I've developed a discret voltage stabilisator without a feedback loop. The output impedance I measured is about 0.03 Ohms from DC to 100kHz, slightly rising above that frequency because of the inductivity of the caps. Noise or something else I cannot measure: belows the limits of my measurement equipment because there's much rf around me. The static performace is not worse than a LM317/LM337 but a big improvement dynmically.
The 0.47R resistors in the rectifier lines together with the 100nF capacitors forms a low pass filter witch effectivly filters the recovery noise generated by the HEXFRED diodes. Another CRC filter lowers the ripple from the unregulated DC. Cut off frequency is about 25Hz so the 100 Hz ripple and yet more the harmonics are filtered in a simple but effective way.
Output voltage is about 27V, slightly arising with temperature. Voltage range can modified quite easy, just change the ZDiode and the current limiting resistors for the LEDs. For 15V just use a 16V Zener and decrease the 4k7 resistors to 2k2. The current for the LED should be about 8ma. The 0.47R resistors are 2W types, do not use any metall-oxide resistors here wire wound or metal foil is impotant to use. Other resistors are metal film. Caps are Panasonic FC-Type (150µF) and TPSH (6800µ). 100nF caps are WIMA MKP4. LED are 3mm red ones.
Output voltage :
Va = Vz - 0.6V
Vz is the Zener Voltage
The soundstage is quite good in my preamp, warm and good colored. No harsh sound or something else. And dynamically very good...
The 0.47R resistors in the rectifier lines together with the 100nF capacitors forms a low pass filter witch effectivly filters the recovery noise generated by the HEXFRED diodes. Another CRC filter lowers the ripple from the unregulated DC. Cut off frequency is about 25Hz so the 100 Hz ripple and yet more the harmonics are filtered in a simple but effective way.
Output voltage is about 27V, slightly arising with temperature. Voltage range can modified quite easy, just change the ZDiode and the current limiting resistors for the LEDs. For 15V just use a 16V Zener and decrease the 4k7 resistors to 2k2. The current for the LED should be about 8ma. The 0.47R resistors are 2W types, do not use any metall-oxide resistors here wire wound or metal foil is impotant to use. Other resistors are metal film. Caps are Panasonic FC-Type (150µF) and TPSH (6800µ). 100nF caps are WIMA MKP4. LED are 3mm red ones.
Output voltage :
Va = Vz - 0.6V
Vz is the Zener Voltage
The soundstage is quite good in my preamp, warm and good colored. No harsh sound or something else. And dynamically very good...
An externally hosted image should be here but it was not working when we last tested it.
I simulated the reg with simmetrix.
I run a simulation with 0.2A load, and one with 1A load
then, I calculater R=delta(U)/delta(I)
I found +- 0.1R
Does someone know how to make a current source that vary it's drawn current during the simulation? (to calculate more rapidly the resistance, but also the ripple when the load vary)
bocka, I was looking for a tutorial about discrete voltage regulators. Yours measures very good, can you explain me how it works, why you designed it this way... ?
I run a simulation with 0.2A load, and one with 1A load
then, I calculater R=delta(U)/delta(I)
I found +- 0.1R
Does someone know how to make a current source that vary it's drawn current during the simulation? (to calculate more rapidly the resistance, but also the ripple when the load vary)
bocka, I was looking for a tutorial about discrete voltage regulators. Yours measures very good, can you explain me how it works, why you designed it this way... ?
My simulation shows about 0.015 Ohms (@0.1A), but that was not the design goal...
Some years ago I experimented with shunt regs (no TL431, discrete circuit) very good sounding for a preamp but getting awfully hot. So I tried to make an improved reg, better said stabilisator because I do not feed back anything here.
