Here is a nifty way to snub rails. Maybe you could call it the Ksnubber or Kdamper. Maybe I like the letter K too much.
Take a schottkey diode, say the 2N5819. Low Cj but reasonable Ifmax. Give it a variable bias to achieve a low snubbing resistance. 22mA-100mA covers a range of .5R-2R. This solves the problem of finding non-inductive resistors in this range and provides a single knob adjustment.
This could also act as a "resonance scattering snubber" or whatever, based on what I wrote here:
http://www.diyaudio.com/forums/solid-state/193923-simple-symetrical-amplifier-65.html#post3184349
Although I am not actually sure if ordinary resonances could push the diode far enough to cause this.
Take a schottkey diode, say the 2N5819. Low Cj but reasonable Ifmax. Give it a variable bias to achieve a low snubbing resistance. 22mA-100mA covers a range of .5R-2R. This solves the problem of finding non-inductive resistors in this range and provides a single knob adjustment.
This could also act as a "resonance scattering snubber" or whatever, based on what I wrote here:
http://www.diyaudio.com/forums/solid-state/193923-simple-symetrical-amplifier-65.html#post3184349
Although I am not actually sure if ordinary resonances could push the diode far enough to cause this.
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pretty advanced snubber
the diode
I have noticed a few fixed 78XX regs mounted with one(or more) diode 'shunted' in the ground leg
whats it doing ?
and what happens if its a LED instead ?
the diode
I have noticed a few fixed 78XX regs mounted with one(or more) diode 'shunted' in the ground leg
whats it doing ?
and what happens if its a LED instead ?
After some staring at my ESS dac's regulator boards, this is what the circuits, more or less, seem to look like.
The AVCC is a dual output regulator, where the second regulator is identical but sharing the same reference - the positive inputs of the two opamps are tied together. Resistor values depend on the led references and need to be adjusted for precise 1.2v and 3.3v outputs. Current source is quite basic as there is only 5.25v of input voltage.
The topology is otherwise very similar to some of the circuits discussed in this thread.
The AVCC is a dual output regulator, where the second regulator is identical but sharing the same reference - the positive inputs of the two opamps are tied together. Resistor values depend on the led references and need to be adjusted for precise 1.2v and 3.3v outputs. Current source is quite basic as there is only 5.25v of input voltage.
The topology is otherwise very similar to some of the circuits discussed in this thread.
please, I won't 'disturb' further, but I found the answer
a diode to ground is a common battery charger trick....to raise voltage 1.5V above ground, and gives 13.5V out from the 12V reg
Hello Tinitus. Here is a highly relevant link from the website Martin Clark linked to earlier:
Using 3-pin regulators off-piste: part 2
This is why I get the feeling conventional chip regs are old technology and can use some improvement. There are discrete SMD regs with 3 pins available for drop-in replacement of chip regs and there are a number of different ones to choose from. However from what little information there is about their design and performance, I get the feeling many of them are inferior in some ways to the chipregs! I think it is about time for an open-design SMD chipreg drop-in upgrade.
At the same time it is perhaps easier, more expedient and less expensive to do nested regs as done on the same website (that's a good one!). And that is a simple solution many could upgrade to.
Using 3-pin regulators off-piste: part 2
This is why I get the feeling conventional chip regs are old technology and can use some improvement. There are discrete SMD regs with 3 pins available for drop-in replacement of chip regs and there are a number of different ones to choose from. However from what little information there is about their design and performance, I get the feeling many of them are inferior in some ways to the chipregs! I think it is about time for an open-design SMD chipreg drop-in upgrade.
At the same time it is perhaps easier, more expedient and less expensive to do nested regs as done on the same website (that's a good one!). And that is a simple solution many could upgrade to.
scary
but something I dont understand
how he can evaluate a crudely assembled reg ?
I haven't bought anything yet and will gladly change it if theres something better and simple
ehh, the gyrator or multiplier is only dumping voltage, and not a regulator, right ?
my trafo old C-core is perfectly stable, and oversized for the project
so that would be fine with me, actually
ok, throw it at me, and will try to catch 😀
but something I dont understand
how he can evaluate a crudely assembled reg ?
