Hello
Planning to build a BPA200 with two lm 4780. I am locking for Schematic for this. There is ofcourse schematic in the BPA200 documentation. But i would i would like to get one that some one has made.? i have search the forum and found some but they are not complete schematics? maby i have missed some then i would like very much like to se ..
So if you got a tested schematic please PM me or email me
my_name_is_nobody@telia.com
Planning to build a BPA200 with two lm 4780. I am locking for Schematic for this. There is ofcourse schematic in the BPA200 documentation. But i would i would like to get one that some one has made.? i have search the forum and found some but they are not complete schematics? maby i have missed some then i would like very much like to se ..
So if you got a tested schematic please PM me or email me
my_name_is_nobody@telia.com
Not the best alternative, but less likely to switch off due to overtemperature.
Just curious, what would be the "best approach" (if there is one) in your opinion?
Lo_tse
For several hundred Watts of output power class D is the most reasonable thing. Chip amps are good for 50-60 W per channel. Solid state and hybrid ICs for the power range in between. Driver ICs like the LME498xx reduce the complexity of solid state amps, if not the cost.
Several chips in BTL or parallel can make sense in an active speaker when you need different power levels for different drivers or the same power level for drivers with different impedances and from the same rail voltage.
Building BTL, PAR and BPA as full-range amps makes for a nice pastime, but they don't offer any significant advantages over other amps. They are as expensive or even more so. And they are also nearly as complex. The schematics may appear straightforward. Routing power, speaker and line signals past each other without interference is not. Neither is grounding. So you either make compromises that result in an inferior amp or you put so much brainpower into it that you might as well build a solid state or class D amp.
The best way o learn is to test and make mistakes
And that what i like about it then you learn the hard way
So adopt a wise man's approach to getting your schematic - draw one up (imperfect though you know it be) and put it on this thread. Then you'll get lots of posts pointing out your mistakes. When those postings stop, you've got yourself a good schematic to build from. Evolution
Building BTL, PAR and BPA as full-range amps makes for a nice pastime, but they don't offer any significant advantages over other amps. They are as expensive or even more so. And they are also nearly as complex. The schematics may appear straightforward. Routing power, speaker and line signals past each other without interference is not. Neither is grounding. So you either make compromises that result in an inferior amp or you put so much brainpower into it that you might as well build a solid state or class D amp.[/QUOTE]
Thank you for your comments. Would you mind elaborate on why the chip amps (at least the BPA) are "inferior amps"? All the issues you mentioned applies to building other types of amps too, am I right? Or these issues only asociate with chip amps?
The explanation on why bridging LM4780 is not practical (thermal load is too great) is the type of answer that I really appreciate - it is based on solid science, not personal feelings. I fully understand that everyone has his/her own personal take on any topics. Hey, this is a free world and everyone entitles his/her own opinion. However, being a newbie, I really want to differentiate what are sound scientific facts/judgements and what are personal opinions.
Regarding the way of learning, I do have a few years experience teaching university students and had some interesting observations regarding learning . One thing I discovered was that different students learn things "differently". Some followed the way I showed them (the way described in the current textbooks) and picked up quickly. For whatever reasons, a few "odd ones" would approach the topics in a more "convoluted" manner. Then, I had to try to look at the topics "their way", which at times I found to be silly, and tried to answer their queries. Anyway, my philosophy is that as long as they learn how to solve the problems and exams I gave them, then everything is rosy. Bottom line, does not matter how one learns (like a modern man or a prehistoric man), as long as one learns, the goal is accomplished. Being a scientific researcher for 25 years, I have seen some great scientific discoveries from people who approached a problem differently from the established/commonly accepted ways.
So, mynameis_nobody, use whatever "modes" of learning you want. I will cheer you on.
Lo_tse
Thank you for your comments. Would you mind elaborate on why the chip amps (at least the BPA) are "inferior amps"? All the issues you mentioned applies to building other types of amps too, am I right? Or these issues only asociate with chip amps?
The explanation on why bridging LM4780 is not practical (thermal load is too great) is the type of answer that I really appreciate - it is based on solid science, not personal feelings. I fully understand that everyone has his/her own personal take on any topics. Hey, this is a free world and everyone entitles his/her own opinion. However, being a newbie, I really want to differentiate what are sound scientific facts/judgements and what are personal opinions.
