DIYHiFi.org

Apologies to Frank Zappa. Blame CG for giving me the idea.

"I am gross and perverted.
I'm obsessed and deranged.
I have existed for years, but very little has changed.
I'm the tool of the moderators and their groupies, too.
For I am destined to rule and un-educate you.
I may be vile, and pernicious, but you can't look away!
I make you think that I am factual, with the stuff that I say.
I'm the best you can get.
Have you guessed me yet?
I'm the slime oozing out from the INTERNET!!!

You will obey me while I lead you,
And believe the garbage that I feed you.
Until the day that we don't need you.
Don't go for help, no one will heed you!
Your mind is totally controlled, it has been stuffed into my mold.
And you will do as you are told until the rights to your IP is sold!

'That's right folks, don't touch that soldering iron........'

Well, I am the slime from the forum, oozing along on your workshop floor.
I am the slime from the forum, can't stop the slime, people, lookit me go!"


I know......a lot of you have trouble taking anything technical that I post, when I have a propensity of posting sarcastic gibberish like this. (We will see how twisted your mind is when you get to my stage in life! Too bad I probably won't be here then.)

But look at what passes for expertise on those other forums. Real experts are denigrated at every turn. Wanna-bes rule the day, and no one challenges them.

And when one of the real experts does, they are stifled.

Translation: Don't believe everything that you read on the forums. Anyone can be wrong. Yes, even me. You guys are best served when you use your intuition and curiosity to try stuff before you take it as gospel. Sure, a lot of what you read will work. But there may be better ways. You just have to the desire to sort through it all. And by all means, try it yourself before you take it as gospel.

Jocko

_________________
"Because, I hate you guys. I hate you guys so very, very much.

Yours,
General Cartman Lee"

Brilliant.
I still have to try that vietnamese soup.

_________________
Carlos Filipe

"Any intelligent fool can make things bigger, more complex, and more violent. It takes a touch of genius - and a lot of courage - to move in the opposite direction." Albert Einstein

Maybe I should make everyone who reads this write a 25 word essay on everything that they know more about diodes in power supplies than John Curl does.

OK, here is mine:

It is easier to design low current supplies, because there are things that you can do to limit peak charging currents. Keeps the diode noise down.

26 words...............went over budget. Time to Sin Bin me.

Jocko

_________________
"Because, I hate you guys. I hate you guys so very, very much.

Yours,
General Cartman Lee"

OK.

I told somebody about soft recovery diodes who told someone who told John Curl. After I read a half liner from Ben Duncan.

What was that about "Steal the best, invent the rest?"

After further contemplation, I *do* feel insulted over your comments...

I'm at a loss understanding the context of this and why is CG feeling insulted. (?!)
It's not my business, anyway.

There was a good thread on soft recovery diodes from Phred back in the old days, at The Pub.

_________________
Carlos Filipe

"Any intelligent fool can make things bigger, more complex, and more violent. It takes a touch of genius - and a lot of courage - to move in the opposite direction." Albert Einstein

Phred' s postings were totally misleading as well as his recommandations for Panasonic FC c(r)aps.......



(14 words)

CG is referring to someone who lectured The Devil, and was in turn insulted when The Devil told him to shove it. They want it both ways over there. Unless you are The Devil, in which case, he gets it stuck to him both ways.

I need to point out that CG claims he didn't make me do this.............The Devil made me do it!

In retrospect, I suppose he was right.

Jocko

_________________
"Because, I hate you guys. I hate you guys so very, very much.

Yours,
General Cartman Lee"

Great. More of that sycophant fan boy stuff we always get accused of...

I haven't read many of John Curl's power supply ramblings, but here's my 10 line essay:

"You want the longest diode conduction time you can achieve."

And the best way to get started on this path is to download a copy of LTspice. Yes, there's plenty of people who say "oh, but SPICE is entirely theoretical simulation, building and listening is way more important", please remain quiet for now while I explain.

Some people think "oh, I'll build the best power supply I can for my amp" and use a toroid transformer with next to no leakage current, ultrafast recovery diodes designed for SMPS, and put half a farad of low ESR capacitance (ie, the aforementioned Panasonic FC) on each rail. In theory, this should give you an extremely low impedance power supply, right?

Well, lets build this power supply up in LTspice. Lay it out something like:

- AC voltage source (25VAC or whatever)
- Series inductor, equivalent to the secondary side referred leakage inductance of the toroid.
- Ultrafast rectifier, there's plenty of stock models in LTspice, or get a model from Fairchild's site.
- Low value (1mOhm) resistor in series with the rectifier. You want this for measuring rectifier current.
- Bulk capacitor, with a series ESR resistor and ESL inductor lifted from the capacitor datasheet.
- Load resistor.

