What is high gain?

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DorraineStanley

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Can someone explain high gain, please. Is high gain only associated with condenser mics?

Thank you.
 
DorraineStanley said:
Can someone explain high gain, please. Is high gain only associated with condenser mics?

Thank you.
Click to expand...

Let's start by defining "gain". From Wiki:

"In electronics, gain is a measure of the ability of a circuit to increase the power or amplitude of a signal. It is usually defined as the mean ratio of the signal output of a system to the signal input of the same system. "

In other words, gain is how much the device amplifies the incoming signal. Microphone preamps need to provide a fair amount of gain to amplify the relatively weak signal output from a microphone up to the substantial, line level signal needed by other audio gear.

It's often expressed in decibels or dB:

Gain = 10 * log (P(out)/P(in)) in units of dB, where P(out) and P(in) are the output power and input power, respectively.

Many audio devices operate in voltage amplifier mode, so you can also express gain as:

Gain = 10 * log (V(out)/V(in))**2 = 20 log(V(out)/V(in))

"High gain" means a bigger ratio of amplification. The amount of gain needed varies a lot, depending on the sound pressure level of the sound into the mike and the sensitivity of the microphone (the signal level it produces for a given sound level).

Obviously, loud sounds like close miked drums will need less gain while quiet sources like nylon string guitar solo playing miked at several feet will need more gain. Microphone sensitivities also vary widely. Actually condenser microphones, because of their external power and active electronics, tend to have high sensitivities and high outputs that require less gain, while dynamic mikes, being passive, generally have lower outputs and require more gain. Ribbon microphones are a type of dynamic mike (though some new ones are externally powered) and tend to have the lowest senstivity and require the most gain (unless they are one of those newer, externally powered models). A condenser microphone used to close mike a drum might need a "pad" to keep the mike's internal electronics from being overloaded and may only need only 10 dB of gain from a preamp. OTOH, a ribbon mike used on a quiet source might need 70 dB or maybe even 80 dB of gain.

Microphone preamps are generally capable of a broad range of gain from a low of 0 dB to 20 dB up to a high of at least 60 dB of gain and typically people are thinking of around 60 dB to 70 dB of gain when they refer to "high gain". Many preamps have a maximum gain in the range from 66 dB to 72 dB. AEA makes a preamp designed for passive ribbons that has 80 dB of gain. My old Altec 1567a has both an input stage and a master control and can provide more than 90 dB of gain with both knobs cranked, but in general that amount of gain is never needed.

Hopefully that clears it up.

Cheers,

Otto
 
ofajen said:
Let's start by defining "gain". From Wiki:

"In electronics, gain is a measure of the ability of a circuit to increase the power or amplitude of a signal. It is usually defined as the mean ratio of the signal output of a system to the signal input of the same system. "

In other words, gain is how much the device amplifies the incoming signal. Microphone preamps need to provide a fair amount of gain to amplify the relatively weak signal output from a microphone up to the substantial, line level signal needed by other audio gear.

It's often expressed in decibels or dB:

Gain = 10 * log (P(out)/P(in)) in units of dB, where P(out) and P(in) are the output power and input power, respectively.

Many audio devices operate in voltage amplifier mode, so you can also express gain as:

Gain = 10 * log (V(out)/V(in))**2 = 20 log(V(out)/V(in))

"High gain" means a bigger ratio of amplification. The amount of gain needed varies a lot, depending on the sound pressure level of the sound into the mike and the sensitivity of the microphone (the signal level it produces for a given sound level).

Obviously, loud sounds like close miked drums will need less gain while quiet sources like nylon string guitar solo playing miked at several feet will need more gain. Microphone sensitivities also vary widely. Actually condenser microphones, because of their external power and active electronics, tend to have high sensitivities and high outputs that require less gain, while dynamic mikes, being passive, generally have lower outputs and require more gain. Ribbon microphones are a type of dynamic mike (though some new ones are externally powered) and tend to have the lowest senstivity and require the most gain (unless they are one of those newer, externally powered models). A condenser microphone used to close mike a drum might need a "pad" to keep the mike's internal electronics from being overloaded and may only need only 10 dB of gain from a preamp. OTOH, a ribbon mike used on a quiet source might need 70 dB or maybe even 80 dB of gain.

Microphone preamps are generally capable of a broad range of gain from a low of 0 dB to 20 dB up to a high of at least 60 dB of gain and typically people are thinking of around 60 dB to 70 dB of gain when they refer to "high gain". Many preamps have a maximum gain in the range from 66 dB to 72 dB. AEA makes a preamp designed for passive ribbons that has 80 dB of gain. My old Altec 1567a has both an input stage and a master control and can provide more than 90 dB of gain with both knobs cranked, but in general that amount of gain is never needed.

Hopefully that clears it up.

Cheers,

Otto
Click to expand...

You never know when you're going to want to record someone talking in another zip code with a ribbon mic though, so that 90dB of gain might just be necessary. Of course, the second a car drives by the house, you are going go deaf listening over headphones :D
 
Gain is amplification (power, voltage or current), associated with any stage of the signal chain, whether it be microphone, preamp, other intermediate stage, or power amplifier. The higher the gain, the more it amplifies the signal. It is usually expressed in decibels (dB), a logarithmic scale relating the input to output levels.

Condenser mics, in general, amplify the signal more than dynamic mics, and so are considered "high gain." They need less amplification in the subsequent stages (preamp in particular) to produce an equivalent signal level further down the signal chain.

Edit: I guess others answered while I was posting this. Anyway, mine's shorter. :D
 
cusebassman said:
You never know when you're going to want to record someone talking in another zip code with a ribbon mic though, so that 90dB of gain might just be necessary. Of course, the second a car drives by the house, you are going go deaf listening over headphones :D
Click to expand...

Indeed! Actually, my 1567a has been modded with 6 dB pads on each of the mike inputs. The unmodded model has 97 dB of gain! :eek:

Cheers,

Otto
 
Otto and Crazydoc,

Wow, thank you. Loads of information to absorb, but just what I needed. I'm a court reporter, and I use an HGM-1 condenser, and it's advertised as high gain. I was curious to know, in my shopping for new mics, if I should look for simply condenser or if I should look for condenser with high gain.

If condenser mics are high gain anyway, why would the seller advertise that a particular mic is high gain? Would it be because it has an especially high dB rate?

Question 2: Is "preamp" the battery pack attached to the mic cable?

Question 3: Our courtroom has an XLR line out that I plug my Marantz into. Could I also plug my laptop or tiny handheld Olympus digital recorder into it as well? Someone mentioned that the power/strength coming from the line output would be too strong for a laptop and may do damage? Is this so?
 

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Oh, boy. I'll go straight away to read the posts.

Thank you.
 
DorraineStanley said:
Question 2: Is "preamp" the battery pack attached to the mic cable?
Click to expand...
In short, yes. In this case, it looks like a self-contained 48v phantom power and a preamp in one unit.


DorraineStanley said:
Question 3: Our courtroom has an XLR line out that I plug my Marantz into. Could I also plug my laptop or tiny handheld Olympus digital recorder into it as well? Someone mentioned that the power/strength coming from the line output would be too strong for a laptop and may do damage? Is this so?
Click to expand...

Whoever told you that is retarded. It's a LINE out to go into the LINE in of whatever you want, laptop etc. Assuming it is a standard line level output, you would simply need a linelevel mixer to split between your different devices.
 
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