Quote from: GuitarLord66 on July 15, 2010, 07:23:14 PMI know I have been asking a lot but what extra values of transistors, capacitors, resistors, etc, should I buy to start "tinkering" with? I don't want to make an order and think, "I should have got some of those..."

That's a tough question really. You'll always be saying, "I should have," it sort of comes with the territory! It really depends on your budget, as new parts assortments can be expensive. I get most of mine disassembling and scavenging old electronics that are on their way to the landfill anyway.

Welcome to the wonderful world of datasheets. Bookmark this. Any time you see a chip, diode, or part number you can start there and see if there's a datasheet for it. The passive components have sheets too, but you have to know part numbers or manufacturing identifiers. Use the hell out of this, and try to learn what the mysterious abbreviations and graphs mean. I'm not all the way there yet, but I've learned more from datasheets than any other single source.

Here's my take on start up parts.

Passive components
Resistors, Capacitors, and Inductors fit in here. You'll probably never have to use an inductor, and that's a good thing. These have a set of 'preferred values' called the E series. There's a company called Velleman who makes blister packs of resistors and capacitors in a few different series, and those can be a good way to stock up for the first time. I don't think you can buy direct from them, but lots of places resell the kits. You can use the Velleman part number to search around. Don't sweat tolerances too much yet, especially on capacitors. A big set of brand new 1% metal film resistors can eat into your starting budget.
Important! Learn how to use two or more caps and resistors in series and in parallel to get values you don't have handy and improve their matching (there are programs that help with this), it'll stretch an E3 cap set and an E12 resistor set to cover almost anything.

Diodes
I get heaps of these scavenging. You can divide them up into roughly three categories: rectifier, signal, and zener. The rectifier diodes are used mainly in power supplies and as protection. The most common are the 1N400X series, where X is from 1 to about 7, and their are other types designed to be fast for use in switching power supplies. Signal diodes are faster acting (usually) and designed for low power signals like logic gates and line level audio. The diodes in your distortion pedal are small signal, for example. Zener diodes are specially designed power diodes used to regulate voltage or limit a signal at a higher level than one diode drop (~0.6V). You probably won't have a big pile of these on hand until you get really serious. Consider picking up a dozen 1N400X series diodes with your order (x=4 should be ok), and a dozen spare signal diodes.

Transistors
There are about eleventeen million different types out there. They can be divided into groups by polarity (NPN vs PNP), architecture (Field Effect [FET] vs Bipolar Junction [BJT]), power rating, case style (TO92, TO220, and TO3 are most common, see chip carrier), and a dozen other ratings. For just starting I'd grab an extra half dozen 2N3904 and 2N3906 and order more as you build different things, always picking up a half dozen or so spares. They're not the best for audio work, but they'll get the job done most of the time. They are complimentary, meaning that the first is NPN and the second is it's PNP equivalent. They tend to cost about a dime each until you get into the bigger, higher current power transistors like the TIP series or larger. Transistors, especially FETs, are sensitive to Electrostatic Discharge (ESD). This means that if you build up a small static charge (smaller than makes a spark) and touch the leads it can degrade or ruin the part. That's a research topic for you, and another rant altogether for me.

ICs
There are about twentyteen billion different types out there. I'm not even going to try to state the different types, but you'll be primarily concerned with opamps. Opamps are like tiny complete amplifiers self contained in a chip package. There's a lot to learn about their use, and I can swamp you with things to read if you like. Here's some part numbers for audio opamps to run through the datasheet catalog: TL07x (x=1, 2, or 4), 4558, NE5534, LM386, LM3886 (technically an opamp, but often though of as a monolithic power amp). There's a bunch of other chips that are useful that aren't opamps, like voltage regulators (75xx [fixed regulator, last two digits = voltage], LM317 and 337 [pos and neg adjustable]), timers (NE555), gates (Don't ask, it's ugly), comparators (LM339), the list goes on. My advice would be to wait until you get to a project that uses them, buy three or so extra, and experiment.
Important! Be careful to buy exactly what you need. Chips are usually sold in multiple carriers (see chip carriers above) and it can be disappointing to order a part and have it arrive as the surface mount version when you need through hole.

