What is gain?

[gtrfinder]

What is the difference between volume and gain and how are they related to each other.
It seems as though they are used interchangeably by some... "this has over 30db of gain available" and so forth...
Aren't db's a measurement of volume?
This is probably an easy explanation, but I dont know the difference.
Thanks

[hasserl]

Volume = decibels, sound pressure levels. Gain = amplification, the increasing of signal voltage level from smaller to larger.

In many amps there is a Volume control placed immediately after the first gain stage. It is actually a variable voltage divider; it sends part of the signal on to the next stage of the amp and the rest of the signal not sent on to the next stage is dumped off to ground. Obviously, the more voltage sent to the next stage, the louder the volume the amp produces out at the end, from the speaker. That is because the higher voltage level from that point drives each succeeding stage a little higher, providing a higher voltage level to the power amp. And since each stage is driven a little harder, they can be driven to the point of clipping, causing distortion. So sometimes this Volume control is labeled Gain instead, because technically it is controlling the level of gain from the preceding stage that is allowed to be passed on to the following stages.

A Volume control does not need to be placed after the first gain stage, it can be placed farther down the line in the preamp, or even between the preamp and the power amp. Sometimes there are multiple Volume controls, letting the user adjust the level of attenuation at various points along the signal path.

[Scrutinizer]

Originally Posted by gtrfinder

What is the difference between volume and gain and how are they related to each other.
It seems as though they are used interchangeably by some... "this has over 30db of gain available" and so forth...
Aren't db's a measurement of volume?
This is probably an easy explanation, but I dont know the difference.
Thanks

The decibel is simply a ratio of two known quantities.

In electronics, dB is often used to describe gain of a circuit. Voltage gain (in dB) = 20log10(Vout/Vin).

In acoustics, dB is used to describe sound pressure level (SPL), relative to the threshold of human hearing.

[Old Tele man]

GAIN = OUTPUT/ INPUT

...expressed as raw value ratios:

Voltage gain: Av = Vout/Vin
Current gian: Ai = Iout/Iin
Power gain: Ap = Pout/Pin = efficiency

...expressed as logarithmic ratios (dB):

Voltage gain (in dB) = 20log10(Vout/Vin)
Current gain (in dB) = 20log10(Iout/Iin)
Power gain (in dB) = 10log10(Pout/Pin) <---assuming same load-resistance for each power!

[rcargs96]

I'm in the wrong forum.....

[Jef Bardsley]

All of the above are true, and technically correct.

The problem is, a long time ago, someone realised that by pushing the power tubes harder he could get more sustain, so the "high gain" preamp was created. Now, in common usage among guitarists, "gain" is often used to describe compression. You'll hear statements such as "I want more gain at lower volumes."

[epluribus]

Originally Posted by Glass Snuff

All of the above are true, and technically correct.

The problem is, a long time ago, someone realised that by pushing the power tubes harder he could get more sustain, so the "high gain" preamp was created. Now, in common usage among guitarists, "gain" is often used to describe compression. You'll hear statements such as "I want more gain at lower volumes."

Funny how such a seemingly simple question is such a good one. I was puzzled for quite some time about why amps have both a Gain knob and a Volume knob. Pedals are big offenders as well. I think it's to confuse the aliens.

--Ray

[Nick Patterson]

Originally Posted by epluribus

it's to confuse the aliens.

--Ray

We have to do everything we can!

[gtrfinder]

Well. Consider me confused. I've never really understood these terms, and still don't to some degree, but thanks to all who have answered.
It seems to me that "gain" is synonomous with "distortion" in alot of marketing material for various guitar, amp, pickup, and pedal manufacturers.
Maybe the confusion on this subject is part of the strategy to sell.

[VacuumVoodoo]

I think the confusion is in semantics to a high degree. Being an engineer (a dirty word to some) I have no problems with technical definitions but these don't often correlate with what a musician means or tries to convey.
So I've learned that "more gain" is often used to express "I want more magic". Starting with this we go on to listening either recorded examples of what this "magic" is or have the musician play and point to a sound that he wants "more" of.

"More gain" translates often to "compression & sustain" which paradoxically is en effect of progressive gain reduction above certain signal level - technically speaking.

There can be two amps with exactly same total gain (in db) but completely differently sounding: a 2 stage preamp with no attenuation between stages can easily achieve gain of about 50db, same can be achieved with a 3 or 4 stage preamp with attenuation between stages. The first will not compress, the second will if properly designed for that purpose. The "magic" can be had in both but it will be a different kind in each.
Yeah, I believe in magic.

[hasserl]

Originally Posted by Glass Snuff

All of the above are true, and technically correct.

The problem is, a long time ago, someone realised that by pushing the power tubes harder he could get more sustain, so the "high gain" preamp was created. Now, in common usage among guitarists, "gain" is often used to describe compression. You'll hear statements such as "I want more gain at lower volumes."

I disagree. "High gain" amps don't push the power tubes harder so much as they just have more gain stages in the preamp. This causes clipping and distortion of the preamp gain stages. Often these high gain amps are run with very clean power tubes just providing the volume to pump the sound created in the preamp out thru the speakers, and adding very little distortion themselves. Gain is not equated so much with compression as with distortion, which has other components besides compression.

[Jef Bardsley]

Originally Posted by hasserl

"High gain" amps don't push the power tubes harder so much as they just have more gain stages in the preamp. This causes clipping and distortion of the preamp gain stages. Often these high gain amps are run with very clean power tubes just providing the volume to pump the sound created in the preamp out thru the speakers, and adding very little distortion themselves. Gain is not equated so much with compression as with distortion, which has other components besides compression.

What you say is true, however as described, they are not "high gain" preamps, simply preamps with a high number of gain stages.

If you still think you disagree with me, see Alex's answer.

[hasserl]

Originally Posted by Glass Snuff

What you say is true, however as described, they are not "high gain" preamps, simply preamps with a high number of gain stages.

If you still think you disagree with me, see Alex's answer.

My disagreement is with your description "pushing the power tubes harder he could get more sustain, so the "high gain" preamp was created". My point was to clarify that the "high gain" was not from pushing the power tubes harder, it was from multiple gain stages causing clipping of the preamp. And that there is more to the distortion than compression.

Alex's post does not contradict that.

[Swarty]

Unfortunately, ther term gain in the guitar world has morphed into distortion just like class A has turned into cathode bias. Are they just sexier sounding words?

[rockon1]

Semantics....I think we all understand what somebody wants if they ask for recommendations on some "high gain" amps. Bob