First it's necessary to get a stable reference. Nothing complex, a zener will do this job very well. I tried to use a resistor to set up the correct current but with some calculations I could see, that the regulation factor is quite bad, only 1/50 refered to the input signal because the intrinsic resistance of the zener is much too high. This will give a bad rejection of the 100Hz ripple. Next i tried to filter out tis voltage with a RC-Filter in the signal path of the zener. Good at high frequencies but bad in the low frequency region. Of course I can use a large cap but I won't. Seems not a good solution.
So let's make the resistor in the series with the zener higher, much higer, because the ratio between this resistnace and the zener resistance is the regulation factor. This can be done with a CCS, a simple diode (LED in this case), transistor and a resistor from emitter to the input voltage. This forms a 5 ma CCS - quick and simple.
To get rid of the zener noise I use a simple RC-Filter, 150µF are laying around 220 Ohms I need to adjust the current through the zener, thats my filter. With some experience I expect that the cut-off frequency should quite low, low enough to filter nealy any noise out of the zener voltage.
Typically anyone would now take a multi emitter follower as current amplifier. Well, in the middle of the 90'th I made amps with CFB output stages because these have a lower output resistance compared to the standard emitter follower. Seems to be good in this stabilisator too. Another advantage is that ther is only one junction between the base and the output so the output voltage is less dependant from temperature changes. It is important to drive the first stage in a CFP - the 2SA1209 and 2SC2911 transistors - with quite a large current, this minimises the output resistance. If any change in the output current has no effect of modulating the collector current of the first transtistor of a CFP then the output voltage would be independant from the output current. In this way the output resistance is... 0!
But this is not the reality. Of course output current changes are reflected to the basis of the second Transistor Ib = 1/ß * Ic. So a transistor with a high ß is needed. The larger the ratio between the current in the first transistor and modulation of this current by output current is, the better this circuit will work.
This is why maybe the differences come from: This is not a 1A regulator, it delivers about 300 ma, above this current ß of the 2SA1930/2SC5171 goes down, at 1A it's only the half @0,1A and this causes a higher output impedance at 1A. Additonally ß is higher at high temeratures and my Transistors get quite hot @3W dissipation power. All in all this results in a higher output impedance of the simulation than that I measure. 3 times higher seems to be right in this way.
Bonne nuit
Some years ago I experimented with shunt regs (no TL431, discrete circuit) very good sounding for a preamp but getting awfully hot. So I tried to make an improved reg, better said stabilisator because I do not feed back anything here.
First it's necessary to get a stable reference. Nothing complex, a zener will do this job very well. I tried to use a resistor to set up the correct current but with some calculations I could see, that the regulation factor is quite bad, only 1/50 refered to the input signal because the intrinsic resistance of the zener is much too high. This will give a bad rejection of the 100Hz ripple. Next i tried to filter out tis voltage with a RC-Filter in the signal path of the zener. Good at high frequencies but bad in the low frequency region. Of course I can use a large cap but I won't. Seems not a good solution.
So let's make the resistor in the series with the zener higher, much higer, because the ratio between this resistnace and the zener resistance is the regulation factor. This can be done with a CCS, a simple diode (LED in this case), transistor and a resistor from emitter to the input voltage. This forms a 5 ma CCS - quick and simple.
To get rid of the zener noise I use a simple RC-Filter, 150µF are laying around 220 Ohms I need to adjust the current through the zener, thats my filter. With some experience I expect that the cut-off frequency should quite low, low enough to filter nealy any noise out of the zener voltage.
Typically anyone would now take a multi emitter follower as current amplifier. Well, in the middle of the 90'th I made amps with CFB output stages because these have a lower output resistance compared to the standard emitter follower. Seems to be good in this stabilisator too. Another advantage is that ther is only one junction between the base and the output so the output voltage is less dependant from temperature changes. It is important to drive the first stage in a CFP - the 2SA1209 and 2SC2911 transistors - with quite a large current, this minimises the output resistance. If any change in the output current has no effect of modulating the collector current of the first transtistor of a CFP then the output voltage would be independant from the output current. In this way the output resistance is... 0!
