My 2¢: Try to be a bit less defensive, "just an idea". Really! LOOK UP "bleeder resistor" in the book, and online. You'll find it is a small-current bypass resistor that drains the current from the powersupply capacitors rapidly enough not to let them hold viciously dangerous high voltage ... for many many minutes past when you turn off the amp. In other words: really valuable at preventing "gotcha!!!" type electrocutions.
Also, the advice of "working on lower voltage stuff first" is really sound. Here's why: you will learn JUST as much, yet, when you're fiddling around in there with the ohm-meter probe and touch something "wrong", you'll get a nice big pop, but no ambulance call. Big scary (but otherwise fairly innocuous) pops are a great way to learn ... what not to touch as a rule. Moreover, they're MUCH cheaper to implement at the low-to-mid power level. You can further learn a lot about constant current sources, constant voltage sources; you can learn about the effect of various components at various positions in the circuits.
You can build such wonders on little white "breadboards" - which are truly the gift of the gods - helping you to quickly set up circuits, try things out, then break them down again to re-useable parts. It can be so fun! Yet, even here, you should adopt an attitude of, "I should build tools to help build circuits".
For instance, if you're going to do the little-white-breadboard approach, then you should have a nice power supply to provide power, without the overhead of having to build one for every project. You also should get one of the new "USB oscilloscopes", which allow your computer to capture the signals that you generate. They can do all sorts of stuff for a few hundred bucks, which we used to (1970s) pay tens of thousands for. They're wonderful. Also, that laptop of yours can act as a signal source. It has a headphone jack. That there would be a signal source.
But you might want to build a "protector/interface" for it! This would be a little project-box with a headphone and microphone cable coming out (to the computer), and on the other side, stripped, tinned (soldered) wires to plug into the breadboard. What does the box do? It has series resistors and clamping diodes to shunt dangerous overvoltages that might come from your designs to ground ... protecting the computer. Good little project too, for a Saturday morning.
No just an idea ... I would not recommend getting your feet wet in electronic-circuit building until you've spent some "quality time" with good old "sand (silicon) electronics". There's much to be learned, and nothing to be wasted
GoatGuy
Also, the advice of "working on lower voltage stuff first" is really sound. Here's why: you will learn JUST as much, yet, when you're fiddling around in there with the ohm-meter probe and touch something "wrong", you'll get a nice big pop, but no ambulance call. Big scary (but otherwise fairly innocuous) pops are a great way to learn ... what not to touch as a rule. Moreover, they're MUCH cheaper to implement at the low-to-mid power level. You can further learn a lot about constant current sources, constant voltage sources; you can learn about the effect of various components at various positions in the circuits.
You can build such wonders on little white "breadboards" - which are truly the gift of the gods - helping you to quickly set up circuits, try things out, then break them down again to re-useable parts. It can be so fun! Yet, even here, you should adopt an attitude of, "I should build tools to help build circuits".
For instance, if you're going to do the little-white-breadboard approach, then you should have a nice power supply to provide power, without the overhead of having to build one for every project. You also should get one of the new "USB oscilloscopes", which allow your computer to capture the signals that you generate. They can do all sorts of stuff for a few hundred bucks, which we used to (1970s) pay tens of thousands for. They're wonderful. Also, that laptop of yours can act as a signal source. It has a headphone jack. That there would be a signal source.
But you might want to build a "protector/interface" for it! This would be a little project-box with a headphone and microphone cable coming out (to the computer), and on the other side, stripped, tinned (soldered) wires to plug into the breadboard. What does the box do? It has series resistors and clamping diodes to shunt dangerous overvoltages that might come from your designs to ground ... protecting the computer. Good little project too, for a Saturday morning.
No just an idea ... I would not recommend getting your feet wet in electronic-circuit building until you've spent some "quality time" with good old "sand (silicon) electronics". There's much to be learned, and nothing to be wasted
GoatGuy
Thanks, but thats exactly what I am doing. As you caring chaps of DIY AUDIO have gone to the trouble of making a tread regarding safety with high voltages, lets go ahead and assume I will read that before I actually start building... and probably serveral times during the build... but as I've still got most of that thick book to read, probably a few times over first... I don't feel in any immediate danger yet.
