Hello all! Just looking for advice here. I have successfully completed a 1W amp based of LM386N-4 and played with it a bit to modiy gain, etc to learn what I could. I would LIKE to make an amp that I can use at gigs, etc. However, the learning experience has been almost nightmarish with SEVERAL path changes and not knowing where to go. So, I will ask a simple question (and expect complex answers as they just come with the territory). What IC should I look into to start building this project? I was something that has a wide bandwidth and fidelity. I also want it to be lou.d Mind you, this may dreaming, but I picture a 4X12 speaker cabinet....or 2....lol. And this dreaming is what's holding me back. I keep getting too complicated for my own good. I need something that uses 110V main to power it. Or....possibly a tutorial on designing power supplies to step main power down to needed voltages...
Forgive the rambling, but my wishes are beyond my knowledge and it's frustrating (As I'm sure you unerstand and have at some point experienced.) 🙂
Forgive the rambling, but my wishes are beyond my knowledge and it's frustrating (As I'm sure you unerstand and have at some point experienced.) 🙂
Read some of these to get an understanding so you know which questions you need to ask.
DIY Audio Articles
Frank
DIY Audio Articles
Frank
I second the reading of the natsemi app notes, excellent and very thorough, plus i believe they are currently the best driver chips available
I am all for pouring over datasheets 🙂. However, What I am trying to get a grasp of, what numbers should I aim for? What voltages, output wattages, etc will be a "safe amount" for a beginner to work with? Not being a specialist in this field (yet?), It's like me trying to pick a car having time travelled from 1492....lol
Yes, a very good analogy except I would use it differently. It would be more like you trying to drive a car having travelled from 1492 when you have no idea what the road rules are. In which case, I'll say goodbye now because you won't be alive much longer if you aren't prepared to read some things that will SAVE your life, such as about proper wiring, earthing and to use mains voltage.
Electrocution
Having said that, I use three LM3886 amps per box in an active three way, with active crossover, speaker protectors, transformer, power supplies (yes, two - one for +-15V), and balanced driver for bridging the woofer amp all in the bottom of the cabinet.
But it is pointless you knowing all that because you won't have learnt enough about the dangers of using electricity. R.I.P.
Frank
All the warnings are great. however, the way it comes across is that you seem to think I disregard safety. Quite the opposite is true. I am WAY overcautious. This is why I ask the questions I do. I would gladly take a college course if I could afford it. ALL I'm really asking for is a way to LEARN the safe way to do these things. Notice I said the safe way. I dont want a "tutorial" that says plug this here, and that there. I want to know the theory of it all. I want to be able to recognize that what I'm about to do is dangerous AND why. I do not proceed with any builds until I am POSITIVE that I can do it safely, and even then I will proceed slowly and excessively carefully with attention to every little detail. I get that you have to be cautionary the way that you are. HV is dangerous. NO one is immune. The idiots that think they are die. That is understood by me. I do not intend this message as anything more than "I get that I need to be careful. I will. where do I go from here?" If anyone is offended by this, I apologize.
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Class AB chip amps probably wont be loud enough for you.
Go for a discrete class AB design of 500 watts plus.
Go for a design off DIYAUDIO as there are some internet designs that just dont work.
Go for a discrete class AB design of 500 watts plus.
Go for a design off DIYAUDIO as there are some internet designs that just dont work.
Nigel,
The guy is a beginner and you want to set him loose on supply rails that would kill an elephant?
OK, Cory, understood. What "gigs" are you talking about so we have an idea of what you are driving and do you have a speaker at the moment or is that part of the grand plan?
Frank
The guy is a beginner and you want to set him loose on supply rails that would kill an elephant?
OK, Cory, understood. What "gigs" are you talking about so we have an idea of what you are driving and do you have a speaker at the moment or is that part of the grand plan?