But this is not the reality. Of course output current changes are reflected to the basis of the second Transistor Ib = 1/ß * Ic. So a transistor with a high ß is needed. The larger the ratio between the current in the first transistor and modulation of this current by output current is, the better this circuit will work.
This is why maybe the differences come from: This is not a 1A regulator, it delivers about 300 ma, above this current ß of the 2SA1930/2SC5171 goes down, at 1A it's only the half @0,1A and this causes a higher output impedance at 1A. Additonally ß is higher at high temeratures and my Transistors get quite hot @3W dissipation power. All in all this results in a higher output impedance of the simulation than that I measure. 3 times higher seems to be right in this way.
Bonne nuit
I understand the voltage reference (led+2sa1209+zpd27+220r+4k7r), that's a classical voltage reference.
OK for the RC filter on the zener, even if a C seems to measure better on my sims.
But why is the 2sc2911's base connected between R and C and not directly at the zener? Is this the CFB? (regulating the output voltage according to the ripple that is filtered on the voltage reference?)
I'm also trying to understand the output stage.
As said before, the 2SC2911 seems to be controlled by the reference-ripple, and outputs current according to this.
This output current creates a voltage drop across the 33R, and this voltage controls the 2SA1930's current.
Am I right?
BTW, do you have some tutorials to teach me the basics about discrete regultaors, so I could be able to design mine myself?
Jocko: do you know how to use simmetrix? I'm still trying to find how to do mathematical operations on the results (even the basic + - * / ). For the momment I can only measure I and U.
So if you know how to measure output Z vs Frequency, please tell me
Thanks
Alex
OK for the RC filter on the zener, even if a C seems to measure better on my sims.
But why is the 2sc2911's base connected between R and C and not directly at the zener? Is this the CFB? (regulating the output voltage according to the ripple that is filtered on the voltage reference?)
I'm also trying to understand the output stage.
As said before, the 2SC2911 seems to be controlled by the reference-ripple, and outputs current according to this.
This output current creates a voltage drop across the 33R, and this voltage controls the 2SA1930's current.
Am I right?
BTW, do you have some tutorials to teach me the basics about discrete regultaors, so I could be able to design mine myself?
Jocko: do you know how to use simmetrix? I'm still trying to find how to do mathematical operations on the results (even the basic + - * / ). For the momment I can only measure I and U.
So if you know how to measure output Z vs Frequency, please tell me
Thanks
Alex
Don't mention sim's to Jocko - he'll get excited
In fact I bet his lightning fast soldering iron hand would have this circuit built faster than most of you can find the models...
The o/p Z you've simulated at present seems to be a DC spec, which is almost irrelevant for audio, try adding an AC current source in Simetrix as a load for the reg, then run an AC sim.
Set the current source to 1mA, then using the add trace function (From Graphs and Data, Add Curve) in Simetrix plot: -
abs(1000*Vout), where Vout is the vector of the voltage at the reg o/p.
You'll get a nice trace showing the output impedance, directly displayed in Ohms!.
Andy.
P.S. if you attach the file here, I'll show you how!
some more measurements
jocko:
Of course I'm always looking at comercial designs and posts it as my own...
Yes I've seen many commercial designs and the more I see the less I like. There are only a few good designs with good ideas. Most build that stuff with a diff input pair, a VAS stage and output stage sometimes with emitter follower, sometimes a CFP pair aor a MOSFET output stage. I think, about 90% are build in that way. Typical OpAmp design.
So it's important to use my own brain. The last years I made some designs together with my local dealer. I mesured and build this circuits, he listened. Takes a lot of time but it was very useful. And never these designs get into commercial products.
Nice to see that I've stolen your ideas
bricolo:
I don't think there are any books available which describes transistor based stabilisators. The circuit I've posted is my own design, of course similar to the basic stabilisator. I'm only using these basic circuits and modify them a bit. Hmm, try to use the Tietze/Schenck Halbleiter Schaltungstechnik. It seems that this book is also available in English, its called Electronic Circuit Design.
