merlyn wrote:To add to what has been said above I understand dB from a maths angle. Using dB allows multiplication to be replaced with addition.
I've noticed 0dB can be a sticking point. 0dB means multiply by 1.
This is because dB are to do with powers of a number and any number to the power of 0 is 1. Kind of counterintuitive maybe, but mathematically correct :
x^0 = 1
Positive powers of a number make the number bigger :
2^2 = 4
and negative powers of a number make the number smaller :
2^-1 = 0.5
so positive dB mean the signal is getting bigger (has a higher amplitude) and negative dB mean the signal is getting smaller (has a lower amplitude).
You will also see -infdB which means -infinity dB and this corresponds to an amplitude of 0.
For me this works as a good explanation and a useful reminder that dB's are logarhythmic.
CS70 wrote:The reason for levels going from 0 to negative values is because a fader is just another form of a volume knob, and volume knobs are attenuators. They can't increase a voltage level, but can decrease it. This in opposition to gain devices - amplifiers - that can increase a signal amplitude.
I think this is not correct. Cadets aren't just attenuated, they can both increase the signal voltage level (if adjusted upwards from 0db position) or decrease/attenuate the signal voltage level (if adjusted downwards from 0db position)
On most mixers the fader scale goes from -infinity to +10 dB (or something similar) with, as Merlin says, 0dB equalling 'no change in level'. That makes sense but historically the first faders were passive attenuators which can't increase gain, when faders with some gain became available they just adjusted the scale accordingly?
It all depends on the circuit and application. Faders themselves, as Sam says, are attenuators, and if used purely an an in-line device can only maintain or reduce reduce the signal level.
But they can also say form part of an active boost circuit, where the signal is first boosted by say +10 dB before the fader and then passed to the fader (which will have markings up to +10dB on it). At the fader's 0dB point, it will be attenuating the signal by -10dB.
Wonks wrote: ↑Thu Sep 29, 2022 11:51 am
It all depends on the circuit and application. Faders themselves, as Sam says, are attenuators, and if used purely an an in-line device can only maintain or reduce reduce the signal level.
But they can also say form part of an active boost circuit, where the signal is first boosted by say +10 dB before the fader and then passed to the fader (which will have markings up to +10dB on it). At the fader's 0dB point, it will be attenuating the signal by -10dB.
This^ is all true and I know many 'musical people' don't want to get into the electrical facts of sound but it can help. Douglas Self's book Small Signal Audio Design is virtually devoid of mathematics but gives an very good introduction to the world of audio electronics and the ever present challenge between noise at one extreme and distortion at the other.
He also debunks a great many audio myths which can trap and confuse the newb.
IMHO the OP would also benefit from purchasing a small mixer and playing with its faders and gain controls. Many charity and Cash Genny shops have small Behringers and Mackies for little money. A mixer is in any case a very handy box to have around.
Technical Editor, Sound On Sound...
(But generally posting my own personal views and not necessarily those of SOS, the company or the magazine!)
In my world, things get less strange when I read the manual...
Technical Editor, Sound On Sound...
(But generally posting my own personal views and not necessarily those of SOS, the company or the magazine!)
In my world, things get less strange when I read the manual...