Frank
Cory, you're wanting to build an amp running off 110V - any of them are potentially exposing you to lethal voltages. You're wanting enough power to drive speakers fairly loud, any amp capable will have power rails with high enough voltage to cause harm.
There isn't a lot to say about safety except the things which are obvious, don't go touching live circuits, shorting things with metal tools, or powering up a design without inspecting/double-checking it, and ideally do not work on such projects when tired, late at night, etc when mistakes are more likely to be made. In the end, you power it up and stand back hoping it doesn't make snap crackle pop boom type sounds.
You mention "IC" but you're probably wanting not a single chip solution but rather a driver IC like LM4702 LM4702 - Stereo High Fidelity 200 Volt Driver with Mute for your dream project, but how about an intermediary project for more amp building experience first, like a basic gainclone using same parts other amp builders are using?
There isn't a lot to say about safety except the things which are obvious, don't go touching live circuits, shorting things with metal tools, or powering up a design without inspecting/double-checking it, and ideally do not work on such projects when tired, late at night, etc when mistakes are more likely to be made. In the end, you power it up and stand back hoping it doesn't make snap crackle pop boom type sounds.
You mention "IC" but you're probably wanting not a single chip solution but rather a driver IC like LM4702 LM4702 - Stereo High Fidelity 200 Volt Driver with Mute for your dream project, but how about an intermediary project for more amp building experience first, like a basic gainclone using same parts other amp builders are using?
Electronics is a big field, and can be a difficult study. It encompasses some of the subtlest physics in common use. The variety of components is huge, and while some are superficially similar, the differences between them can be critical.
Having said this, it's important to recognise that some people will seek to mystify the subject, and not to brook any discouragement.
Most people have an understanding of the very basics, and can build a simple circuit with a battery, some wire and a lightbulb. This simple achievement can be built on practically without limit, because the subject is now so vast that it probably exceeds the capacity of a single individual to grasp it all.
Some of the best introductions to the subject are to be found in amateur radio handbooks. These have been produced on a yearly basis for many years by the ARRL and RSGB, and old secondhand copies are inexpensive and the contents remain valid. There are also now many internet sites offering explanations of aspects ranging from the simple to the advanced.
An understanding of Norton's and Thevenin's equivalent circuits is fundamental to a firm grasp of Ohm's law. Once this is understood, power, AC, inductance (coils) and capacitance round out the basics, introducing magnetism, static charge and conductors and insulators.
While most educators will have their favourites and be familiar with a wide variety of texts dealing with the basics, one book which s considered outstanding in terms of dealing with practical theory and design issues in a modern context for both undergraduates and graduates is 'The Art of Electronics' by Paul Horowitz and Winfield Hill.
Building an (audio) amplifier can be undertaken on no more demanding a basis than 'painting by numbers'. Many datasheets for chip amplifiers, such as those already mentioned from National, contain very complete instructions and diagrams of practical application circuits. These are not merely guidelines, but often present ways of achieving the best performance that the devices are capable of.
Low power amplifiers are, in general, less demanding to build than high power amplifiers, but an amplifier up to 100W should be achievable by even a comparative novice, but in the case of such higher powers a design with comprehensive instructions which has been built by numerous people would be a less risky choice. Problems can arise for the novice builder if an error has been made in construction and the amplifier fails to work. For this reason it is in some ways more advisable to start with simpler, low power designs and work up, building confidence and experience in the process, with less risk of a discouragement causing a complete abandonment of interest. Of course, if you have no use whatsoever for a low powered amplifier this may not appeal, just be aware of the potential problems.
You will find this site, or Rod Elliott's site (already mentioned) reliable sources of workable designs.
While it's important to be careful, many amateur experimenters survived the days of valves, when low voltage circuits for most amplifier applications were simply not available.
Take care, good luck!
Having said this, it's important to recognise that some people will seek to mystify the subject, and not to brook any discouragement.
Most people have an understanding of the very basics, and can build a simple circuit with a battery, some wire and a lightbulb. This simple achievement can be built on practically without limit, because the subject is now so vast that it probably exceeds the capacity of a single individual to grasp it all.
