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pros and cons of monolithic bridge rectifiers for power amp PS
pros and cons of monolithic bridge rectifiers for power amp PS
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Old 12th August 2017, 08:26 PM   #31
Mark Johnson is offline Mark Johnson  United States
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pros and cons of monolithic bridge rectifiers for power amp PS
Bring it over to my house in Area Code 408 and we'll Quasimodo it together. It will take 5 minutes to set up the experiment, 5 minutes to run the experiment, 5 minutes to write down the results, and 45 minutes to knock back the agave bevs + eat the guacamole & gazpacho. Did this same thing a year ago with a DIYA member from Denmark who happened to be in the area, and it was a lot of fun. I learned to pronounce "Copenhagen" the Danish way: Koeehh - bin - HOBB - ann. Don't shoot me, Karsten!

Last edited by Mark Johnson; 12th August 2017 at 08:30 PM.
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Old 12th August 2017, 08:49 PM   #32
CharlieLaub is offline CharlieLaub  United States
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pros and cons of monolithic bridge rectifiers for power amp PS
I found this article on snubbers in linear power supplies that is easy to read (or so it seems to me). They give some ballpark values and explain the rationale behind them. This would not be as good as measuring, but might be better than no snubber at all:
snubbering | DIY-Audio-Heaven
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Old 12th August 2017, 09:18 PM   #33
Mark Johnson is offline Mark Johnson  United States
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pros and cons of monolithic bridge rectifiers for power amp PS
If you actually use the Wing And A Prayer procedure from DIY-Audio-Heaven, I suggest you make certain that your DIY-Audio-Heaven-snubber's capacitor is big. I mean, really REALLY big. At least 680 nF {the value I used on the PSU linked in my sig} and perhaps even bigger, since you're not bothering to actually measure your transformer.

Then size the resistor so that the 60 Hz power dissipated in it equals 1/3 watt (and buy a 1 watt resistor!!). You'll need to do a little vector summation to find the current (hence the power), because the secondary's AC voltage is across the SERIES combination of Rsnub and Csnub. Or just run a quick LTSPICE simulation at 60 Hz and plot the resistor heat -- the icon with the thermometer. Jack around with the simulated R value until the heat is 0.33 watts.

The result from this bastardized, schlocko lazy procedure will be seriously and horrifyingly non-optimum. And you'll use math, unlike the "No Math" procedure mentioned above. But the odds are favorable that the resulting circuit which pops out, will do more good than harm. Probably.
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Old 12th August 2017, 11:29 PM   #34
CharlieLaub is offline CharlieLaub  United States
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pros and cons of monolithic bridge rectifiers for power amp PS
Not as horrifying as no snubber at all, I would guess...

Anyway, I may take you up on your offer. It's about a 2 hour drive for me if I don't run into any traffic. Since I have six of these trannies it's probably worth the drive.
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Old 13th August 2017, 01:06 AM   #35
Mark Johnson is offline Mark Johnson  United States
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pros and cons of monolithic bridge rectifiers for power amp PS
Wonderful, send me a PM when you're ready to visit. Need a few days advance notice so that The Boss Of The House is appeased. 3.6 miles from red arrow (intersection of CA-85 and CA-17) in attached image.

BTW on workdays, commute flow in the morning is: (North towards Oakland on CA17) and (North towards Mountain View on CA85).

Commute flow in the afternoon of workdays is: (South towards Los Gatos on CA17) and (South towards Morgan Hill on CA85)

The density of vehicles is (forward commute)/(reverse commute) = 3.0X.
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Last edited by Mark Johnson; 13th August 2017 at 01:11 AM.
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Old 13th August 2017, 04:34 AM   #36
CharlieLaub is offline CharlieLaub  United States
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pros and cons of monolithic bridge rectifiers for power amp PS
Thanks Mark! I know the area more or less. I lived at 280 and Saratoga Ave for a few years back around 2000 before I got married and moved up here. My brother lives in Willow Glen, so I can make a stop in to see him to kill time if I need to work around the commuter flow, etc.
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Old 13th August 2017, 08:50 AM   #37
AndrewT is offline AndrewT  Scotland
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You should have disclosed this important piece of information from he beginning .............
Many here do not know how to formulate a question.
They think we are magicians.

But one needs to know enough to enable the question to become clear.
That's where beginners (in any subject/topic) need guidance.
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Last edited by AndrewT; 13th August 2017 at 08:57 AM.
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Old 14th August 2017, 12:18 AM   #38
CharlieLaub is offline CharlieLaub  United States
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pros and cons of monolithic bridge rectifiers for power amp PS
OK, I have a question for you Mark...

I took a look at your Ring Not power supply board schematic and read over your Linear Audio article. In the Ring Not schematic I see that you place a capacitor of 3.3 nF across the secondary, and then have the snubber (series RC) in parallel with that. These components are in between the transformer and the bridge.

Following your paper and other sources, the model of the transformer used to illustrate ringing is a parallel inductor (Lt) and capacitor (Ca). From what I can tell, the capcitance in this model is likely to be in the tens of pico Farad range. If you put another capacitor of in parallel with the secondary (labeled Cx in your paper) like you do in the Ring Not board, and make the value of Cx>>Ca, the equivalent parallel capacitance value can be approximated by Ca||Cx=Cx. Given this value, it seems one would you only need measure the leakage inductance to be able to determine the optimum value for the RC snubber from equations.

Not that I have ever done one, but it seems possible to do a leakage inductance measurement by shorting the primary and using relatively simple measuring equipment (e.g. LCR meter) instead of a scope and the Quasimodo board. I'm just thinking about the relative access of a more novice DIYer here, who might not have a scope or want to spend the money to buy one, etc.

Is this a procedure that you think could work or are there pitfalls that I don't know about that would prevent it from being successful?
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Old 14th August 2017, 12:40 AM   #39
Mark Johnson is offline Mark Johnson  United States
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pros and cons of monolithic bridge rectifiers for power amp PS
Quote:
Originally Posted by CharlieLaub View Post
... it seems one would you only need measure the leakage inductance to be able to determine the optimum value for the RC snubber from equations.

Not that I have ever done one, but it seems possible to do a leakage inductance measurement by shorting the primary and using relatively simple measuring equipment (e.g. LCR meter) instead of a scope and the Quasimodo board. I'm just thinking about the relative access of a more novice DIYer here, who might not have a scope or want to spend the money to buy one, etc.
I thought so too. And then I tried it. And then I read about Morgan Jones's miserable results when he tried it (link).

Necessity was the mother of invention of Quasimodo. The "simple" measurement was not simple and it gave ambiguous results / nonsense results / no results at all. Thus was born the Bellringer concept, which is the fundamental underpinning of Quasimodo et al.

However I am happy to admit that I might have fouled up my dozens of attempts to perform the "simple" measurement. I am less likely to accuse Morgan Jones of fouling up. Perhaps somebody, somewhere, is able to directly measure the leakage inductance of the secondary of a super-excellent, modern, toroidal transformer like the Antek AS-2222 (link 2). But I doubt it. And I would point out that a Quasimodo + USB scope with 2 MHz bandwidth, costs 5X less than a 2 MHz capable LCR meter / impedance bridge, even a used HP instrument on eBay.
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Old 14th August 2017, 12:58 AM   #40
CharlieLaub is offline CharlieLaub  United States
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pros and cons of monolithic bridge rectifiers for power amp PS
Is it necessary to make measurements at a couple of MHz around where one would expect the ringing frequency to be located? That's not so simple.

Do you need a DSO to make these measurements? Can an analog scope also work?
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Last edited by CharlieLaub; 14th August 2017 at 01:04 AM.
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