to bobellis
sir i have made this circuit the basis circuit is all the same except o/p devices r 3055&2955 it seems to work fine even wth the the lowest bias setting although i dont have a oscilloscope to check Cross over dis...... still most probably u r right as u have much more experience than me
regards
sekhar
sir i have made this circuit the basis circuit is all the same except o/p devices r 3055&2955 it seems to work fine even wth the the lowest bias setting although i dont have a oscilloscope to check Cross over dis...... still most probably u r right as u have much more experience than me
regards
sekhar
You're really in dangerous territory trying to design a kilowatt amp as a first project. Have you designed/built other amps? There are lots of things that can go wrong and cause expensive and dangerous mishaps. Do you have an oscilloscope to check stability of your build? Do you know about laying out a PCB to minimize oscillation problems? Blowing up a 3 output pair amp is annoying, but losing 28 or 30 devices at once really stings.
You need to do a bit of reading on protection circuits. It sounds like you have Sloane's book, that should be a good start. The nutshell version is as soon as the protection transistor gets .6-.7V on its base it turns on, cutting drive to the output driver.
Event Horizon's suggestion of 4KW worth of output devices seems sound, especially since you are looking to drive 2R loads to a KW. 14 pairs of your chosen output devices should work, although they will need massive drive current.
Sloane probably also has a section on thermal runaway, read up. Short version: As temperature increases BJTs need less base voltage to turn them on. With fixed bias voltage, the devices get warmer and conduct more, making them warmer and conduct more... So if you don't have a way of compensating by reducing the bias voltage as it gets warmer, POOF! The magic smoke comes out of your output stage. There are several ways to do this, Mounting your Vbe multiplier transistor on the output (or in your case driver) transistor or heat sink is one method. Each method has its drawbacks, it is an engineering trade off.
Be prepared to spend considerably more developing this amp than buying a decent used PA amp.
We posted at the same time. Perhaps your early amp wasn't driven too hard - most home amps aren't except for subwoofer duty. It takes a bit of heat to get to thermal runaway started. It also looks like the Miller cap is large - helps prevent oscillation at the expense of HF response. Your 3055s are slower than the outputs you want to use this time - meaning more potential problems. While it is tempting to cut and paste building blocks, you should be aware of the potential issues when shooting for 1KW output. You are a little safer at "only" 80V rails than you would be if you were trying for 1KW into 8R.
I don't have as much experience as a lot of guys here, but I've hung out here long enough to pick up a few things.
You need to do a bit of reading on protection circuits. It sounds like you have Sloane's book, that should be a good start. The nutshell version is as soon as the protection transistor gets .6-.7V on its base it turns on, cutting drive to the output driver.
Event Horizon's suggestion of 4KW worth of output devices seems sound, especially since you are looking to drive 2R loads to a KW. 14 pairs of your chosen output devices should work, although they will need massive drive current.
Sloane probably also has a section on thermal runaway, read up. Short version: As temperature increases BJTs need less base voltage to turn them on. With fixed bias voltage, the devices get warmer and conduct more, making them warmer and conduct more... So if you don't have a way of compensating by reducing the bias voltage as it gets warmer, POOF! The magic smoke comes out of your output stage. There are several ways to do this, Mounting your Vbe multiplier transistor on the output (or in your case driver) transistor or heat sink is one method. Each method has its drawbacks, it is an engineering trade off.
Be prepared to spend considerably more developing this amp than buying a decent used PA amp.
We posted at the same time. Perhaps your early amp wasn't driven too hard - most home amps aren't except for subwoofer duty. It takes a bit of heat to get to thermal runaway started. It also looks like the Miller cap is large - helps prevent oscillation at the expense of HF response. Your 3055s are slower than the outputs you want to use this time - meaning more potential problems. While it is tempting to cut and paste building blocks, you should be aware of the potential issues when shooting for 1KW output. You are a little safer at "only" 80V rails than you would be if you were trying for 1KW into 8R.
I don't have as much experience as a lot of guys here, but I've hung out here long enough to pick up a few things.
