"Require" me some readin'

[ChrisPtacek]

So I am a newb, and I'm cool with that.  I've built a Marshall amp kit and modded it, and built a BYOC and done a lot of guitar electronics wiring, but I'm basically a total newb.  I know what resistors and caps are... I know diodes, etc.  That is to say "I know what they're doing" in several applications.  But I feel like I know enough to play with things, but not enough to be confident when sourcing parts or screwing around more seriously.

Can you guys recommend web links or books for basic electronics?  Right now, for instance, the thing that's kicking my butt is knowing what's appropriate for voltage ratings on caps, or power ratings for resistors, etc.  When I'm reading about mods, for say, a wah pedal, and thinking "I'd love to try that" I am often stopped in my tracks because part of the info I would think I need is missing... when someone says "Try 0.068µF for a bass wah" and I go looking for a part, how do I know what voltage to choose?  Do I just assume that it has to be 9v at minimum because of the pedal's draw?  How do I know what type of cap to choose?  Orange Drop, polyprop film, etc... I can't help but feel that there's something "I should know" that I don't, for doing this stuff.  Happy to do my homework... but can anyone assign some? 

[O]

I would start reading everything... yes, everything at www.geofex.com There is more than enough there to get you started on your way. Read and re-read especially "The Technology of *" R.G. breaks down popular circuits and explains how each block works and inter operates with the other circuit blocks.

[caress]

hmmm...to start with, there's a lot of useful information in the wiki http://www.diystompboxes.com/wiki/index.php?title=DIY_FAQ

also plenty of good tips here.  try searching for terms and different combinations of terms to find some good threads.
http://www.diystompboxes.com/smfforum/index.php?topic=56241.0  - on resistor wattage
http://www.diystompboxes.com/smfforum/index.php?topic=52125.0  - on capacitor ratings
http://www.diystompboxes.com/smfforum/index.php?topic=53207.0
http://www.diystompboxes.com/smfforum/index.php?topic=55507.0  - both on reading material

a local public library or university library will also probably have some good info.

as far as sourcing parts, ebay can be your friend for bulk.  smallbear electronics has parts specifically for stompboxes, so the ratings, etc. are what you are looking for.  pedal parts plus has cheap enclosures.  i use mouser most of the time, but have made some errors in the past buying surface mount components or HUGE caps or the wrong size pots...get a catalog mailed to you and use that.  just double check first!  hope this helps.

[R.G.]

It sounds like you're well on your way to learning. Most of the learning electronics sites do not tell you the practical matters you're asking about. But I can help with some short ones.

Caps:
Capacitors except for electrolytic (polarized + and - ) must have a voltage rating modestly bigger than the highest voltage they will encounter. The maximum DC voltage for a capacitor is called it's "working voltage" and is what you commonly see in catalogs. In amplifier circuits which do not involve voltage multipliers (more on that in a minute) you buy caps with voltages at least the power supply voltage, and for 9V batteries, that's maybe 10Vdc, since some batteries are actually 9.5Vdc when fresh.

It is quite difficult to buy non-electrolytic caps which are that LOW. In general, the lowest voltages you can get non-electrolytic caps in is 50V, which is fine. You do not need higher voltages in most cases.

For circuits which increase voltage with inductive kickback or charge pump techniques, you need voltage ratings which are larger than the maximum voltage which will be applied to the cap - no surprise there. The working voltage is a "withstand voltage".

Electrolytic caps are polarized caps mostly. Aluminum electro is most common, and tantalum is sometimes found but is quite expensive compared to aluminum. In general, over 1uF capcitance is electrolytic, although there are a very few 1uF and 2uF plastic film caps. The same rule applies: get a working voltage modestly larger than your power supply voltage, or the highest voltage applied if you're doing a power supply that boosts voltage. For electrolytic caps you must never let circuit conditions or signal reverse the polarity of a polarized cap. It damages the cap.

Most often you want the smallest physical sized cap you can get for the correct capacitor value.

Usually, you will be buying polyester (also called mylar) film caps. You don't need brand named "orange drops" in spite of whatever mojo discussions you hear. Polyester is the cheapest of the plastic film caps. In general, if you can buy it in polyester and that fits in the space, do it. In certain instances you need precision, which will call for either a preselected 1% or 2% mylar or polystyrene or teflon, or high capactance high quality, in which you might want polypropylene. It is very unusual in most effects to need anything for a signal cap except polypropylene.

You may need ceramic caps. Ceramic is a technology which produces higher quality (i.e. freedom from parasitic effects) caps in the RF sense, and also very small values. Most values under 100pF are ceramic. Many power supply bypass caps are ceramic, because this produces a good bypass at radio frequencies. Only use ceramic for power bypass or RF filtering in small sizes unless you have specifically been told to or unless you know what you're doing because ceramic has a reputation for sounding slightly "grainy".