Some of the best introductions to the subject are to be found in amateur radio handbooks. These have been produced on a yearly basis for many years by the ARRL and RSGB, and old secondhand copies are inexpensive and the contents remain valid. There are also now many internet sites offering explanations of aspects ranging from the simple to the advanced.
An understanding of Norton's and Thevenin's equivalent circuits is fundamental to a firm grasp of Ohm's law. Once this is understood, power, AC, inductance (coils) and capacitance round out the basics, introducing magnetism, static charge and conductors and insulators.
While most educators will have their favourites and be familiar with a wide variety of texts dealing with the basics, one book which s considered outstanding in terms of dealing with practical theory and design issues in a modern context for both undergraduates and graduates is 'The Art of Electronics' by Paul Horowitz and Winfield Hill.
Building an (audio) amplifier can be undertaken on no more demanding a basis than 'painting by numbers'. Many datasheets for chip amplifiers, such as those already mentioned from National, contain very complete instructions and diagrams of practical application circuits. These are not merely guidelines, but often present ways of achieving the best performance that the devices are capable of.
Low power amplifiers are, in general, less demanding to build than high power amplifiers, but an amplifier up to 100W should be achievable by even a comparative novice, but in the case of such higher powers a design with comprehensive instructions which has been built by numerous people would be a less risky choice. Problems can arise for the novice builder if an error has been made in construction and the amplifier fails to work. For this reason it is in some ways more advisable to start with simpler, low power designs and work up, building confidence and experience in the process, with less risk of a discouragement causing a complete abandonment of interest. Of course, if you have no use whatsoever for a low powered amplifier this may not appeal, just be aware of the potential problems.
You will find this site, or Rod Elliott's site (already mentioned) reliable sources of workable designs.
While it's important to be careful, many amateur experimenters survived the days of valves, when low voltage circuits for most amplifier applications were simply not available.
Take care, good luck!
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A lot depends on the person.
I am lethal with high voltages so dont work on them if I can help it.
I remember my first valve pre amp that ran on 200 volts.
I built it and tested it, I switched it off and touched the circuit and of course got a shock from the charged up power supply capacitor. My tutor said that I had to dsicharge it first because it held a charge. So the next time duly shorted it out with a resistor and crocodile clip leads. I touched the ciruit and again got a belt, I had forgotten to turn it off !
+1
They're fairly simple and can get loud too. A pair of LM3886 chips in bridge mode will do over 100W into 8Ohms, with no unsafe voltages anywhere in the amp circuit. That's a pretty good start. If you want more power, you could use a separate amp for each speaker in a 4*12 box for about 500W total.
You'll need to make a power supply to convert 110V mains to about +-30V DC. That's simple too, but it's where you need to be careful safety-wise as you're dealing with mains voltage.
Beware of cost with this kind of project though. The chips themselves are quite cheap, but what really eats money is the power supply, heatsinks and box.
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References to unsafe practices around significant voltages have been deleted. Any voltage 12V and over at an appreciable current can be hazardous. Please adhere to forum requirements when discussing these issues. Safety comes first here!Please dont do this to me 🙂
I'm not really talking about using it in anything more than a few people. I have to admit, the project is more of a "bragging rights" of the end result. *Pounds chest rapidly* Me Made! lolol. I do not have a speaker, or too many requirements. I simply want a setup that CAN get loud if I want it too 🙂 There is no need for onboard gain as I have looked into making effects pedals too.
Yes. One of these sound nice. I have been recently considering the LM3886 Mono Kit from ChipAmp.com. Good intermediate choice?
