tone stack section

[vince76]

When I look to a schematic I always wonder a thing, it's a noob question and surely someone with experience can easily answer.
I noticed that in many amps the tone stack section is located after the first tube. I interpret this thing: A modified freq spectrum is sent to the next tube stage to be amplificated. So not all the original frequency are amplified by the same factor.
The answer is: Is this solution adopted to get something specific? Are there other amps with tone stack just before the power section to achieve different sounding results?

Thank you, Vincenzo.

[black_labb]

i think that there is very little difference where you put it as long as you have enough gain to get a big enough swing to the output tubes and the impedance into the tone stack is suitable. having said that, the pots and wires in tone stacks introduce hiss/hum, so people will often try to avoid having too much gain after it. also, if you have a frequency band that distorts a certain stage, having the tone stack earlier can be advantageous. the tone stack could stop the offending frequency from distorting, making the sound more linear. then again, that effect may be desireable on some amps.

[chipaudette]

First, just in case you didn't know, tone stacks are critical to getting anything approaching a classic guitar sound. Even with all the tone controls at 12:00, a typical guitar amp tone stack still cuts a significant amount of the mid frequencies. 12:00 does not equal a flat frequency response. If you had a flat frequency response, you'd probably feel that your guitar sounded, well, very flat. Most people feel that you've got to scoop out some of the mids so that the treble and bass are more prominent. That's what most tone stacks do.

Now, to your last question in your post...do other amps put the tone stack just before the power section? Yes. If you consider the phase-inverter to be the beginning of the power section, then nearly all classic Marshall amps have the tone stack just before the power section. I think that this is true in modern Marshall amps, too, if it weren't for the insertion of the effects loop. Marshall got their idea for this location from the late 50's Fender Bassman, which also had the tone stack after the pre-amp gain stages.

Also, don't forgot that you also have a "tone stack" before your first pre-amp tube. It's the tone knob in your guitar.

Good luck!

Chip

[CRU JONES]

Hi,
Depending on the amount of gain the channel has, it will make a huge difference in tone to where in the chain you put the tone stack.

Distortion adds harmonics. The sooner in the signal chain the tone stack is, the less effect it has on those added harmonics. That being said, I really like some amps that crunch out pretty hard and have the tone stack early. It's more subtle, but you get a bit of control over what frequency range get's saturated the most. Then, as the note dies away, the tone stack has a sort of "come in" effect. Kinda nice.

Tone stacks do a similar thing when put before or after compression... Which tube amps have! Voila! ( I have been saying voila all day, I can't stop)

Cheers,
Cru

[daz]

I've always equated it to the kind of difference you hear when you put a graphic EQ before or after the source of distortion. Like in a effects loop verses in the front end. A marshall's tone section is after all the distortion in the preamp takes place. In a amp where it's designed mainly for preamp drive thats the equivalent of the EQ in the effects loop in my analogy. Fenders are usually closer to the front end, probably because most fenders do get much preamp distortion aside from more contempo models, and i imagine some or even most of those probably put the TS further back in the chain than vintage style fenders. I like amps with preamp distortion, so i always prefer the later tone stack like in marshalls.

[black_labb]

good point guys, wasnt thinking high gain amps.

i've always thought that a graphic equaliser or onboard eq (like an active bass) would make for very versatile distortion by determining which frequencies are being pushed. the post overdrive eq can get things back to a normal frequency spectrum, but different frequencies are distorted.