This is called DIY. So I post simple circuits. Feel free to build it. Measure as much as you can. Modify the values. And so on. This will feed into success and a lot of acknowledge. I started this way nearly 30 years ago. Of course a EE degree will help (and I have), but it's not nesessary. Basical mathematics are enough. And if something blows up... It doesn't matter there are only penny parts inside.
jan:
Another output Transistors? I don't know. I've tried these because they are laying around. I'm using these ones in my DIY-amps in the driver stage too. For more power a MJL1302 should work. DC output resistance of about 0.03 ohms is enough for any preamp.
And some more measurements:
I've changed the zener for some more common voltages to 2 x 6.2V. With a 220 ohm load and 18.1V input DC voltage I get an output voltage of 11.87V, with an additional 33 ohm load this voltage drops to 11.86V. In my opinion there's no need for further improvement. When I'loaded the regulator with a 6.8 ohm resistor the output voltage fall to about 8V. Too much current for these transisors. BTW a the 2SA1837/2SC4793 and 2SA1538/2SC3952 pairs also work very well.
PS: with a MJL1302 this stabi delivers 2A DC with 50mV voltage drop. And my load resistor is smoking...
PPS: Nelson - the one and only - posted that this is DIY not DIS (do it simulate). Best statement I've heard ever
jocko:
Of course I'm always looking at comercial designs and posts it as my own...
Yes I've seen many commercial designs and the more I see the less I like. There are only a few good designs with good ideas. Most build that stuff with a diff input pair, a VAS stage and output stage sometimes with emitter follower, sometimes a CFP pair aor a MOSFET output stage. I think, about 90% are build in that way. Typical OpAmp design.
So it's important to use my own brain. The last years I made some designs together with my local dealer. I mesured and build this circuits, he listened. Takes a lot of time but it was very useful. And never these designs get into commercial products.
Nice to see that I've stolen your ideas
bricolo:
I don't think there are any books available which describes transistor based stabilisators. The circuit I've posted is my own design, of course similar to the basic stabilisator. I'm only using these basic circuits and modify them a bit. Hmm, try to use the Tietze/Schenck Halbleiter Schaltungstechnik. It seems that this book is also available in English, its called Electronic Circuit Design.
This is called DIY. So I post simple circuits. Feel free to build it. Measure as much as you can. Modify the values. And so on. This will feed into success and a lot of acknowledge. I started this way nearly 30 years ago. Of course a EE degree will help (and I have), but it's not nesessary. Basical mathematics are enough. And if something blows up... It doesn't matter there are only penny parts inside.
jan:
Another output Transistors? I don't know. I've tried these because they are laying around. I'm using these ones in my DIY-amps in the driver stage too. For more power a MJL1302 should work. DC output resistance of about 0.03 ohms is enough for any preamp.
And some more measurements:
I've changed the zener for some more common voltages to 2 x 6.2V. With a 220 ohm load and 18.1V input DC voltage I get an output voltage of 11.87V, with an additional 33 ohm load this voltage drops to 11.86V. In my opinion there's no need for further improvement. When I'loaded the regulator with a 6.8 ohm resistor the output voltage fall to about 8V. Too much current for these transisors. BTW a the 2SA1837/2SC4793 and 2SA1538/2SC3952 pairs also work very well.
PS: with a MJL1302 this stabi delivers 2A DC with 50mV voltage drop. And my load resistor is smoking...
PPS: Nelson - the one and only - posted that this is DIY not DIS (do it simulate). Best statement I've heard ever
About the zener........
Put a diode in series with it. Will add some temperature compensation, and add one diode drop to offset the diode drop due to the folower.
Right......DIS......I hate simulators. Never used one, never will. Only problem, not all guys have tons of test equipment to measure how this stuff works. So, for them, it may provide some insight to how things work.
