Beginners' Curriculum

[Skruffyhound]

But when I post a fully-worked real-world computation like this, it lays like a dead deer.

Had it bookmarked too.

I also check your recent posts through your profile on a regular basis.

Please don't feel you are wasting your time, you have a distinct audience here.

In addition to general electronics you are also the resident guru for "old junk" that needs identifying/fixing/re-purposing, which makes you an invaluable resource for people like me. Thanks for all the help.

[Keppy]

A lot of great ideas here.

If I had to add anything, it would be a warning in the intro about "why are you looking to get into this?"

Someone just looking into this doesn't really realize how much there is to learn, how much money they will have to invest on parts and tools, and just how much of their time it will take (not just building, but sourcing parts, studying, etc.) and that they will have to deal with a lot of failures and frustrations.

Not to try to scare anyone away, but I know when I first looked into it I thought it'd be a good way to play with effects and save a few bucks. Nah. For the money and time I've spent, I could've stocked my board with lots of boxes and been playing all that time. I wouldn't take it back, though. I love learning new things and I'm having fun with it.

I think a good analogy would be about food. Just because you like to eat good food doesn't mean you're going to love learning how to farm. The final meal might be pretty good, but expect to buy a lot of tractors, shovel a lot of manure and spend a lot of days sweating in the field first.

I got into this because an old college friend of mine posted some stuff on facebook. When I asked him how he got into this hobby, he directed me to this forum and then gave me all the warnings you posted above, and more. Having someone give me that advice definitely helped a lot.

[teemuk]

Indeed. In a sense, I feel the hobby is, while giving, also taking away something.

Spending more time into learning / inventing / designing / building than actually playing guitar excluded...  
...I can't remember the last time when I had something finished and "boxed up" and would have been content with it for a moderately long time period. More often it's 15 min - 30 min with guitar + the new effect, preamp, amp, whatever, and I'm already thinking about tearing the thing apart (again) just to change a few components to other values, add a new feature, change some feature, and so on. ...Or I have a next thing in mind that I should build to pair up with the latest one. In the end, of all the effects and amps I've built I've scrapped the most to make room for the newer ones.

Yep, it's damn sure easier and longer-lasting to enjoy of something when you just buy it.

Curse you audio electronics hobby!  

[culturejam]

My biggest issue with learning theory is that I have trouble making the leap from general theory to a practical application for an effects circuit.

Most of theory I've read, at least seemingly, doesn't directly apply to 9v single-supply effects. I think that's because a lot of pedal circuits are intentionally outside of "good practices" for electronics....well, the dirt circuits anyway. The theory teaches how to make stable amplifiers with minimum THD. That's the opposite of what *we* want to do with them, at least a lot of the time.

I'd pay $100 for a comprehensive textbook that explained DC electronics from the perspective of, and with practical examples pertaining to, effects circuits.

[arawn]

check out Brian wampler's stuff, he has like 4 books on modding and building effects pedals

[Resynthesis]

But when I post a fully-worked real-world computation like this, it lays like a dead deer.

Please don't feel you are wasting your time, you have a distinct audience here.

+1

Coincidentally, today I copied what you (PRR) and RG had written in that thread and reading it gave me a couple of those "aha" moments. Thanks and please don't stop!

I've only recently got the DIY habit so my knowledge is sketchy but working through some of these threads has certainly ramped it up pretty quickly.

[artifus]

lateral thinking seems to be the key.

ie how to implement these basic electronic principles? for example, ye olde knight rider led display to seek wha style circuit.

this is why i think building block circuits are so important. small, easily digestible, individually understood and immediately implementable ideas that may be inter connected with each other with various results, successful or otherwise but educational none the less.

the majority of fuzz circuits are derived from the first couple of chapters of most text books it seems,and there's some interesting stuff to be had from the ttl and cmos cookbooks and the like. lego logic, if you will.

the block of understanding may then be reduced and reduced again and again to the level of electron if required.

power of ten

what, how & why:

buffers
lpf/hpf
envelope detectors
filters
sequencers
fuzz
etc... please add...

whenever i see a pot in a circuit i think ldr? and whenever i see a dynamic led in a circuit i think what could that control?

for example:



hope that makes sense... may edit this post in future for clarity...