You might be right though about the breadboard, that does sound like fun to play around with whilst learning.... can anyone recomend a good kit and a book to accompany it, or do I have to order all the parts seperately?
The "fun" is in ordering the parts, actually. DIY audio has that darn Do It Yourself thing in there! 
And it is fun too to build stuff. You can "scab" all sorts of stuff to get you going in the short term: a toss-away left-over computer power supply (working, of course!) becomes a cheap source of +12V and -12V. Not much power, but you don't need much for your first experiments. TWO of the "throw away power supplies" gives you powerful +12 and -12 volts, for more substantial amplifier experiments. You'll have the delight of using an undersized heat sink, and having your output transistors fry with a magnificent and smokey "pop!". You'll burn up resistors, you'll hook capacitors backwards (no matter how many times you read the spec-sheet). After a dozen of these kind of minor catastrophes (which require NO soldering - also a can-of-worms when you finally get around to it) ... minor catastrophes RESOLVED into running circuits ... you'll have tons more confidence to take on the tube projects.
I don't want to sound "parochial" or "parental" or "pontificating" to you - really, I don't. But there's SO much fun in learning "without danger", at the beginning. I just wish I was in your shoes! The early years of my electronics learning was filled with dreams and wonder at the simplest ideas: Ohm's Law (E = I R), the Power law (P = I E ... nice mnemonic), the simple equations for transistor amplification Ic = Hfe * Ib, the simple equation for FET current amplifcation Ids = gm * (Vcutoff + Vgate), and so on.
Electronics, just an idea is mostly about math, in the end. Really! The various topologies of circuits, from cathode followers (emitter followers for transistors, source-followers for FETs), to cascode (fixed plate, collect, drain voltages!) and so on all map onto each other, across domains. You will be able to test out "cascode" amplification, and "fixed bias", and "constant current" and a WHOLE lot of other ideas ... all on that darn breadboard. And, 'cuz you're not soldering anything for the testing, all the componets can be used again.
Yep. I really wish i were (as I was) 10 years old again, and had the benefit of a box of cool electronics stuff, a nice power supply, and a good breadboard. Those slow, but "learning" years would have been 10x to 20x faster. I'm jealous of you!
Good luck, and don't spend a fortune on fancy stuff. Just get bog-standard components and economy breadboards, and so on ... while you're learning. I went to one of the world's most prestigious electrical engineering universities ... and we had nothing but "bog standard components" to learn with. And simple power supplies, and simple breadboards. And we learned! Because that's where the basics lie.
GoatGuy
And it is fun too to build stuff. You can "scab" all sorts of stuff to get you going in the short term: a toss-away left-over computer power supply (working, of course!) becomes a cheap source of +12V and -12V. Not much power, but you don't need much for your first experiments. TWO of the "throw away power supplies" gives you powerful +12 and -12 volts, for more substantial amplifier experiments. You'll have the delight of using an undersized heat sink, and having your output transistors fry with a magnificent and smokey "pop!". You'll burn up resistors, you'll hook capacitors backwards (no matter how many times you read the spec-sheet). After a dozen of these kind of minor catastrophes (which require NO soldering - also a can-of-worms when you finally get around to it) ... minor catastrophes RESOLVED into running circuits ... you'll have tons more confidence to take on the tube projects.
I don't want to sound "parochial" or "parental" or "pontificating" to you - really, I don't. But there's SO much fun in learning "without danger", at the beginning. I just wish I was in your shoes! The early years of my electronics learning was filled with dreams and wonder at the simplest ideas: Ohm's Law (E = I R), the Power law (P = I E ... nice mnemonic), the simple equations for transistor amplification Ic = Hfe * Ib, the simple equation for FET current amplifcation Ids = gm * (Vcutoff + Vgate), and so on.
Electronics, just an idea is mostly about math, in the end. Really! The various topologies of circuits, from cathode followers (emitter followers for transistors, source-followers for FETs), to cascode (fixed plate, collect, drain voltages!) and so on all map onto each other, across domains. You will be able to test out "cascode" amplification, and "fixed bias", and "constant current" and a WHOLE lot of other ideas ... all on that darn breadboard. And, 'cuz you're not soldering anything for the testing, all the componets can be used again.
Yep. I really wish i were (as I was) 10 years old again, and had the benefit of a box of cool electronics stuff, a nice power supply, and a good breadboard. Those slow, but "learning" years would have been 10x to 20x faster. I'm jealous of you!
