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baffled by the tonestack


blindopher

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Hi, before I go any further: yes I've got the Duncan tool, I've read all the gurus: Aiken, Valve Wizard etc. etc.

 

I have some specific questions concerning the classical fender tonestack. I have no trouble understanding the treble control with it's high pass filter, but I just don't get the other ones because they seem to have the cap in series with the load, whereas a low pass filter is defined as one having the cap in parallel with the load, so it can block the low frequencies form going to ground, forcing them to the pot, while having the high frequencies shunt to ground via the cap.

 

What am i missing here? It's the routing of the signal that's confusing me with the bass and mid controls.

 

The way it appears in the schematic is that a low pass filter for the bass and mid is created by merely placing a cap in series with a resistor in series with the load. Maybe that's true, but it goes against all low pass filter definitions i''ve read.

 

Or are the filters for the bass and mid controls not really low pass filters...?

 

thanx!

 

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In order to understand a tone stack you need to understand caps better. Caps pass AC voltage (or at least emulate passing AC) and block DC.

 

The terms High pass and Low pass can mislead you from understanding how the circuits actually work. They only explain the resultant effects on frequencies. Not how the circuits work so you should abandon the attempts of using high pass or low pass to understand how caps work in those circuits.

 

Caps only do one thing. Pass AC in varying amounts depending on their values. (it actually emulates passing AC but we'll skip that for now)

 

The rule is, in parallel to the signal, high frequencies are conducted to ground first because the cap responds to faster changes in polarity over slower changes which are closer to DC which does not pass through a caps. Then you have the higher the value, the lower the frequencies are passed up to the point where all frequencies are grounded out with very high cap values and it essentially works as a short to ground.

 

In series a cap passes AC too, except you aren't shorting the high frequencies to ground. With a low value cap, only high frequencies get through the cap and the bass frequencies are left behind. As the capacitance is increased, more and more frequencies get through until all frequencies pass and the cap again acts like a acts like a conductor.

 

 

The difference with these two circuits is, if you use a similar cap in each, the treble is removed and bass is unaffected in parallel.

Treble is passed and bass is left behind in series.

 

If you use a cap in parallel which rolls off the treble at say 5K, then use another cap in parallel that blocks bass up to say 500HZ before it begins conducting, you are left with nothing but midrange right?

 

The bass knob turned all the way up lets all bass frequencies through. As you turn the knob down, it gradually passes bass through a cap with a specific value in series. This passes the high frequencies but the bass is left behind. Its called a High pass filter because only high frequencies get past the cap.

 

The treble control pass all highs when its turned up. When you turn it down, the cap conducts the high frequencies to ground.

 

Depending on the treble and bass caps, all you're left with is midrange when both of those are turned down. If the roll off of the treble cap is low enough and the bass cap high enough you could have it so no midrange is left.

 

How steeply the roll off is critical too. The Q (quality) of a cap is a value. It tells you how sharp or gradual a cap rolls off. If the bass and treble caps have sharp roll off, the midrange that's left will have a sharper peak.

 

 

In many Fender circuits, they use a slightly different method of getting frequencies through. Its easier if you view it as a mixer with three channels, but its essentially a combination of series and parallel circuits.

 

 

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The caps can block or pass frequencies depending on the values of the caps and how those three legs are varied in resistance by the pots.

 

The pots here are more like pan pots on a mixer. They pan over to one caps feed in one direction, and pan over to another feed in the other direction. Lets follow that path.

 

The output comes off the treble pot. If the brush on that pot is moved up to the top of the diagram, nearly all of the treble passing through the low value cap will be coming out of the circuit and very little from the bass of mid caps.

 

If you move the slider down, the feed from the mid and bass caps will be greater then what's coming from the treble cap.

 

If the bass slider is moved up, the .1 cap will pass most of the bass and feed it through the treble pot and on to the next amplification stage. If its turned down, most of the bass will remain behind leaving whatever the mid pot is set for. The mid cap is between the bass and treble. It will pass frequencies in the middle of the audio spectrum. When its turned down, most of those higher frequencies go to ground. Turned up most of those frequencies pass upwards and out through the treble pot.