[BubbaMc]

Nice thread.

I might add that learning about transfer functions of circuit elements, determining gain, determining input and output impedances, goes a long way to understanding how to approach analog electronic design.

[BubbaMc]

If anyone is interested I could upload my university notes on analog design. They cover all the nitty gritty frequency domain transfer function stuff, along with nyquist stability theory, and more.

[jafo]

Speaking as a beginner, I have to say that I have high hopes for this thread!

It's easy enough to figure out and build basic circuits (I've got a nice amount of clutter here already) as long as you don't think too much about the theory, but this is not understanding. Example: a low-pass filter

Edit: Oops, wrote "high-pass" originally -- D'oh!

sends high frequencies to ground. As long as you don't think about the fact that electrons come from the ground, you're good -- just calculate a cap and resistor value and test. Never mind that it actually works the other way around -- electrons come up through a resistor and backwards into the capacitor. I think.

Or take impedance and loading. Why do they work in reverse? If impedance is like water pressure in connected pipes, you want to connect the out of a high pressure pipe to the in of a low pressure pipe -- since you want all the water to go from one pipe to another. However, in electronics it seems to work the other way around -- low output impedance connected to high input impedance. Somehow that makes current work... even given the whole hole/electron thing, it seems so counter-intuitive. People talk about loading previous stages, so maybe it does work in reverse.

Plus, there's the combination of these two issues -- it's as if electrons moved not only from the ground into your circuit, but also from the output to the input. Messrs. Heisenberg, Planck, and de Broglie want royalties. Or maybe I simply don't know what "ground" is. (That's where I'm placing my money!)

Or alternating current -- are electrons reversing directions? What exactly is a negative voltage, anyway? If it's all electrons, it's all negative, right? Similarly, given that a guitar pickup produces positive and negative voltages (starting from a zero) when the string is plucked, does a downstroke cause the cycle to begin in a different way than an upstroke? (I mean, does one stroke cause the voltage to go from zero to a positive first and the other stroke makes the voltage go from zero to a negative?)

And what is a voltage drop, and why is it a Good Thing to drop voltage across, say, a drain resistor? Surely you want it to go out to (in from?) the output and not to the battery?

I believe it's the theory, not the math, that scares people away. There are a lot of terms and concepts most of you take for granted, but honestly, they can seem awfully ambiguous to us n00bz.

[LucifersTrip]

> Some real-world math solutions would really help I think.

But when I post a fully-worked real-world computation like this, it lays like a dead deer.

I'm going to guess that when you leave a detailed explanation, people feel it's a definitive end. There's nothing much left to say, except "thank you"...and btw, thank you for all those explanations I've read, but haven't commented on.

[LucifersTrip]

Is it possible to do a better job? The greater community here was mostly non-technical people who have learned by reading and doing.
- what worked for you to learn?

Schematics & breadboards.

It's a cliché, but a hands on approach...and a lot of curiosity.  From reading and helping beginners, I believe that their biggest problems are:

1) using a layout or pcb instead of schematic. Just simply looking at a schematic shows orientation and patterns that are extremely helpful.
If you just plop components down into a paint-by-numbers layout or pcb, you won't learn much, except how to solder and follow directions.

2) not breadboarding 1st. I find it surprising how few beginners actually breadboard first to test and experiment with a circuit. Instead, they buy a kit and paint-by-numbers

2a) not experimenting enough. I come from a circuit-bending background, where you have an existing circuit and try everything to get strange and unusual sounds from it. So, when I built my first bunch of fuzzes, I swapped out EVERY single component to see what altering them would do.  This is DIY, so it is again surprising how many ask, "will it sound better with..." or "how will it sound if I put this here instead of that..."

- what stumbling blocks existed and how did you sidestep them?

Schematics were easy since they show nothing more than point to point connections, but I do remember when I started I had trouble with all the different input and output jacks symbols & connections. There was easily enough info online that I was able to quickly understand those...After repeated breadboarding, I no longer had to think about it.

- what would you advise for a generic beginner curriculum?

probably start with a simple pre-existing, working circuit on a board and following a schematic from left to right swapping and altering each component to show the effect of each....then slowly move into the math explaining each change.

