Idiot question of the day - difference between gain and volume

jellyroll

My understanding is that in an amp context, "gain" refers to preamp signal strength and "volume" refers to the power amp signal strength. 

So, in a pedal that comes before the pre-amp, if gain and volume were to both control signal strength, they would both be doing the same job since they're both controlling the signal strength going into that pre-amp. 

Is it more correct to say that only the volume knob controls the signal strength whilst the gain knob actually doing something different, eg adding synthetic distortion? Or are they both controlling the signal strength in different ways?

Cirrus

"Gain" is used to describe the amount of signal boost performed by an amplifying stage - be it in a pedal, preamp, power amp, valve, solid state, whatever. It's a technical term measured in db(v), or as a multiplication factor. Gain stages can be asked to increase the signal strength by more than their actual rated output. At that point they start to clip and this creates distortion.

"Volume" is used to describe acoustic loudness, so it's a measure of how loud a sound is in the air to our ears.

In guitar amp controls, gain, volume, overdrive and distortion are often interchangeable and don't necessarily mean what they say.

monquixote

What is usually labeled "Gain" is preamp gain 

What is usually labeled "Volume"/"Master" is power amp gain.

The effect of a clean boost is very similar to turning up the preamp gain, but many have other properties (mid boost for example) which colour the tone.

close2u

This should be a very useful read for you

 

http://justinguitarcommunity.com/index.php?topic=33317.0

 

jellyroll

So the "Volume" control on the pedal controls power amp amplification while the "Gain" control on the pedal affects the pre-amp? 

With my lack of understanding of the physics, I had always assumed that things happen in a sequential way so that the pedal could only affect the pre-amp since that's where it sits in the chain. 

I think you're saying that the pedal can affect the power amp even though the pre-amp sits between the two. 

monquixote

jellyroll said:

So the "Volume" control on the pedal controls power amp amplification while the "Gain" control on the pedal affects the pre-amp? 

With my lack of understanding of the physics, I had always assumed that things happen in a sequential way so that the pedal could only affect the pre-amp since that's where it sits in the chain. 

I think you're saying that the pedal can affect the power amp even though the pre-amp sits between the two. 

No that's not quite it.

On an amp you have pre and power amp gain knobs which control the amount of amplification in those stages. 

A pedal with a gain and volume control is going to have some kind of clipping circuit and isn't going to be a pure clean boost. Gain will equate to the gain pre clipping (i.e. it's going to make it louder and more distorted) while the volume is going to be post clipping (i.e. it's going to make it louder without getting more distorted) 

Regardless of which you turn up the increased signal is going to hit the preamp. 

Kebabkid

One goes up to 11!

stickyfiddle

It's better to think as the amp gain and volume being either side of the preamp, and then consider a dirt pedal as a secondary preamp in front of all that. So the gain knob controls how much signal goes into a pedal (and hence how much it distorts) and the volume knob controls how much comes out (ie controlling the output volume).

It's a little more complicated in reality, but that's the essence of it.

Dave_Mc

Technically "gain" is power output/power input.

When used on guitar amps it's normally a volume control in the preamp section which controls how much preamp distortion you get.

randomhandclaps

Although you professed this to be an idiot question, confusion is quite understandable as both terms seem to be abused in the guitar marketing world.

ICBM

Essentially they are all exactly the same thing - signal level controls - but at different points in the signal path. The earlier in the path they are, the more they control the amount of distortion and the less they control the final sound level, and vice versa for the ones later in the path. 'Gain' almost always means a level control early in the signal path that only affects the amount of distortion, 'volume' usually - but not always - means a control later in the path that affects the sound level but doesn't change the amount of distortion much.

It's frequently confused not only by the knob on the guitar being called 'volume', but by misuse of the term 'master' volume - it rarely means that, it's normally applied to the level control of a distortion channel. (Obviously on a single-channel amp it can be both.) If you're pushing the amp hard enough all the controls affect the amount of distortion though.

It's not an idiot question at all. It's not helped by different manufacturers having their own pet naming schemes - for example, Marshall used to call "gain" "Preamp Volume", and Peavey call "gain" "Pre" and volume "Post".

ChrisMusic

I have a slightly different take on this.   Anyone, please feel free to correct me if I'm wrong.

Volume is kind of like a tap or sluice gate - it will control how much of the "stuff" thats there passes through to whatever is next.

Gain or boost is a multiplication - you put a bit in and a lot more comes out.

If you create enough gain, then, whether deliberately or not, (or by design ie fuzz, distortion pedals etc), the electronics are driven to start clipping the signal, and you can progressively go from clean to distortion tones.

At the same time that will give much more volume which needs to be controlled, so this will probably be followed by a volume control (unless it's already designed into the unit).

As I see it, you can put either of these factors "volume control" and "gain" anywhere in the signal chain, but thats mostly determined by the manufacturer, whether that is a pedal or an amp.

Obviously you can choose where you put various pedals, and that can significantly affect the type of sound and tone you achieve.  Lots of fun playing around with that.

On some amps you can even choose to put pedals and effects in front of the amp, or in the middle of the amp's signal path if it has a effects loop.  (usually the more expensive ones, and that opens another minefield of opinions and issues too).

~ ~ ~ ~ ~ ~ ~

So you have volume on the guitar which controls how much of the pickup output gets passed on down the lead to the next stage.

(you may possibly have an active guitar which uses on board electronics to boost and tonally manipulate the signal from the pickup, using a battery to provide the power to amplify or create the gain wanted, and a volume to control how much of that signal is passed down the lead…)

Then you may want to go into various pedals.  Boosts and overdrives / fuzz / distortions have gain and volume control, which may give you the knobs to play with and balance to your personal taste to create the tone you want out of the whole rig (often everything inter-relates and can be a little unpredictable).  Which knobs you get to play with depend on the designers and manufacturers.

Then into the preamp (the bit on the amp with all the controls) and you may have a volume control to control what comes in, a gain control to vary the amount the signal is multiplied up possibly driving the preamp into musical distortion, and then you may have another volume control to stop that massively increased distorted signal level driving the power amp hard enough to blow your speakers and your eardrums (if your power amp can deliver that sort of power / volume)

The power amp stage by its very nature creates the gain / amplification needed to boost relatively low level and low power signals from the pickup and pre-amp levels, to significantly higher level signals with enough power to drive the speakers to deliver whatever sound pressure levels you want to create in the room for the listeners, (or what you perceive as "volume").

I've tried to keep it simple (honest), to avoid competition with Leo Tolstoy's War and Peace, one of us is a literary genius, and it certainly isn't me.

So anyway, I hope makes some sense and I hope that it helps a bit. 

Any corrections welcome.

jellyroll

Thanks guys. I'm taking away from this that Gain is pre and Volume is post the pedal's distortion circuit. That might be a simplified fiction but it works in my head. Glad nobody drifted into Ohm's law or any such technicalities that still haunt me from schoolboy physics.

thermionic

Lots of good advice here. It really annoys me when people use the word "gain" when what they mean is "amount of distortion". Technically I suppose they are applying more gain at some point in the signal path even if they are reducing it at a later stage to keep the volume the same.