Just as long as they don't believe everything that it tells you. Yes, 30+ years of doing this will turn you into me in more ways than one.
Jocko
Put a diode in series with it. Will add some temperature compensation, and add one diode drop to offset the diode drop due to the folower.
Right......DIS......I hate simulators. Never used one, never will. Only problem, not all guys have tons of test equipment to measure how this stuff works. So, for them, it may provide some insight to how things work.
Just as long as they don't believe everything that it tells you. Yes, 30+ years of doing this will turn you into me in more ways than one.
Jocko
Bocka
As you may have noticed, in a different thread i desribed a simple shunt regulator. I intended to follow this with several other types of regulators and compare the sound. A variation of your circuit was also on the list so after you posted i built it immediately Used a 2SK170 as a current source for the zeners (3x5v6) as i think it provides better performance plus it's simpler. Outputs are TIP34C.
The sound is significantly better than the 431 based circuit in every respect: freer, better flow, less electronic hash, more natural. I really like it, thanks! I'll probably also try something similar with a MOSFET pass device before i get to Jung/ALW types.
cheers
peter
As you may have noticed, in a different thread i desribed a simple shunt regulator. I intended to follow this with several other types of regulators and compare the sound. A variation of your circuit was also on the list so after you posted i built it immediately
Used a 2SK170 as a current source for the zeners (3x5v6) as i think it provides better performance plus it's simpler. Outputs are TIP34C.The sound is significantly better than the 431 based circuit in every respect: freer, better flow, less electronic hash, more natural. I really like it, thanks! I'll probably also try something similar with a MOSFET pass device before i get to Jung/ALW types.
cheers
peter
bocka said:
Hello -
Unfortunately, we don't have a very precise terminology for different types of feedback in audio amplifiers. However, this circuit uses a CFP, or complementary feedback pair. Of the three transistors, one is a current source for the zener, and the other two form the CFP. Clearly there is feedback around the CFP, and it is in the form of a loop. It is a relatively short loop, as it is only around 2 transistors, but a loop nonetheless.
I'm sure that it sounds far superior to high feedback 3-pin regulators, but I've prefer the sound of regulators made only with emitter-followers.
Best regards,
Charles Hansen
peter:
yes I've noticed your thread also before I started this. Because this is not a shunt regulator I decided to start a new one.
Nice that you like the sound. To my experience this regulator is also getting better with better parts, similar to what's changing in the amp. I'm thinking using a bipolar is better than a FET too. But a FET is a good solution when you have to get gid of the FETs you've selected for a single FET stage which did not match there.
jocko:
Yes a diode will perform some temerature compensation. But when I looked into the datasheet I noticed that I need about 10 diodes co compensate the zener. This is because ot the high voltage of the zener I use. At lower voltages this is a good method of compensating the voltage depencies.
Well, I like simulators, but it's important what do to. And you have to compare the results with the reality. Yet more: One have really to understand the theory (of semicons as well of SPICE in
itself) and the practice. I fully agree with you it's a good tool when haven't tons of test equipment. But the best test equipment anyone (i believe so) has on the left and the right side of his head.
Charles:
Yes, a CFP uses some feedback more precisely I should have written over all feedback. A simple emitter follower is also not free from feedback mechanism, because is called voltage controlled current source and any load performs that feedback mechanism.
I don't want to get a acdemical here, which is the one and only correct description of a topology. I can live with the feedback in the CFB.
2 all:
My intention was to post a circuit which sounds good to my opinion, which is simple and costs only a few bucks. Anyone should be free to test it. If it sounds better than that you've used before use this. If not just throw this CFP stabilisator away, it's not worth it.
This easy stabi is also usable for that guys which haven't much experience with electronics. It also works on my experimentation board without oscillation. It simulates good, it measures good and it sounds good (to my opinion).
I've also tried this with a MOSFET as pass transistor. Does not work well.