That is the attention to detail I was mentioning 😉 lol
Thats an idea.....4 little amps in 1 unit. Could I bridge all the inputs from a single mono input....reasonably? I see a potential issue with response times...as in 1 speaker being a millisecond behind per second or something....that could get annoying. lol 🙂
Seeing as I have kicked a little to "earn my way" into the learning arena 🙂, I will now ask a question that I have been unable to find a reasonable response to. More so, I will ask you to verify that my assumption is correct (It's probably not lol)
If the datasheet on a chip calls for a Operating Voltage Range of say +-20V~+-100V that means it can operate ANYWHERE between with those as the high and low recommendations? As such, I take it should aim for the higher end for better performance?
Thanks!
Yes/no/maybe
You'll learn more if you just buy the PCBs then pick your own parts separately, that will make you think more about the components and what effect a choice has. On the other hand, this draws out the project instead of receiving a kit in the mail and being able to finish all but the case for it the same evening.
At this point, further questions I have I will open up a new thread for 🙂. I appreciate all the advice and good mojo going here now, but I respect that threads need to stay specific. I have decided to proceed with a LM3886TF as an intermediate project.
@ "!" I plan on going that route regardless 🙂 Buying a kit would defeat the purpose I have in this.
@ "!" I plan on going that route regardless 🙂 Buying a kit would defeat the purpose I have in this.
Sort of, with a couple of caveats.
In general, a higher supply voltage means you can get more voltage across the speaker and thus more power.
Problem 1: To deliver the higher power, the chip also has to put higher current through the speaker, but there's a limit to how much current the chip can deliver. So when you hit the current limit, there's no point increasing the supply voltage. This isn't normally a problem with 8Ohm speakers, but folks trying to use 1Ohm or 2Ohm car subs are going to run out of current long before they run out of voltage.
Problem 2: Increasing the supply voltage means the chip get's hotter, even at the same output power. When chips get too hot they either die or save themselves by cutting the output.
Example: Let's say you make an amp with an LM3886 on a smallish heatsink with a +-30V supply. It can deliver almost 50W into 8Ohms all day. Now try increase the supply to +-40V. Now the amp can deliver 85W into 8Ohms, but not for long. Even at 5W output the chip will be getting hotter than it ever did with the lower supply voltage.
There's no "right" answer here; it's a matter of choice. If you listen to music with a high dynamic range, an amp that can deliver 85W peaks, but only 5W average might be a bit better than one that can deliver 50W continuously. Or you can blow more $$$ on a much bigger heatsink and get 85W continuous. If you listen to heavily compressed music, the continuous rating is more important. NB: 85W is not much louder than 50W. The difference is less than 3dB.
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Changing the subject a bit - if you want "LOUD", then loudspeaker sensitivity is more important than amplifier power. A 3dB increase in speaker sensitivity is equal to a doubling of amp power. A 10dB increase in speaker sensitivity is equivalent to 10 times the amp power. So a 10W amp driving a 99dB/1W/1m speaker will be as loud as a 200W amp driving a 86dB/1W/1m speaker.
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Back on topic: The datasheets normally give sensible advice regarding supply voltage etc. Snippets below are from the LM3886 datasheet.
Attachments
OK. So essentially, I want to (based on the charts in the datasheet) run the lowest voltage possible to deliver the results I want? If I understand this correctly, It will simultaneously save my electric bill, keep thermal problems under control, and be "safer" to work with? 🙂
Well, sort of. The lowest voltage may NOT deliver the results you want, the power saved will be negligible, thermal problems will be minimised but safety is, largely, based on how you respect mains voltage.
If you want to use the LM3886TF (I do and do like them), then a 20CT20 to 25CT25 (CT= centre tap) transformer will be fine and give +-28 to +-35 volts. If you are going to build an active speaker then one of these attached to each driver will provide you with plenty of roof raising "grunt".
Frank
If you want to use the LM3886TF (I do and do like them), then a 20CT20 to 25CT25 (CT= centre tap) transformer will be fine and give +-28 to +-35 volts. If you are going to build an active speaker then one of these attached to each driver will provide you with plenty of roof raising "grunt".
Frank
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