I haven't bought anything yet and will gladly change it if theres something better and simple
ehh, the gyrator or multiplier is only dumping voltage, and not a regulator, right ?
my trafo old C-core is perfectly stable, and oversized for the project
so that would be fine with me, actually
ok, throw it at me, and will try to catch 😀
That's not a crude assembly. Not compact, but it is a legitimate ground plane construction AFAIK.
Your input isolation would be greatly improved with a simple C-multiplier before the regs. It's not a regulator, but it's much faster hence more RF rejection. If your current draw is below 30mA I would use the BC5xx. The BC3x7 are better and work at higher currents. For higher currents I would use a K-multiplier like I linked to earlier. A Darlington or CFP C-multiplier is not a regulator but can be made unresponsive to rail sag, which makes it still a good deal.
Your input isolation would be greatly improved with a simple C-multiplier before the regs. It's not a regulator, but it's much faster hence more RF rejection. If your current draw is below 30mA I would use the BC5xx. The BC3x7 are better and work at higher currents. For higher currents I would use a K-multiplier like I linked to earlier. A Darlington or CFP C-multiplier is not a regulator but can be made unresponsive to rail sag, which makes it still a good deal.
will be glad to forget the IC regs
a bunch of supply caps is all it takes to make me happy
I only have to lower voltage, thats all
a bunch of supply caps is all it takes to make me happy
I only have to lower voltage, thats all
And here again is the link to the webpage I wrote about it, in case anyone missed it the first time... I have troubleshooting and other sections, plenty of information that won't be found in the thread.
http://www.fidelityforce.com/keantoken/content/Kmultiplier.html
http://www.fidelityforce.com/keantoken/content/Kmultiplier.html
got a good sleep, new day 😀
please give me a pointer which one I should look at, the 'cleaned up' last version from the thread or one on your website
but maybe its the same just drawn slightly different
need to have another closer look at it
Im fresh again, almost
but Im unsure of the voltages, and adjustments
will the symmetric handle the +/-30 down to +/-12V
and to take the next, could a positive CFP only handle +36V down to +30V
I will try and study it closer now
please give me a pointer which one I should look at, the 'cleaned up' last version from the thread or one on your website
but maybe its the same just drawn slightly different
need to have another closer look at it
Im fresh again, almost
but Im unsure of the voltages, and adjustments
will the symmetric handle the +/-30 down to +/-12V
and to take the next, could a positive CFP only handle +36V down to +30V
I will try and study it closer now
Bears repeating -- in the regulator shootout, noise was least important among the 3 factors considered.
Use the schematic in the webpage. It is much newer, and less likely to fail. Read the Design Considerations section to understand which changes you need to make for your specific application. If you need something explained, ask me.
I like how you drew the schematic Tinitus! Maybe I will draw it that way in the future, it looks less messy.
I would still put snubbers on the input and output, and this applies for any regulator really.
Jackinnj, I wouldn't know because I haven't been able to get my hands on anything past volume 0. I'm so far behind I don't think I'll ever catch up. And it's ironic because I won Jan's quiz to get free boards from the DIYAudio store and still haven't chosen the boards I want.
I would be grateful if you could tell a bit about the results to sort of guide me towards how I should design my circuits.
Still, I have suspected that the focus on low thermal noise for a regulator at the expense of other specs was a bit misguided.
I like how you drew the schematic Tinitus! Maybe I will draw it that way in the future, it looks less messy.
I would still put snubbers on the input and output, and this applies for any regulator really.
Jackinnj, I wouldn't know because I haven't been able to get my hands on anything past volume 0. I'm so far behind I don't think I'll ever catch up. And it's ironic because I won Jan's quiz to get free boards from the DIYAudio store and still haven't chosen the boards I want.
I would be grateful if you could tell a bit about the results to sort of guide me towards how I should design my circuits.
Still, I have suspected that the focus on low thermal noise for a regulator at the expense of other specs was a bit misguided.