My other post about the AC15C1's tone yielded some discussions about the tone circuits in Vox and Fenders and their interactivity, so what was a quick response became much longer. I figured I'd dedicate a whole post to it. I think you'll find the info as enlightening as I did. Also, I'm incredibly keen to understand this subject more even more clearly, so Amp / Electrical people, if I say anything flagrantly incorrect, please inform me. That's info I definitely want to hear! ------------------------------------------------------------------ So in the quest to understand why the Vox tone controls work the way they do, I stumbled across this total gem of an article: http://pickroar.com/1003/the-tone-stack-explained-in-english-for-humans/ This is an important read for understanding the tone stack of most go-to valve amps: Fender, Vox, and Marshall. The author admits himself a layman, and endeavors to translate the relative arcane language of electronic engineering into simpler English. And as an even further removed layman myself, I will now attempt to distill it moreso: The controls of most old-school tone stacks do not independently add nor subtract the amplitude of their namesake frequencies. They are a highly interactive series of capacitors and resistors that together form a giant filter as the signal flows through the sequence. The fact that it's a sequence was news to me. For some reason I had always thought of these controls as working simultaneously, but that simply isn't the case. The electricity has a definite path, and each subunit is wired differently, and importantly, the output of one flows into the input of the following one. So understanding the sequential nature of the tone stack is probably the most important conceptual element to understanding how it's actually affecting your signal, which is to say, much more complexly than you've likely been assuming. Speaking of, that sequential order is roughly: IN >> Treble Circuit >> Bass Circuit >> Mid Circuit >> OUT The signal always hits the Treble first, which basically determines if your sound will be biased towards the treble frequencies or toward the rounder sounds. Diming it says "I want to listen to all the Treble, AND Mostly The Treble. The other frequencies can slag off." Cutting it says "Treble cannot come to the party. We're hanging out with Mids and Bass today." Treble Summary: Treble is a balance control *for the entire signal*--biasing the signal towards or away from the highs. Then the signal hits the Bass. The boundaries of what you'll hear as "Bass" are partially dictated by the rules set by the Treble pot. Other than that, the Bass is a simple Low-Pass filter. Turning it up widens the response range of what Bass frequencies will be listened to by the circuit, turning it down narrows that range. Bass Summary: Determines the scope or width of Bass Frequencies in the signal-- or how many bass frequencies can come to the party. The final control in the circuit is the Mid control, which is the only potentiometer that effectively controls amplitude. The rest can vaguely be understood as character-tweaking. The Mid is the most straightforward: The amp has a natural Mid profile--you only get to turn those frequencies up or down. The one caveat is that because the other two potentiometers are ultimately wired to the Mid knob, turning it down causes a chain reaction which dumps those frequencies to ground, lowering the amplitude of the whole signal in reverse sequence--as you dial back, Mids get killed first, then Bass, and then Treble. The author argues that if you're scooping the mids really hard, you probably just don't like the way your amp sounds. Interesting consideration given the mechanics, as it would mean you're creating a large gap in the amplifier's natural voice, and then accentuating the extremes Mid Summary: Controls the amplitude (volume) of the amplifier's predetermined Mid-range, but pulls the signals of the other two circuits up and down with it... This --I think-- will ultimately effect how the signal slams into the power section, so its setting will have a lot of sway with regards to how the amp behaves as you turn the master volume up.** ** That very last bit is entirely inductive reasoning. I am inferring based off other things I've read. This is what I've been able to glean from my reading of both this article and a few others. I recommend you read the whole contents of it and attempt to understand it. The author even includes his source material as a PDF: An Introduction to Tube Amplifier Theory by Sorlien and Keller, which he recommends reading. You know, this leads me to an interesting question: What happens when there is no Mid control? How do the Bass and Treble interact in a two-tone amplifier? My hypothesis is that on amps like this--given that the mid voice is likely already set--all you can do is control how much of the middle frequencies are overlapped by the controls, and therefore how much make it to the output. This would explain why when you dime both the Bass and Treble on an AC15C1, you get such an aggressively scooped and spikey sound... you're driving the amp to literally only listen to the most extreme portions of the signal.The treble is biasing the amp toward the highest it can read, and then the bass control is as wide as it can get given that parameter... the parametric EQ curve would look like a looong,oomy bass section, and then a hole, and then a very loud treble curve that peaks the most at the highest end it can read. Like a turtle seen from the side, walking to the right, with its head perked up. HERE IS AN IMAGE I MADE OF THAT VERY METAPHOR FOR EDUCATIONAL PURPOSES: Whereas setting the controls both closer to 12:00 brings out the mid voicing much clearer. It would then make sense to give the treble a bit of a push for articulation and overdrive character, and narrow the bass response a bit to tighten the signal up while still keeping the most vital low frequencies in the signal mix. Putting that good-good at 10 and 2, my d00d. *(over)Drive* like a pro. Keep the controls at 10 and 2. *Big dumb wink*. Discuss.