Good luck, and don't spend a fortune on fancy stuff. Just get bog-standard components and economy breadboards, and so on ... while you're learning. I went to one of the world's most prestigious electrical engineering universities ... and we had nothing but "bog standard components" to learn with. And simple power supplies, and simple breadboards. And we learned! Because that's where the basics lie.
GoatGuy
Ok, having come at this fresh, I would like to apologise for interpriting your concern for something else and for my iritation in you quickly and easily finding the big obvious holes in my knowledge. I'm going to start right at the beggining, and although I will (hopefully) find a lot too basic it will be the only way to make sure I haven't missed anything. The book I will buy to start me off is electronics: learning by descovery and I'll get a breadboard and start playing around from there. Thanks all.
I don´t know in what area you are located but if you ask around there´s probably some electronics or ham people around.
To get a mentor is a very good way to start.
And that way you get access to both knowledge and equipment without having to spend a fortune in the beginning.
On top of that it´s a lot of fun when yore a bunch of people with same passion.
To get a mentor is a very good way to start.
And that way you get access to both knowledge and equipment without having to spend a fortune in the beginning.
On top of that it´s a lot of fun when yore a bunch of people with same passion
.Go with LM3886 as you first audio amp you can get tons of support on different forums regarding it. I might suggest implement it no-inverting so you will get a better BW and can play around with different types of decoupling capacitors same way as if it was tube project.
Parts you can easily order via Internet. Often they are less pricey via Internet than purchasing same parts from a local store. Newark, Farnell, Digikey etc. Newark has most user friendly web IMHO.
You may go to Google Images and type Manhattan style PCB you will see it is a real joy for DIY no less fun than a tubies project.
Consider back loaded horn like Fe206 for your speaker build later on and you will and up with nice sounding stereo that really stands out from mass-consumer market electronics.
And do not get upset by messing up stuff being on a safe side. It is normal learning curve. That is why safety rules are most important to obey first.
Parts you can easily order via Internet. Often they are less pricey via Internet than purchasing same parts from a local store. Newark, Farnell, Digikey etc. Newark has most user friendly web IMHO.
You may go to Google Images and type Manhattan style PCB you will see it is a real joy for DIY no less fun than a tubies project.
Consider back loaded horn like Fe206 for your speaker build later on and you will and up with nice sounding stereo that really stands out from mass-consumer market electronics.
And do not get upset by messing up stuff being on a safe side. It is normal learning curve. That is why safety rules are most important to obey first.
I disagree on the chipamp for first project if learning basic electronics is the main thing.
Get something basic discrete like the Amp Camp amp or similar.
That way you can follow a schematic and get to know the basic building blocks.
A Chipamp is fast way to a descent amp but not to learn the basics of an amplifier.
Get something basic discrete like the Amp Camp amp or similar.
That way you can follow a schematic and get to know the basic building blocks.
A Chipamp is fast way to a descent amp but not to learn the basics of an amplifier.
I think it might be useful to study some of the old books from the vacuum tube era. Building a vintage design will help you understand the basic concepts, and you can go back and update your vintage amp with more modern power supplies, etc., which will make for more learning (as well as improve your amp).
I would start with something that uses guitar amp tubes like 12AT7 (ECC81), 12AX7 (ECC83), 6V6 (or equivalents), EL84, etc. or very commonly available tubes like 6DJ8 (ECC88).
You can adapt the Dynaco ST35 circuit to use 6DJ8 and a push-pull pair of EL84, using Edcor or other inexpensive output transformers. What's wrong with starting with this?
http://www.diyaudio.com/forums/tubes-valves/185823-unexpectedly-good-el84-amp.html
It doesn't use any solid state ccs or other support circuitry, but that could be added later. It has its EL84 output tubes wired in triode, so it should be pleasant sounding without a global feedback loop, making it very simple. But it will be low powered, maybe 5 or so watts per channel.
What do you think?
[EDIT]
OK, I see why not... Some things in there are wrong.
- First off, the cathode resistor for the EL84's should be 200 ohms, not 400 ohms. Or, there should be a 400 ohm for each EL84 (not shared), each with its own bypass capacitor.
