What's that tone control doing there?

[edvard]

I have recently noticed that while most distortion/overdrive units have the tone control at the very end of the gain chain, many (not all) older tube amps have the tone controls up towards the front, usually right after the first tube but before all the gain happens.
Which makes me think...
Would moving the tone controls up front in your average dirt box possibly work a little of the same mojo, especially if said box claims "tube-like" sound?
Please, let's not go flogging the dead horse of transistors vs. tubes, I was just wondering if moving the tone control to the front of the chain in any given multi-stage distortion unit might be a beneficial design choice.
Whaddya think?

[aron]

Do a search on pre and post distortion tone controls. A similar method is turning down your tone control on your guitar making it less bright before the signal reaches the distortion part of the circuit. It does not make any circuit more tube like though.

[edvard]

Right. I was trying to avoid that line of thinking anyways.
I suppose a 2 or 3-band EQ/Buffer box at the head of your pedalboard would do much the same business as well.
I've never liked fiddling with my guitar's tone control except perhaps when playing clean, which I don't do a whole lot of, so maybe the whole idea is a bit moot for me personally, but I was wondering what others had thought or come up with.

I'll do the search you suggested, thanks.

[PRR]

> many (not all) older tube amps have the tone controls up towards the front

Older amps were not designed for gross distortion; why would you want to make ugly noise?

The tone control comes after enuff gain to overwhelm hiss, but before any risk of distortion.

The exception you are thinking of is the 5F6A Bassman. By this time the guitar was LOUD. The problem was filling the lowest musical octave. So why would a bassist splatter tone up out of the bass? Leo was expecting bass to play clean. He let the gain build-up 2 stages, and the tonestack driver works hard. The amp was disappointing for bass (the speakers were not serious enough) but guitarists adopted it for the significant and tone-able strain in the driver-tonestack area.

When you WANT gross distortion (as in "distortion/overdrive units"), your aims are different. The raucous racket burns the ear; you want a way to mellow it out to-taste. Also the mangle level of many distortion schemes is far higher than the acceptable level into a guitar amp... passive tone controls are handy attenuators.

[edvard]

True enough.
But before amps were being built to make guitarists into spotlight heroes, renegade stringbenders were forging the sounds we now know as the "classic" tube sound, dirt and all.
I don't know, it just struck me that many devices that claim to be "tube-like" don't really follow time-honored topologies when perhaps they should since they are audacious enough to make such a claim in the first place.
So, I can't help but wonder...

Or maybe I ought to just shut up and do some breadboarding to prove (or disprove, as the case may be) my curiosity. 

[darron]

Controlling tone after clipping of course changes how we hear it, we can make it less bright, more punchy, etc.

Changing tone before clipping changes how the distortion will behave. For example fuzzes have very little filtering before clipping which lets through a flabby farty noise.

As said, in think that in most tube amps there's a tone control before the major 'amp' stage. Usually you wouldn't push a tube amp much further than the limits of clipping, so you wouldn't need much filtering to get the distortion you wanted (if any!). Some of the expensive amps these days have very  sophisticated and complex clipping and the final 'amp' stage way very well be driving within limits but just amplifying an already clipped signal from a pervious stage which has been filtered before and after.

That was hard to write. Hope it made sense. And I'm not a tube amp expert...

[PRR]

> renegade stringbenders were forging the sounds we now know

Quite true. But few of them opened-up their amps to swap things around.

Leo Fender and cohort did "tune" sound. But mostly by beefing the POWer stage.

The invention of "fuzz pedal" was a revolution. Now you could get distortion _before_ tone-shaping _and_ after it. So while you hear some overdrive in the 1950s even on "mellow" stuff like Texas Playboys, the very strong tones came later and mostly by add-on boosters, then by building boost INto the amp. Marshall's switchable extra stage, Master Volume taken from mixers and mis-used to good effect.

> many devices that claim to be "tube-like" don't really follow time-honored topologies when perhaps they should

I can't help but agree.

Many of the things done after 1980 look "stupid" to an old stick-in-the-mud like me.

OTOH... axes and playing technique have changed a lot since the old days. The Old Guys started with giant acoustics and obviously had strong arms to fill a room big enough to pay OK. The early amplifiers lessened the strain but they still hit hard. Guys who started on HOT pickups and HIGH gain amps don't have that muscle/stamina.

So have amps. In all but the most mondo-grind gigs, an amp must have a pretty-clean sound. You can do a LOT with an amp that is clean to 50W and simple-clipping beyond that, with some bass and treble boost to widen-up the nasal tone of a naked string. Transistor amps have totally filled that need. So a tube amp is mainly about "strong flavor". And kids who grew-up with transistors and fuzzes may not be attuned to different kinds of flavors. So to SELL a higher-price tube amp (or elaborate simulation) a design/marketing team has to include some over the top WOW! sounds.

> do some breadboarding to prove

Yes.

I would suggest that "some" breadboarding may not be enough. Many of the Classic amps were evolved over many years; some have "happy accidents". Hey, it keeps us busy and out of other trouble.

And what Darron said.

[darron]

this is what you need:



the top-right is a tone stack board with shielded wires in/out and 4x true bypass stacks. it has fender, marshall, baxabdall and big muff from left to right. and then all of the components are socketed to that you can easily change values without taking up breadboard space. the bottom is a big earth plate.

i made a few boards but don't have enough components around yet to make one for before and after clipping, both seem pretty important huh (:

edit: and a closer look