code (0 dBFS) level, and that a +4 dBu signal will cause them to read between -12 dB and -20 dB on those meters (assuming a +4 dBu input on the DAT). You don’t want to change the metering on the DAT as you suggest because this causes too many assumptions, and the one thing you certainly don’t want to be assuming is how close you are to 0 dBFS. Some DAT machines do have output level controls, but they are rare because most people don’t want the added variable in line.
So, while the DAT and mixer meters may disagree about what zero means on their meters, they do generally agree electronically with the levels they are dealing with. When your mixer hits +4 dBu it still has a lot of headroom and so does your DAT.
The metering problem is aggravated by the extremely loud and compressed recordings we make today. If the meters on your mixer are set up so there are only three red LED lights between zero (+4 dBu) and maximum (say +26 dBu), and only one LED between, say +16 dBu and +26 dBu, then it is likely they are going to appear to be pegged with a lot of music created today. Digital recording has really emphasized the need to have maximum levels most of the time, and a lot of popular music today is so compressed that the levels rarely fall to what would be +4 dBu on an output. Just plug a CD player digitally into your DAT recorder and look at the levels, than pass that through to the analog output and the 2-track input on your console. It’s scary. But as long as your console has the headroom to deal with those levels it’s not a problem. You’re just further away from its noise floor.