Members Parallex Posted September 8, 2005 Members Share Posted September 8, 2005 At one time I thought I had this figured out, and maybe I did, but if I did, I forgot. Now I know what these do when I see them, but I want to know what they mean. So I don't miss anything, I'm going to ask everything, even if it is silly and basic. Explain "0" or unity. It's the optimal spot, but why? When you increase gain, the dB have a - number in front of them. Explain the + and - signs. Why does negative get louder and positive get more quiet? I hope I've explained these clearly. For myself, knowing what something does isn't always enough. I want to know the why too. Link to comment Share on other sites More sharing options...
Guest Anonymous Posted September 8, 2005 Share Posted September 8, 2005 Simply put: unity gain is when the knob, or meter is at "0" dB. This "spot" is when the device doesn't attenuate or amplifiy the signal. Basically: what comes in is what goes out. Generally VU is calibrated in reference to 1mW of power into a 600 ohm load. Check ANSI C16.5-1961 Link to comment Share on other sites More sharing options...
Members dboomer Posted September 8, 2005 Members Share Posted September 8, 2005 Originally posted by Parallex At one time I thought I had this figured out, and maybe I did, but if I did, I forgot. Now I know what these do when I see them, but I want to know what they mean.So I don't miss anything, I'm going to ask everything, even if it is silly and basic. Explain "0" or unity. It's the optimal spot, but why?Unity simply means no gain or loss. What you put in is what you get out. Sometimes it's optimal, sometimes not ... it depends on the situation. When you increase gain, the dB have a - number in front of them. Explain the + and - signs. Why does negative get louder and positive get more quiet?"-" is less and "+" is more same as everywhere. Are you thinking about sensitivity numbers here? When the sensitivity is -10dB compaired to +4dB those numbers specify what signal strength the input is expecting. So it you put a given signal into both of these, when set to -10 it will be amplified more and therefore sound louder.I hope I've explained these clearly. For myself, knowing what something does isn't always enough. I want to know the why too. Hope that helps Link to comment Share on other sites More sharing options...
Guest Anonymous Posted September 8, 2005 Share Posted September 8, 2005 Originally posted by Parallex When you increase gain, the dB have a - number in front of them. Explain the + and - signs. Why does negative get louder and positive get more quiet? I would assume you're maybe referencing a compressor here? Link to comment Share on other sites More sharing options...
Members Parallex Posted September 8, 2005 Author Members Share Posted September 8, 2005 Originally posted by Audiopile I would assume you're maybe referencing a compressor here? not really, no....but dboomer kind of touched on it. Gain knobs, or trim knobs, or whatever you want to call it, I've seen them before where the numbers around the knob all have a negative sign in front of them. Yet the bigger that negative number, the higher you're turning up the gain. I'm talking about mixing consoles. Boards I mix on a lot are Mackie (various models big and small), Soundcraft, Yamaha M2000, and occassionally some old Studiomasters. But it was recently on a small Soundcraft board on the gain that made me think about it. At about the nine o clock position it had a "U" for unity, then negative numbers increasing clockwise after that. And I've always thought, 'why do I see so often decibels expressed with a "-" sign in front of them?" Link to comment Share on other sites More sharing options...
Members agedhorse Posted September 8, 2005 Members Share Posted September 8, 2005 Good point of confusion... It comes from some legend indicating nominal sensitivity of the input and others for amount of gain. So, for example (many) Yamaha mixers turning input sensitivity/gain/trim control clockwise increases the "-" number because that's the nominal level that the preamp is amplifying to get to some unity or nominal gain. Link to comment Share on other sites More sharing options...
Members Parallex Posted September 8, 2005 Author Members Share Posted September 8, 2005 Which seems ass-backwards, because you'd think if it was amplifying the signal, it would have a PLUS in front of it....? Link to comment Share on other sites More sharing options...
Members agedhorse Posted September 8, 2005 Members Share Posted September 8, 2005 Originally posted by Parallex Which seems ass-backwards, because you'd think if it was amplifying the signal, it would have a PLUS in front of it....? But it's indicating input level that, times gain (depends on knob position) that will get you to theoretical zero point. Link to comment Share on other sites More sharing options...
Members Daniel Smart Posted September 8, 2005 Members Share Posted September 8, 2005 Originally posted by agedhorse But it's indicating input level that, times gain (depends on knob position) that will get you to theoretical zero point. Which is actually quite clear (in a confusing sort of way ) as many devices quote a spec for output signal level. -Daniel Link to comment Share on other sites More sharing options...
Members Carey D Posted September 8, 2005 Members Share Posted September 8, 2005 OK, as we have got a bit 'dB' heavy during some recent threads on console gain structure and preamp performance, I shall add some more to the wealth of response from the experts here... Originally posted by Parallex Explain "0" or unity. It's the optimal spot, but why? Unity, meaning a gain of one. The output level is the same as the input, no gain (amplification or attenuation). It is 'optimal' because it means the signal is proceeding at the same level through the circuits of the console, that level determined by the manufacturer for best performance and marked as '0' on the console meters. When you increase gain, the dB have a - number in front of them. Explain the + and - signs. Why does negative get louder and positive get more quiet?] Be careful here to understand the difference between 'gain' and 'sensitivity'. Console manufacturers vary in how they mark up the channel gain control. Some mark the scale as 'sensitivity', the setting required for an input with the marked level to be amplified to the optimum operating level of the console circuits, For example, a marking of '-40dBu' means a mic signal of -40dBu would be amplified by 40dB to the 0dBu level required. Others, like A&H, mark the actual gain of the preamp. For example the same position would be marked simply '+40dB' meaning the preamp has a gain of 40dB. In short, 0dB means unity (1x) gain, +dB means there is amplification (higher output than input), and -dB means there is attenuation (lower output than input). A preamp PAD switch may be marked -20dB as it is a 20dB attenuator. A channel fader may be marked '-30', '-20', '-10', '0', '+10' to show the relative signal level through the fader from attenuated, through unity, to some boost. Here is a bit I wrote for the GL2400 and 2800 user guides. In fact, there is quite a bit more on other related topics such as gain structure, using inserts, matrix mixing and so on. You may find some of this helpful http://www.allen-heath.com/DL/gl2400ug_ap5597_2.pdf -----------------------------------The Link to comment Share on other sites More sharing options...
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