Regarding the way of learning, I do have a few years experience teaching university students and had some interesting observations regarding learning . One thing I discovered was that different students learn things "differently". Some followed the way I showed them (the way described in the current textbooks) and picked up quickly. For whatever reasons, a few "odd ones" would approach the topics in a more "convoluted" manner. Then, I had to try to look at the topics "their way", which at times I found to be silly, and tried to answer their queries. Anyway, my philosophy is that as long as they learn how to solve the problems and exams I gave them, then everything is rosy. Bottom line, does not matter how one learns (like a modern man or a prehistoric man), as long as one learns, the goal is accomplished. Being a scientific researcher for 25 years, I have seen some great scientific discoveries from people who approached a problem differently from the established/commonly accepted ways.
So, mynameis_nobody, use whatever "modes" of learning you want. I will cheer you on.
Lo_tse
Please read that sentence again. I did not say they are inferior amps. They are on the contrary hard to beat, when applied within their specs. And sometimes even outside of their specs.
What I said was, that you have two choices when building composite amps, whether bridged, parallel or both. One leads to careless designed routing and grounding, resulting in a compromised amp. The other requires nearly as much effort as a solid state or class D amp that gives the same or better performance at lower cost.
Absolutely true that different people have different ways of learning. Wasting other peoples time asking question when you don't care about the answers anyhow is none of them. Neither is taking offense and walking away at the first chance.
What I said was, that you have two choices when building composite amps, whether bridged, parallel or both. One leads to careless designed routing and grounding, resulting in a compromised amp. The other requires nearly as much effort as a solid state or class D amp that gives the same or better performance at lower cost.
Absolutely true that different people have different ways of learning. Wasting other peoples time asking question when you don't care about the answers anyhow is none of them. Neither is taking offense and walking away at the first chance.
I stand corrected. You are right. You message meant "insufficient/compromising designs lead to inferior amps". I totally agree. But then again, that applies to all amp designs.
I thought one of the beauty of this open forum was that anyone that interested in DIY electronics are welcome to this forum, experienced or not. Experienced member/"wisemen" can share their knowledge, if they are willing, with less knowledeable people. I know that at times, the same question is asked many times and it get annoying, that's why there are FAQ's and Stickies. Kindly direct them to the right place. If one think the newbie's questions are a waste of timee, then ignore them. If the situation gets unbearable, ask to change the forum polices and state that Newbie are not welcome. Remember, one do not have to respond to any threads, it will not waste you anytime. Please move on to something that are of more interest to you.
mynameis_nobody asked a second question, after learning that the LM4870 is not good for bridging - why people still built multi LM3886 chip amps in BPA (an example came to mind is Alexw88's BPA300) form if there are so many issues associate with this approach. Bottom line, if he still want to build it, let him be. May be he does not mind learning to build amps by blowing up a few few first. No need to get annoyed because he does not want to "wise up" after someone has said it is not good to do that. As I told my student years ago, I will always give advices and suggestions if someone ask for it, I will not be offended if you decided not to take them.
Personally, I always appreciate comments and advices that I get from this forum. However, at times, I saw some of the comments were made in a condecending manner (to certain degree) which I personally felt that was uncalled for. We are all adults, I think we should show some sensitivity towards each other.
This will be my last message on this thread and I think I have said all that I think is appropriate. I will spend more time building or blowing up amps
Lo_tse
Hello,
I've been the questions, answers and the comment given. As said, some comments went off topic in my opinion.
I would like to give my opinion about "BPA with LM4780 / LM3886", including why or not BPA, difficulties, class D, LM498xx, schematics and some of the issues mentioned in this topic.
The LM3886 excists for quite a long time, and the LM4780 a few years.
The application note from National Semiconductor with the BTL PA & BPA amps was published soon after the release the LM3886.
The LM3886 is a very good sounding amplifier. The last few years it has gained a lot respect and interest in the DIY and hifi world, even in the Audiophile world.
I talk about "good sounding" and not about "good specifications" like THD, SNR etc. etc.
I will come back to that later.
Why BTl, PA or BPA?
With BTL, you will have double the voltage, with PA you have double the current.
With BPA you have both, double voltage and double current.
You have a "good sounding" amplifier of 50W rms, but you would like to have 100W rms of the same goodness? THAT is a good reason for BTL or PA (depending on the impedance of your speakers).
Just double the number of output transistors of raise the voltage of a discrete transistor amp gives the same result right? Yes and no. Regarding power, yes, regarding sound, not totally. Paralleled LM3886s keep their sound quality and specifications.
Just doubling the number of output pairs (can) brings extra work to optimize.
In the period that the application note of National was released, good sounding classs D amps were not that easy to build. Mostly because the needed components were not that good and also difficult to get. Nowadays, all circuitry, except the MOSFETS and LPF, is integrated into one IC. That time, stages needed to be build seperatly, making it also more difficult to build.
LM498xx didn't excist at all that time.