 

The key item in this tone stack besides the caps is the resistive balance between ground and passing the signals through the caps. The resistance of the pots and fixed resistors bleed varying amounts of frequency. With all three pots centered, all frequencies of the legs of the tone caps cut in half but the frequency response is essentially flat to the ears (as much as a midrange guitar amp can be. Guitar amps are far from being full fidelity) The pots from there pass or cut the amount of AC frequency depending on how much resistance is added or removed.

 

Don't know if that fully explains it. Studying a simple two frequency tone stack would be easier where you pass either treble or bass. Having the third midrange leg can confuse you if you fail to understand how caps both pass and cut frequencies.

 

The mid cap is put in semi parallel with the pot turned in one direction and semi series to ground in another direction and a combination of series parallel in the center to both pass and block frequencies. That 100K resistor keep the mid cap from being 100% in series or parallel, that's why I mentioned viewing this more like a mixer having three channels and pan pots easier to wrap your head around it, but its still tricky to understand because you're not dealing with 100% series or 100% parallel. You're dealing with a variable series parallel signal feed.

 

Having a strong understanding in the basics is essential if you want to understand more complex circuits. Its allot easier to understand it if you learn both the theory and mathematics. There's really no short cuts if you want a full understanding. Electronics is a branch of physics and you have to study RLC filters, as well as series parallel circuits, ohms law, AC vs DC circuits and all those basics before you can fully grasp what's occurring. I tried to keep it simple so a laymen can understand but In doing so it misses many key items that are essential.

 

I could probably do allot better using an animated presentation using color coded flows and showing you how those colored legs mix and vary the three in varying degrees. Its just not easy to describe in words, especially when you aren't there to answer questions as they come up. I taught electronics for awhile and it can be most difficult to teach by words alone. You really have to mix instruction with hands on lab work using test equipment so a student can tie the physical results to the abstract science together. If you use only one of the other its like using only half a brain to develop and mental picture. What's there in that that cross section may be accurate, but its ultimately incomplete unless both sides of the cross section are united.

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Thanks guys. As I said it can be difficult to explain things in simple language and not use all the technical aspects. I've always found, if you can develop a good mental picture of what's actually happening, the technical stuff just plugs in easily and enhances the mental image of what's actually going on.

 

If you're getting into designing and building electronic gear then you definitely have to use the math to figure all your parameters out. But I know many in the business who know electronics from a purely mathematical standpoint. If you were to ask them how a specific component works, they have a hard time painting an image.

 

Caps and coils are two of the cooler components used in electronics because they both use a field effect. Caps use a static field to push the electrons. Its basically the same kind of static you get when you comb your hair and get sparks. As a kid I did a bunch of experiments from books building a Jacobs ladder, Lynden Jar to store static electricity and dozens of others. You can trace back the early experiments back to Ben Franklin and beyond. A Lynden jar is probably the earliest capacitor ever made and dates back to before the Egyptians I believe.

 

Coils are cool too. I built my first Crystal radio back when I was six or seven. I'm still amazed at how you can get sound from a coil cap and diode with "No" battery power. The radio waves themselves provide the power as well as the earths magnetic field. Because those magnetic fields are invisible I had to use imagination to visualize them. From there building simple motors, Telegraphs, Guitar pickups etc all started making sense.

 

The educational part teaches you how the components work together. If you want to build quality filters you really need caps, resistors and coils to get a good RLC circuit. Your best EQ's are still made from these passive components. The only time they use transistors or op amps is to make up gain lost by the passive filter components and keep the signal strength at line level. In the case of a Tube amp, the tube stages do that so any losses caused by the passive tone stack components is juiced back up by the next tube stage.

 

 

Coils work in an opposite manor to caps.

 

Caps block DC and pass high AC frequencies better then low ones.

Coils pass DC and pass low AC frequencies and block high frequencies.

 

Coils block changes in voltage because the magnetic field takes time to fully develop or bloom like a flower.

While the field grows, it fights the signal trying to pass through the coil. A field will generate around a single wire and

by using a simple right hand rule you can figure out the polarity of that field http://upload.wikimedia.org/wikipedia/commons/thumb/3/3e/Manoderecha.svg/2000px-Manoderecha.svg.png .

 

When you have many wires together in a coil these magnetic lines of force act like a shock absorber to the current flow.

 

Then when you remove the power or reverse directions (in the case of AC voltage) that field collapses and all that magnitism

gets converted back into electricity, so a coil has two aspects. Its like pushing a car up a hill when your apply voltage and its like a car coasting down the other side once its reversed direction. .

