How do I design a circuit?

[mikestahlme]

Hey, it looks like you and I have similar goals! I'm pretty much in the same boat you're in, and while I've built a couple of clones I'm still trying to learn how the circuit actually does what it does to change the guitar's tone.

One resource that's really been helping me understand different "blocks" in a schematic and how it all fits together is Brian Wampler's book: Advanced DIY Effect Pedals. He released it for free over on freestompboxes.org, which I think is where I found it....
You can probably find it through google anyway.

[WhenBoredomPeaks]

LTSpice actually will tell you something about the tone of distortion.  Transient analysis shows what you can expect it to do in an oscilloscope kind of way.  If that's not good enough, you can have it spit out a .wav file using either the internal sources or another .wav file as input so you can actually hear some approximation of what it will do.

that thing with the .wav files sounds magical, is that actually an useful feature? i mean is it sounds like it should? could i just feed it with direct recordings of my guitar instead of prototyping with real pcbs and solder and stuff?

[ashcat_lt]

that thing with the .wav files sounds magical, is that actually an useful feature? i mean is it sounds like it should? could i just feed it with direct recordings of my guitar instead of prototyping with real pcbs and solder and stuff?

Is that sarcasm?  I'll assume the best here and say that I have just recently switched to LT from 5spice, and haven't had the chance to mess with it a whole lot.  I have heard the .wav files of a sine wave (actually a mixed set of sine waves) through a nasty distortion circuit that I've been messing with.  It did something, but I can't say how close it actually is to the real thing.

[therecordingart]

Hey, it looks like you and I have similar goals! I'm pretty much in the same boat you're in, and while I've built a couple of clones I'm still trying to learn how the circuit actually does what it does to change the guitar's tone.

One resource that's really been helping me understand different "blocks" in a schematic and how it all fits together is Brian Wampler's book: Advanced DIY Effect Pedals. He released it for free over on ....org, which I think is where I found it....
You can probably find it through google anyway.

I tried going the route of reading articles and books, but had trouble pulling all of the info together. I started from the ground up and now I'm doing the associates degree program through CIE. I'm about 70% through it, and have learned a lot! I highly recommend it if you need more structure to your learning, and want to get into the details of how things work. The most useful things so far are Ohm's law, Kirchoff's law, transistor theory, superposition, and how to Nortonize/Thevenize a circuit. I'm still no expert, but I can now look at schematics and get an idea of how the electrons are moving.

I should add...now I can read responses from RG, PRR, Mark Hammer, etc and understand (mostly) what they are saying. I'm a dunce that is probably in way over my head with this electronics stuff.

[tubegeek]

I tried going the route of reading articles and books, but had trouble pulling all of the info together. I started from the ground up and now I'm doing the associates degree program through CIE. I'm about 70% through it, and have learned a lot!

Respect. What a fantastic choice. Your recognition of what wasn't working, which then led you to something which is, is absolutely the most important part.

I highly recommend it if you need more structure to your learning, and want to get into the details of how things work. The most useful things so far are Ohm's law, Kirchoff's law, transistor theory, superposition, and how to Nortonize/Thevenize a circuit. I'm still no expert, but I can now look at schematics and get an idea of how the electrons are moving.

I should add...now I can read responses from RG, PRR, Mark Hammer, etc and understand (mostly) what they are saying. I'm a dunce that is probably in way over my head with this electronics stuff.

No way. Opposite of dunce: lifelong learner. EVERYBODY is way over their head with audio electronics: it is a VERY deep and broad subject! And I think your selection of the most important topics reflects a very good understanding of what you've learned so far. Any teacher who read this "takeaway" summary would feel they had done a good job with you, and you with them.

Anybody can learn anything if they care enough. I am a teacher myself and I think that your post is a perfect, concrete example of why we should never have abandoned the vocational school model. When students see their coursework as relevant to a goal or personally-held interest, even very difficult material is MUCH more accessible.

The emphasis we have in the US on an identical, all-things-to-all-people high school curriculum, and compulsory education, is a huge mistake, I am convinced. The end result includes boatloads of students who can't see the relevance of what they learn and then tune out. If more alternatives, each with a clearer focus, were available, I think many students would be picked up and brought farther by their own curiosity and desire to follow a clear path with a specific goal. Not everybody - especially 15-year-old everybodys! - can get excited by the abstract "love of learning," "learn how to learn," "liberal arts" educational model, and this often includes MANY students with technical, practical interests.

I've had by most measures an extremely successful academic experience, Ivy League B.A., M.S., yadda yadda. The course I most wish I had had in high school? Metal shop.

Whew. What a rant.

[PRR]

> is that actually an useful feature?
> Is that sarcasm?

I'm pretty sure WBP is honestly excited at the idea.

For whut it's worth: that feature has been in SPICE for a very long time, back when I ran it in MS-DOS on a 30286. It's actually a trivial hack. However I have *never* gotten around to trying it.

My suspicions:

A low-resolution WAV in any distortion circuit will give very un-musical results. When SPICE runs a normal source, and comes to a place the waveform changes abruptly, it slow-steps the source to follow the fine detail. When the source is time-samples at a fixed rate, and there is a large change one to the next, what can it do? Is interpolation valid? Is it linear? (Remember SPICE does not know and can not care logic-spikes from fine blues guitar.) Or does it assume the user wants only the accuracy implied by the original sample-rate?

