# Carlosfm...Snubber Guide Lines?

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#### moray james

Carlosfm: seems you have a lot of successful experience with snubbers. Can you tell me how you go about decideing what values to use in your snubbers? I assume that once you have a basic value that you play with it up and down by ear to fine tune?
The standard filter equation: F = 1 / (2 pi R C). So what criteria do you use to pick you chosen frequency? As the value of R comes down what kind of impact is there (aside from heat) on the circuit? Thanks for any help from those who know.
I put a snubber on the secondary of an Acoustat 0ne plus 0ne high voltage step up transformer and was very pleased with the results. I have not played with the values, I used 10 ohms in series with 0.01 uf. Best regards Moray James.

#### jackinnj

I think the formula used is to be found in this paraphrase of a quote from the Bogart movie "Treasure of the Sierra Madre":

"Formulas, we don't need no stinkin' formulas".

#### moray james

Ok if formulas don't count?

There has to be some criteria with which to judge at the very least a starting point. I have no problems with listening to choose a best value however you need to have a value to start with! Regards Moray James.

#### carlosfm

jackinnj said:
I think the formula used is to be found in this paraphrase of a quote from the Bogart movie "Treasure of the Sierra Madre":
"Formulas, we don't need no stinkin' formulas".

That also sounds like Jocko.

#### carlosfm

Hi Moray,

I can calculate the values for the snubber but to be spot-on (or almost) I would ideally need an impedance graph of the PSU.
Easy when we're talking about linear regulators, because they are well documented.
Measurements would also do, of course, if you have a way to make them.
Without that, I can make a calculation based on guessings, that you may need to fine-tune.

The formula is secret...

I can give you a first hint, though: you don't want a 10R resistor for the snubber on a PSU. You need a much lower value.

#### peranders

Paid Member
Re: Ok if formulas don't count?

moray james said:
There has to be some criteria with which to judge at the very least a starting point. I have no problems with listening to choose a best value however you need to have a value to start with! Regards Moray James.
Thorsten simulated the whole circuit and it was pretty accurate, as much as can be expected.

One for sure (right Carlos) is to loose the unsnubbed capacitor.
have you seen my "Enhanced Carlos Snubberized Power Supply"

The first thread became pretty enlighting and my first question in my frist post was answered by measurements that Carlos' basic idea had no or little effect, seen in measurements but "my" idea had.

No offence Carlos but you won't kill the peak resonance only with adding a C + R. You must loose the lonely C also... 100 uF // 100n+1R (or so) will do the trick.... to remove the "big" peak of 4-6 dB at 2-4 MHz... altough this is still a bit of a sugarpill but at least it can be measured.

#### carlosfm

Re: Re: Ok if formulas don't count?

peranders said:
No offence Carlos but you won't kill the peak resonance only with adding a C + R. You must loose the lonely C also... 100 uF // 100n+1R (or so) will do the trick.... to remove the "big" peak of 4-6 dB at 2-4 MHz... altough this is still a bit of a sugarpill but at least it can be measured.

100uf electrolythic?
Nah...

No offense, but I don't like to see you calling your speculations the "Enhanced Carlos Snubberized Power Supply".
Specially coming for you, who doesn't have the honesty to give an oppinion if the snubber is an improvement or not.
Objectively or subjectively speaking, you simply don't say what you think.
You are just dicking around.

#### jackinnj

I was just having fun at Carlos' expense. There is a notable lack of maths from some quarters

#### peranders

Paid Member
Carlos, I have noticed that you haven't commented neither Thorsten's simulations nor Joseph_K's real world measurements saying that you still have a peak which you claim will be removed be your solution. You haven't commented my solution either so I'll guess you circuit will or remove something we don't know about.

This is what I think, now and before: It's not particular important and it makes not a huge difference.

Notice also that I don't say: It's totally unimportant and it makes absolutely no difference.

#### carlosfm

peranders said:
Carlos, I have noticed that you haven't commented neither Thorsten's simulations nor Joseph_K's real world measurements saying that you still have a peak which you claim will be removed be your solution. You haven't commented my solution either so I'll guess you circuit will or remove something we don't know about.