 

When you have both of these components in a circuit they can do wonderful things in audio. Coils block high frequency, so they are ideal for using in a crossover. They allow the bass frequencies to get to your woofer and block the highs from getting to it. You can then use a Cap that Only passes highs over a certain frequency. You then have a two way EQ filter with these two components that feed your two speaker drivers. Lows are blocked from the tweeter and because these lows are very strong signals the cap prevents them from blowing the fragile tweeter coils.

Treble isn't needed by the woofer. It only needs to produce what the tweeter cant. Pumping it additional high frequencies to the woofer will only makes the coil buck which is a cause of harmonic distortion. You filter out the high frequencies and keep the signal feeding that woofer simple and it wont be interrupted by frequencies it cant reproduce anyway.

 

Its all cool stuff. Once you know how these components do things then finding a simple on line calculator to figure out the math parts isn't that hard. Its a little more complex than that of course. You're dealing with impedance which have phase differences between voltage and current. That's where the real fun begins. Unfortunately you really have to follow the full theory and math behind it at that point. You're dealing with trigonometry at that point. something I hated when I took it in school. It only made sense when I applied it to electronics.

 

Its funny because a buddy of mine whose and Architect was having problems figuring stress on a beam he was designing for a building. I asked him to show me the formula and I told him you simply stick this value here and that one there and take the square root. He was dumb founded because I obviously didn't spend 4 years in college studying architecture like he had. I simply told him they were the exact same formulas I used in electronics to figure out circuit values. If you learn physics in one field, I don't care which field it is, you can simply reapply those formulas using different sets of values. It may be Mechanics, Chemistry, Astronomy, you name it. The same formulas are used in all.

 

That's one thing I didn't know as a child and if I had, I'd likely be making double what I am now. I would have hit the math books allot harder growing up. Unfortunately I had no one in my family or even teachers that could explain how math and algebra would be relative in so many ways and in so many fields.

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I wish I had been more inclined towards mathematics and physics when I was in school! I'm rediscovering it now but at a very slow rate. I'm basically a guitar player and teacher who builds the occasional amp or pedal but i'm in love with the whole technical theoretical aspects of it. Anyway I need time to internalize your first article and once i'll do that, i'll be able to ask you questions which are much more focused. Being a teacher of many years myself, I totally agree about having to supplement the theory with practice to really unfold the mystery. I'm wrapping up my rangemaster clone these days (in the tweaking stages) and about to start laying down the plans for a new amp. Thanks again!

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... Being a teacher of many years myself' date=' I totally agree about having to supplement the theory with practice to really unfold the mystery ... [/quote']

 

I had an interesting experience in electronics school that solidified the concepts of Induction (and, by extension, Capacitance) along with Ohm's Law for me. I was checking the continuity of a choke (inductor / coil of wire) with an Ohmmeter. The battery in the Ohmmeter generated a current through the choke. When I removed the meter's leads, I still had one hand on each of the wires from the choke. The Inductance of the choke maintained the current flow (which is a property of Inductance) but now the Resistance in the circuit (me) was suddenly very high. Since Voltage is a product of Current times Resistance there was a significantly high enough Voltage between the leads of the choke which I was holding with both hands that I felt a real shock - fortunately there was not enough Current available to do any damage but it is something I never forgot.

 

Having that "hands on" practical experience gave me a new understanding of what the math in the classroom was attempting to describe with formulas and equations. I no longer had to memorize the formulas they just made sense to me after that - a Peter Parker moment perhaps?

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I had an interesting experience in electronics school that solidified the concepts of Induction (and, by extension, Capacitance) along with Ohm's Law for me. I was checking the continuity of a choke (inductor / coil of wire) with an Ohmmeter. The battery in the Ohmmeter generated a current through the choke. When I removed the meter's leads, I still had one hand on each of the wires from the choke. The Inductance of the choke maintained the current flow (which is a property of Inductance) but now the Resistance in the circuit (me) was suddenly very high. Since Voltage is a product of Current times Resistance there was a significantly high enough Voltage between the leads of the choke which I was holding with both hands that I felt a real shock - fortunately there was not enough Current available to do any damage but it is something I never forgot.

 

Having that "hands on" practical experience gave me a new understanding of what the math in the classroom was attempting to describe with formulas and equations. I no longer had to memorize the formulas they just made sense to me after that - a Peter Parker moment perhaps?

