Greetings Gang. Fender rumble 500 has a control on the panel marked “Gain.”
Can someone enlighten me what that control does versus the master. Seems like they both work as volume controls?
Where should the gain be set? Is it better to control volume with gain versus the master volume control on the right side?
Thank you very much!
Think distortion. Gain can drive the signal to get the natural crack in the tone. Volume is loudness and master volume is just overall loudness. That’s in the nutshell.
Gain boosts the signal that comes into the amp and can affect the overdrive circuit and anything in the effects loop.
Master boosts the signal on the way out.
Use the Gain in setting up your sound and use the master for over all volume.
I’ve had this same question on my mind lately and did a bit of research. This is how I think it works (feedback welcome for things I’ve gotten wrong):
In the chain of instrument to sound, ignoring external effects your chain looks like this:
Bass → Pre-Amp → Power Amp → Speaker
Gain is between your bass and the pre-amp. It is the level of input into the Pre-Amp. High gain “overloads” the pre-amp to create distortion (yay!). This is the pleasant kind of distortion that you pay extra for.
Master Volume controls how much amplifying the power amp does. It should not add distortion (in the real world pushing the master volume beyond the capability of the speaker can also lead to “distortion” but this kind is much less pleasant and unintended).
The sound from the speaker (“pitch”) is the frequency (how fast it oscillates) of the speaker cone moving back and forth to push air around. The volume (“loudness”) of the speaker is based on how far it’s moving back and forth (amplitude). I guess it makes sense to call it an “amplifier” to add “amplitude” to the speaker.
What about effects?
An effects loop in an amp is usually between the pre-amp and power amp so the chain would be this:
Bass → Pre-Amp → Effects → Power Amp → Speaker
Effects is the “I brought some more pre-amp to customize my sound” part of the amp. But because of where it is in the chain you could potentially bring your own pre-amp entirely. Maybe you have a pre-amp and DI set up already dialed in. You could make a chain that looks like this
Bass → Effects (with your own pre-amp) → Power Amp → Speaker
You would do this by plugging the output of your effects/DI into the return on the effects loop of your amplifier connecting it directly to the power amp section.
You got it right.
That’s part of the reason for the separate gain and master controls. So you still have control of the output, even if you skip the built in preamp.
It’s about making the equipment more versatile.
Took me a while fiddling with the gain knob as it just seemed like another volume knob to me as well. But like they explained, it’s basically like a sensitivity adjustments to how much information your amp picks up from your guitar.
I found that playing with the gain turned up higher that I can hear a lot more finger noise , even just my fingers hitting the strings on faster songs where you don’t have time to land softly on a note/fret. I guess you can overdo it in that regard, but I’m found that running the gain up a bit allows me to have really clear sounding notes ( especially the higher notes) without having to use as much plucking pressure.
Play around with it. Turn it to the extreme in both directions and you’ll get a sense of it.
Thanks for this guys. I often get confused about the gain vs. volume thing, so now I put it in a doc for reference next time I forget how it works. 
EDIT: Also, I love the idea of using higher gain to hear more of your technique. I’m going to experiment with this during my practice sessions.
TL;DR: High gain go brrrrrrrrr
I love this! Need moar Brrrrrrrrr!
Hopefully this is a correct way to think about it. With a passive bass, you must set the gain on a Fender Rumble to something other than zero otherwise you’ll hear nothing. If you’ve got an active bass, with it’s own preamp, you can set the gain on the Fender to zero, and use the pre-amp volume on your bass to set the signal gain. I generally set my gain (Fender Rumble 100) to somewhere between 10’oclock and 12’oclock.
And this is why I love this forum! Thanks for the education.
Thanks, this is really helpful.
Follow-up question: my bass doesn’t have active pickups, but it does have a 3-band EQ and uses a battery. Does that mean it has a preamp?
Back to the topic, I too have a Rumble 100. I’ve played around with the gain on it (I don’t use the overdrive), and I haven’t noticed any real difference in the sound unless I turn the gain all the way up. Putting the knob anywhere else just all sounds the same to me. What am I missing here? lol
Yes you have a preamp on your bass if you’ve got a 9v battery and 3 ban eq. Not many basses have active pickups (from what I understand) but I meant preamp when I said active bass.
Thank you!
Nothing. The Rumble amps are really clean.
I’m not even sure the gain will affect the overdrive on the Rumble. Since I live in an apartment, I’ve never been able to turn the gain up loud enough to really test it out.
Wait a minute @Barney gets to play loud.
Hey Barney, can you crank the Drive on your Rumble and then crank the Gain to see if the Gain increases the overdrive?
This is great info! I have a Rumble 40 and all I’ve ever done is turn it on and set everything to mid! 
Well, except they have a giant scoop in the mids
They are clean in terms of distortion but not flat at all. You need to boost the mids to make them flat.
Yeah, same. I don’t even know what my amp sounds like above half volume.
Yes, clean as in no distortion. Definitely not neutral.
You can get close to neutral by setting the knobs like this…
Low and High at 10 o’clock
Low Mid and High Mid at 2 o’clock