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Vintage threads from the first ten years
O'Connor's Diode Noise Filter?
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 10/24/2004 2:51 PM |
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| Ethan Walker | O'Connor's Diode Noise Filter? Has anyone tried the power supply technique shown in TUT3 where you use 10 ohm/10 watt resistors and a few .01 caps to cut diode switching noise? I was thinking about trying it and wanted to see if anyone has any experience with it- Ethan |
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| 10/24/2004 4:19 PM |
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| jbrew73 | i've been wondering the same thing. |
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| 10/24/2004 4:52 PM |
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Dr. Photon |
I don't have TUT so I can't acurately comment on the exact circuit since I don't have a schematic. But if it involves putting small capacitors in parallel with each diode, then it should work out to cut out the switching noise (capacitors accross diodes is fairly popular, especially in power supplies that must pass some sort of EMI test). If it involves a series resistor acting as a PI filter (that 10 ohm, 10 watt resistor HAS to be in series w/ something), then it should also cut down on switching noise drastically (since even those small caps will have a low impedance to ground at the frequency of the switching noise). In one of my amplifiers (a "fenender" no-name (literally!) amplifier which just happened to have a fender-esque circuit), they used silicon diodes with a 5 watt, 25 ohm resistor in series before the first filter node (as a GZ34 sag simulator). I added a standby switch (in series with the 25 ohm resistor, to limit the arcing when flipping it), and also added a cap to ground directly at the rectifiers. This cut down quite dramatically the 120 Hz ripple. any switching noise was also eliminated (I have not noticed any). |
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| 10/25/2004 1:59 PM |
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| kg |
some theory: http://ken-gilbert.com/images/pdf/snubber.pdf http://ken-gilbert.com/images/pdf/Calculatin_%20Optimum_Snubbers.pdf i've used them... see http://ken-gilbert.com/techstuff/preamp.html hth ken |
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| 10/25/2004 3:01 PM |
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| Ethan Walker | Thanks for the replies. The circuit, from TUT 3 is this: The 2 PT outputs go to a fuse each, then 2) .01 caps are run across the legs with the junction of the caps going to ground. Then, each leg has a 10 ohm/10 watt and 2 1N4007 diodes. Both B+ legs then connect, go thru another 10 ohm and on to the filter caps. According to O'Connor, it's a simple RC network. I wonder if you need all 3 resistors. Ethan |
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