 

One of the first items that comes to mind for inductance is the old Spark coils for an automobile. The points in a car would break the primary contact to the coil and the secondary coil would discharge making the spark across the spark plug.

 

I had an arsenal of old popular electronics magazines from the 60's. Every volume for 10 years and it was full of cool electronics projects you could do as a beginner. One project was to convert an old style spark coil into a static electricity generator. They referenced an old Model T spark coil which weren't available when I was doing it but I found a newer one I could use.

 

Getting the coil apart was the tougher part. The one I had was packed with tar. I soaked it in kerosene and was able to get most of that off.

From there you use the iron core as an electro magnet to act as a vibrator switch. I used a piece of iron and mounted it close to the iron core. When you applied power to the primary, the coil would charge and pull the iron towards it opening the switch and the secondary would discharge. Then the tap would close again and the process would start over.

 

The secondary high voltage output could be connected to a number of things. I used two coat hangers close together and was able to get the sparks to ride up the ladder, something like you'd see in a Frankenstein movie. This arching caused hell with the Television which was all air transmission back then.

 

Later I leaned to use that spark generator to transmit Morse code via an antenna. I learns allot of radio stuff back then and was fascinated by what magnetic waves could do. I eventually got contacted by the FCC for having an unlicensed radio and causing interference in the CB bands. I quit those experiments after finding out what I was doing. I doubt they'd mess with a kid of 9 years old.

 

I got into building radios and learning to tune the RF coils. You'd inject the circuit with an RF generator then tune the coils so they would peak on a meter, scope or through the audio amp. I got to the point where I could convert AM radios into long band or short wave receivers. You could also build cool radio jammers and play tricks on people. I'd take a little AM radio and set it to make another set squeal like a banshee. I later learned that was the essence of a Theremin and built some of my own unique versions.

 

Later I got my first class license but I never put it to use in that industry. I forgot most of the Morse code I learned as well. I still use some of it playing music however. I'll be playing a lead and will pick notes in Morse code patterns so I guess I found a use for it eventually.

 

There's a ton of cool stuff you can learn that's quickly becoming forgotten. All this digital high tech stuff is making people think that's all there is to electronics any more. I do acknowledge there's allot to do with that as well, but the basic electronic stuff is where the real fun is, especially with music gear which still uses allot of it..

 

The Digi Techs are still trying to make easy money substituting their cheap parts and software driven hardware but its no substitute for many basic things. In others its beginning to work along side with the old which is what it should have done all along. You should only throw out technology that has a better quality replacement, not a cheaper one. Mosfets come close to tubes for example but you don't see coils added to those circuits to emulate the sag power transformers and diode tubes created. Sunn did that on some of their older amps and they really sounded terrific. There were things that Phono cartridges did to the sound that could surely be revisited. Some kind of electromechanical device you can place between a CD player and amp that would give the CD player an actual magnetic cartridge sound.

 

There's so many possibilities, if you know your basics well. There are thousands of old patents out there that failed or ran into dead ends because the technology to make the leap to something really cool just wasn't possible at the time. It just takes a new point of view that links the old with the new and you could invent your butt off making new and useful tools.

 

 

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Ok, now that I've read your reply at least 5 times, I would like to venture a more specific question. I'm still referring to the classic Fender TBM tonestack.

 

1. Since the input signal arrives at a junction right off the bat, what prevents treble frequencies from traveling down past the slope resistor, through the bass cap and then back up to the treble cap and out, thereby negating whatever the treble pot is trying to do? Is it a case of a path of less resistance?

 

Or do they do just that, and i'm still missing the point?

 

thanx, (I feel like an idiot. Took me a relatively short time to understand something like how a triode amplifier works, but the tonestack is driving me crazy.)

 

 

 

 

 

 

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Yes its a resistance thing. Its basically a resistive mixer. The dry full frequency coming in splits in 3 directions. to the three caps. The 100K resistor is there to attenuate the size of the signal to the bass and mid caps because bass frequencies are much stronger then treble frequencies. 100K is about the level of a guitar volume put turned down 1/3 so you're feeding those caps with a weaker signal from the beginning.

 

To understand the circuit better just remove all the input wires to the caps.

 

If you feed a full frequency signal to the top cap with a very small pico cap in series whats going to happen? Only treble frequencies will make it through to the other side right?

