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Gain versus Volume versus Pedal Boost

Discussion in 'Amp Central Station' started by cc50fralin, Sep 19, 2018.

  1. cc50fralin

    cc50fralin TDPRI Member

    Age:
    61
    89
    Sep 5, 2018
    Queens, NY
    Hello, all; fairly new member here.

    What is the technical difference between the gain control on a guitar amp, and the volume control?

    Once you get these two set to your liking, where does the boost of a pedal come in?

    How does that change things?

    I know there's no such thing as the best tone, but what are some of your recommendations for a full, round Blues-type tone such as David Gilmour?

    This is my set up:

    Michael Kelly 50s Telecaster with Lindy Fralin pickups.
    Marshall AVT-20 amp 1x10" speaker.
    Boss Blues Driver Waza pedal.

    I'm just starting to experiment with all three, and I'm having a good time fooling around with them, but I'm open to any suggestions and explanations any one has.

    The Gilmour tone is just a starting point for the tone I'm after.

    Thanks.

    Mike ;)
     

  2. -Hawk-

    -Hawk- Friend of Leo's

    Oct 14, 2015
    IL, USA
    It’s not all-inclusive, since different amp makers can label things different ways, but generally:

    Gain = amount of distortion
    Volume = loudness

    Some amps will have a channel volume and master volume, just to make things a little more confusing.

    Boost just boosts the signal going into the amp. It can make it louder or just increase the distortion, depending on how close the amp is set to its volume limit.
     
    JustABluesGuy likes this.

  3. peteb

    peteb Friend of Leo's

    Apr 25, 2003
    Cascadia

    technically, the volume control is a gain control, no more no less.


    raising the volume raises the gain and the distortion.

    gain is an increase in signal voltage or loudness.


    the volume on the guitar, the volume on the boost pedal, the volume on an amp, a master volume on an amp, a gain control on an amp all do the same thing, let more signal thru or not, the only difference is where they are in the signal path, before, early, middle or late.
     
    Tony474 and Wally like this.

  4. schmee

    schmee Friend of Leo's

    Jun 2, 2003
    northwest
    In layman's terms:
    What is the technical difference between the gain control on a guitar amp, and the volume control?
    The volume makes it louder, the gain makes it nastier. That's a big generality, because they are not totally independent of each other.
    Once you get these two set to your liking, where does the boost of a pedal come in?
    A boost or OD effect will change based on where you set the amp Gain and Volume. Basically, the pedal drives the amp harder with "more preamp" boost in front. Not to mention the pedal also has built in dirt.
    How does that change things? The more preamping done up front the nastier the sound. Some have even plugged the output of a small amp into a bigger amp. NASTY!
    These are all generalities and of course there are exceptions.
     

  5. codamedia

    codamedia Friend of Leo's

    Apr 4, 2009
    Western Canada
    Most people consider Gilmour Tone to be the end goal, not just a starting point :D Just sayin... ;)
     
    Last edited: Sep 19, 2018

  6. archtop_fjk

    archtop_fjk Tele-Meister

    288
    Aug 4, 2009
    Lebanon, NH
    This is one of the better videos which explains (for TUBE amps) how volume and distortion are created in your signal chain. Note that "Input Volume" in the video is synonymous with "Gain" (i.e. it's the preamp gain). Also note that it is assumed that you're getting all your distortion from the amp itself, driven by your raw guitar signal. If you boost your guitar signal with an overdrive pedal, then you will already have a clipped signal going into your amp, which is why people tend to use pedals to drive solid state amps (which are typically set clean).



    [edit] I should ALSO note that many tube amps have a 1/2 preamp tube stage before the volume/gain control, with additional stages (and tone stack) before hitting the power amp. So consider the video to be a simplified representation.
     
    Last edited: Sep 19, 2018

  7. Silverface

    Silverface Poster Extraordinaire Platinum Supporter

    Age:
    66
    Mar 2, 2003
    Lawndale CA
    Gain may be viewed that way by some. But it's most commonly the signal level from the preamp into the power amp. Raising the gain control beyond a certain point *may* cause preamp distortion.