Whew, and that's just a start. I really can't recommend salvage highly enough, it really cuts down the cost. Get a nice soldering/desoldering kit put together and other people's junk is your treasure!

Quote from: GuitarLord66 on July 15, 2010, 07:23:14 PMAgain, thank you so much you have been so much help

No worries. Getting started is the hard part, if you can muscle through the hard part it pays off immensely. Just keep at it!

Wow, I really rattled on this time. Hope that helps.

You'll almost certain to have to make some changes and adjustments, as they don't have the same pinout (or even the same number of physical pins).

This is how I'd approach things . . .

Start out by printing up the respective datasheets. Take the Frontman schematic and figure out what the gain is set for, and why the surrounding components are there. Odds are pretty good that the power amp block is similar to the datasheet. Then you can translate that over to an equivalent circuit for the 3886.

That would do most of the legwork for the pros, and they'd have an easier time spotting trouble in a prototype circuit than having to design it from the ground up. I'll help if you get stuck, but I've got to get some rest at the moment so I don't have time to drive into the details right off.

Hope that helps some.

Quote from: GuitarLord66Thank you  And sorry for the dumb question I should have looked around better...

You're most welcome. It's not a dumb question at all, and the whole story on capacitors is complicated and requires background knowledge to understand. It always helps to try your own research first, even if it fails miserably. I've always had the most luck getting help online when I can show that I've banged my face on a problem for a while and I'm stumped. Don't feel badly though, often it's hard to know just how to ask the right question.

Quote from: GuitarLord66 on July 15, 2010, 10:24:03 AMIs this a full preamp? would I be able to use it to get a different sound? I'd be combining this with the distortion circuit and running it either straight into my Peavey Bandit 112 or into the Bandits power amp.

It looks like a simple preamp with a simple tone stack, and with a gain of 22 it should be fairly clean right up near it's utter limits. However, if you put a +/- 15Vp-p signal into the Bandit's input or effects return it'll sound horrible and may damage something, as it's probably designed to run at line level or lower. Whatever you try, start with low settings and work your way up. This preamp would likely sound different than the Bandit, mainly because the tone controls are likely to be different.

You might consider building your distortion circuit in such a way that you can simply insert it into the effects loop. If the Bandit has pre- and post effects EQ that's excellent, as both will have a noticeable effect on the sound of your distortion. If not, consider tacking a tone stack on your distortion circuit on whichever side needs it.

Quote from: GuitarLord66 on July 15, 2010, 10:24:03 AMIs it a decent amp? like are any of these DIY circuits going to compare to Peavey and Boss piece of equipment and give me a unique but still professional sounding sound? thanks again and remember I'm a newbie when it comes to audio electronics

If you were building an amp from the ground up it'd be a great start. You could tinker with it and learn a lot, and build it to suit. DIY is all about experimenting to get what you want. Think of it as a large investment with the payoff being that you'll begin to understand how to make different tones. You can build an amp that's tougher than anything you can buy, fix your own rig, and design custom gear to get any sound you can find. I won't say it's always cheaper, but you have total control over the end result, the workmanship, and you'll eventually never have to pay someone to fix your stuff.

As for a professional sound? Depends on what you mean exactly. DIY gear won't sound worse than commercial gear without a reason. Don't like the tone? Tinker away. Too little/too much gain? That problem is usually solved by a single resistor. Distortion not sound right? You can make a dozen different distortion circuits in a weekend and stage a crunch off! The only limit is how much of yourself you'd like to invest. Many find it easier to pay for the gear and focus on the music, and there's nothing wrong with that. Keeps the technicians fed! It's not unheard of for big name musicians to have a technician at their back to help them find a new tone, or tinker with their distortion. Knowledge is power.