 

The bass cap is .1uf. Its going to pass most of the frequency through, but there's a trick here. With the pot turned upwards, most of that bass will feed the fill frequency towards the output. Turned down its going to feed more of that signal through the mid pot towards ground. The bass pot acts as a series parallel switch to a good degree. Not all of it goes to ground in parallel to the signal, and not all of it feeds in series to the output.

 

The mid cap's value is between the treble and bass cap at .047uf. This is going to block lower treble frequencies in parallel and pass upper mid frequencies in series. The pot sends the signal to ground 100% so all the upper mids and treble frequencies will go to ground. But, low and behold that pico cap at the top isn't being affected by that mid pot. It will allow treble to get through and replace the treble frequencies the mid pot is sending to ground. Its a second path for those treble frequencies to get through even though that mid pot is rolling those same frequencies off to ground.

 

One is working independent to the other and acting as a separate doorway and its how the signal gets mixed together in varying amounts. Instead of the three being independent volume level pots feeding only treble bass and mids, the bass and mid pots are pan pots that pan between series and parallel. Caps work backwards in series and parallel in a purely capacitive circuit. With variable pot resistance added you do two things. You vary the amount of capacitance. and you toggle between series and parallel. The treble cap is simply a high pass but the treble pot does get the other frequencies coming up from the bottom side. If the mid pot is panned up in series, its feeds those upper mids up through the bass pot and mixes with the treble frequencies coming from the top of the pot.

 

With the treble pot set in the middle you should have a neutral signal. No treble added no treble removed. If you turn the pot up you get more of the treble cap and less feed from the two lower bands. If you turn the treble pot down your get most of the feed from the bass and mid bands. What you hear is a simple treble cut but your actually panning towards the mid and bass frequencies and less from the pure treble feed.

 

As you can see thinking it through is more difficult then just hearing the results. by ear all you hear is treble mid or bass when you turn the knobs. You don't normally think of it as dual or triple feed.

 

You could color code the feeds. If the treble is yellow, the bass blue and the mid red. If you mix red and blue together you get violet. If you mix mids and treble together you get orange. If you mix bass and treble together you get green. Depending on the pot settings you can dial up all the colors in the rainbow.

 

Maybe this will illustrate, With all tone pots cranked to max you get series/additive color mixing.. The white in the center would be all frequencies mixed so you get "white" (full frequency) sound from the mix.

 

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With all pots turned down you get subtractive mixing with most of the frequencies going to ground. With fenders, the tone pots don't attenuate the signal completely down. Some tone stacks do cut off all of that frequency and with all three turned down you get no sound.

 

This of course isn't the most ideal illustration for tone stack mixing but it may help to visualize how the frequencies mix. This second diagram uses Cyan, Magenta and Yellow instead of red green and blue, however, when the pots are turned less then 50% you are making the caps parallel instead of series so you could think of the first diagram as 100% series additive and the bottom as 100% parallel subtractive.

 

With pots in the center you have series and parallel (additive and subtractive) mixing going on. You could overlap the two diagrams and wind up with Gray in the center with the pots cranked to the middle. Nothing boosted, nothing cut. This would then become your zero mark where you could add or subtract frequencies depending on which direction you turn the pot.

 

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Well it's definitely becoming much clearer. I'm curious as to your approach of refraining from mentioning a low pass filter. All the technical articles i've read so far practically wallow in complex explanations of low pass filters morphing into high pass filters to create band pass filters etc. I must admit your approach is much easier to grasp. As far a i can see, there isn't a single low pass filter in the entire tonestack. I see 3 high pass filters with different cut off frequencies feeding into the pots, to be mixed as 3 channels.which are slightly interactive.

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They are there you just don't realize they are working both ways depending on the pot settings. The key is differences in potential. when a signal is closer to hot it has more potential to pass a signal then block it. When its closer to ground it has a potential to block more then pass.

 

I don't even like calling them high pass or low pass because those terms can be misleading.

 

Instead, in a series, they pass or fail to pass frequencies depending on their value.

