KC>           2) Anything between +4v to +10v is considered to
 KC>                 professional line level.
 KC>           One way to test your equipment is to send a 10 decibel signal
 KC>           For example, if you send 10 db of white/pink noise through 
ur
 KC>           you should always start out with 0db (no 
 KC> signal) and slowly move
Obviously from the list of equipment you gave, you've been around some pro 
gear.  It's amazing how many people working with pro gear have absolutely no 
idea what a deciBel is, as you just demonstrated.  
0 dB is the same level as some other level, often a cited reference, though 
possibly just an arbitrary level at some point.  Any given level in dB is 
10*log(P1/P2), where P1 and P2 are power levels at any two points.  By 
defining P2 to be some fixed reference level, the numberr of dB relative to 
it can then define absolute levels.  eg, 0 dBm is 1 mW, usually spec'd with 
reference to a nominal 600 ohm circuit.  6 dBK is 4.0 KiloWatts, used in 
spec'ing transmitter power outputs.  35 dBrnC is the same as -55 dBm measured 
through a C-message filter, with the rn being the telco relative noise 
refence level of -90 dBm.  
10 dB means 10 times some other level, and is meaningless as to absolute 
levels without some reference.  You likely mean some range of levels around a 
voltage equivalent of -10 dBm or -10 dBV (they're about 2 dB different, much 
less than the tolerance inaccuracy of consumer gear).  -10 dB means P1 is one 
tenth of P2, whether microwatts, MegaWatts, or anything in between.  3 dB is 
about 2:1 power ratio, while 20 dB ia 100:1, 30 dB is 1000:1, 60 dB is 
1,000,000:1, or -30 dB is 1/1000:1.  
"no signal" in dB is "- infinity", or for practical purposes -5 to -150 dB 
re: whatever operating level or other reference in most cases.  
There's one major practical compromise that leads to accepted misuse of the 
term dB.  Most level measurements are done with voltmeters of some sort, not 
true power meters.  This yields valid dB comparisons so long as all equipment 
is operated at the same impedance for relative dB voltage based measurements, 
or at a defined impedance such as 600 ohms for voltage scales calibrated in 
dBm.  With consumer gear, this is rarely true, while with pro gear it's also 
decreasingly common.  
That's what one of the threads here recently has been about.  dBu is one term 
that's starting to gain some acceptance to mean the voltage that on a 600 ohm 
circuit would be the same as dBm, regardless of actual impedance.  
Look to the telephone industry for the real standards that established dBm as 
a major professional unit, and from which we borrowed much of early balanced 
line technology.  
Terry
--- Maximus 2.01wb
---------------