Click here to purchase the entire book in PDF format. Addendum: ``Professional'' vs. ``Consumer'' Levels Once upon a time you may have learned that ``professional'' gear ran at a nominal operating level of +4 dB compared to ``consumer'' gear at only -10 dB. (Nowadays, this seems to be the only distinction between the two...) What few people ever notice is that this is not a 14 dB difference in level. If you take a piece of consumer gear outputting what it thinks is 0 dB VU (0 dB on the VU meter), and you plug it into a piece of pro gear, you'll find that the level is not -14 dB but -11.79 dB VU... The reason for this is that the professional level is +4 dBu and the consumer level -10 dBV. Therefore we have two separate reference voltages for each measurement. 0 dB VU on a piece of pro gear is +4 dBu which in turn translates to an actual voltage level of 1.228 Vrms. In comparison, 0 dB VU on a piece of consumer gear is -10 dBV, or 0.316 Vrms. If we compare these two voltages in terms of decibels, the result is a difference of 11.79 dB. One other thing to remember is that, typically, professional gear uses balanced signals (this term will be discussed and defined in Section 6.5.2) on XLR connectors whereas consumer gear uses unbalanced signals on phono (RCA) or 1/4'' jacks. If you're measuring, then the +4 dBu signal is between the hot and cold pins on the XLR (pins 2 and 3 respectively). If you measure between either of those pins and ground (pin 1) then you'll be 6 dB lower. In the case of consumer gear, you measure between the signal (the pin on a phono connector, the tip on a 1/4'' jack) and ground.