In parallel they "block" or "fail to block" the frequencies depending on their values

 

When looking at the right side of those caps. If the resistance between the top output leg and say the bass cap, is the same as the resistance from that leg to ground. What comes out of that cap is going in both directions at the same time. Half of the signal is feeding up to the output in series. Its also feeding down to ground in parallel "At the same Time"

 

You see its a complex circuit and you cant view it as being only this or that. That's the tough thing you have to wrap your head around and see a hose coming to a T and feeding out in two directions at the same time and doing two different things to that signal at the same time.

 

If you turn the bass pot up 1 number. You take that equal balance and shift the amount of frequencies passing towards the output and lessen the feed to ground. You are shifting the circuit more series then parallel so the frequencies shift as the ratio of series vs parallel shift.

 

 

Another visual. Light waves are similar to audio waves, just at a much higher frequency. That's why I like using them because you can see the effect of light and get a better mental image.

 

Think of this picture as the audio wave spectrum.

 

 

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The low end is your 20HZ, the reds are your treble frequencies 20K. In between you have your upper mids, mids, lower mids etc down to the bass.

 

Say I put a cap in series with the signal, a low value cap. It would be like placing a blank piece of paper over the left side of that picture. Only the high frequencies pass through the cap. The low frequencies fail to pass. If I use a higher value cap its like sliding the paper over to the left to reveal more of the spectrum. Still anything to the left of it fails to pass.

 

Now instead of series I use the cap in parallel. Instead of covering up the left side, I cover up the right side and block those high red frequencies. As I increase the cap value, the paper blocks more colors moving towards the left and begins to block the yellow, the green the blues and eventually all colors.

 

Now this is the trick. We're using a complex series parallel circuit. Place a piece of paper on the left and the right. Block the blues and the reds. What do you have left? Midrange.

 

What happened if I decrease the parallel cap? It moves the right paper over to the right and exposes the red.

What happens if I add more capacitance of a high value in series? Right, the left page moves left exposing more blues and purples and you get more bass frequencies.

 

How do you decrease mids and leave the highs and lows? Well you turn the treble pot up which makes the right page narrow. That right page becomes transparent where the dark reds are.

 

The mids are turned down This extends the right white page over to the left to block the yellows and greens.

 

The bass bass cap is in series passing lows already so you turn that up and allow all of the lows through in series as a "band pass" Bit you are also removing any highs that may pass through that cap as the mid pot is turned down.

 

Its the parallel action of the mid cap being panned to ground that pulls that white sheet over towards the left. The bass cap passes all frequencies so it removes the paper blocking the frequencies on the left to expose all the blues. The end result is the bass cap passes the lows in series, the mid cap blocks the highs from the reds all the way down to green. The treble cap passes highs in series and replaces whatever the mid cap cuts.

 

Remember what I said earlier. Its a Difference in Potential thing. If you have one cap blocking a frequency and one cap passing it in equal amounts, the two cancel each other out. If the treble pot is turned to the center and the mid pot is turned down, the mid pot is cutting everything above say 500hz, by turning the treble pot op, the difference in potential is shifted to feed more of the treble pass pot and that treble increases even though that mid cap is still blocking everything below that treble pass cap Q point.

 

Whew!!! Enough. I'm passing out from all the banding here.

 

You can reverse my example there and get a mid boost. If you want I can walk you through it, but you're probably learn more by attempting to do it yourself. Just remember these two key items.

 

Instead, in a series, they pass or fail to pass frequencies depending on their value. (Left blocking Page)

In parallel they "block" or "fail to block" the frequencies depending on their values (Right blocking Page)

 

This again is not the only way of doing things. You can uses blocking pages coming from the bottom up or top down. where there is full frequency but less of it in comparison to the rest of the spectrum. In stead of using a stack you can use three tuned filters that go from 0 to 10 and one pot has no effect on the other. There is no interaction between one filter and another nor is there a series/parallel shifting going on, its simply a 3 band mixer. Those are a little easier to understand. If you learn how a filter using a cap and coil work to pass and block specific frequencies, those filters remain fixed, much like a graphic EQ is, then you just pan up the gain of that filter.

 

There's many ways of skinning a cat in electronics depending on the components you use and the wiring of those components. I love them all and think they can all be a blast to tinker with. It just takes time to reason how and why things work.

 

When I was in college for electronics the head of the electronics school had his doctorate in electronics. We were busy learning about series parallel electronics using complex circuits of different values. Stuff like a three dimensional box with all the edges made of resistors. or pentagon shaped circuits with all the pots connected by resistors, all kinds of crazy stuff.