    I prefer the term "loudness" when describing audible levels, since a control labeled "volume" may or may not be combined with other terms and significantly alter the meaning. But with a "Gain" and "Volume" control on an amp the most common functions are Gain increasing the preamp output signal and Volume increasing the overall loudness....to a point. At some point the amp's headroom (clean sound) limit is usually reached, and beyond that "Volume" will distort the sound and have no significant effect on loudness.

    Respectfully, pete, this is wrong in the context of the OP's post and is subject to several conditions - especially concerning raising the volume. Please look at the OP's question again - there are two controls. You haven't defined one's function vs the other and the volume control does not specifically work as you've stated in every amp.

    In the OP's example the volume control would not normally be considered a gain control. What it does electronically is irrelevant - he's asking what it will do functionally/audibly - and that is increase the overall loudness level...to a point.

    See the comments above by Hawk and my additions - they may clarify it for you.

    The Volume control will not increase distortion (or more correctly, CAUSE audible distortion) until the headroom limit is reached or the speaker's clean capabiities exceeded.

    Until then it simply makes the amp louder.

    And in this context the gain control is a preamp level control. NOT a loudness control because in some circumstances it may not increase loudness one bit.

    Example: If the Volume (loudness) control is cranked while the gain control is set low, the amp may be running perfectly clean - but right at the top of its headroom. If so, and you increase the gain control you may not have any loudness/volume increase at all - just an increase in distortion.

    Part of the confusion may be that the function of a "Gain" control doesn't universally affect "amplifier gain". It does a job in only one section of the amp, sending it on to the power amp. And in the power amp, "increasing gain" has nothing to do with the preamp "Gain" control. "Gain" can mean different things, which is why it's so important to stay within the context of the OP's stated question (I'm going outside it to try to pull it back INTO context).

    One use of the word gain is an electronic process (i.e. you can "increase gain" in any gain stage of the amplifier by making component changes - some amps have only one gain stage, some may have 2, 3, 4, even 5 - but there are reasons to limit the number - primarily noise related);

    The other use of "gain" is as a control over the signal level in one amplifier section (commonly the entire preamp) - and not a variable control for each gain stage.

    That's much more than I think the OP bargained for, but I hope it clears up some confusion.

    So make it REALLY simple for the OP ( and there's LOTS more to it, but these are the essentialls):

    The "Gain" control generally increases preamp signal and may increase preamp distortion (the "buzzier" type of distortion).

    The "Volume" control generally increases overall amp loudness, output stage distortion (the thicker/smoother type of distortion) and speaker breakup.

    That's the whole thing in a nutshell!
     

  8. peteb

    peteb Friend of Leo's

    Apr 25, 2003
    Cascadia
    Thanks Silverface that is a good description of the difference.

    Mine, is more about what they have common.


    Raising gain or volume controls raises both the volume and the gain.

    An exception was pointed out, with additional circuitry there is an amp that the volume does not go up with an increase of gain. This is an advertised feature as that is not usually the case.



    Usually volume controls are voltage dividers to ground, determining how much signal goes on and how much signal gets dumped to ground.


    In the digital realm, I see gain controls affecting the feedback loop, and I suppose in tube amps the gain control and even the volume control could be in a feedback loop.



    How are gain controlls typically done in tube amps? I’ve seen the circuitry for gain controls very little.
    My guess is that gain controls in tube amps are typically voltage dividers to ground, just like the volume control.


    3C76CC96-01C8-47EB-B6EB-588010D573C3.png


    Check out the upper left hand corner of the schematic of the common hot rod deluxe. The drive (gain) control looks an awful lot like the volume control, both a 250k pot as a voltage divider to ground in exactly the same place in their respective channels.

    In both the clean and drive channels it goes:

    Plate V1A > cap > resistor > pot > grid V1B



    There is not a lot of difference to speak of there, if any, other than the circuitry that follows, that would act as Silverface says, would allow the volume control to act like a volume control and the gain control to act as a gain control.




