[roymail]

I have a Luxman receiver that I have used mostly as a power amp for many years.  So for a change, I put it back into integrated mode to hear the difference.  With the tone controls disengaged, the overall sound was not very open or revealing which was disappointing but not unexpected.  So I engaged the tone controls with the bass at 12 o'clock and the treble at 3 o'clock.  Now this sounded much nicer and more revealing in the treble region.

This got me to thinking, surely tone controls cannot really add treble to what is being produced by the source recording... can it??? 

My question then, what do tone controls really do when they change the sound that is being heard?  I'm hoping for some explanation I can understand without EE training.  Thanks!

[Letitroll98]

Yes, they actually boost or cut bass and treble.

[jimdgoulding]

What Let said. 

[*Scotty*]

Back in the day some tone controls were still altering the output from the amplifier even when they were in the 12 o'clock position. If you actually have a switch that takes the tone controls out of the signal path then you hear what you hear.
 It nice that you can get the sound you want by engaging the tone controls. I think there still may be a place in the system for tone controls,
heretic that I am.
Scotty

[G Georgopoulos]

This got me to thinking, surely tone controls cannot really add treble to what is being produced by the source recording... can it??? 

no,but they can amplify it and make it prominent

[ricardojoa]

What does your 12 clock tone mean? Usually tone control can cut or boost a specific frequency. At 12 oclock it might just be neutral where counter clock wise means cutting.

[roymail]

Yes, they actually boost or cut bass and treble.

OK, boost or cut bass and treble. But they don't add bass and treble that's not already on the source recording, right?  This is what I'm getting at, but I could be wrong.  I'm still learning.

I actually prefer hearing only the sound of the source recording which I can get by using a quality passive attenuator like a Goldpoint, Bent or an LDR.

[HsvHeelFan]

Bass and Treble controls ONLY boost the signal that's already present in your recording.

Think of them as a very poor, 2 band Equalizer...

If you have a datasheet or specifications list on the receiver/pre-amp, it'll usually tell you how much it can cut or boost the sound and at what frequency it's centered around.

The filter characteristics are usually a bell shape type curve.  The width of the bell is typically called the "Q".

HsvHeelFan

[G Georgopoulos]

So I engaged the tone controls with the bass at 12 o'clock and the treble at 3 o'clock.  Now this sounded much nicer and more revealing in the treble region.

With treble at 3oclock you have actually boosted treble compared to bass at 12oclock
at 12oclock is the mid point of all controls.However you might not get total balance at
12ocklock (depending on circuit )what i do is adjust both controls in comparison to each
 other and use my ears to listen for the sound i want,my 2 cents...

[Letitroll98]

OK, boost or cut bass and treble. But they don't add bass and treble that's not already on the source recording, right?  This is what I'm getting at, but I could be wrong.  I'm still learning.

I actually prefer hearing only the sound of the source recording which I can get by using a quality passive attenuator like a Goldpoint, Bent or an LDR.

Correct, they boost the level of bass or treble, but don't add any magical signal.  However the effect is as if you added something because the relative level is increased.  So it sounds brighter or heavier.  It may also sound muddied because there's no free lunch in audio, the circuit introduces a phase shift that can also be heard, to greater or lesser degrees depending on the design of the controls and your ears.

[roymail]

Letitroll98, and all the other posters, thanks for taking the time to help me to answer this question and understand it better.  I actually prefer having no tone controls in a simple circuit that allows the purity of the source be heard for better or worse.  But that's not possible with the receiver, so I just use the amp section only which is passive friendly and sounds good.  I appreciate everyone who added to discussion.  I realize this is basic stuff, but thanks for clearing it up for me.

[RDavidson]

Back in the day some tone controls were still altering the output from the amplifier even when they were in the 12 o'clock position. If you actually have a switch that takes the tone controls out of the signal path then you hear what you hear.
 It nice that you can get the sound you want by engaging the tone controls. I think there still may be a place in the system for tone controls,
heretic that I am.
Scotty

I agree. Purist? Definitely not. But tone controls can be very useful in some cases. If they increase your listening pleasure, go for it. It is important to understand what they're doing, though, so I commend the OP for asking.
Here's an example of a friend that didn't understand tone controls : He's a fairly typical iPhone and headphone user. When he's in the car, he uses Bluetooth to connect his phone to his car stereo. One day he asks me, "Why is it that when I connect my phone to my car audio system, it sounds distorted regardless of how I hook it up? When I use my headphones it's fine." Doing some digging, I found that he liked to use one of the iPhone's EQ settings which boosts bass and treble. OK. That's fine. The problem is that he ALSO used the EQ in the car's stereo to boost these same frequencies. Guess what? He was basically double boosting the signals, which made the sound ridiculously distorted from his car speakers (which I knew weren't the problem, because they're Dynaudios).

[werd]

They give you distortion and a false sense of security that you are making it better. It's a lazy man's fix.

[RDavidson]

They give you distortion and a false sense of security that you are making it better. It's a lazy man's fix.

Opinionated much?.........with your lazy man's response to a useful discussion.
Not having an anechoic chamber for a listening room has nothing to do with being lazy or insecure.

[Davey]

They give you distortion and a false sense of security that you are making it better. It's a lazy man's fix.

Distortion?  Not inherently they don't.

If a users objective is to achieve a flatter target (or maybe something else) then their usage can indeed make it better and not instill a false sense of security.

Tone controls are simply equalization.  It's a tool that properly used can improve (or not improve) a systems performance.  Much is up to the user to figure out how to best utilize them.

Distortion, false sense of security, lazy man's fix, is just silly rhetoric and incorrect.

Dave.

[werd]

Opinionated much?.........with your lazy man's response to a useful discussion.
Not having an anechoic chamber for a listening room has nothing to do with being lazy or insecure.

Opinionated? You are on a thread where the OP has asked a direct question. I answered it.

[werd]

Distortion?  Not inherently they don't.

If a users objective is to achieve a flatter target (or maybe something else) then their usage can indeed make it better and not instill a false sense of security.

Tone controls are simply equalization.  It's a tool that properly used can improve (or not improve) a systems performance.  Much is up to the user to figure out how to best utilize them.

Distortion, false sense of security, lazy man's fix, is just silly rhetoric and incorrect.

Dave.

The rhetoric is based and falls directly on your response. It's clearly obvious since tone controls are inherent distortion-adding devices. It's easily proved. You can actually see the distortion on an oscilliscope. 

[Davey]

It's easily proved. You can actually see the distortion on an oscilliscope.

Prove  it.  Show me/everybody.

Dave.

[werd]

What kind of distortion are you talking about? The minute one starts tinkering with a line-level signal the out put is a distortion. This is old school stuff.  I haven't had access to an oscilliscope in about 8 years.

[HsvHeelFan]

Article on equalizers in audio:

http://en.wikipedia.org/wiki/Equalization_%28audio%29#Parametric_equalizer

My Parasound pre-amp has tone controls, but it also provides a switch to take the tone controls out of the signal path.   

HsvHeelFan