| Re: Filter caps--perhaps a crazy notion [message #338644 is a reply to message #338633 ] |
Fri, 02 May 2008 17:29   |
 J Hinson
Messages: 84
Registered: December 2007 |
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| dcollins wrote on Fri, 02 May 2008 14:36 |
In that case, there's a lot of designers that aren't serious!
DC
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Yes there are.
Of the designers that are capable of designing a discrete shunt or series regulator instead of throwing in a 3 terminal chip, I wonder how many of them have actually listened to the difference between the two? It isn't subtle.
Possession is 9/10ths of the problem.
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| Re: Filter caps--perhaps a crazy notion [message #340075 is a reply to message #339633 ] |
Fri, 09 May 2008 13:25 |
J Hinson
Messages: 84
Registered: December 2007 |
Member |
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Hi Sam,
| Sam Lord wrote on Wed, 07 May 2008 14:46 |
We used 4001s in lots of places; I did worry about a noise penalty, but never calculated or measured it. We used those pretty glass-encapsulated rectifier and zener diodes where the old (purchased) circuits had them. Mmm, we did finally replace some zeners with quiet voltage references. I would have some concern about dissipation in the 4148, but the 20R would help.
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There were a series of articles by Ben Duncan several years ago that dealt with power supplies. I blatantly stole the '4148 + resistor' trick from there. Also several other nifty tips which have stood me in good stead.
| Sam Lord wrote on Wed, 07 May 2008 14:46 |
A crusty old tech once told me that the 4007s, the 1000V guys, actually behaved better wrt noise and/or distortion than 4001s. I don't remember if he meant for forward or reverse biasing--I guess that would matter... 
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Interesting, I haven't tried that. Thanks.
I have noticed that there is an optimum current for diodes wrt noise. I'm talking more specifically of when using a diode, led or zener as a reference etc.
I'm away from home and most of my scribbles at the moment but here's a link to a series of tests done on simple regulators. The graphs of a 317 three terminal reg against a discrete series and discrete shunt show substantial improvements with discrete. I also tested a Sulzer and a Jung regulator and arrived at similar results when comparing to a 317, 1085 etc.
http://www.tnt-audio.com/clinica/regulators_noise1_e.html
J.H.
Edit: Link corrected
Possession is 9/10ths of the problem.
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