The commercially available amps out there are designed by folks a lot like the best of the DIY crowd, but they have different goals. They have to make it profitable, so sometimes they or their management have to leave out neat options, or necessary protections, or the proper parts! There's nothing inherently magical about a $5K amplifier, the designers are as much a slave to physics as we in the DIY crowd. The real magic, to me, is getting lots of people to pay $5K for a mediocre design made up of $250 worth of parts! There's a lot of hard sweat and real innovation in the commercial amp world, but it doesn't always get respect, and all to often amps or companies get more respect than they deserve.

Ok, finished ranting about the injustices of the music world. Sometimes I get a bit . . .   :loco

In all honesty, it's likely that the only way anyone ever gets a unique and professional sound is custom work, be it hardware or post production. By learning to tinker, you don't have to be rich or famous first!

Hope that helps. I got a bit gabby today.

With questions like these, always try Wikipedia for a first stop (Capacitors). Capacitors have about a half dozen different properties that change depending on the type. The three types you might start with are ceramics for the small stuff (<1nF), electrolytic for the big stuff (1uF+), and pick your plastic (whatever's cheap) in the middle.

It helped me a lot when I first started to make a cheat sheet for caps so I could learn to convert pF/nF/uF and their markings (103, 474, etc.) back and forth. Beware, electrolytic and tantalum caps (and some others) have a polarity, so if you hook them up backwards (or exceed their voltage rating) they explode, violently enough to injure. The caps in your project are 100nF and 220nF, so any non-polar cap will be fine. There's reasons to be picky, but don't worry too much about it getting started. You can always pick up several types and play, but I think you'd be hard pressed to find much difference in this circuit.

Hope that helps.

The transistor reversal thing means that if you use the transistors he suggests you need to flip them over so the curve is facing left. For various reasons, transistors don't follow a standard pinout. The three terminals of a bipolar transistor are Base, Collector, and Emitter, and the small transistors you'll probably be working with are labeled on the long flat side. Looking at the label, the pins on the transistors he used in his schematic are (left to right) CBE, and the 2N3904 is EBC. See how it just flips over? Sometimes it gets ugly.

I went looking for the original post for more context, and I found this one. For some reason, his more evolved idea seems to come before the first one. Sounds like this fella started tinkering too.

The first response to the first link above is an excellent start. That's Teemuk, and you should definitely download a copy of and read through his book. If you get stuck, check the pages in All About Circuits for reference. Teemuk's book has a section on clipping on page 250 that's a good place to start, and here's the AAC page on common emitter amplifiers.

Hope that helps.

Sounds like you've made a lot of progress already. I'm a bit of a noob, but I'll try.

Do you have access to schematics? What's that 120Ω resistor doing for a living (bias, etc.)? Is the racket from the amp after warm up volume dependent?

If it were me I'd start with the power side. You're probably looking for a bad connection or heat sensitive component, but it won't necessarily be hot itself and may just be responding to a temperature change from a nearby component. If you have freeze spray you can puff it about until you hear a change, and you'll know roughly where to start. I'd be starting in the bias network and feedback network.

Replacing the resistor probably won't help you much, it'd just treat the symptom and not the problem.

Hopefully that helps a little, perhaps gives you a direction to test.

Many thanks for the feedback, sorry it took a while to get back.

Work on this has been postponed a while by my friend, but it just gives me more time to plan.

I like the powered enclosure idea. I think I'll be remaking the guts of his little practice amp, as it's got some terminal issues. Who ever heard of powering a 4558 with +/- 25VDC!!!  :loco It's actually designed that way in the schematic! Still, the modular approach would work perfectly for him, as the powered enclosure wouldn't have to ever leave their practice area, and we can focus on rebuilding the little amp that couldn't. I'm really looking forward to tone tasting with him and tweaking things to taste. It'd be a whole lot easier if I spoke musician, but I can't even play a kazoo!  xP

In case anyone else is interested, I picked up the transformer I mentioned from Fair Radio Sales in the US. It's in their Transformer/Choke section under Low Voltage, part number 701-121 (use browser find to get there quick, usually ctrl-F). I picked up two sets of banana jack to alligator clip test leads to make the $10US minimum order (~$12US total). They use standard UPS rates for shipping, so it was ~$22US shipped. It was in new stock condition with factory leads and well packaged. Pretty sweet deal if you're not set on toroidal! They've got a bunch of other transformers there as well.

