Well the AD825 will run with even more standing current if you use a FET.
Have you considered an off-the-shelf 40A switch mode power supply?
I believe it is possible to make such a power supply, even if it is very atypical.
My first doubt was if your interest is how to perform the simulation in LTSpice rather than getting such a power supply made in praxis. I am not familiar with LTSpice but know power supplies quite well.
For special needs, like for the specifications you mention, I always start with the power part in order to understand what will be required. Unless you have a very particular load characteristic, you normally find a way to stabilize the loop.
A stupid question: do you really need 40A from 15V? That corresponds to 0.4Ohm loading! For audio this is very unusual, even for pure class A. 40Amp will cost you (a lot) in decoupling capacitors, series-transistors and in particular for cooling where forced cooling may be needed. Even your connectors and bus-bars (no PCB tracks) will not be trivial.
I once had to use more than 10 power FETs in parallel and water-cooling.
You write: "...I want super regulator level performance". 40Amp with top-performance doesn't make it easier. But, you may have to compromise here - designing top-performance for a 1 Amp regulator is very different from for a high current regulator.
You can start with the positive part (+15V) and make that work before you continue with the negative part.
Are you ready to start big work?
My first doubt was if your interest is how to perform the simulation in LTSpice rather than getting such a power supply made in praxis. I am not familiar with LTSpice but know power supplies quite well.
For special needs, like for the specifications you mention, I always start with the power part in order to understand what will be required. Unless you have a very particular load characteristic, you normally find a way to stabilize the loop.
A stupid question: do you really need 40A from 15V? That corresponds to 0.4Ohm loading! For audio this is very unusual, even for pure class A. 40Amp will cost you (a lot) in decoupling capacitors, series-transistors and in particular for cooling where forced cooling may be needed. Even your connectors and bus-bars (no PCB tracks) will not be trivial.
I once had to use more than 10 power FETs in parallel and water-cooling.
You write: "...I want super regulator level performance". 40Amp with top-performance doesn't make it easier. But, you may have to compromise here - designing top-performance for a 1 Amp regulator is very different from for a high current regulator.
You can start with the positive part (+15V) and make that work before you continue with the negative part.
Are you ready to start big work?
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It's my understanding that off the shelve SMPS are too noisy for audio use. I also read that regulated SMPS are exceptionally hard to design so that takes DIY off the table for me.
The power supply will be feeding a class A transconductance amplifier. I don't know if I will need 40A yet because I am still working out the details of the load but I think 40A will be the upper threshhold of what I may end up requiring so I am setting 40A as a design parameter goal. I could always scale down from there. If I had it my way I would have the output @ 5v, not 15v. I'm still figuring out the details of that.
Here is the thread I made about the amplifier I'm building.
Direct drive ribbon amp power requirement?
I've posted a schematic or two and I've since altered the design a bit but the general principle is the same.
Whatever it takes to achieve the results I want.
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Class A means a rather steady consumption. Fine, no need for a very fast loop. Top-performance is then noise.
I gladly use Darlingtons but only until about one third of their ratings. A power transistor run near its limits is no longer a good performer. Luckily Darlingtons are cheap and you get a much better thermal coupling to the heat-sink by dividing the losses between many.
If you find a slow-running (large diameter) fan unacceptable, water-cooling may be an option.
I assume you intend to use a transformer at the input (custom made). A decoupling capacitor of 50000uf sags 1Volt in 10ms with a discharge current of 5Amp. Thus, the voltage ripple with 40Amp and 50000uf would be 8V! You will need at least 100000uF buffer on each voltage, and a combination that can handle large ripple currents. You can see, it is going to be heavy duty.
Let us hear when you know the exact specs.
I gladly use Darlingtons but only until about one third of their ratings. A power transistor run near its limits is no longer a good performer. Luckily Darlingtons are cheap and you get a much better thermal coupling to the heat-sink by dividing the losses between many.
If you find a slow-running (large diameter) fan unacceptable, water-cooling may be an option.
I assume you intend to use a transformer at the input (custom made). A decoupling capacitor of 50000uf sags 1Volt in 10ms with a discharge current of 5Amp. Thus, the voltage ripple with 40Amp and 50000uf would be 8V! You will need at least 100000uF buffer on each voltage, and a combination that can handle large ripple currents. You can see, it is going to be heavy duty.