I'm very interested of any feedback of the sound of this and other regulators. My experience shows to make a better sound it's important to make the circuits a simple as possible without performance loss. Try to minimise the feedback paths and the amout of feedback. Feedback in itself is not bad, too much kills the sound no feedback results in a indifferent soundstage quite often. Feedback is like salt in the soup: none tastes bad and too much is terrible.
Use good quality components, compare them sonically to theses you've used before. There is no automatism that expensive components are better than the cheap ones, although some of the very expensive parts are the best. For example: Vitrohm 526 Series resistors are cheap and sounds really good. They are capless, no NOS stocks, pretty small and so on. I use them everywhere in the signal path.
Cheers
yes I've noticed your thread also before I started this. Because this is not a shunt regulator I decided to start a new one.
Nice that you like the sound. To my experience this regulator is also getting better with better parts, similar to what's changing in the amp. I'm thinking using a bipolar is better than a FET too. But a FET is a good solution when you have to get gid of the FETs you've selected for a single FET stage which did not match there.
jocko:
Yes a diode will perform some temerature compensation. But when I looked into the datasheet I noticed that I need about 10 diodes co compensate the zener. This is because ot the high voltage of the zener I use. At lower voltages this is a good method of compensating the voltage depencies.
Well, I like simulators, but it's important what do to. And you have to compare the results with the reality. Yet more: One have really to understand the theory (of semicons as well of SPICE in
itself) and the practice. I fully agree with you it's a good tool when haven't tons of test equipment. But the best test equipment anyone (i believe so) has on the left and the right side of his head.
Charles:
Yes, a CFP uses some feedback more precisely I should have written over all feedback. A simple emitter follower is also not free from feedback mechanism, because is called voltage controlled current source and any load performs that feedback mechanism.
I don't want to get a acdemical here, which is the one and only correct description of a topology. I can live with the feedback in the CFB.
2 all:
My intention was to post a circuit which sounds good to my opinion, which is simple and costs only a few bucks. Anyone should be free to test it. If it sounds better than that you've used before use this. If not just throw this CFP stabilisator away, it's not worth it.
This easy stabi is also usable for that guys which haven't much experience with electronics. It also works on my experimentation board without oscillation. It simulates good, it measures good and it sounds good (to my opinion).
I've also tried this with a MOSFET as pass transistor. Does not work well.
I'm very interested of any feedback of the sound of this and other regulators. My experience shows to make a better sound it's important to make the circuits a simple as possible without performance loss. Try to minimise the feedback paths and the amout of feedback. Feedback in itself is not bad, too much kills the sound no feedback results in a indifferent soundstage quite often. Feedback is like salt in the soup: none tastes bad and too much is terrible.
Use good quality components, compare them sonically to theses you've used before. There is no automatism that expensive components are better than the cheap ones, although some of the very expensive parts are the best. For example: Vitrohm 526 Series resistors are cheap and sounds really good. They are capless, no NOS stocks, pretty small and so on. I use them everywhere in the signal path.
Cheers
off topic...
Nice new avatar, Jocko
"Bite My Shiny Metal ***"
Nice new avatar, Jocko
An externally hosted image should be here but it was not working when we last tested it.
"Bite My Shiny Metal ***"
Hi Bocka,
nice circuit! Just a few comments:
- temperature compensation of the Zener: I believe 6V8 Zeners actually have a TC of near zero
- I believe I have read that Zeners of this value also have the lowest dynamic impendance, but I don't know if stacking them will still result in lower impedance than one large-value component
- another improvement of the current source: placing an electrolytic across the LED would shunt its noise and probably give you some more line rejection
- ripple rejection would also improve if you take the reference from the output, as Jocko suggested, but I am not sure about the startup behavior of this circuit
- you like high fT, sustained beta TO-126 transistors, don't you? unfortunately, these are hard to get here (where do you buy yours?), and if you get them at all, there is a high chance they will be dubious second source devices or outright fakes. An adequate replacement in my eyes are devices with an enlarged TO92 case. Reichelt carry both A1145/C2704 and A124/C2632 at reasonable prices, and their current stock are original Toshibas and Matsushitas.