Hope that helps, and thanks for the idea! I'll keep this thread posted as things progress.

Edited: Hit post instead of preview when I was half done. 

Welcome

Getting started is the hard part. I hope you like reading! Use and abuse every resource you can get your hands on via the internet. I've just started back into electronics myself last October and I still have a monster reading list to go through. In particular, this forum is the proud home of Teemuk's Book, which might be a bit heavy if you're just in to electronics but I'd call required reading for anyone making their own amp from scratch.

When you get ready to build something, I'd start small. Most seem to begin with pedal effects, and this is a great way to learn the basics in relative safety (from electrocution anyway) and still have something neat to show for it. Runoffgroove has a page with heaps of pedal effects, sound samples, and build details.

Hope that helps some

I've been reading and reading, so much to know!

I had a quick question about this transformer I picked up on the cheap. I think it may be a candidate for a medium sized amp but I'm getting dizzy swimming through all the datasheets. I'm on the brink of being sure of this, but I figured I'd better check my math.

This amp will be for a friend who's likely never to gig with it, but will occasionally be practicing with a band. He's been getting drowned out with his current 15W practice amp so we thought we'd build something a bit better.

The transformer is an EI with bell shielding and was listed as 36VCT 3A with a shipping weight of about 3.5Kg. Once it arrived I tested it at 21.7VAC RMS on each secondary with no load. I'm guessing that it'll settle down nicely to about +/- 25VDC or so once I get the power supply built. As a bonus, it's got a 5.73VAC RMS winding on it tempting me to add some freaky digital circuitry for no good reason.

The voltage seems just about right for a LM1875, and I think there may be (more than) enough current to do a two channel build. I like the idea of using the 1875 as opposed to most of the other chips in this range I've found on Mouser. They seem to try to do everything for you to cut component count and the 1875 seems to keep things fairly simple.

Does this seem like a good way to go?

Yet more reading material.

These are the first two sizable documents I found on opamps when I began working with them. TI puts out some great stuff, and they do an excellent job of keeping their pdf files small so they're easier to use on mobile devices.

Op Amps For Everyone - This 464 page monster covers everything opamp, and the second edition is available in print form. TI distributes the first edition for free for people just like us.

Handbook of Operational Amplifier Applications - This is a more historic document resurrected from old application notes from the 60's crafted by Thomas R. Brown (co-founder Burr-Brown). There are some very interesting insights here into the early limitations of opamps.

Hope you find those useful.

Quote from: Jack1962 on June 24, 2010, 05:04:46 PM
Went to your link there for the Jack Darr , book they want you to sign up it is a pay site

Sorry it took so long for me to get back, things were interesting here in a Chinese curse sort of way for a while.

Aarrgh! I hate those sites sometimes. I just tested it again and it works ok, but you have to know how to dodge through all their crap.

I put up a pair of pictures to guide you through. I'd just attach the pdf but it's 4.25MB so it's too large. I also uploaded it with rapidshare's free service, but it'll go away after 10 downloads. Just hit the "Free user" button. If all else fails I can email it, just send a private message.

Hope that helps

Quote from: J M Fahey on June 19, 2010, 11:05:40 PMYou might want to download and read first (search for it) Jack Darr's book, which gives a lighter but wider focus on guitar amps in general, including tube and transistors, and then advance further through Teemu's.

I wanted to hold off on a first post until I had something useful to say, and boy did it take a while.

I had a bit of an adventure finding Jack Darr's "Electric Guitar Amplifier Handbook", so I thought I'd post a link in case anyone's struggling trying to find it.

http://www.filestube.com/3fb5efb6f207ba4903ea/go.html

Hope that helps someone