Power Gain & Decibels Conversion Help.

[TomD]

Hello Gents,

I'm new to the site after a recommendation from a friend, I'm in no way shape or form an Electrician. But you'll probably see a few questions from me now an again.

I understand that this is more so a communications question but please bear with me as I am about as useful as a chocolate teapot.

In short: is it possible to be able to (on theory paper) calculate and find a power output if you only have the Input and Decibels.

For example if the decibels is 9 dBs and my power input is: 5W. I shift log 9dBs divide 10 and i get an approx of 8 Power Gain.

Am I right in saying that I can Multiply 5 W by my Power Gain of 8 to get the correct Power Output to match the gain and decibels?
In conclusion is this a correct way calculating?

Hope this makes sense and thank you in advanced.

Tom

 

[marconi]

Yes. If you have a 5W input to an amplifier which has a power gain of 9dB then the power output will be as you have calculated - 40W - assuming the amplifier is operating in its linear region and no clipping.

 

[Pete999]

Welcome along Matey

 

[TomD]

Excellent, Happy with that mate. I was scratching my head for ages on whether that was the correct way.

Thank you for confirming that for me, You'll no doubt be seeing more of me in the near future haha.

Cheers Pete, glad to be along for the ride!!

 

[static zap]

Nice to agree with Marconi , (confidence boosted)
3dB is double the power , so maths in head .
( Double , double , double = 5->10->20->40 )
( --Ignore math/logic symbols--)
Sadly our hearing needs 10X the power to perceive a doubling !
.. or have I been talking to too many HiFi salemen ? ..

 

[marconi]

Re#5: I seem to remember that's why potentiometers for volume control are logarithmic rather than linear - others can confirm.

 

[jackhammerJIM]

Nice to agree with Marconi , (confidence boosted)
3dB is double the power , so maths in head .
( Double , double , double = 5->10->20->40 )
( --Ignore math/logic symbols--)
Sadly our hearing needs 10X the power to perceive a doubling !
.. or have I been talking to too many HiFi salemen ? ..

A 3db increase in volume is percieved as twice as loud by the human brain .

 

[static zap]

A 3db increase in volume is percieved as twice as loud by the human brain .

Cheers for correcting me , obviously guy wanted to sell me an Amp ,I could use outdoors !

 

[Jim_e_Jib]

A 3db increase in volume is percieved as twice as loud by the human brain .

I think it's usually accepted to be around 10db for SPLs

 

[jackhammerJIM]

Ive got that wrong . Every 3db of gain requires a doubling of amplifier power .