- Isn't CFP stability an issue with either strong load transients or low impedance caps on the output? I played with them in power amps for a while, and they were temperamental, to say the least.
Greetings,
Eric
nice circuit! Just a few comments:
- temperature compensation of the Zener: I believe 6V8 Zeners actually have a TC of near zero
- I believe I have read that Zeners of this value also have the lowest dynamic impendance, but I don't know if stacking them will still result in lower impedance than one large-value component
- another improvement of the current source: placing an electrolytic across the LED would shunt its noise and probably give you some more line rejection
- ripple rejection would also improve if you take the reference from the output, as Jocko suggested, but I am not sure about the startup behavior of this circuit
- you like high fT, sustained beta TO-126 transistors, don't you? unfortunately, these are hard to get here (where do you buy yours?), and if you get them at all, there is a high chance they will be dubious second source devices or outright fakes. An adequate replacement in my eyes are devices with an enlarged TO92 case. Reichelt carry both A1145/C2704 and A124/C2632 at reasonable prices, and their current stock are original Toshibas and Matsushitas.
- Isn't CFP stability an issue with either strong load transients or low impedance caps on the output? I played with them in power amps for a while, and they were temperamental, to say the least.
Greetings,
Eric
Hi capslock,
you can get the Toshibas from Spoerle. Maybe you can get the other transistors from heho elektronik in Germany.
6.8 - 9.1V zeners have the lowest dynamic resistance. In this way the are best. It's very difficult to obtain the same DC performance from a discrete regulator compared to an integrated one. But I can't see any problems when the voltage drifts slightly with the temperature. When using as 5V reg just put a diode in series with a 5.1V zener. Works very well without any temerature drift.
Maybe a cap across the LED helps to reduce some high frequency noise. It has no influence of the ripple rejection because the LED has a very low dynamic impedance (< 10 ohms). Noise filtering is effectivly obtained by the 220R and 150µF RC Filter after the zener.
Low impedance of the output caps is not a problem, because they also have some intrinsic resistance (at least 10 milliohms) and inductivity of about 6-30nH which is enough to make the CFP stable in an extraordonary way. The transistors I've used are at least 10 times faster than any high power bjt in an output stage. Simulation and my tests shows a very good transient resonse probably much better than you expect. The input caps becoming the problem now...
Because the output voltage is smaller than the zener voltage there's no way to feed the zener from the output unless you give the CFP some gain.
Feel free to experiment with the stabi.
you can get the Toshibas from Spoerle. Maybe you can get the other transistors from heho elektronik in Germany.
6.8 - 9.1V zeners have the lowest dynamic resistance. In this way the are best. It's very difficult to obtain the same DC performance from a discrete regulator compared to an integrated one. But I can't see any problems when the voltage drifts slightly with the temperature. When using as 5V reg just put a diode in series with a 5.1V zener. Works very well without any temerature drift.
Maybe a cap across the LED helps to reduce some high frequency noise. It has no influence of the ripple rejection because the LED has a very low dynamic impedance (< 10 ohms). Noise filtering is effectivly obtained by the 220R and 150µF RC Filter after the zener.
Low impedance of the output caps is not a problem, because they also have some intrinsic resistance (at least 10 milliohms) and inductivity of about 6-30nH which is enough to make the CFP stable in an extraordonary way. The transistors I've used are at least 10 times faster than any high power bjt in an output stage. Simulation and my tests shows a very good transient resonse probably much better than you expect. The input caps becoming the problem now...
Because the output voltage is smaller than the zener voltage there's no way to feed the zener from the output unless you give the CFP some gain.
Feel free to experiment with the stabi.
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