A PSU filter can be viewed as a voltage divider. In any voltage divider, some voltage goes one way (to ground, in a PSU), and some goes another (to your speakers, ultimately).
Here's a small thought experiment regarding the efficacy of power supply filters. Inject a large quantity of noise onto the AC line. Will *any* of that noise appear in a circuit fed by a power supply? Questions regarding the audibility of any noise coursing past the PSU filter can be laid to one side for this question.
Here's a small thought experiment regarding the efficacy of power supply filters. Inject a large quantity of noise onto the AC line. Will *any* of that noise appear in a circuit fed by a power supply? Questions regarding the audibility of any noise coursing past the PSU filter can be laid to one side for this question.
Yep, I think so too, still cannot hear the difference with a normal setup with standard diodes or the schottky ones.
Thx SY, that's what I figured. Not a whole lot is often a euphemism for squat measurable difference.
For what it's worth I haven't played with different silicon rectifiers but approach it by using a stage or two of filtering comprised of a uHenry-size RF inductor followed by a small film cap in the B+ supply to do the RF duties as most supply chokes resonate well into the audio band. I think it makes a worthwhile difference and as scientific proof offer burnt candles, feathers and deceased chickens: my personal voodoo.
For what it's worth I haven't played with different silicon rectifiers but approach it by using a stage or two of filtering comprised of a uHenry-size RF inductor followed by a small film cap in the B+ supply to do the RF duties as most supply chokes resonate well into the audio band. I think it makes a worthwhile difference and as scientific proof offer burnt candles, feathers and deceased chickens: my personal voodoo.
The math suggests a PSU would require infinite capacitance (with zero ESR/ESL) and resistance to achieve zero noise... audible or not. Also, a rather spendy method.
The point remains however, if your filter cannot reduce diode noise to acceptable levels... what other types of noise (line borne) are then welcome to pass right through?
RDF,
The chickens taste good afterwards as well.
🙂
Spendy indeed! Whether a given level of noise is acceptable depends on many factors, including one's experience. My acceptable level has consistently lowered over time.
There's no law stating all power supply impedances must be between B+ and ground. Spice sims of small air-core inductors between stages of capacitive filtering suggests huge gains in RF rejection. Cheap, cheerful and comes in BBQ or deep-fried. 🙂
Those gains occur because you've changed the position of the tap on the voltage divider. Noise still divides between ground and amplifying device, etc.
Yep... but these things can have decent numbers attached and some reduction in capacitor cost can be realized.
I think the diode quest falls apart when you ignore another PSU plugged into the same mains. For that matter, just look at the mains themselves!
RDF,
Play with some common-mode chokes someday... also ferrite beads... marvelous little friends they are.
I had to get a brush motor to pass CE testing once... in a REAL hurry. Looped the wires through a hex nut a few times and added a 0.1 uF cap... passed easily.
🙂
I think the diode quest falls apart when you ignore another PSU plugged into the same mains. For that matter, just look at the mains themselves!
RDF,
Play with some common-mode chokes someday... also ferrite beads... marvelous little friends they are.
I had to get a brush motor to pass CE testing once... in a REAL hurry. Looped the wires through a hex nut a few times and added a 0.1 uF cap... passed easily.
🙂
And for all you winos (SY) out there:
Get Thine A$$ down to the liquored-up store, wherever that maybe in your local locale, and buy the HECULA spanish wine that is making the rounds these days. Sells for $13.98 in Canada, (lower $in the states etc) and buy many a case. World ending numbers. Like it's the last bottle you will ever have. It scores a 92, on average, which puts it in the $50-75 a bottle price range, but it's only about $13 in the US. Supposedly, about 18,000 cases ended up being issued, so it should be easy to find. Matures late 2008, absolutely fine right now.
Get Thine A$$ down to the liquored-up store, wherever that maybe in your local locale, and buy the HECULA spanish wine that is making the rounds these days. Sells for $13.98 in Canada, (lower $in the states etc) and buy many a case. World ending numbers. Like it's the last bottle you will ever have. It scores a 92, on average, which puts it in the $50-75 a bottle price range, but it's only about $13 in the US. Supposedly, about 18,000 cases ended up being issued, so it should be easy to find. Matures late 2008, absolutely fine right now.
yeah, you dip the diodes in this wine, yeah. Treated. Special. etc. With a side of low fat inductance.
Schottky Barrier Diodes
see: http://en.wikipedia.org/wiki/Walter_H._Schottky / http://en.wikipedia.org/wiki/Schottky_diode
Inventor of the diode, really. And his first success was the best. All but forgotten until Shockly et al, invented the transisor ....
These diodes are ultra fast, quick recovery and almost magical when used in parallel with ordinary silicon diodes in producing a very fast recovery bridge rectifiers = "soft" recovery and in specialized detectors and microwave detectors ... and to prevent static discharge across CMOS chip inputs ... like op-amps.
... we couldn't have gigaHertz computers with out 'em.
see: http://en.wikipedia.org/wiki/Walter_H._Schottky / http://en.wikipedia.org/wiki/Schottky_diode
Inventor of the diode, really. And his first success was the best. All but forgotten until Shockly et al, invented the transisor ....
These diodes are ultra fast, quick recovery and almost magical when used in parallel with ordinary silicon diodes in producing a very fast recovery bridge rectifiers = "soft" recovery and in specialized detectors and microwave detectors ... and to prevent static discharge across CMOS chip inputs ... like op-amps.
... we couldn't have gigaHertz computers with out 'em.
Schottky Barrier Diodes
When used in parallel across the inputs of Complimentary Oxide Metal Semi conductor, Schottky type diodes protect these inputs from static, and dramatic or very rapid changes in voltage.
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input
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^
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When used in parallel across the inputs of Complimentary Oxide Metal Semi conductor, Schottky type diodes protect these inputs from static, and dramatic or very rapid changes in voltage.
+
|
^
|
input
|
^
|
-
- Status
- Not open for further replies.