 

The doctor came in and gave us a task. He said I want all of you to come up and fill the chalkboard with resistive circuits and give me an input and output to the circuit

 

 

He then left the room for maybe a half hour while all 12 of us drew up complex series parallel resistive circuits on the board.

 

He cab back and started circling the various resistor combinations and started grouping their values together. 800+400 in series is 1200, in parallel with 1200 is 600, in series with 300 is 900 etc. He want through the entire board of maybe 300 resistors in about 30 seconds and said the answer is This within 5%.

 

Everybody sat back dumfounded. You can guess what he made us do next. We had to get out our calculators and prove weather he was right or wrong and if he was wrong ho much he was off by. When we got done we had some number with a .020507 at the end, well within 5%

 

The he came back and showed us ho he narrowed it down so fast. He then said don't waste so much money on all those parts, you only needed a 500 ohm resistor in place of those 300 you had up there. When you design a circuit its all about profitability. If you can make a circuit do what you need with only 6 parts instead of 16 you're going to have less failure and and make more profit.

 

In other words KISS. Keep it simple stupid. That's the key to a fender tone stack. Its ultra simple to build yet it does so much.

379aca505d5b79ef5db2247fc95e292f.jpg.b69e59a4211d10da24e62124c04031a1.jpg

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This is really a great explanation. I am just now getting started with guitar effect building but I have no electronics training (just an audio engineering background from a musical standpoint). Thanks for taking the time to distill this in language us non-EEs can understand.

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Welcome to the Forum. This is what the DIY site is all about. Sharing ideas and helping others to understand some basic stuff.

 

You should note I do leave out allot of the scientific basics in that description. Someone formally trained in electronics could probably add many things I missed but it was written for a laymen to get some kind of visual idea of what's actually happening in those circuits. As I said, If I could do a visual computer representation I'd zoom down to an atomic level and reveal what's going on at an atomic level. Something that didn't exist back when I was first learning.

 

Today they can use an atomic microscope to actually see how atoms move through different materials and discovered many things they didn't expect. That technology is what's lead to the super fast computer chips we're using today.

 

I got into DIY stuff back in the 60's and its what lead to a career in the industry. I still do projects to this day. I was given some wise advice by one of my instructors long ago. He told me electronics isn't something you master and say OK I know it all now.

 

Its one science where the learning goes on for you entire lifetime. I'm glad his advice was true because it never gets boring like many other fields do. Just when you think you've plateaued and exhausted all the possibilities, some new idea comes along either through your own inventiveness, or from someone else and away you go again.

 

I've rediscovered the same basic concepts over and over from different vantage points and it never gets old. Its not like you have to learn things from only one narrow perspective. Even what I wrote in this thread was envisioned as I wrote it. If I were to rewrite it again I'd likely use all different methods and examples to describe things from yet another vantage point.

 

The science is exact of course based on mathematical formulas so there are many things that wont and cant change no matter what, but once you've learned and understood those basics, things can be very creative using those fundamentals. Its really not that much different then music. You learn those basic scales and fundamentals, then you put them to use in creative ways. That's what engineers do, thay take the technology and use it in new and creative ways.

 

Anyway thanks for your comment and don't be a stranger here. Be sure to post pics of any projects you are working on. It inspires others to get involved do the same.

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Well, for a newbie layperson I have built some pretty complex circuits, and not just by buying a PCB. I go to a great web site called Tagboard Effects (http://tagboardeffects.blogspot.com/) where they take many common pedal schematics and design them for using regular through-hole components on Vero (perf or stripboard). So, while it is still somewhat "paint by numbers" it is more than just filling in the spaces. You get a chance to really experiment if you want. I have built about 25 of the circuits there and boxed about 8 of them. That includes some of Craig's original effect designs from his books. I recommend the site for people who want to get more hands on with guitar effects - including tone stacks.

 

One of the members there just took all of tone stacks in the Duncan Calculator and laid them out with an LPB following so you regain any loss introduced by the tone stacks. Marshall, Fender, etc with gain stage following.

 

Most of the new projects are showing up in the forums now since the sites main editor has been laid up since January, but there are already hundreds of his projects there and many contributed by others.

