# Understanding Volume and Gain....



## Beach Bob (Sep 12, 2009)

I was trying to describe the difference between what a volume knob does and what a gain knob does and realized, that I THINK I know the difference...but am not 100% sure... Googling the issue just brings up tons and tons of conflicting opinions.... 

So..here is what I believe is happening... based upon my minimal knowlege of a three tube pre-amp (call the tubes V1, V2 and V3).... 

The signal goes from the guitar to V1 and gets boosted up to a usable level...

The volume knob reduces the signal based upon the volume level (i.e. full volume = 0 reduction)

The boosted signal goes to V2 for further boosting... the amount of boost determined by the GAIN knob. The gain knob is controlling the voltage differential on the tube and does not actually interact with the signal directly.

From V2 the signal goes thru the tone stack and into V3 for boost to make up for the loss caused by the tone stack.


At a very simplistic level, is this correct? In my head the primary distinction between volume and gain is that volume is a resistor on the signal path and directly interacts with the signal whereas gain controls the amount the voltage differential (i.e. boost) of V2 and doesn't directly interact with the signal.....


----------



## Cups (Jan 5, 2010)

Gain comes first. Volume is usually after the tone stack right before the phase inverter. (I'm aware of volumes being placed in different areas, like post phase inverter)


----------



## Wild Bill (May 3, 2006)

Beach Bob said:


> At a very simplistic level, is this correct? In my head the primary distinction between volume and gain is that volume is a resistor on the signal path and directly interacts with the signal whereas gain controls the amount the voltage differential (i.e. boost) of V2 and doesn't directly interact with the signal.....


In a word, no! :applouse:

In both cases, the knob is controlling signal. What makes it more confusing is that there is no standard point to insert a control that is called GAIN. That is something some marketing guy pulled out of his butt!.

Think of it this way. A signal is amplified by a tube stage and tube stages can be cascaded, stage following stage until finally the signal is fed to the power tubes and then out to the speaker. 

In the early days, there was only one control for the signal level, called a VOLUME control. Usually, it was after the very first amplifying stage. Then the JMP evolved to a higher level and an additional control was added, right between the output of the preamp and the phase inverter stage that drove the power tubes. This was called a master volume - the idea was that you could crank up the input level of the signal for more distortion yet have the master volume cut that signal (now distorted) down to reduce the final volume from the speakers. You would have a distorted tone but not necessarily loud!

By playing with the two volume controls you could have a clean or a distorted signal at any volume you wanted. However, the KIND of distortion you got was all preamp distortion, which tends to sound crunchier and fizzier than the classic power tube distortion, which was more thick and creamy. It is IMPOSSIBLE to get power amp distortion when the master volume is turned down! It comes from the power tubes working very hard, which means they are LOUD! Reduce the signal into them with the master volume and the tubes start to loaf along, being very clean and hifi.

That being said, LOTS of players LIKED preamp distortion! So designers added even more stages of preamp gain. They then added another control to vary the gain, or how strong was the signal AT THAT POINT IN THE AMPLIFICATION CHAIN! Hence the "GAIN" control was born. You now had more control of how much a particular stage was overdriven, thus more control of the amount and sound of the distortion.

So now we have input volume, gain and finally master volume. All 3 controls vary the strength of the signal, just at different points along a path of stronger and stronger signal. Since you have oodles of gain it is easy to overdrive succeeding stages, relying on the master volume at the end to determine how hard the final power tubes are driven and thus how much power is leaving the speakers.

Gain is a measure of how much an amplifying stage can boost a signal. A low gain stage can boost it only a little bit and a high gain one the reverse. Whatever, they still affect the signal and any control determines how much boost the stage gives it.

Some simpler amps just have an input volume and a master volume. Sometimes they call the input volume a GAIN control. Not because there is any design standard as to what to call the first adjustment control. It's just marketing! GAIN sounds cooler than just VOLUME, that's all!

Hope this helps!

Wild Bill/Busen Amps


----------



## mhammer (Nov 30, 2007)

And here's another slant on it. "Volume" controls technically take away signal. That is, the signal is amplified by some amount, and the volume control divides that down such that most of the amplified signal is bled off (low volume), more of it is retained (higher volume) or all of it is preserved/retained (pedal to the metal, knobs going to 11).

Technically, a "Gain" control adjusts how much amplification a given stage is applying to the signal. Realistically, though, many manufacturers will call something a "Gain" control that is essentially acting as a volume control. That is, there may be a stage with fixed gain, followed by a volume/attenuator control, followed by one or two subsequent fixed gain stages, then by another volume control. Neither of those two controls _technically_ adjusts the gain. But consider it this way. If I cut something in half, before it is multiplied by 100, then any dividing-down that follows it, is working with something that is 50x as big as the input. Cut it down to a quarter of the original before the fixed gain stages, and the volume control is working with something that is only 25x bigger than the input. 

So even though the first control is not technically changing the _gain_ of any given stage, its net result/effect on the signal is *as if* it has changed the gain.

Depending on the manufacturer, such controls may be legended/labelled differently. So, one amp may label them "Gain" and "Master", where another may call them "Pre-amp" and "Volume", or "Gain" and "Master", or any of a host of possible relevant terms. Fundamentally, though, the "first" control is adjusting how much signal will hit any stages after than control, and the second control will adjust how much of the amplification before it will be preserved.


----------



## Gnobuddy (May 17, 2014)

In the world of linear audio amplification (i.e. all audio except electric guitar amps), the two words are mathematically identical. A loss in signal is the same as a gain of less than unity, equivalently, it is a negative gain in decibels. So there is also no real distinction between a passive control and one that alters the voltage gain of an actual amplification stage.

Things are different in the world of guitar audio. There, "gain" seems to mean "this one will create distortion if you turn it up", while "volume" means "this one will make it louder, but it will more or less stay clean". Pretty much what Wild Bill said.

-Gnobuddy


----------



## amphead (Jan 9, 2007)

Very well said!


----------

