More precisely, I have 19 of them.
I was thinking of building a stereo amplifier using 16 of them (8 per channel), in a quasi-complimentary configuration.
However, this would be the first time I've ever attempted to build a fully discrete class AB amplifier.
My goal is to build this using mostly recycled and surplus parts that I have available to me at no cost (thus the MJ11033 transistors).
Are these transistors even worth using for an audio amplifier?
Using 8 transistors, what kind of output power can I expect to achieve into 4 ohms, while remaining well within the transistor's SOA?
Any recommended reads about quasi-complimentary amplifier design?
Thanks.
I was thinking of building a stereo amplifier using 16 of them (8 per channel), in a quasi-complimentary configuration.
However, this would be the first time I've ever attempted to build a fully discrete class AB amplifier.
My goal is to build this using mostly recycled and surplus parts that I have available to me at no cost (thus the MJ11033 transistors).
Are these transistors even worth using for an audio amplifier?
Using 8 transistors, what kind of output power can I expect to achieve into 4 ohms, while remaining well within the transistor's SOA?
Any recommended reads about quasi-complimentary amplifier design?
Thanks.
Look at the SOA diagram in the datasheet and determine your rail voltages for your desired load impedance, 1A at 50V is pretty bad, so i'd say max 2x35V rails and a max power of 100 watts per channel into 4 ohms.
However these are PNP devices, so the output stage is gonna be a bit different from the usuall stuff, a bit like my pchannel amp with with your transistors in place of the fets.
However these are PNP devices, so the output stage is gonna be a bit different from the usuall stuff, a bit like my pchannel amp with with your transistors in place of the fets.
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Hi,
I'd research and build a 2 devices per channel amplifier using a baxandall diode
for output biasing and not particularly shooting for maximum power output.
Then decide if you really need a big amplifier with 6 devices per channel.
Those devices are not cheap, around £10 a pop.
rgds, sreten.
I'd research and build a 2 devices per channel amplifier using a baxandall diode
for output biasing and not particularly shooting for maximum power output.
Then decide if you really need a big amplifier with 6 devices per channel.
Those devices are not cheap, around £10 a pop.
rgds, sreten.
Heres an example based on what you describe: http://i.imgur.com/KDUz1.png
Even that is on the very edge of SOA for your devices. Thats 35V supplies and a 4 ohm load.
Datasheet: http://www.onsemi.com/pub_link/Collateral/MJ11028-D.PDF
The SOA is not that much different than SOA for a MJE15033 driver transistor above 30 volts.
Even that is on the very edge of SOA for your devices. Thats 35V supplies and a 4 ohm load.
Datasheet: http://www.onsemi.com/pub_link/Collateral/MJ11028-D.PDF
The SOA is not that much different than SOA for a MJE15033 driver transistor above 30 volts.
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Hi,
No idea what you are talking about, the above is miles off.
SOA curves for a device aren't the same as an amplifiers
SOA curves, each device is rated at 80V at 1amp, x 8.
rgds, sreten.
It's a good idea to stay away from the second breakdown part of the SOA curve.
But still 8A into 4 ohms is still only around 250 watts, 8A into 8 ohms however would be over 500 watts.
Heres another sim with current(3A per output device pair) vs supply voltage set to right AT SOA, 3A for 50V:
http://i.imgur.com/6gYiu.png
So i rate this a 200W RMS amp into 4 ohms.
Now keep in mind this is merely an EXAMPLE of how it COULD be done, rather than a actual design.
But still 8A into 4 ohms is still only around 250 watts, 8A into 8 ohms however would be over 500 watts.
Heres another sim with current(3A per output device pair) vs supply voltage set to right AT SOA, 3A for 50V:
http://i.imgur.com/6gYiu.png
So i rate this a 200W RMS amp into 4 ohms.
Now keep in mind this is merely an EXAMPLE of how it COULD be done, rather than a actual design.
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Your image links aren't working. It just says "the image you are requesting does not exist or is no longer available".
Anyways, if I'm not mistaking, the highest stress (maximum instantaneous power dissipation) on the output transistors in a class AB amplifier occurs at about half the peak of the audio waveform. Thus, an amplifier with 50V rail voltage for example, at 4 ohms would have a peak current of 12.5 amps, however since the voltage across the transistors at this point is very small, transistors with an SOA of 50V/12.5A is not required, a smaller SOA will suffice. What I'm trying to find is the math calculations for determining maximum instantaneous power dissipation.