[Morocotopo]

The way I started is I built something from an instruction pdf or web page. The biggest challenge was, first, recognize the different parts and their values and peculiarities (polarity, anode, cathode, codes, wattage, etc), then how to read a circuit diagram , and then relating all that to the actual physical thing (protoboard, PCB) including all external connections. And also how to solder, trim wires, all the hardware related stuff.
Then I started learning the theory of things, mostly by reading on the web (I don´t own a single theory book).

I think the best way to learn would be by starting with a simple project (let´s say, a transistor booster on pad-per-hole board), using that to learn about:

- Parts identification
- Board trimming
- Non PCB construction: layout (designing or following a pre designed one), connecting things, soldering, relating that to the schem, and also introducing schem reading: power, ground, etc.
- Testing and debugging. Measuring voltages. Using an audio probe.
- Pot trimming and wire soldering. Connections to jacks, battery, etc.

Once the thing is completed and working, the feeling of having made something that works, might be enough to generate desire to learn more.

[Mark Hammer]

Thinking about it some more, I'm going to put on my cognitive development hat for a bit.

People of just about any age learn best when they have a purpose in mind.  Part of what that helps to accomplish is provide a framework within which to nest all the little pieces of information, and assign them a role and priority so that they can be interconnected to form and extend expertise.  Stated more bluntly, if you don't have a "Why", the "What" tends not to stick.  That is part of the reason why co-op programs, that intervleave practicuums and placements between coursework, produce more robust outcomes; people get more out of their coursework if they can see where it is applied.

So I think whatever "basic curriculum" there is to establish here, needs to be clustered together into practical themes that consider the likely goals that a member has.  One would be naive to presume that all such curriculum/knowledge could be neatly parsed into segments with clean borders.  After all, how one reads a schematic is ultimately harnessed to what you wish to understand about it, and what you wish to understand depends on knowing a bit about the category of effect/circuit.  And, as I think many would agree, there are aspects that keep showing up in every conceivable learning path taken, whether the person is interested in ONLY modding, in ONLY distortion, in ONLY successful boxing, in ONLY improving reliability, etc.

[robmdall]

impedance and loading are my problem. I simply cannot grasp the concept. I have read a multitude of web pages on the subject and I do not understand it. I realize how important of a concept it is. Does not make a lick of sense to me.

Understanding the basic function of our general components was easy, following a schematic for me came easy, like reading a blueprint. Bread-boarding and swapping out components (well, some components anyway) is fun. One of my favorite pastimes is using Eagle and designing pcb's (from other peoples schematics) - most fun I have had in years.

I truly believe that not understanding impedance is holding me back from achieving the next level. I will keep reading and keep absorbing the teachings of the RG's, PRR's and the Mark Hammers of the world (and everyone else here). Some day I'll progress...

As for:
'But when I post a fully-worked real-world computation like this, it lays like a dead deer.' Heck, I am happy that I'm at a point to not have to Google every third word now  

[aron]

Don't forget the Wiki:

http://www.diystompboxes.com/wiki/index.php?title=Common_Terms_and_Abbreviations

[amptramp]

impedance and loading are my problem. I simply cannot grasp the concept. I have read a multitude of web pages on the subject and I do not understand it. I realize how important of a concept it is. Does not make a lick of sense to me.

The way I think of impedance is like a car transmission.  If you are starting up, you select first gear because that gives you the increase in torque and reduction in speed that you need and you can trade speed for torque, but with the product of speed and torque (power) remaining constant.  Then you go up through the gears to get the engine to operate within a speed range that suits it.  A transformer does the same thing - takes a given value of voltage and current and transforms it into a different value that has the same product.  Impedance is voltage / current and power is voltage x current.  No doubt, since you have read all the available materials on it, you have seen that the greatest power delivery is from a source of a given impedance to a load of the same impedance or conjugate impedance if there is reactance involved.  The two reactances act as a series tuned circuit tuned to the frequency you are working at.

If you take a source as a voltage source with a resistance (the impedance) in series, you can show that the greatest power delivery to the load is if the load has the same resistance.  If you have a source of four volts at eight ohms, you can deliver two volts into a load of eight ohms or 0.25 amps delivering 0.5 watts.  If the load is 24 ohms, you can deliver 3 volts at 0.125 amps or 0.375 watts.  Similarly, if you have a load of 2 ohms. you can deliver 0.4 amps but at only 0.8 volts or 0.32 watts.  The highest power delivery is with the load matched to the source.

