Why Is +4 dB Considered To Be The Professional Standard?

From inSync reader Vic S. (and several others) comes the following questions:

1. Why is +4 dB considered to be the professional standard? Is it because it outputs a hotter signal, or does +4 also give you better signal to noise ratio and frequency response?

   +4 dBu, being a higher level is slightly more robust – although frequency response and other specs are not inherently improved just by raising the level. Minor improvement (not really related to the level) comes more from the fact that because it is slightly more expensive to implement, +4 tends appear on higher end equipment, with better specs. But even more importantly, +4 gear is usually balanced, which gives benefits in noise rejection and cable length issues.

2. Some of our gear give us the option to use -10 dB or +4 dB. Is it better to stick to -10 dB throughout the signal chain if not all our gear can be switched to +4 dB?

   Certainly you should always run -10 dBV to -10 dBV and +4 dBu to +4 dBu. If you must interconnect two pieces of gear with different operating levels, use a level matching amplifier for best results. If most of your gear is -10 unbalanced, there will be little improvement in using only a few pieces at +4 balanced levels.

   The only exception might be if you can set up one entire isolated part of your system +4 balanced, while having the rest remain at -10. For example, if you can run a mic into an external mic pre, come out of the pre at +4, into a compressor at +4, out of the compressor at +4 and directly into a recorder at +4, it makes sense to do so. Then even if the rest of your system is -10 unbalanced, you’ve gained the benefits of balancing on the way to the tape deck.

3. If there is no option, are we to assume that it is operating at -10 dB?

   If there is no apparent option, consult the unit’s manual or back panel for the correct operating level. Failing that, you can usually assume that RCA and TS 1/4" connectors are -10 unbalanced, and that TRS 1/4" and XLR connectors are +4 balanced.

4. Should we set our DAT to +4 dB even if the rest of our gear is at -10 dB?

   It depends on the gear the DAT is directly interfacing with (is it +4 or -10?). Given the option, we would probably keep all the gear operating at the same level for the sake of simplicity, especially if this is the only +4 item you own.

5. Can we achieve professional sounding mixes on -10 dB?

   Definitely! The results depend on the quality of gear you are using, and far more importantly on your skill as a mixer – assuming your system is put together correctly, the operating level of the equipment has little to do with it…