- Also, the EL84 grid stoppers should probably be 4k7, not 1k.
But the general idea is OK, I think. A really basic PP EL84 amp, with a single B+ supply of about +340V, using a 6DJ8 or 6N1P with a pair of triode wired EL84's per channel.
I would start with something that uses guitar amp tubes like 12AT7 (ECC81), 12AX7 (ECC83), 6V6 (or equivalents), EL84, etc. or very commonly available tubes like 6DJ8 (ECC88).
You can adapt the Dynaco ST35 circuit to use 6DJ8 and a push-pull pair of EL84, using Edcor or other inexpensive output transformers. What's wrong with starting with this?
http://www.diyaudio.com/forums/tubes-valves/185823-unexpectedly-good-el84-amp.html
It doesn't use any solid state ccs or other support circuitry, but that could be added later. It has its EL84 output tubes wired in triode, so it should be pleasant sounding without a global feedback loop, making it very simple. But it will be low powered, maybe 5 or so watts per channel.
What do you think?
[EDIT]
OK, I see why not... Some things in there are wrong.
- First off, the cathode resistor for the EL84's should be 200 ohms, not 400 ohms. Or, there should be a 400 ohm for each EL84 (not shared), each with its own bypass capacitor.
- Also, the EL84 grid stoppers should probably be 4k7, not 1k.
But the general idea is OK, I think. A really basic PP EL84 amp, with a single B+ supply of about +340V, using a 6DJ8 or 6N1P with a pair of triode wired EL84's per channel.
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Well I do remember my first tube amp. I couldn't read the schematic, it was FUN. I had zero knowledge of the dangers involved with caps, I just knew electricity bites. Didn't get shocked. I would say that the great danger comes when passion gets a hold of you. You forget about safety and that's when I first got zapped. But I do play guitar and guitar players have extra danger.
The classic amps is where my real interest lies, and in stripping down and rebuilding something otherwise scrap... old stuff can be found here in thailand, but the prices that get put on absolute s++t is unbeleivable, let alone the reasonable stuff. I'm constantly keeping an eye out though.
That dynaco circuit looks quite appropriate, I'll store it away until I'm ready to approach it.
That dynaco circuit looks quite appropriate, I'll store it away until I'm ready to approach it.
harumph....
The "Tube Guys" (which are the crows (me too) which hang out in the Tube Forum) will tell you "try tubes!" ... "try tubes!" ... "here's a simple circuit!" ... "use tubes!"
I've done it all, my friend. I advise - being that this is the 21st Century, and we have amazingly useful tools that have been invented in the last 50 years - to stick with "learning the ropes" with breadboards, and lots of "build it tonight, test, and break it down tomorrow" sand-circuits (semiconductors). Learn by doing, learn by breaking, learn by making little mistakes that make big popping noises. Then, merely weeks later, try tubes.
First though... breadboards.
And I know with this forum, that few if any will say "well, the Goat is right. Its the best way to really learn about electronics" ... but it is.
[I started in the very early 1960s. There were few alternatives except cheap tubes (they were literally "discards" from the TV and Radio repair shops), and expensive semiconductors (which the tube guys didn't trust / understand / want to understand). Yet, they teach well. And you can get away with "scabbing" stuff from lots of discarded things around you. I rest my case.]
GoatGuy
The "Tube Guys" (which are the crows (me too) which hang out in the Tube Forum) will tell you "try tubes!" ... "try tubes!" ... "here's a simple circuit!" ... "use tubes!"
I've done it all, my friend. I advise - being that this is the 21st Century, and we have amazingly useful tools that have been invented in the last 50 years - to stick with "learning the ropes" with breadboards, and lots of "build it tonight, test, and break it down tomorrow" sand-circuits (semiconductors). Learn by doing, learn by breaking, learn by making little mistakes that make big popping noises. Then, merely weeks later, try tubes.
First though... breadboards.
And I know with this forum, that few if any will say "well, the Goat is right. Its the best way to really learn about electronics" ... but it is.
[I started in the very early 1960s. There were few alternatives except cheap tubes (they were literally "discards" from the TV and Radio repair shops), and expensive semiconductors (which the tube guys didn't trust / understand / want to understand). Yet, they teach well. And you can get away with "scabbing" stuff from lots of discarded things around you. I rest my case.]
GoatGuy
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