And as Martin Clark will probably point out again, you can make a tracking pre-regulator to improve a 7805 or super reg etc.
Just like this one! Although tbh, if was going to that much trouble I'd build something a little better!!
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Yeah, but that's half the point: for less than 1euro you can approach 100dB ripple rejection if you want.
Replace R2 with a red LED and C2 with 1uF+2R7 in series (or 100nF +10ohms if you like) and it'll perform even better noise-wise. Not the ultimate, no: but dirty-cheap, and very effective.
Replace R2 with a red LED and C2 with 1uF+2R7 in series (or 100nF +10ohms if you like) and it'll perform even better noise-wise. Not the ultimate, no: but dirty-cheap, and very effective.
Hi Martin, Do you have a photo of "one you made earlier"?
Not certain about the position of C2 refered to above. Why does the LED and small cap/resistor inprove on the ripple rejection?
Not certain about the position of C2 refered to above. Why does the LED and small cap/resistor inprove on the ripple rejection?
cough, like this:
It's the tracking pre-arrangement, not the minor changes that makes for good performance. Look at how it's arranged: the first 317 ensures there is *no* ripple voltage appearing across the second, in fact the second reg sees a constant voltage difference across it regardles of whayt the load does. So the second reg applies all its gain to load regulation, while the first deals only with the ripple/noise on the input. This is a subtley, but it audibly improves on just using two regs in series.
So - my suggestions are using an LED voltage drop to set c.2.8-3v across reg2, which absolutely minimises noise from the first reg (because the led at 5-10ma has a dynamic impedance of only c.20-30ohms). The added resistor(in blue) critically-damps the input to the second reg, stopping any spurious oscillation due to high loop gain / layout strays. Use 10R with C2 = 100nF down to a min. 2R7 for 1uF, or 1ohm with 10uF.
A circuit well worth playing with for the very low cost of entry.
It's the tracking pre-arrangement, not the minor changes that makes for good performance. Look at how it's arranged: the first 317 ensures there is *no* ripple voltage appearing across the second, in fact the second reg sees a constant voltage difference across it regardles of whayt the load does. So the second reg applies all its gain to load regulation, while the first deals only with the ripple/noise on the input. This is a subtley, but it audibly improves on just using two regs in series.
So - my suggestions are using an LED voltage drop to set c.2.8-3v across reg2, which absolutely minimises noise from the first reg (because the led at 5-10ma has a dynamic impedance of only c.20-30ohms). The added resistor(in blue) critically-damps the input to the second reg, stopping any spurious oscillation due to high loop gain / layout strays. Use 10R with C2 = 100nF down to a min. 2R7 for 1uF, or 1ohm with 10uF.
A circuit well worth playing with for the very low cost of entry.
Hi Martin
Can this be used as a preregulator for a shunt ?
I would like to experiment reducing ripple psu before a shunt so I can benefit from the output low Zo and lower the noise floor.
Ricardo
Can this be used as a preregulator for a shunt ?
I would like to experiment reducing ripple psu before a shunt so I can benefit from the output low Zo and lower the noise floor.
Ricardo
Hi Ian,
Yes been a member for a while but not posted much. Enjoyed reading about many mods hear though.
The diagram posted is a basic tracking reg and I am actually using Avondale's pretrackers for my 5v supplies. Old Les has added a few bits to the basic layout to reduce ripple so I am not certain that Martin's tidy mod applies and that's why I asked a couple of questions.
Regards
Yes been a member for a while but not posted much. Enjoyed reading about many mods hear though.
The diagram posted is a basic tracking reg and I am actually using Avondale's pretrackers for my 5v supplies. Old Les has added a few bits to the basic layout to reduce ripple so I am not certain that Martin's tidy mod applies and that's why I asked a couple of questions.
Regards
Ah, thought you were interested in a 'from scratch' ideas. I'd leave LesW's TPRs alone, not much to be gained by chopping them about 🙂
RCruz - not necessarily. A tracking reg arrangement requires about 5-6v minimum headroom or 'dropout' voltage from input to output, whihc you may not have. A good shunt reg uses a current source to feed the load anyway, so what it upstream should be fairly irrelevant. If you want to add anything, a little RC decoupling before will help at high frequencies when the active current source starts to become less effective (but a little RC ahead of most regs is rarely a bad idea IMO!)
RCruz - not necessarily. A tracking reg arrangement requires about 5-6v minimum headroom or 'dropout' voltage from input to output, whihc you may not have. A good shunt reg uses a current source to feed the load anyway, so what it upstream should be fairly irrelevant. If you want to add anything, a little RC decoupling before will help at high frequencies when the active current source starts to become less effective (but a little RC ahead of most regs is rarely a bad idea IMO!)
Thank you Martin
I really do not have the required headroom.... anyway I just asked because I found your idea really interesting.
I already have a RC ahead of the shunts and this combination is very good.
Regards
Ricardo
I really do not have the required headroom.... anyway I just asked because I found your idea really interesting.
I already have a RC ahead of the shunts and this combination is very good.
Regards
Ricardo
Ray, did your daughter get her Christmas present ?
Simply Swank Pink Solder Iron 60W Jewelry Crafts Tool on eBay (end time 23-Jan-11 13:15:29 GMT)
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Simply Swank Pink Solder Iron 60W Jewelry Crafts Tool on eBay (end time 23-Jan-11 13:15:29 GMT)
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Wow, they actually make them in Pink! Very swanky! 😱 😀
I'll have to live up to my signature some day of course, but for now we started with some Lego Duplo, which she likes very much! 🙂
I'll have to live up to my signature some day of course, but for now we started with some Lego Duplo, which she likes very much! 🙂
Any ever hear of or try a metal cap that fits over the laser lens and focuses the beam? I had one years ago but it didn't fit, so I gave it back. Just remembered...
I guess that means no? a mystery tweak. I have no idea where they came from or if they really worked. The guy who found them was a serious DIY'er (Swiss) and swore by them. They worked on his big beautifull Sony cdp ( CDP-X707ES) but were too tight for the Marantz. End of tale I guess.
Not so early; 1985. I have looked everywhere but there is no existing reference to this.
Bonne année Frenchie! Il vas faire beau parait-il.
à propos... of nothing and everything. I turned off the current, opened up the wall sockets, tightened the wiring connections and treated everythig with Craig Gold cleaner and enhancer. Nice cheap and effective
tweak. Sounds cleaner too!
Bonne année Frenchie! Il vas faire beau parait-il.
à propos... of nothing and everything. I turned off the current, opened up the wall sockets, tightened the wiring connections and treated everythig with Craig Gold cleaner and enhancer. Nice cheap and effective
tweak. Sounds cleaner too!
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