Let us hear when you know the exact specs.
Because I'm driving a transconductance amplifier the current swings will be half of the idle. If I draw 40A idle then the AC current draw will be 20A p-p. Not quite steady at all.
I don't see the need. Lots of high current transformers on mouser.
Yeah, more reason I'm hoping to get the output voltage low as possible. Supercaps would be nice here.
You seem to be operating on the basis of Purity without Purpose.
Anything that deviates from your misplaced path is rejected out of hand without any meaningful reason other than those that suggest you do not really know what want, cannot implement what you want and...
"Meh! Must be Class A and that does not sound like what I want because it is not the right shade of Blue and anyway I do not care because Duck Billed Platypus."
Looking at your other thread at what seems to be your 'Transconductance Amplifier', and in this thread at your other circuits, suggests you do not know how to use LTSpice outside of Etcha-Sketch mode and otherwise just slap down random 10Meg and 100uF capacitors arbitrarily connected to other stuff in an indecipherable way.
At the risk of getting slapped because I should be wary about current sharing... and other stuff. Here you go. 15V @ 40A with about 40W of dissipation. Did I mention you will need to feed it with a Synchronous Buck regulator?
Vishay - MOSFETs - IRF540, SiHF540 - Power MOSFET
https://www.vishay.com/docs/90183/sihf540.lib
Save the second link via a text editor to your LTSpice lib/sub directory as IRF540.lib
Oh 1)... Don't bother trying to do the same for a negative rail. Drive your ribbon with a bridge amplifier.
Oh 2)... Don't have kittens about the Synchronous Buck. After all you are quite happy laying out the circuit board for a 15V @ 40A regulator with a bandwidth of 2MHz.
For a particular level of 'not going to happen' I am sure they would.
...
Anything that deviates from your misplaced path is rejected out of hand without any meaningful reason other than those that suggest you do not really know what want, cannot implement what you want and...
"Meh! Must be Class A and that does not sound like what I want because it is not the right shade of Blue and anyway I do not care because Duck Billed Platypus."
Looking at your other thread at what seems to be your 'Transconductance Amplifier', and in this thread at your other circuits, suggests you do not know how to use LTSpice outside of Etcha-Sketch mode and otherwise just slap down random 10Meg and 100uF capacitors arbitrarily connected to other stuff in an indecipherable way.
At the risk of getting slapped because I should be wary about current sharing... and other stuff. Here you go. 15V @ 40A with about 40W of dissipation. Did I mention you will need to feed it with a Synchronous Buck regulator?
Vishay - MOSFETs - IRF540, SiHF540 - Power MOSFET
https://www.vishay.com/docs/90183/sihf540.lib
Save the second link via a text editor to your LTSpice lib/sub directory as IRF540.lib
Oh 1)... Don't bother trying to do the same for a negative rail. Drive your ribbon with a bridge amplifier.
Oh 2)... Don't have kittens about the Synchronous Buck. After all you are quite happy laying out the circuit board for a 15V @ 40A regulator with a bandwidth of 2MHz.
For a particular level of 'not going to happen' I am sure they would.
...
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Seeing all the threads you started you are clearly aiming for a corner position and the goal is obviously set high. Insights are often found in the extremes but solutions seldom find their homes there. Anyways, I'm curious on how it will all end so please keep posting your endeavours and findings.
Sincerely - Good Luck!!
//
Sincerely - Good Luck!!
//
I'd say more like purity in order to avoid the possibility of end result imperfections. Is it overkill? Probably. Will I hear a difference between my overkill transconductance amplifier and hot power supply and a more typical solution? Probably not. Still, I'd rather not have to wonder. Besides it's something new and different, this is DIY after all.
I have a lot to improve on but wouldn't quite say I'm that bad
I'm just spice lazy.I was originally going to do that but since it's a current drive amp I decided there was little point. But now that I'm getting into high current territory I see your point...
No faith...
In any case, thanks for the file I'll look it over
.At least someone's cheering me on.. Thanks
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