That peak is not important, you're pickink on something that is ridiculous.
The snubber attenuates the peak.
Very important for an audio amp IS a low impedance PSU.
Any cap of a smaller value that is placed after the big PSU caps will create a peak.
That means if you use 10,000uf caps on the PSU, you would have to use this value everywhere, including as a "bypass" cap on the chip.
Your suggestion of 100uf to bypass the big caps will bring the peak to a much lower frequency, not good.
You are walking in circles here.

You caught me in the mood, because I don't have to comment anything you say.

And you still didn't say if the snubber improves you amp, while those who have tried it on YOUR amp will never go back.
What makes you think that a bridge and a cap makes a good PSU?

#### peranders

Paid Member
carlosfm said:

That peak is not important
The reason for adding the snubber is for reducing the peak.... which you feel is very important, the snubber that is.

Anyway, you don't understand what I mean, nor can I get any explaination, not in theory neither in measurements so I'll guess we can get any further.

#### jackinnj

zinsula said:
Check out this:

http://www.calex.com/pdf/3power_impedance.pdf

Well, it worked for me, but I'm slow on the uptake.

Tino

if we work the math backwards, then Carlos values (100nF/1R) are attempting to null a peak in the supply impedance at 1.59MHz.

#### carlosfm

peranders said:
The reason for adding the snubber is for reducing the peak....

No, it's not the main objective, of course not.
You are still fighting to understand this...

#### jackinnj

carlosfm said:

No, it's not the main objective, of course not.
You are still fighting to understand this...

Well, what is it, spitz or swallows to paraphrase Austin Powers? In your prior post you said it was to eliminate the peak.

An unregulated power supply without an error amp is going to have pretty darn low impedance, unbothered as it is with the need for compensation, adequate phase margin, etc.

Of course, empiricism is a lost art...

#### carlosfm

jackinnj said:
Well, what is it, spitz or swallows to paraphrase Austin Powers? In your prior post you said it was to eliminate the peak.

Hey, try to understand what I said.
It does attenuate the peak, but that's not the main objective to use the snubber.
The objective is to have very low impedance up to the Mhz.
These amps need it (others too), and the improvement is clearly audible.

jackinnj said:
An unregulated power supply without an error amp is going to have pretty darn low impedance, unbothered as it is with the need for compensation, adequate phase margin, etc.

It does, but not enough.
The inductance of the big caps will have the side effect of a climbing impedance towards the high frequencies.
Paralleling small caps doesn't work as well as intended (or thought) because of the unavoidable trace inductance.
The snubber is there to improve this.
Of course regulators have much higher output impedance, starting much lower in frequency.
But my recommended values for the LM338 are much different from the values for the unregulated PSU, aren't they?

If you understood this and how to use it you would snubberize every PSU.
With the right values for every occasion.
There's no turning back.
It doesn't make "little difference", as P-A says.

jackinnj said:
Of course, empiricism is a lost art...

Posts like this, and the story of my original thread since the beginning are the reason why I don't reveal everything.
Who cares?
Do you?
I don't.

P-A seems desperate, since the beginning.
I don't know why he cares, if it makes "little difference".

#### jackinnj

put the snubber where it belongs:
here's a quick and dirty bode plot -- using a MUR860 Diode and 40uH of power transformer secondary impedance -- in the real world there is also (several hundred PF) of capacitance across the transformer secondary -- which isn't modeled here --.
An externally hosted image should be here but it was not working when we last tested it.

#### chris ma

therefore we need 4 sets of snubber cap/resistor for a bridge rectifier?

#### peranders

Paid Member
zinsula said:
Check out this:

http://www.calex.com/pdf/3power_impedance.pdf

Well, it worked for me, but I'm slow on the uptake.

Tino
If you have understood the document, what is your conclusion if you compare "my" snubberization and Carlos?

carlosfm said:

No, it's not the main objective
The purpose of the snubber is....

carlosfm said:
P-A seems desperate, since the beginning.
I'm not particulary desperate. I'm just trying to understand why using a snubber if you don't want to reduce impedance peaks...

#### jackinnj

chris ma said:
therefore we need 4 sets of snubber cap/resistor for a bridge rectifier?

quite frankly, I have done this (4 diode snubbers), but I don't think that it is necessarily the best thing or necessary. i haven't the time right now to fiddle with it.

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