 

It isn't rocket science - but it is a lot of fun. Here are some pics:

http://i1304.photobucket.com/albums/s527/Paul_Motter/plexi1_zps1374fd8d.jpg

http://i1304.photobucket.com/albums/s527/Paul_Motter/DSC02995_zpsohw75dfw.jpg

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Assembling isn't that hard to do if you have good diagrams and work systematically. Much of the gear you buy from china is built by unskilled workers who just plug the parts in. The main thing is you develop good soldering skills so you get good connections and heat sink the parts that can be damaged by the heat. The rest is just reading a road map. Maps use a key and leger to identify items on the map. A schematic basically does the exact same thing. Getting to know your electronic symbols will help you read a schematic. You may not know what they all do or how they do it but you at least know the difference between an FET or Transistor when you see the symbol and aid you in understanding how parts work together.

 

Its funny though. I been an electronic tech for over 45 years now. I've spent a good deal of that time doing repairs for a living on all kinds of gear from Music electronics, radio, TV, Computers, you name it. Other then maintaining my own gear I don't do allot of building. I guess I got enough of that on the day job. That and the fact I can usually buy what I want pre made cheaper then it costs to build it.

 

I used to do allot more building back when parts were dirt cheap. Resistors and caps a penny apiece, connectors a quarter, transformers $5 and stuff like that. Today they charge you more in parts then it does to buy a unit and since there's not much learning experience in building for me, I'd rather just buy what I want and save the builds for unique or hard to find items. I still have tons of spare parts. I worked for several companies that went out of business and collected parts that were being thrown away.

 

If I do build I can usually find most of what I need. I think the last item I built was a Moserite FuzzRite build that came out very well. The originals were selling for around $350 which is totally ridiculous for maybe $20 worth of parts so I just built my own. Truthfully, I used it for a few weeks and then its been sitting on a shelf in the studio for several months now. I have allot of gear and can get from it just about anything I need so that box will likely sit there until I'm inspired to use it again.

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I am building to learn something about electronics - I want to know the difference between a Tubescreamer (and there is no tube, by the way ;-P) and a Klon.

 

But I hear YOU. I wouldn't waste my time either if I already knew what you know, but I wonder if you have ever built a new-to-spec original LA2A or Pultec EQ. I saw a lot of hand-made (new) "vintage gear" at the last NAMM, because the schematics are out there and would not be overly complicated for someone like you.

 

I worked in 24-trks in the 80s and had access to such great tube outboard gear and mics, and it does sound great. I just sold my Neumann U-67 last year, had it for 35 years. Tube mics are another area where new builders are custom building some high-dollar electronics.

 

Anyway - I don't mean to steal the thread - but you mentioned it. If I had the knowledge you have, and a recording studio, I think I would be doing that.

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I used to use a pair of UREI LA-4's to record which I loved. I paid $25 each for them. Now its hard to find them for under a grand. I still have allot of gear from when I had my analog studio running. Since I went digital allot of that stuff is in storage collecting dust now. I do use the things that make the recordings sound good but there's only so much I can get in there and still be able to get some players in to record.

 

Some of the Plugins available do a killer job and they can all be added when mixing. Hardware in a digital world has to either be used before the daw tracking, or you have to play back the digital mix, convert it back to analog, pass it through hardware, and convert it back to digital as a newly recorded track. That can work if the gear is really good , but you do take a hit on the track quality doing the D/A - A/D conversions. In many cases its best to keep the recording digital and not convert it back to analog until its being played back as a CD or on a computer. Weird artifacts show up and the more mathematical computations you do the worse they get. A good quality plugin can do just as good a job as many hardware devices did and with a whole lot less trouble if you keep the tracks digitized.

 

I do use hardware, especially for guitar and bass. I'm experienced enough to dial up the exact tones I need before I track and use very little additional tweaking mixing. Comps are often something you want to use mixing and by then everything is digital already. The exception would be for drums where pumping them up with some nice compressors can sound excellent results. I don't use that technique much however because I usually record other instruments at the same time and the comps on drums usually cause even more bleed over issues which can make for allot of unwanted noise pumping.

 

Again, I don't do allot of building because I have what I need to do what I want. I have to restrain myself from buying things I don't need. For example I bought a pair of 12" alnico speakers Friday. I got so many cabs now I really didn't need to do that but I do have one cab that's got some old Eminence speakers that don't sound so hot. I'll likely swap those out with these alnicos for some vintage tones and get my Bassman head back in the lineup.

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