Ofcourse, nowadays there are good, or even better alternatives. One of my currents projects is a amp using the LM49810 with 6 Darlington Output transistors!!!
Same for classs D, take the IRF2092 (DIP version) from IR with just 2 output pair FETs (one FET pair in a TO220 housing) + LPF filter and you have a 500W RMS amp!!
All build on a pertinax experiment board!!!!!
Regarding problems with powerlines, grounding etc. etc.
All kind of topologies can give problem; solid state, class D, chipamps, tube amps. Are some toplogies less sensitive for probs then others? Yes and no.
If you are inexperienced, even the most simply setup can have problems.
But, chances of problems by using a simple topology will be less.
Thermal issues with chipamps in BTL, PA or BPA configuration?
No, staying with specifictations, there's no difference between stereo use, mono use of BTL, PA, BPA.
Modern man or historic man / method?
Just build!!! Simple of complicated, if you wanna blow up parts 3 to 4 times, or be really carefull, it's all up to yourself.
I would say, start simple, go difficult, learn from mistakes, and enjoy!!
Conclusion:
BTL, PA and BPA with chipamps are in some ways out of date.
But that doesn't make them less.
In ways of availability, price and simplicity, they can be or are an advance.
I would say; go build an BTL, PA or BPA using a chipamp like LM3886, or LM4780.
The application note can help you a lot, the different setups are explained in detail and advice to improve and prevent is given.
Got a stereo amp excisiting of 2 PA amps using LM3886 running in my livingroom, sound great.
Like I said: this is my opinion, hope it can be of use making your decision.
I've been the questions, answers and the comment given. As said, some comments went off topic in my opinion.
I would like to give my opinion about "BPA with LM4780 / LM3886", including why or not BPA, difficulties, class D, LM498xx, schematics and some of the issues mentioned in this topic.
The LM3886 excists for quite a long time, and the LM4780 a few years.
The application note from National Semiconductor with the BTL PA & BPA amps was published soon after the release the LM3886.
The LM3886 is a very good sounding amplifier. The last few years it has gained a lot respect and interest in the DIY and hifi world, even in the Audiophile world.
I talk about "good sounding" and not about "good specifications" like THD, SNR etc. etc.
I will come back to that later.
Why BTl, PA or BPA?
With BTL, you will have double the voltage, with PA you have double the current.
With BPA you have both, double voltage and double current.
You have a "good sounding" amplifier of 50W rms, but you would like to have 100W rms of the same goodness? THAT is a good reason for BTL or PA (depending on the impedance of your speakers).
Just double the number of output transistors of raise the voltage of a discrete transistor amp gives the same result right? Yes and no. Regarding power, yes, regarding sound, not totally. Paralleled LM3886s keep their sound quality and specifications.
Just doubling the number of output pairs (can) brings extra work to optimize.
In the period that the application note of National was released, good sounding classs D amps were not that easy to build. Mostly because the needed components were not that good and also difficult to get. Nowadays, all circuitry, except the MOSFETS and LPF, is integrated into one IC. That time, stages needed to be build seperatly, making it also more difficult to build.
LM498xx didn't excist at all that time.
Ofcourse, nowadays there are good, or even better alternatives. One of my currents projects is a amp using the LM49810 with 6 Darlington Output transistors!!!
Same for classs D, take the IRF2092 (DIP version) from IR with just 2 output pair FETs (one FET pair in a TO220 housing) + LPF filter and you have a 500W RMS amp!!
All build on a pertinax experiment board!!!!!
Regarding problems with powerlines, grounding etc. etc.
All kind of topologies can give problem; solid state, class D, chipamps, tube amps. Are some toplogies less sensitive for probs then others? Yes and no.
If you are inexperienced, even the most simply setup can have problems.
But, chances of problems by using a simple topology will be less.
Thermal issues with chipamps in BTL, PA or BPA configuration?
No, staying with specifictations, there's no difference between stereo use, mono use of BTL, PA, BPA.
Modern man or historic man / method?
Just build!!! Simple of complicated, if you wanna blow up parts 3 to 4 times, or be really carefull, it's all up to yourself.
I would say, start simple, go difficult, learn from mistakes, and enjoy!!
Conclusion:
BTL, PA and BPA with chipamps are in some ways out of date.
But that doesn't make them less.
In ways of availability, price and simplicity, they can be or are an advance.
I would say; go build an BTL, PA or BPA using a chipamp like LM3886, or LM4780.
The application note can help you a lot, the different setups are explained in detail and advice to improve and prevent is given.
Got a stereo amp excisiting of 2 PA amps using LM3886 running in my livingroom, sound great.
Like I said: this is my opinion, hope it can be of use making your decision.
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