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to bobellis
sir u r very right about a 1KW amp as my first project as a very dangerous issue ..... I have enough knowledge about PCB desiging u can have a look at the thread "amp for everybody"
I have given the pcb layout for the small version of this amp using 3055&2955 the amp seems to work fine even under 4E load .
I actually want a subwoofer amp within 600W to 850W rms may be 1KW was a over kill kindly guide me through the design for such an amp.
regards
sekhar
sir u r very right about a 1KW amp as my first project as a very dangerous issue ..... I have enough knowledge about PCB desiging u can have a look at the thread "amp for everybody"
I have given the pcb layout for the small version of this amp using 3055&2955 the amp seems to work fine even under 4E load .
I actually want a subwoofer amp within 600W to 850W rms may be 1KW was a over kill kindly guide me through the design for such an amp.
regards
sekhar
SEKHAR,
stop. Think about what you know and what you still have to learn.
Find a cheap small project, eg. a 10W chipamp and learn how to put that together.
Learn what each component does and how altering the value of each of the components alters the way the amplifier performs.
Understand why the simple stripped down chipamp relies on a lot of luck to perform correctly, whereas a fully componented chipamp is virtually guaranteed to perform to specification.
When you understand the chipamp and it's twenty or so components, then you are ready to move on to a small cheap discrete component project. Maybe an active pre-amp with a little gain and a volume control. Joining this to the chipamp will teach you a lot, a LOT!
When you have done your research/homework, come back to this amplifier design project.
stop. Think about what you know and what you still have to learn.
Find a cheap small project, eg. a 10W chipamp and learn how to put that together.
Learn what each component does and how altering the value of each of the components alters the way the amplifier performs.
Understand why the simple stripped down chipamp relies on a lot of luck to perform correctly, whereas a fully componented chipamp is virtually guaranteed to perform to specification.
When you understand the chipamp and it's twenty or so components, then you are ready to move on to a small cheap discrete component project. Maybe an active pre-amp with a little gain and a volume control. Joining this to the chipamp will teach you a lot, a LOT!
When you have done your research/homework, come back to this amplifier design project.
taking it in steps
Hey Sekhar -- Andrew does have a good point -- it is best to take this in steps - in your last thread, which you seem to have abandoned and brought it in here, with respect, you talked about doing an amplifier -- then it exploded into bridge mode complicating the design.
I started with a single stage valve amp 27 years ago which was happier to oscillate at 2Mhz rather than amplify audio.
Then I did a state-of-the-art headphone amplifier - first one was single rail - 2nd was dual rail.
Than an old Sincalir amplifier kit (*cough which I blew up accidentally* cough)
take your journey in smaller steps -- you'll get a lot more enjoyment out of it that way.
Hey Sekhar -- Andrew does have a good point -- it is best to take this in steps - in your last thread, which you seem to have abandoned and brought it in here, with respect, you talked about doing an amplifier -- then it exploded into bridge mode complicating the design.
I started with a single stage valve amp 27 years ago which was happier to oscillate at 2Mhz rather than amplify audio.
Then I did a state-of-the-art headphone amplifier - first one was single rail - 2nd was dual rail.
Than an old Sincalir amplifier kit (*cough which I blew up accidentally* cough)
take your journey in smaller steps -- you'll get a lot more enjoyment out of it that way.
To phaselockloopy
I did nt abandoned the thread Amp for everybody i got enough valuable data from all the highly respected members and truely speaking I made the amp in the design according to the modification and is very pleased with the output of amp it happlily drives 150W in 4E...
I have taken up a sub amp as my second project it may seem i am going a bit fast but believe me i devote my entire time in doing this stuff may be even 20hrs a day ....... Plz bear with me I want to learn and apply it quickly cause i want to learn more & more every day who other than u people can help me ................
regards
sekhar
I did nt abandoned the thread Amp for everybody i got enough valuable data from all the highly respected members and truely speaking I made the amp in the design according to the modification and is very pleased with the output of amp it happlily drives 150W in 4E...
I have taken up a sub amp as my second project it may seem i am going a bit fast but believe me i devote my entire time in doing this stuff may be even 20hrs a day ....... Plz bear with me I want to learn and apply it quickly cause i want to learn more & more every day who other than u people can help me ................
regards
sekhar
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