Simulate this, and plot the current in the 1mOhm resistor. Voila, that's your conduction angle. Don't be surprised if the conduction angle is in the single digit degrees, and despite the 1A load that you have on the supply, the diode current is hitting 30A peaks.

Secondly, plot the voltage at the node where the leakage inductor meets the diode. Ugly, right? And thirdly, plot the voltage across the capacitor bank. During the diode conduction interval, do you see a bunch of hash on the power supply? Thought so. What's the frequency content of this? Pretty high, right? It probably travels directly through your linear regulators since they have limited loop bandwidth. After that, the PSRR of your amplifier design, op-amps and other chips you're using probably suck at that frequency also.

Now, time for some enlightenment.

- The 1mOhm resistor, increase its value. What happens to the conduction angle?
- How about snubbing the transformer output with a small C, or R+C? How about the diode?
- Are you sure you're using the right kind of diode in the first place? Directly reading the SPICE models for different types of diodes may provide further enlightenment.
- How about replacing your bulk capacitance bank with a fairly small C, a series L, and a big bank?

Anyway, play around for a while. Change things and see what happens. For that last idea, try replacing the small C with a diode so the thing looks like a buck regulator. Make notes.

Once you get some ideas in your head, start modifying your equipment with some of the things you've discovered. Make some notes on how its sounds while you're at it. After all, SPICE is entirely theoretical simulation, and building and listening is way more important.

Not to mention that the output current of the amplifier itself goes through this very same filter cap in most cases. Spice isn't needed to draw a picture of the current paths.

You also need to consider the various stray and inadvertent coupling mechanisms between the amplifier and everything else attached to the same AC mains.


BTW, I'll bet that my contribution to this thread will end up tragically. *Every* single time I decide to poke my head up and offer something to one of these forums, somebody somewhere is offended and responds as such. You'd think I'd learn, wouldn't you? Oh well - at least Jocko finds it amusing.

CG, I apreciate very much your contributions here and whatever you guys are talking about (?) just don't take it personally.
There must be some misunderstanding, or else it is just me that don't get it.
I don't need to "get it", anyway. As I said, it's not my business.
Go on...

_________________
Carlos Filipe

"Any intelligent fool can make things bigger, more complex, and more violent. It takes a touch of genius - and a lot of courage - to move in the opposite direction." Albert Einstein

Carlos,

I shouldn't be so obscure, especially when there are folks reading this who might not get the subtleties of what we quaintly call the English language over here. At least our version of it.

Earlier, I joked about how a number of people were personally insulted elsewhere because somebody disagreed with them. That was poking fun.

This time I was just expanding on that. I just *know* that somebody somewhere will take my power supply comments (and gmarsh's as well) as heretical and offensive. That's okay by me - people are entitled to their own foolish beliefs.

Back to more Peaches En Regalia...

That is exactly what I was not getting - that your contribution and also gmarsh's on PSUs can be considered... "heretical and offensive" by someone else. (?!)
I guess I'm just a normal kinda guy.

_________________
Carlos Filipe

"Any intelligent fool can make things bigger, more complex, and more violent. It takes a touch of genius - and a lot of courage - to move in the opposite direction." Albert Einstein

I wouldn't be surprised. Offending people seems to have turned into a hobby of mine - and I'm starting to think I'm pretty good at it, even though it usually happens by accident or as an unintended consequence of something.

Here's a recent one. In Nova Scotia, they're talking about turning every school zone into a 30km/hr zone, effective 24 hours a day, 7 days a week, even on holidays. All because a kid got hit by a car in front of a school during school hours, and the mom has lobbied/petitioned the government. Even though the kid wasn't badly hurt.

So we're at a bar on a sunny saturday afternoon, talking about this; we all think it's a stupid idea. I say "man, if I walked out in the middle of the road and got hit by a car, my dad would hit me right after for doing something so dumb. And that's the way it should be." .. Well, this woman who overheard me tapped me on the shoulder, fuming red in the face. "Do you have kids?" "no" "WELL I HOPE YOU NEVER DO!" - she proceeded to yell at me about child abuse, and how horrible it was that I'd even remotely suggest hitting a child. Got half the bar staring at me.

Suggesting, and relating to the world we grew up in, are 2 different things.

There used to be a thing called personal responsibility.

Anyway, Carlos..............all this stems from a certain Mod Squad lecturing The Devil. First one way, then the other. Sometimes, we have enough spare moments in a day to watch the hypocritical fun and games that passes for edification on some other sites. We are grumpy old farts, who have spent too much time listening to Frank Zappa, designing RF gear, and as a result are warped individuals. We are amused by things that may not seem amusing to you.

Trust me, if it was you instead of The Devil, you would get it. (You probably already have.)

Jocko

_________________
"Because, I hate you guys. I hate you guys so very, very much.

Yours,
General Cartman Lee"