Is this what you were trying to show in the images?
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Hi.
FWIW, Tekko has admitted via PM that he's got SOA completely wrong,
but hasn't bothered to come back to you and tell you. Also FWIW the
design he was linking to as an example with 5 pairs of devices he has
now upped to 10 pairs "because he can". Why ? I've no real idea.
For given transistor ratings you can work out the optimum load for power.
I'd expect 8 devices per channel to give most power in a bridged arrangement,
and without bridging around 2 ohms load being needed to get the same power.
I know quasi designs, complementary darlington designs,
but have never seen a quasi darlington design described.
None of this helps really for a first amplifier design. Darlington devices
mean your output stage is going to be triples and they can be a pig
regarding mysteriously oscillating all over the place and expiring.
Given the output stage symmetry issues of class aB I'd be
temped to go Class A JLH /Death of Zen style, no bias
issues, and you don't need complementary devices.
Don't build a high power amplifier as your first build, not a good idea.
rgds, sreten.
FWIW, Tekko has admitted via PM that he's got SOA completely wrong,
but hasn't bothered to come back to you and tell you. Also FWIW the
design he was linking to as an example with 5 pairs of devices he has
now upped to 10 pairs "because he can". Why ? I've no real idea.
For given transistor ratings you can work out the optimum load for power.
I'd expect 8 devices per channel to give most power in a bridged arrangement,
and without bridging around 2 ohms load being needed to get the same power.
I know quasi designs, complementary darlington designs,
but have never seen a quasi darlington design described.
None of this helps really for a first amplifier design. Darlington devices
mean your output stage is going to be triples and they can be a pig
regarding mysteriously oscillating all over the place and expiring.
Given the output stage symmetry issues of class aB I'd be
temped to go Class A JLH /Death of Zen style, no bias
issues, and you don't need complementary devices.
Don't build a high power amplifier as your first build, not a good idea.
rgds, sreten.
You're probably right.
Come to think about it, I've already got a 2x400W amplifier based on Hypex UcD400HG modules.
What would be more useful would be a 7 or 8 channel amplifier, for my future home theater setup. Two output devices per channel would probably be enough. Sound quality would be very important though. However, I don't want a class A design, as that's a waste of power (and I'm paying the power bill).
How would the MJ11033 fair in such an arrangement? Or should I be looking at other transistors instead?
A quasi-complimentary PNP Darlington amp? Whoa, that's swimming in the deep end... I suppose it's been done, but I'd be cautious about using Darlington transistors. I'd ebay them and buy something more useful.
WOW, how the hell did I mess that up? I thought for sure these were NPN but that would be MJ11032.
Yeah, there's no way I'm going attempt a quasi-complementary PNP amplifier.
I'd still like to build that 7 or 8 channel amplifier though. I suppose I'll have to buy some different transistors (preferably TO3 style as I have lots of heatsinks and mounting hardware for TO3s). Got any recommendations on a AB design and transistor selection for approx 100W into 4 ohms with good sound quality and low distortion? I know that sounds like a lot of power for just a home theater amp but I like to have a lot of headroom and my intention is to drive full-range speakers not only for movies but also for music. I like to keep my options open, so if the amplifier is a bit overkill, that's ok.
Yeah, there's no way I'm going attempt a quasi-complementary PNP amplifier.
I'd still like to build that 7 or 8 channel amplifier though. I suppose I'll have to buy some different transistors (preferably TO3 style as I have lots of heatsinks and mounting hardware for TO3s). Got any recommendations on a AB design and transistor selection for approx 100W into 4 ohms with good sound quality and low distortion? I know that sounds like a lot of power for just a home theater amp but I like to have a lot of headroom and my intention is to drive full-range speakers not only for movies but also for music. I like to keep my options open, so if the amplifier is a bit overkill, that's ok.
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any circuit using npn's in the output will work, just make the required rearrangement...
you can look at the lm4702 drivers also....
Hi,
Eloquently put, I assumed the difficulties were self evident and taken on board.
rgds, sreten.
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