I have the input boost set to Control Switch 1. Scene 1 is a basic crunch. Scene 2 is a lead, where I am using that CS to engage the input boost. It is set as neutral. I am wildly turning the input boost level up to max and there is no discernable volume increase.
Most likely you're driving the Amp block into distortion. Understanding how tube amps distort is important.
In a real tube amp with no master volume, the power amp runs at 10 always, so the "volume" control in the preamp basically controls the signal strength going to the power amp. There's a point where the preamp sends more signal than the power-amp can handle cleanly, and it saturates the tubes and transformer, and the signal shifts from a sinewave into a squarewave because the amp can't put out any more volume and clips off the top and bottom of the wave. That transition between the sine and square wave is very desirable as far as a single-channel tube-amp goes for rock or the blues because that's where "that sound" is. The downside is they're usually really loud at that point. (That's where a decent quality attenuator helps but that's an entirely different discussion.) If you hit this sort of amp with an input boost and the power amp wasn't already distorting, the boosted signal will get passed through the preamp to the power amp and push it into distortion. That change will cause a volume jump.
Tube amps with master volume controls aren't generally used the same way; Most people let the preamp handle the distortion and they run their power amp clean so it doesn't distort, which reduces the volume, but it also affects the sound of the distortion. Preamp distortion tends to be very raspy in comparison to the power amp. Hitting distorting preamp tubes with an input boost won't increase the volume because they're already distorting and can't pass more signal to the power amp. That's why many master-volume equipped amps also have a "solo" switch, that toggles between two settings that change how much signal is passed to the power amp. Since the power amp is probably running cleanly, it has the power reserve to output a clean sine wave at a higher volume.
I'm one of those players who picks the amp based on the size of the room and anticipated stage volume. I have one amp that's about 22 watts, equivalent to a Fender Deluxe, and another that's about 30 watts but I can pick the output wattage. On either amp, I want the power amp to work hard so it's right on the edge of distortion, and run the preamp so it's hot enough that I can use the guitar's volume to control whether the amp is running cleanly or distorting. It's old-school, and the young'uns who use my amps are intimidated by that at first because they want their pedals in front of it all, but they love them after playing through them for 10 minutes because the amps respond to everything their fingers do.
That's a high-level explanation of what happens. Create a separate thread if you want to learn more.
Ok thanks. Is there any tried and true method for a solo boost? EQ mid bump? EQ block with higher output, etc?
There are several ways but they boil down to adjusting the output level of any block that occurs after the Amp block, including the Level of the Amp block.
The issue with adjusting the Amp block's level with a modifier is it makes it more difficult to level the preset, so I don't really think it's an overly useful way to do it.
Some people add a VolPan or Filter as the next to last block and do it there, or they put it just before the time-based blocks, so the boost has a higher volume in any tails that are ringing when you drop the volume.
Personally, I tie the level of my Out 1 to CS1 and have a switch defined in my Scene, Effects, and Per-Preset layouts to let me toggle it. I set the modifier to 0 dB <--> 3 dB. YYMV.
If you're interested, I attached the Out block I use. You'll need to define it in your layout.
PS - Because the modeler has both the preamp and power amp, their tubes, and the power supply and transformers modeled, it will behave like a tube amp when you hit the input to the Amp block with additional input, whether that comes in front of the block, or inside the preamp section of the block.
