Guitar amps have tone controls. Always have, always will… maybe.
More tone controls are better – treble, middle, bass – a tone stack for every channel! Always has been, always will be… maybe not!
Tradition is a powerful thing and change is hard to make. But, if you consider how tone controls affect an amp’s signal chain, investigate what a guitar and amp sound like with minimal tone controls (or none!) and then decide if you REALLY need them, you might be surprised at your conclusion.
Tone controls change or modify the tone of an electric guitar signal as it passes through an amp. However, the primary determinant of how your electric guitar sounds is the instrument itself, the amp’s overall design (gain stages, pre vs. power tube overdrive, etc.), its tubes, the speaker(s) and YOU the player. Tone controls are but one in a long line of factors strung between your brain, your gear and your ears.
We all have used tone controls to change the sound that our amp produces. Roll off the bass for a humbucker equipped guitar; trim the treble when you plug in that ice-pick Tele; peg the bass when playing your Strat; boost the mids to cut through the mix. All useful stuff. But, what would you sound like if you didn’t have tone controls at all?
In my opinion, despite their tone tweaking usefulness, traditional tone controls can detract from the quality of the tone… if you consider what your amp would sound like without them. Let’s dive into the nature of tone controls to find out why I hold this wacky belief!
Virtually every tone control you’ll run across, at least in a typical tube amp, is a ‘passive’ device. That means that it cuts or reduces the volume of certain frequencies. A passive tone control cannot boost frequencies.
Terminology check: tone controls are often referred to as ‘tone stacks’. The passive components that comprise tone controls – resistors, capacitors and potentiometers – are connected in such a way that when they are drawn on a piece of paper – a schematic – the treble, middle and bass controls look like they are ‘stacked’ on each other. That’s where the term tone stack comes from.
Because tone stacks are constructed from passive components, even if you turn the knobs up to 10, each tone control still reduces certain frequencies.
Yes, that’s right. With passive tone controls there is no such thing as a TRUE ‘flat’ setting where the signal is not affected in any way there is always some signal loss.
What the heck does all that mean?
Below is a graph that shows the frequency response of a typical treble, middle, bass (TMB) tone control often used by an amp company originally located in southern California. The graph depicts the level of frequencies with all the tone controls set to 10. As you can see the signal level at all frequencies is well below 0 dB — that means that the signal level is being attenuated or reduced as it goes through the tone stack – even at a 10 setting (yes Nigel, the same would hold true at 11 too!).
What does this mean? Two things.
First, a tone stack reduces the overall level of your signal. That’s why amps with traditional tone stacks need an extra gain stage to return the signal to its level before it got hosed down by the tone stack – more components, more cost, more complexity.
Second, even when all the knobs are on 10 the stack is changing the tone profile of your signal. The tone stack’s frequency response as shown in the graph has a big dip centered on 300 Hz. That means that the volume level of those frequencies around 300 Hz is a lot less than the rest of the frequencies – a cut in the low mids.
Here’s our tone stack’s frequency response set to provide a flat frequency response. Note that although the tone controls are not shaping the tone – all frequencies are being passed at an equal level -the signal has been severely attenuated across the board.
- 100 Hz
- 1000 Hz
- 10000 Hz
You’ll likely be surprised to learn that to produce this ‘flat’ response the controls have to be set as follows:
- Bass = 1
- Middle = 8
- Treble = 0
I bet that’s not where you set your tone controls!
There are a few things at play here. First, at this flat response point you have to really boost the volume to compensate for the gain loss through the tone stack. Second, it shows how much the typical tone stack scoops mids – bass and treble have to be severely attenuated to match the low mid-frequency response of the stack. Finally, this shows that the tone controls are highly interactive and changes in one dramatically affect the other – you have to dial in crazy settings to get a flat response.
So, if it takes this dramatic an alteration of your tone controls to get a true representation of what your guitar sounds like why bother?
Is all this ‘bad’? Not necessarily. The tone stack in question has been used in dozens of amp designs that produce great tone. Maybe you won’t like the true sound of your guitar!
However, I want to plant a crazy idea in your brain: what would happen if you didn’t have a tone stack or you had a very simple tone control that could make subtle tone changes, but would not suck nearly as much gain and would not dramatically alter the frequency response of your guitar?
Well, in my experience you can really ‘hear’ your guitar (!) … you’ll hear a more balanced tone coming from your rig. Your tone will have more presence and, with an amp that has been designed with minimal or no tone controls, you will experience a more responsive, dynamic feel. If you like that sort of thing it’s VERY cool!
Of course, it’s impossible to properly convey the sound of a ‘tone-stacklessR17; amp on a piece of paper … you have to hear the difference!
So, when you see amps with minimal tone controls don’t dismiss them. Play through them when you get the opportunity so you can see for yourself. You may be surprised at what you hear and feel!
