db levels

A

autonickv

New member
Just curious, can someone explain to me what db is. I know it stands for decibel (or something like that)?

And:
1. Why is +db distorted?
2. Why is -db not?
3. What is the ideal db level for input, is it 0db?

On some instruments it seems I need to record higher maybe around +4 db to get a good signal recorded where as other instruments 0db is fine......?

Thanks,
Nick
 
Db

DB is a unit of measurement and means, at 0Db there is no attenuation, (volume change loosly speaking).

Digital recording is easier than analogue when recording levels. There are less tape and machine variations to worry about. If I had an Analogue multitracker and recorded a hi hat, I would record it about -5 or there abouts. This is because a hi hat has a very bandwidth specific frequency range and may saturate the tape if run up to 0db or higher. Don't overdo the levels on digital recording either... there is no point. Keep things below 0db where possible even if you think it could go higher. Noisy studio? turn up the recording levels or leave them where they should be...!


Regards


Steve....R
 
Decibel

The Decibel (db) is a measurement of sound pressure level (SPL), signal level and and changes or differences in signal level. The decibel is a logarithmic (log) math function which reduces the large numbers into smaller more manageable ones. It is calculated as being 10 times the log of the ratio of 2 powers (power is measured in watts) and 20 x the log of the ratio of 2 voltages.

dBm = Decibels referenced to 1 milliwatt.
dBu or dBv = Decibels referenced to 0.775 volt. (dBu is preferred).
(0 dBm=0.775 volt across 600 ohms, where 600 ohms used to be a standard impedence for audio connections.
dBV = Decibels referenced to 1 volt.
If you are measuring signal power, the decibel unit to use is dBm.

dBu = 20 log V/V ref
where V represents the measured voltage and
Vref represents the referenced voltage (either 0.775 or 1.0 volts).
In other words, when referenced to 1.0 volts, 1 volt = 0dBV.

You should always record at as high a level as possible without clipping. In analog recording (tape recorders), a little clipping is good. In digital recording, it's destructive. Cliping in a digital domain produces harsh staticy sound and must be avoided, although you want to record as higy before clipping as possible.
 
I probably learned most of that in my basic electronics class a few years ago but I must have forgot it. You're right about analog being more forgiving than digital when it comes to clipping. I have been experimenting with my volumes and I'm getting the feel for it .

Thanks for the explanation SleepyJohn!

Nick
 
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