As an aside, if you can't get the value and voltage you need, get the one you can get and replace it with the perfect one later.

Physical size and price will be a good guide.

On resistors:
Do not believe the stuff you hear about magic resistors. Carbon composition resistors DO have an audible effect in some very limited circumstances that exclude almost all effects work. Buy carbon film resistors for most of them, use metal film only if you have a noise critical or precision (2% or better) application. In general, you won't need these in effects until you get into advanced stuff.

A resistor is rated by how much power it can dissipate. A 1/4W resistor can dissipate 0.250W on a continuous basis and have a reasonable life of around 20,000 hours doing it. That's about five years of 8 hours a day. We generally don't run effects that constantly, but we'd like them not to fail in five years anyway, so we derate them. We use 1/4W resistors at 0.125W (1/8W) or less. This makes them much more reliable.   

The power in a resistor is calculated by calculating the product of voltage and current across it: P = I*V

Since we know that I = V/R, we can also calculate P = V*V/R or P= V^2/R, however you write the "squared".

In almost all circumstances, effects use will be far, far below this level, so low you don't even need to calculate them. Just use 1/4W and ignore it unless
(a) you are designing something with a lot of current, like an LED current limiting resistor or a relay driver
(b) you are designing power supplies working from 9V, as in a regulator

So
1. Buy polyester film caps in 50V, 63v, or 100V ratings to get them as small and cheaply as you can. If film won't work, use aluminum electrolytics in voltages larger than the supply voltage. In 9V effects work, get 16V or 25V. 50V is OK if that's all you can find.
2. Where a cap is marked "ceramic", get ceramic
3. Use 1/4W carbon film for everything unless there is some special circumstance.

[ChrisPtacek]

Thanks a bunch, guys!  That's exactly the kind of start I'm looking for.  Thanks!!!

[petemoore]

would start reading everything... yes, everything at www.geofex.com There is more than enough there to get you started on your way. Read and re-read especially "The Technology of *" R.G. breaks down popular circuits and explains how each block works and inter operates with the other circuit blocks.
  A newbie asking for Reads, tuff reads...excellent !!!
  Yes..it's very EZ-breezy reading..you can skim over everything there in one day and gain full comprehension...Nnot. If you're like me, more likely you'll find yourself within brick walls you want to get past, walls which look perfectly impenetrable and made from abstract magic, to become a 'wiz' you need to gather tools from other places, and search both in cursory and concentrated manners for a 'nick in a brick', something you can grab on to, and use to pry info out...suggested subtopics in math and terminology are recommended.
  Problem is, once you do that you're hooked..get an exhaust tube for solder fumes!
  One of the first things I did was print the Austin Treble blaster pages, it's about Rangemaster technology, I used that for a 'brick wall' choice to concentrate on and study, gathering pen and notes as I tried 're-wiring' my brain to follow the curriculum I'd chosen, often visiting other places to gather  related reference material...like at GEO. Reads there are like the top of the pyramid, to get to the top ofthe pyramid is never a straight line, not that I'm even 1/2 way there, but I can say I've been working at it for years now, before I breezed in here, I knew next to nothing, couldn't tell you one end of the non-polar...resistor from the other...lol. After reads on countless subjects, I feel I can speak well enough to get by.
  Every time it's one thing, then three others...example, Starting with a passive Xover the other day, calculating and etc. on that, then dumping that and opting for an Active Xover [thanks RG for the suggest], building that, then finding I can't find 1% or 2% tolerance caps [recommended]..building succesfully' anyway, but looking to compare the improved performance of matched caps...getting into wheatstone bridge territory...which will probably lead elsewheres...I'll let you know if I figure that out.

[Hiwatt25]

I've been here a little over a year and still find myself squarely in newb territory however, I occasionally have one of those "A-HA!" kind of moments when something I've read a gillion (yes, a gillion) times finally makes some sense.  In addition to R.G.'s site, I've augmented my reading with the recent addition of "The Art of Electronics" by Horowitz/Hill.  It's helped me more than any other book I've picked up.  It's written a bit differently than most text books and for me has been easier to understand.  Of course, I still have to reread stuff.  Thing is it's not a cheap book but if you're in this for the long haul, maybe give it a look. 

In fact, I believe there was a link in the Lounge to an "E" version of the book.  Good luck.

You'll find as I have that if you're willing to do some leg work and show some effort, guys like R.G. will go the extra mile to help you out. 

[Mark F]

In addition to what the previous posts have said if you order a few parts catalogs; Mouser , Digi-Key, etc. & just look through them over & over when you have time you will learn a lot about components, size , price, etc. Besides it's just fun to look at parts!