    D7461F09-79E5-4582-894E-B8C9157FFE36.jpeg
     
    Last edited: Sep 19, 2018

  9. JustABluesGuy

    JustABluesGuy Friend of Leo's

    Age:
    60
    Sep 2, 2016
    Houston, TX
    Thanks for saving me the time searching for it. It’s a great primer on gain stages and how the interact. I was going to post it as well.
     
    Last edited: Sep 19, 2018

  10. peteb

    peteb Friend of Leo's

    Apr 25, 2003
    Cascadia
    a gain control and a volume control are the same thing, but they are used differently.



    In a non master volume amp, the volume controls the pre amp gain, the volume and overall gain of the amp.



    In master volume amps, the volume is controlled by the master volume, the pre amp gain is controlled by the gain, and the overall gain of the amp is controlled by both controls together.




    That’s the simplest way to describe it.
     

  11. peteb

    peteb Friend of Leo's

    Apr 25, 2003
    Cascadia
    The video looks interesting, I’ve just watched the start, the guy straight away is calling the gain a volume.
     

  12. peteb

    peteb Friend of Leo's

    Apr 25, 2003
    Cascadia
    010993D2-EBB6-4F9E-B97E-BB0D1328123F.jpeg The blues Junior shows how the gain control is a volume control and that it is used differently, even placed differently. In the BJ the gain is called volume and it is placed in between the first two tube stages like normal, but what is different is the tone controls are in between the next two tube stages. They have added a tube stage before the first tube stage, and added a volume BEFORE the first tube stage. Interesting.


    Not really before the first tube stage, but they have added a tube inter stage before the main one, and the volume control is in the first inter stage, before the main inter stage.
     
    Last edited: Sep 20, 2018

  13. clintj

    clintj Friend of Leo's

    Apr 4, 2015
    Idaho
    Let's try to simplify this way down, using a well known master volume equipped amp like a Mesa.

    At it's simplest, you can say that the Volume controls the output level of the amp - that is, the amount of amp you hear in the room.

    The Gain controls how much preamp distortion is created, more or less independent of Volume. You can raise Gain to change the sound from a light, bluesy breakup to a full out metal type sound without appreciably raising how much the amp hurts your ears - the Volume control keeps the output power to the speaker under control.

    Now, what's the ends of the spectrum of sounds?

    Gain low, Volume high: a big, loud, clean sound that makes full use of the power tubes' potential. Raising the gain or adding a boost pedal will shove the amp over into real amounts of distortion when used right.

    Gain high, Volume low: a heavily distorted, compressed sound at levels that you can talk over.

    Gain high, Volume high: classic rock tone at stadium volume. Think Eddie Van Halen, Deep Purple. The 60s sound of rock, aka the dimed Marshall stack. Your neighbors won't enjoy this nearly as much as you do. :)

    There's websites devoted to chasing Gilmour's tone, but several of his sounds have one thing at their core. A HiWatt 100W amp, and an array of pedals to sculpt his sound. The solo on Comfortably Numb can be done quite well with a good set of PAF pickups in a Les Paul, a Big Muff Pi, and a big clean amp like a Super Reverb for example.
     

  14. peteb

    peteb Friend of Leo's

    Apr 25, 2003
    Cascadia
    Great explanation Clint.



    The video is good, it has good graphics to help with the explanation.


    I was less convinced that he was getting pre amp tube distortion and then power tube distortion. Maybe not so much that. I was skeptical that it made much if any difference. A good video over all for sure.
     
    Last edited: Sep 20, 2018

  15. peteb

    peteb Friend of Leo's

    Apr 25, 2003
    Cascadia
    Here’s an amp that makes the case that gain and volume are different. I pulled up a picture of one of these because it is the amp that convinced me that gain is just a volume. I remembered that this kind of amp, my first amp, had a volume on the right and one on the left. The first thing I did when I got the amp is think, why does it have two volumes? What happens when I turn one down and one up? What if I turn the other one down and the other one up? It was just like Clint Described.