Send me an EMAIL (Don Mackrill) if you would like to discuss this further!
PS: Crystal ball time! I predict you’ll see an increasing number of amps with ‘lift’ switches that take the tone stack completely out of the circuit. A few big name amps have had this feature for years labeled as a “solo” switch. Why call it a solo switch? Because eliminating the tone stack increases gain and midrange response – both perfect for bringing your sound front and center! Wouldn’t that boost in tonality be a good thing all the time?
Consider having your local amp tech add a lift switch to your favorite box so you can experiment for yourself … the stack might get lifted and never put back!
6 thoughts on “Amp Tone Controls: Tone & Gain Sucking Leeches?”
Great article! Thoroughly enjoyed.
I found you by searching on “Gain sucks tone”. Here’s why…
I’m fed up of hearing chainsaw guitars, and I’m convinced that too much gain kills the character of the guitar making them all sound similar. I was trying to find some evidence that would help me convince a fellow guitarist to back his pre-amp gain off a little to let his guitar come through. I’d be really interested on your thoughts on this.
Very best regards from France
I enjoyed your article. Tone is so elusive for many, and not well understood with respect to pots on guitars and amps. I find more clients now forgo the tone control altogether on their guitars, and favour pickup selection / combination, and a single pot for volume. This tells me that my ears are not unique, and makes sense, given that so many guitar players never really use their guitar’s tone controls.
Best regards from Canada!
My 1981 Sessionette:75 amp design (55,000 manufactured) feature an EQ Bypass switch on the drive channel. It was a very popular feature. The amp ceased production in 1988, but we still see demand for them. Used by Dave Gilmour, Eric Clapton, Jan Ackermann, Roy Buchanan (via Mark Dronge), Dave Stewart and loads more… the amp is unashamedly 100% solid state and is a classic here in Europe! More infor here: http://www.award-session.com/sessionette.html You’ll find some of my ‘designer standpoint’ articles on the Manuals page too, if you’re interested!
I am a complete SS convert since 1981! And known (despised) for it! LOL!!!
I’m finding your post rather late but am fascinatingly confused! When I turn my tone control(s) clockwise I hear some band of frequency increasing, so not all frequencies must be attenuated..correct? Also I do perceive a small loss of gain when tone is severely minimized. I tried this with my Fender Blues Junior and telecaster so far, and I must say with that particular combination I did get excellent tone and results. I would like to hear more at your convenience. Thanks!
One thing I have found by playing with tone controls and EQs over the years (applies more to a distorted rock tone, but starts when there is any type of compression of the tone), is that when you add or remove a frequency, the others fill that space in the signal. So if I were to drop lower mids in my crunch tone, magically, a bit more base and treble fill in that signal void. So the concept of tone controls are actually very dynamic when you are working with a compressed (distorted or otherwise) signal. Again, this phenomenon starts right at the point of the tube soft clipping, that is sometimes not perceived as harmonic distortion.
I have come to the point that I recognize my best tones by swapping guitars (that all have different pickups), swapping pickups, or using an external EQ. The thing with using a solid state EQ in front of a tube amp is quite different that having an amp with tone controls. First off, the EQ is generally a ‘clean’ device that can BOTH boost and cut signal bands, and with quite more a degree of precision if you use a 10 band or a parametric EQ.
I have a couple of amps with NO tone controls that were made back in the 1940’s by Valco, and they are indeed SUPERB ! Touch sensitive, and respond phenomenally to any input tonal changes from the guitar pickups, or an EQ. They ‘Morph’ into many different sounding amps with input tonal changes, far more than any amp with built in tone controls, and I’ve owned over my tenure perhaps 50 amps (currently a dozen), and played another 50 in studios and at sessions with friends, so I have a pretty good basis for comparison.
For me ? No more built in passive tone controls. I run a “Raw” bypass switch on my amps with built in tone controls, and tailor the input frequencies by changing guitars and using an EQ pedal up front.
That’s the most flexible and far and away the best sounding approach I’ve ever found.
Hats off to Don Mackrill !!! You have some deep insight, run with it !!!
The first guitar tube amp I built was a single-ended, single 6V6 output, single twin-triode preamp build. I does not have a TMB tone stack and I opted to shape tone by employing switchable cathode bypass caps on both preamp gain stages and the output tube. The preamp(V1 & V2) cathode bypass caps are as follows (on-off-on DPDT switch):on=1uF/off= unbypassed/on=22uF.
The 6V6 output tube also has an on-off-on DPDT switch. on=10uF/off=unbypassed/on=2200uf. The 2200uF tightens bass.
I also installed switchable (on/off), adjustable global negative feedback to further shape tone and clarity. These mods are very useful throughout all volumes.
Even on amps I’ve purchased or built over the years if they have a TMB stack I generally set it and don’t touch it much. I definitely prefer the raw sound of a amp without a tone stack.