[Mass. Wine Guy]

I hear a lot about an amp or pre-amp's gain. What exactly is this? I thought volume was gain. What's the difference and what's the importance of the gain level?

Thank you.

[Pez]

From what understand it's a laundry detergent. 

[Elizabeth]

Aside from laundry cleaning, Gain is the total available increase in the signal created by a product.
The volume attenuates the gain. (actually the incoming signal so the total gain of the product remains the same, just the incoming signal is made smaller, so the output seems less)
So with cleaner laundry.. whiter whites, and brighter colors, Gain is a nice thing to have.

[JohnR]

Gain is the ratio of the output voltage to the input voltage. It's typically expressed in dB = 20 log (Vout / Vin). 0dB is no gain (output same as input), 20 dB gives output of 10x the input.

If an attenuator is in the circuit you are typically talking about the above ratio when the attenuator is set to max which is (typically) no attenuation. An attenuator is "negative gain".

[bummrush]

Excellent John now i dont have to go to audio asylum   lol

[Diamond Dog]

Excellent John now i dont have to go to audio asylum   lol

D.D.

[werd]

The line level signal off a cd player is 2volts (+ - 1volt).

A passive pre amp is what your volume/gain intuition represents. The passive pre amp will only use a full 2 volt signal(thats a full volume) and reduce the volume or voltage. 

An active preamp will add a voltage jump to the signal. It basically makes it louder from the 2 volt signal and then you reduce with the volume control. Johnr equation up above represents how gain is put into formula using dbv gain.

It basically takes your musical signal from 2volts into a louder amplified signal.

Thats my rudimentary take on it.

[Mass. Wine Guy]

John R., I appreciate your explanation but after reading it I had to lie down for a while. I am incapable of figuring out anyhting math related. As I think I see it, gain is the total number of decibels a piece of gear can theoretically put out. Volume adjusts those decibels within whatever range the gain has.

[FullRangeMan]

Gain is the ratio of the output voltage to the input voltage. It's typically expressed in dB = 20 log (Vout / Vin). 0dB is no gain (output same as input), 20 dB gives output of 10x the input.

If an attenuator is in the circuit you are typically talking about the above ratio when the attenuator is set to max which is (typically) no attenuation. An attenuator is "negative gain".

After reading it, Iam thinking in Gain as increase in the signal tension amplitude.
Gustavo

[Ericus Rex]

In car-speak; gain is like horsepower and volume is like speed.

[Quiet Earth]

 I think Elizabeth already gave the very best non-technical explanation. Simple and right to the point. No need to get the aspirin and calculator out. 

 

As I think I see it, gain is the total number of decibels a piece of gear can theoretically put out. Volume adjusts those decibels within whatever range the gain has.

Every active component has a fixed amount of voltage gain. A volume control only reduces the voltage level of the source that comes before it. An active pre amp first reduces the signal via the volume knob, and then immediately re-amplifies and buffers that reduced signal. A passive pre amp merely sends its reduced signal on to the next component, which is usually the power amp. Very simple.

[JLM]

Gain means gain in volume.

dB is the smallest incremental increase/decrease of sound pressure level (volume) that the average person can heard.  It takes a 3 dB increase to sound half again as loud and a 10 dB increase to sound twice as loud.  (Note it takes twice as much power to effect a 3 dB increase and 10 times the power to effect a 10 dB increase.)

For low level pieces (turntable, CD player, pre-amplifier) specify gain in terms of volts or dB.  As mentioned above CD/DVD/BluRay players typically have a rated (maximum output of 2 volts).  Turntables have much less output and need to "translate" their output via the accepted RIAA (Recording Industry Association of American) formula, so  need a phone pre-amp. 

As the signal passes from source to pre-amp to power amp, you should look to make sure the rated output (volts) of the upstream component is at least as high as the rated input sensitivity (volts) of the next component.  Note though that it is not unusual that the rated output of a given component is too high for the next component, leading to system noise and no usable range in the volume control.

[jeffreybehr]

Some of these explanations are correct and some are at least misleading.

'Gain' in a music-reproduction system is simply a change in VOLTAGE from the input-Voltage level to the output-Voltage level.  It can be positive or negative (within one piece of equipment) and is measured usually in deciBels (abbreviated dB).  That's a logarithmic relationship where large absolute differences turn into not-nearly-as-large changes measured in dB.  For instance, double or half power is a change of 3dB, while double or half Voltage is a change of 6dB*.

The Voltage gain in dB of typical audio devices is quite different depending on application.  A moving-coil prepreamp might have 20 - 30dB, a fono stage 30 - 40dB, a linestage preamp 5 - 30dB (with modern ones having less rather than more), a poweramp from zero to around 30dB of Voltage gain*, etc.

BTW, in my and others' opinions, most audio systems have too much Voltage gain, resulting in too-low volume-control settings and too-high noise levels coming from the speakers.


* Here we ignore the fact that a deciBel is an expression of a change (ratio) in power.  Technically, it's inappropriate to use it to describe differences in Voltage but is understood if one uses 'Voltage gain' when applying the term to devices measured in power, not Voltage, output.

[Mass. Wine Guy]

I must admit that I'm a little sorry that I asked. It just seems so damn complicated.

[JohnR]

It's not all that complicated, it's more just how it works. Ask a question about "overdrive" on a car forum and it'll be the same kind of thing I expect

Why did you ask the question? - perhaps that information would help in providing an answer that helps you.

[Mass. Wine Guy]

Good idea. I had an amp recently where there was a question about its gain being set too high and maybe lowering it.

[JohnR]

OK, well, a power amp will produce a certain voltage at its nominal full output power. The input voltage needed to drive the amp to full power will be that voltage divided by the gain.

For example, suppose an amp has 32 dB of gain. That is equal to 40 times.

Suppose the amp produces 200W into 8 ohms at full power. Without writing out the math, that is a voltage of 40V at the amp output. 1/40th of that is 1V, so the amp will produce full output power with a 1V input.

If an amplifier's gain is "too low" then you won't be able to drive it to full power. If it is "too high" then you may have a "hair trigger" volume control and/or have excess noise.

Having said that, I doubt most people have any idea of or care what the gain of their amplifiers is. It's not that critical, for the most part.

[Mass. Wine Guy]

Thanks, John. I'm glad it's not important because I absolutely don't understand it.

[jeffreybehr]

Mass-Wine, gain is the ability of an amplifier to increase Voltage, input to output.  It's basically that simple.

As I half-said earlier, most poweramps have too much gain, resulting in too-low volume-control settings and too much noise.

Which amp do you have? 

My poweramps, Monarchy SE-160 hybrids, had too much gain.  I got rid of 9dB by changing, with the designer's approval, the single tube in each amp.