In voltage amplifier stages, you will usually see a low impedance feeding a high impedance so that the voltage seen by the load is almost equal to the unloaded output voltage of the previous stage.  It is a deliberate power mismatch to preserve voltage.  This is not an exhaustive treatment of the subject by any means, but it may help illustrate the concept.

[BubbaMc]

impedance and loading are my problem. I simply cannot grasp the concept. I have read a multitude of web pages on the subject and I do not understand it. I realize how important of a concept it is. Does not make a lick of sense to me.

With regards to impedance and loading, what exactly are you having trouble with? We're here to help.

For max power transfer it is ideal to have the source and load impedance equal, this is not so if you want max voltage transfer (which is usually the case with effects pedals). For max voltage transfer the source impedance needs to be small and the load impedance needs to be high. This is so the source can supply a voltage signal to the load without having the load suck all the current from the source, and as a result reduce the voltage at the load (which is what would happen if the load impedance was low).

edit: see amptramp's last paragraph, he said it better  

[PRR]

> Example: a high-pass filter sends high frequencies to ground.

No. A high-pass filter passes high frequencies to OUTput. And since we say "high-pass", presumably low frequencies do not pass to output. They may be diverted to ground, or just not allowed to enter the filter.

> electrons come from the ground

Electrons are everywhere.

And meaningless. There is a book {u]There Are No Electrons[/u].

Have you ever seen an electron? If you could, would it do you any good?

There's "current", a mysterious invisible substance which is only interesting when it is moving.

> If impedance is like water pressure in connected pipes

You are mixing our poor metaphors.

Impedance of a water-pipe is the Length-to-Diameter ratio. A long thin hose is a high-impedance pipe. A short fat storm-drain is a lower-impedance pipe. The Mississippi is a really low impedance. 

> you want to connect the out of a high pressure pipe to the in of a low pressure pipe -- since you want all the water to go from one pipe to another.

Yes, but this is exactly why you must keep our poor analogies straight.

Look at your water supply. There is a 24-inch pipe from the water tower. This splits to 8" pipes in the street. Houses are connected with 1" pipe.

When you turn-on all the water in your house, the high-impedance 1" pipe will not suck enough water to drop the pressure in the 8" street-main. Your neighbors do not get a pressure-drop when your toilet flushes. (Actually the goal is to connect multiple 3" fire-hoses to an 8" main and not have a large drop.)

> Or maybe I simply don't know what "ground" is. (That's where I'm placing my money!)

There is no "ground" except what you pick.

A simple series circuit, such as a flashlight (ponder it!) does not need a ground.

Anything complicated, there are multiple current paths which come together. In a car you have lights and ignition and cigar-lighter. You could run a separate wire from each lamp and gizmo back to the battery. However the car body/frame is always handy, already paid-for, and big steel conducts good enough. We bolt the lamp-socket to the body and call it "ground". Even though the car stands on rubber tires and has no contact with dirt.

> alternating current -- are electrons reversing directions?

I've looked real close at wires and I do not see any electrons in there, so I can't say they go back and forth. However we have basic experiments (sadly no longer taught in school) which suggests that an electric current will move a compass-needle (magnet) one way or the other depending which way this current flows. And with a low-low frequency AC current I can actually see the needle jiggle back and forth.

> why is it a Good Thing to drop voltage across, say, a drain resistor?

A single JFET (BJT, tube) is like a one-legged bicyclist. Only goes one way.

We can wire two JFETs (etc) in Push-Pull. That costs more.

We can rig a JFET(etc) to "fight" a resistor. This is kinda-semi-like a one-legged bicyclist with a spring or weight on the un-used pedal. We "bias" the rig for a "fair fight", around 50:50. With a 50 pound weight on the odd pedal, the one-legged bicyclist can press zero to 100 pounds. Result is like 50 pounds on each pedal. We can rig the drain resistor to drop 4V, rig the JFET to drop 4V, then swing up 3V and down 3V.

While single-device operation gives less gain and efficiency, two single-ended stages gives more gain than one push-pull stage with generally less complication.

[Quackzed]

no electrons! 
i dig it!