Is there a way to use decibels with regular units?

[endolith]

For example, if I have an amplifier with a gain of (1+1000/200) V/V, this is also a gain of +15.56 dB.

Is there a way to calculate the dB value from the voltages in Qalculate?

In Maxima I have a convenience function defined:

db(x)  := float(20 * log(x) / log(10));

So I can type dB(1+1000/200) and it will return 15.563. Can I do the same in Qalculate?

[VK2BEA]

I could create a derived unit dBV to convert to and from dBV.
Look at how the dBm and dBW is defined and copy what is done there...

> (1 + (1000 / 200))V to dBV

  (1 + (1000 / 200)) × volt ≈ 15.56302501 dBV

> 10V to dBV

  10 × volt = 20 dBV

> 6dBV + 1V =

  warning: Log-based units were converted before calculation.
  (6 × dBV) + (1 × volt) ≈ 2.995262315 V

> 3dBW + 1W =

  warning: Log-based units were converted before calculation.
  (3 × dBW) + (1 × watt) ≈ 2.995262315 W

>