gain factor question..

[Ansil]

i am searching all over for this and i probally missed  it.  lets say i have a device that i bought that does 20db of boost.  now what does this relate too. lets say as an opamp..  what would a opamp version of this be gain wise.  woudl it be like around 20 or 200 or am i off track here.



edit..  ok so according to the calculator at jacks site, would this be correct  a voltage gain of 10  so is that like i have a mxr dist type pedal set up for clean, and have the a 100k feedback loop resistor and a 10k going to ground.  sorry i have been up way too long, i am probally not lookin at it logically.

[Brett Clark]

you've got it right:

10X = 20dB
100X = 40dB
1000X = 60dB

[R.G.]

DB of voltage gain is numerically equal to 20 times the log to base 10 of the voltage ratios.

Example: You get ten times as much voltage out as you put in. What's the DB ratio?

Answer: ratio is 10:1, or 10. Log 10 (10) = 1    DB=20*log10 = 20*1 = 20

Example: you get two times as much voltage out as you put in. What's the DB ratio?

Answer: ratio is 2:1, or 2. Log 10 (2) = 0.301029995   DB=20*0.301... = 6

DB adds, since it is a logarithm. If you have two boosts of ten, you get +20db plus another 20db, or total gain of 40db. Working backwards, this is a gain of 10 to exponent of DB gain divided by 20 or 10 to the second power, 100x.

Example: you get out 7.4 times as much as you put in. What's gain in DB?

Answer: ratio = 7.4   Log 10(7.4) = 0.869...   DB = 20*0.869 = 17.38 DB.


Power DB is only 10 times log 10 of the power ratios, so while half voltage is at -6db, half power is at -3db. The math works out that way so everything makes sense. Mother Nature gets her shorts in a knot if you try to change the Rules.

[Ansil]

thanks  both of you..    that helps a lot  i was lookin at one of the emg boosters cause they are trying to hook up their mistake.  i had an old one and it was the same specs  so anyway i thought i would check to see if it was worth it.