I'm also sure that any non-trivial circuit on any non-fantastic CPU will simulate much slower than real-time.

[PRR]

> we should never have abandoned the vocational school model.

Hear, hear!!

Around my area, vo-tech school is still an option, however lowly. But I've been in the school and see what they study and work on. Occasionally they do a project that gets written-up in the newspaper. The skills they gain are IMHO nowhere near where they need to be for a journeyman job doing real work. Short-funding is part of it. The carpentry students build a shed, so small they can't possibly all get a hammer on it at once. The Diesel room has one obsolete truck, one older engine, and some fairly useless books.

Indication of the status of vo-tech in this state: big construction company with world-wide contracts needed 140 welders. Paid fairly. They could not hire 140 qualified welders in this state. Sure a few jobs may have been QIG or other exotic technique, but most of it must have been basic arc/gas/TIG welding to recognized quality standards (won't leak). Makes me wish I'd taken a second year of - - -

> The course I most wish I had had in high school? Metal shop.

I had metal-shop (and drafting! with T-squares!), but I had to argue for it because the dumb tests said I was college material. Because it was a town of engineers (cold-war computer boom) and I was leaning that way, metal-shop and drafting could be allowed but I had to be dumber to get into wood-shop.

What have I done off-and-on all my life, and a LOT the last few years? Butcher wood. Firewood. Wood mailbox. House addition. Garage. Shelves shelves shelves.

[R O Tiree]

I can relate to that Paul... At school I had to do all academic subjects (Maths Pure & Applied, Physics, Chemstry) in order to get onto the degree course I wanted (Aero Eng) and what did we end up doing for most of our first term at University? Drafting and metal-work! Utter madness.

[Seljer]

I'm also sure that any non-trivial circuit on any non-fantastic CPU will simulate much slower than real-time.

Yes, its horribly slow. On my computer which isn't that old if you've got anything more than a one transistor circuit it takes 10 minutes to compute the response for a 10 second .wav file. Then you try to do a sweep of the gain range for example and in the same time you could have already built the thing on a breadboard and had been testing and tweaking it for half an hour.

And it's not just sound you're going after, it the 'feel' of it which you can't really simulate.

[Kesh]

I can relate to that Paul... At school I had to do all academic subjects (Maths Pure & Applied, Physics, Chemstry) in order to get onto the degree course I wanted (Aero Eng) and what did we end up doing for most of our first term at University? Drafting and metal-work! Utter madness.

I sometimes teach maths to 1st year engineers. They do a lot of maths these days. Some wish they were getting their hands dirty.

[Seljer]

I can relate to that Paul... At school I had to do all academic subjects (Maths Pure & Applied, Physics, Chemstry) in order to get onto the degree course I wanted (Aero Eng) and what did we end up doing for most of our first term at University? Drafting and metal-work! Utter madness.

I sometimes teach maths to 1st year engineers. They do a lot of maths these days. Some wish they were getting their hands dirty.

I'm just finishing me EE degree. We didn't do anything we could get our hands on until the third semester. You could literally get through the entire thing without touching a soldering iron or a screwdriver at all. So if you're a tinkerer you have to have some self initiative and go by your own accord to a prof/assistant to get something to work on and not be dissapointed with it.

[trevorus]

I'm planning on fiddling a little bit myself. I'm trying to get an EE degree, while having a kid and a job, and the math classes are killing me. I am way more a hands on person. As was said earlier, take some circuits that are already known, and mess with them. I'm planning on picking up a Radio Shack bread board, some transistors, opamps, etc. I've done tube amp work, built a few, but I need to get more of the why and how it works. I understand the general way these things do what they do, but designing is a whole other issue.

[PRR]

> the math classes are killing me

You *may* benefit from this old book:

Basic Mathematics for Electronics, Nelson M. Cooke and Herbert Adams, 1976 1970 1960 (and 1942 under a different title).
0-07-012512-0
$4 on ABE.com.
more editions

McGraw-Hill Book Company, Inc., 1942. "This pioneering text has established a distribution record unequalled by any book on mathematics in the history of the McGraw-Hill Book Company. Developed at the U. S. Navy Radio Material School at the Naval Research Laboratory, Washington, D. C., the text grew out of the author's many years of experience in teaching mathematics to Navy Electricians and radio operators. Here is a text so thorough, so complete, so careful and painstaking in its explanations, that instructors everywhere find that it gives their students a sound mathematical foundation and shows them how to apply this knowledge to the solution of practical radio and circuit problems." ; "it can easily be read by a person who has not had any mathematics, and at the same time is extremely interesting "--Electrical world ; The author was the Executive Officer at the Radio Materiel School at Fort Bellevue, Washington DC

It's very old-school (even in the 1976 edition with new-math page layout). It is exceptionally well presented. It is the stuff that never changes (hence the long publishing history). It WILL need heavy digesting, but may get you started better than many of the new-school textbooks around. (Even though your quizes come from the new books, knowing the basics is always a good foundation for regurgitation.)

> designing is a whole other issue.

Yes. Fingering a guitar is one thing, a big thing true. Composing a song is another thing. Composing a song that others want to play is yet another step. Same when you replace notes with parts. First you buy kits, then you copy plans prepared by others. Then you noodle-up something that is new and exciting to you, but frankly ho-hum. The drive and spark to create something really functional, much less brilliant, is hard, like composing Stairway to Heaven verse and solo and mix.

[garcho]

buy a breadboard!