LM338 regulated snubberized PSU for audio amplifiers

[Dominick22]

I am a fan of Diana Krall as well, so I know what you are talking about with her recordings.

Suggestion for you.
One of my favorite audio recordings is Bryan Adams "Live at the Budokan" Japan 2000.

It is a DVD-A

Out of all of my SACD's, CD's, MD's, etc, this is the best recorded album!
Everything comes out perfect on my system so I can only imagine it on yours. The instruments and ambiant sounds are impeccable.

I hope you give it a try or maybe you already have it? Let me know.

Also, I would love to see some pics if you have them available.
Especially of you LM AMP!!!!

Dominick

 

[carlosfm]

I hope you give it a try or maybe you already have it? Let me know.

No, I don't have it.
Don't take me wrong, I don't discuss musical tastes, it can be a great recording but it wouldn't pass my mind buying something from Brian Adams.
Probably this one I could buy, if I found it.

Also, I would love to see some pics if you have them available.
Especially of you LM AMP!!!!

I don't know where I have those pics now, but I've posted somewhere here on the forum, on someone's theread about grounding problems.
You don't want me to dismantle my system to take some pics now, do you?

 

[Dominick22]

Dismantle....Well YES-Of COURSE since you asked!

LOL--Honestly, it would be nice to see the insides of your set up, but I would be interested in just regular overall type pics if you have some.

I am interested in the size and design of your chip amp enclosure mostly!

I have been enjoying making mine out of wood (red cedar) which I have noticed is a bit of an unusual choice. But they look beautiful!lol

So you dislike Bryan Adams?
"it wouldn't pass my mind buying something from Brian Adams."

Dominick

 

[Mrpong]

Hi Carlos

According to the requlated circuit using LM338 here:-
http://myweb.tiscali.co.uk/nuukspot/decdun/gainclonesnub.html

I followed this thread but I'm not sure about the purpose of using
- R1 & R2
- R7 & C9 and R8 & C10

Can someone please explain to me? Thank a lot.

 

[Nuuk]

Sawadee Mr Pong.

Carlos will be on the beach right now drinking lots of cold beer!

R1 and R2 are bleeder resistors. When you remove the power, the (big) caps store quite a lot of power. The bleeder resistors eneable them to discharge fairly quickly.

The other components form the snubbers. They negate (reduce) the 'bad' effects of using the larger caps in the PSU. Chokdee.

 

[AndrewT]

Hi, referring to reg snub V1.2 2005.

r1 & r2 are smoothing cap discharge resistors, to remove unsafe charge before maintenance. Read decibel dungeon, he explains it clearly.

The series cap and resistor form the snubber.
This is the whole essence of these modified amp/psu combinations, the cap absorbs some of the spiky glitches that can emanate from a resonant system when sudden current demands switch on or off and the resistor damps the absorber so helping to attenuate the resonance. Again decibel dungeon mentions it although not quite in the detail as the dischargers, but he does referr you to the thread. Go do some research.

 

[AndrewT]

Hi Nuuk,
decibel dungeon is your site?

What are the changes in the "new" non reg PSU schematics you have posted from Carlos?

Can you check the snubber and cap values inserted into the schematic and in your text, there are discrepancies.

 

[Nuuk]

decibel dungeon is your site?

Guilty as charged Andrew!

What are the changes in the "new" non reg PSU schematics you have posted from Carlos?

AFAIK, just component values.

Can you check the snubber and cap values inserted into the schematic and in your text, there are discrepancies.

Sorry about that. On the last update, I uploaded the circuit diagram but forgot to update the text. I have changed it now.

 

[frank1]

The other components form the snubbers. They negate (reduce) the 'bad' effects of using the larger caps in the PSU. