8 transistors per channel is overkill. 4 is enough for H bridge unless you're really looking for high power. Using the Fairchild MOSFETs I mentioned earlier, using a B+ of 150v and a RMS current of 20A (into a 4 ohm load) means it is good for 1600w per channel! Not bad for just under $6 of transistors. (Just be prepared to burn out a lot during design, so have plenty of spares.)
And point to point becomes too messy for anything even remotely complex.
I'm behind you on this , give it a shot, after all it's only 20 mins , to see if we could make a true voltage source amplfier ...
It had better be a pretty good output stage to translate over the sound characteristics of the chip itself. Things usually go all to hell in the output stage. Transistors would need to be tightly matched to compete with same die transistors as in a chip, you'd also loose much of the built in protection of the chip itself where as the chip may shut down to protect things but the output stage may not. I'd still be interested in this sort of thing but I don't even have time to build the second amp and bridge them until early December...
Mark
Mark
Some of that was greek to me, but I got the overcurrent protection part and that the matching won't be important (for indoor use).
For outdoor use matching is important in order to reduce reliance on output resistor, for a harder, stronger drive. But, a harder, stronger (harsher) drive is more-than unnecessary indoors (at point blank range) and we can just increase the output resistance slightly, instead of matching. This also applies to your PA150's--Use a tighter match on those LM3886's if the rig is for outdoor use or if the venue is quite large.
I'm behind you on this , give it a shot, after all it's only 20 mins , to see if we could make a true voltage source amplifier ...
Um. . .per channel, not counting enclosure fitments. And, the first time though, I'm going to need help.
Can't do it tonight. I've either got to make a class-D or a hyper-efficient linear, run on 14.6 volts to facilitate a 3-way active system, with only one stubborn woofer. And, this is due before 10 a.m. tomorrow. There is also a 3a limit on amperage along with big expectations on performance and a very high heat environment that also involves occasional splashes of water. Egads!
I think some imbalance in the low and high side MOSFETs is acceptable. The two sides of the H bridge don't need much matching anyways. Just use the same part number MOSFETs.
Whether it's indoor or outdoor does not matter.
I meant that there's a difference between "cohesive at long distance" or "laid back for indoors".
The sound you need to cover great distance may not be as pleasant at point blank range.
This relates to the output resistors--a closer match allows less resistance and the speaker will carry signal a longer distance (a bit harsher too).
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MOSFETs do not need any output resistors. They will self-balance. You don't even need to parallel them until you get to extremely high power levels. (The MOSFETs I mentioned earlier are good for some 1600w, and they're certainly not the biggest ones available.) It might be possible to use high speed IGBTs, which handle even higher power.
Check out Inverter modules for some of the largest (and most beautiful!) IGBTs you will probably ever see. Note that the ones that are paired up are handling a total of up to 50kW! (I wonder what Toyota does with the defective ones... They would make great necklaces...)
Check out Inverter modules for some of the largest (and most beautiful!) IGBTs you will probably ever see. Note that the ones that are paired up are handling a total of up to 50kW! (I wonder what Toyota does with the defective ones... They would make great necklaces...)
which chipamp are you recommending that has these MOSFETs or IGBTs integrated into them?
I have not read the entire thread, but if you are discussing how to get chip-amp "simplicity" at higher powers (more than +/-40V rails and +/-10A output), class D is the way to go.
What star882 is trying to explain is that with two TO-220 output MOSFET, a driver IC, a comparator IC, the LC output filter and some more parts you can get close to 1KW at 4 ohm (+/-90V rails). No bulky heatsinks, no heavy power supplies (class AB wastes more power than what it delivers to the speakers), no dozens of expensive output devices and the chore of mounting them.
Incidentally, all my amplifiers are either chip amps or class D. I don't keep any of my class AB discrete prototypes, they use too many parts for what they achieve.
What star882 is trying to explain is that with two TO-220 output MOSFET, a driver IC, a comparator IC, the LC output filter and some more parts you can get close to 1KW at 4 ohm (+/-90V rails). No bulky heatsinks, no heavy power supplies (class AB wastes more power than what it delivers to the speakers), no dozens of expensive output devices and the chore of mounting them.
Incidentally, all my amplifiers are either chip amps or class D. I don't keep any of my class AB discrete prototypes, they use too many parts for what they achieve.
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Above 100V and 10A you can't expect the output devices t come in the same package as the small signal stuff, the fabrication processes are quite different. Also, PCB layout and thermal considerations and package parasitics prevent everything to be in the same chip.
For example take a look at IRS2092:
www.irf.com/product-info/datasheets/data/irs2092.pdf
It contains a simple class D modulator, rudimentary current limiting and gate drivers, it only requires an output stage and a LC filter. It can be considered a high power class D chip amp.
That happens at three configurations.
1), like the gainclone, large caps locally, is a bit like driving the car in one gear too low. For the amp, its a way to level the frequency response--technically an inappropriate method, but it does work. There are other ways to change the speed: HDOA - High Dynamics Op Amp
2), the "fireball" amp (not a gainclone type) operates as a dynamics expander for a more-live presentation--Class D will emit a great deal of green smoke instead (unless the voltage is decreased).
3), over-reliance on noise filtering at the amplifier board instead of using noise filtering at the power supply--the great tolerances of Class AB are often exploited to decrease power circuit expense at the cost of efficiency, wheras, the smaller tolerances of Class D usually force one to do a good job on the power circuit design.
I really do like the sound of Class D. The chopped signal reminds me of Blackgate or the classic Red Cerafine+Polyester combo. This can make a lovely clarity. Unfortunately, the supersonic pilot tone of Class D is audible to me. After many hours of exposure, I get stuffy ears and it takes about 3 days to recover. One day, I'll explore using Class D in an active 3-way system for bass and midrange.
Its possible for the efficiency of Class AB to match Class D at scales up to 70 watts (run the same little TO220 size heatsink nearly cold), but I don't have personal experience with comparisons beyond that point, so I couldn't tell you about efficiencies on a larger scale amplifier.
I design class D amplifiers for a living, now I'm working in a commercial product with nearly 400 parts in it, smaller than a shoe box and capable of over 4kw on 2 ohms, and I admit that I fail completely to understand what you are talking about.
So sorry for disturbing if you were talking about metaphysics, I thought it was about electronics and acoustics (science)
So sorry for disturbing if you were talking about metaphysics, I thought it was about electronics and acoustics (science)
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I design class D amplifiers for a living, now I'm working in a commercial product with nearly 400 parts in it, smaller than a shoe box and capable of over 4kw on 2 ohms, and I admit that I fail completely to understand what you are talking about.
So sorry for disturbing if you were talking about metaphysics, I thought it was about electronics and acoustics (science)
Do you also include audiology? If so, that would be impressively efficient.
Please lokk here!
Look here
http://www.diyaudio.com/forums/class-d/152980-class-d-audio-who-these-guys-11.html
Look here
http://www.diyaudio.com/forums/class-d/152980-class-d-audio-who-these-guys-11.html
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