MrMarkIII said:
The typical Fender tone stack comes before the first pre-amp tube, while a typical Marshall's come after. Thus the much larger effect Fender tone controls have.
Actually, this isn't quite true. Your general point that Fender tone controls are more effective (meaning, they can have more effect on the amount of bass and treble) than the Marshall tone stack is definitely a true point. It is merely that your interpretation of the circuit that is correct.
So, if I may be so annoying as to step up to the lectern...
It is incorrect to state that the Fender tone stack comes before the first tube stage. The classic Fender tone stack actually comes *after* the first tube stage. What makes a classic Fender clean channel is a tube stage followed by the tone stack followed by a 2nd tube stage to "make up" the overall signal loss in the tone stack. In your most basic fender amp (ie, no reverb), the signal comes out of that 2nd gain stage and goes to the power amp.
Classic Fender Clean: Guitar Input -> Gain -> Tone Stack -> Gain -> Power Amp
The classic Marshall tone stack is similar in that it starts with a typical cathode byassed, plate-loaded tube gain stage...just like the Fender. But, unlike the Fender, the signal is then passed directly to a2nd tube stage, which is configured as a (nearly) zero gain cathode-follower. After the cathode-follower, the signal goes to the tone stack and then immediately to the phase-inverter.
Classic Marshall Clean: Guitar Input -> Gain -> CF -> Tone Stack -> Power Amp
OK. Fine. But what's the difference in tone stack effectiveness?
For the clean channel of each amp, the location of the tone stack actually has little impact on its "effectiveness". If it were the same tone stack in both the Fender and the Marshall, you'd probably hear very little difference in how much swing is in the Treble or Bass knob. Huh? This doesn't match experience. What's happening?
Well, the reason that the Fender treble and bass knobs feel like they have more effect (again, only on the clean channel) is because the Marshall tone stack has a smaller "slope resistor" in its tone stack. The Marshall tone stack also uses pots with different values. Marshall changed these properties of the tone stack so that it would have less overall signal loss (ie, to keep the signal hotter). It's those changes to the tone stack that make it feel less "effective" than the classic Fender tone stack.
Another side effect of those changes is that it changed the corner frequencies on the Treble and Bass knobs. So, that combined with the radically different-sounding speakers used in Marshalls, you get a very different sounding clean channel.
Now, when we kick over to the lead channel, we go in a completely different direction. It is here that you get into the whole "pre-distortion" vs "post-distortion" tone control discussion that sometimes pops up in Boogie vs Marshall debates.
On the classic boogie lead (ie, Mark II through Mark IV and including the Mark V channel 3), the lead channel was created by adding more gain stages to the basic Fender setup. Note that these extra gain stages were added AFTER the tone stack. As a result, the boogie tone controls are "pre-distortion" because the tone stack comes before the main bulk of the distortion is created by the lead circuits. In that position, the tone controls can affect the character of the distortion, but they don't have as big an effect on the distorted sound as, say, the graphic EQ. The graphic EQ is located well after the lead circuit and are considered "post-distortion" tone controls. Being after the distortion, they have full authority to manipulate the distorted tone. As a result, most people would say that the pre-distortion tone controls have a lesser impact on the distortion tone than post-distortion tone controls. Thankfully, a Mark-series boogie with a GEQ gives you both!
Boogie Lead (Mark IIC+): Guitar Input -> Gain -> Tone Stack -> Gain -> Gain -> Gain -> Gain -> Stuff -> GEQ -> Power Amp
On a high-gain Marshall (and its derivatives), the amps were not setup this way. Instead, the extra gain stages for the lead channel were added to the front of the amp's circuit....kinda like putting a boost pedal out front. Therefore, the tone stack is still last in line...making them "post-distortion" tone controls. Therefore, they can affect the distorted tone with more authority.
Marshall High Gain (Soldano): Guitar Input -> Gain -> Gain -> Gain -> Gain -> CF -> Tone Stack -> Stuff -> Power Amp
Of course, the classic Marshall overdrive sound also has a lot of power tube distortion. The power tubes come after the tone controls. Therefore, if you are the kind of guy who plays a Marshall on "10", you're getting some pre-amp distortion prior to the tone controls and then heaping helpfuls of distortion after the tone controls. If this is you, you're likely to feel like the Marshall tone controls have practically no effect at all. You're right...power tube distortion is a hard-to-control thing...it will not be easily tamed by twiddly little knobs on the face of your amp...no, it is a righteous beast with plans of its own.
Mark-series boogies are rarely pushed into power tube distortion. It's just not how we use them. It creates most of its distortion in the preamp. Therefore, its GEQ remains effective in shaping its tone. That's another reason (out of 1000) why they sound different from Marshalls.
Many of you already know all of this. But, some might not have. Sorry it was so long-winded.
Chip