    But now I see it has a master volume on the right and next to the input on the left is a volume and a drive control.



    I think this would answer the question what is the difference between a volume control and a gain control.


    On the PV pacer, what’s the difference between the input volume control and the over drive control?






    4551C55A-5DA6-440D-B041-55762373339C.jpeg
     

  16. peteb

    peteb Friend of Leo's

    Apr 25, 2003
    Cascadia
    It’s coming back to me, how the PV pacer’s controls worked.



    I think the input volume would actually be a gain control because of the way it controls volume.



    The overdrive control, I had forgotten about that, I don’t think I cared for it or used it. I think it dirtied up the sound, but maybe it didn’t affect the volume.



    Maybe the overdrive control was not a real gain control, if it didn’t add volume.
     

  17. MilwMark

    MilwMark Poster Extraordinaire Ad Free Member

    Apr 29, 2013
    near Arnold's
    @cc50fralin -

    Welcome. Hopefully we didn't scare you off. In player's terms:

    1. Gain control on that amp increase the amount of clipping (overdrive/distortion)
    2. Volume control on that amp is the level (loudness) control (until you run out of headroom, anyway).
    3. Boost pedal. This will increase Volume/level if you have clean headroom available in the amp. This will introduce more clipping (overdrive distortion) if you don't have clean headroom available. Available headroom is generally not like an on/off switch so likely your boost pedal will make the amp louder and make it clip more.
    4. You didn't ask but the controls on your Blues Driver work basically the same way as your amp. "Gain" introduces overdrive/distortion from the pedal. "Level" is like the Volume control on your amp. You picked a good one in the Blues Driver. It can be a level boost with the Gain down and Level up. Or it can do mild overdrive to distortion to fuzz with the Level down and the Gain up.

    Gilmour has a lot going on in his signal path usually. The key to his tone IMO is sheer volume. But at home I'd probably set all the BD-2 controls at noon, same with the Amp, roll back the guitar volume and then adjust from there. Too spikey? Take some treble away at the pedal first, then the amp. Too thin, add some mids or Bass. Etc.

    Enjoy.
     
    Last edited: Sep 20, 2018
    cc50fralin likes this.

  18. peteb

    peteb Friend of Leo's

    Apr 25, 2003
    Cascadia


    Never having seen the circuit, or similar circuits,


    I would say “gain” is an input volume control, and “level” is a master volume or output volume.
     

  19. MilwMark

    MilwMark Poster Extraordinaire Ad Free Member

    Apr 29, 2013
    near Arnold's
    I don't know what that is supposed to mean.

    Regardless, have you ever used an amp? If there is one knob labeled "Gain" and one labeled "Volume" I am 100% certain that the "Gain" knob increases clipping while the "Volume" is a level control.
     
    Last edited: Sep 20, 2018

  20. clintj

    clintj Friend of Leo's

    Apr 4, 2015
    Idaho
    A little historical fiction aside, if anyone new to amps is reading along. Amps used to only have a Volume control, and if you wanted distortion you simply cranked up the volume until you got it. That got you a glorious, full throated power tube roar, sag, and compression. And lots and lots of sound in the room, tinnitus, and complaints from club owners.

    Somewhere along the line, probably the 70's (someone feel free to contribute a more accurate date) someone had an idea. What if you could get that same amount of distortion in a more sedate form? Well, let's add another control between the preamp and power amp so we can limit the amount of drive the power tubes get. That way, you can crank up the preamp tubes to get lots of clipping, but not blow people out of the room.

    Now you have a new problem. What do you name this new control? Volume makes sense, you're controlling how loud the amp is. But the previous volume control already had that name! Pop a few brews, grab a pizza, and brainstorm. Volume 1 and Volume 2? Nah, too confusing. Distortion and Volume? Eh, maybe. How about Gain? It's easy to spell and remember, and it's an electronic term that describes what it's adjusting. Perfect!

    Now guitarists have a new control to try to figure out, and club owners are happy that their patrons can order drinks and be heard. Win-win.
     
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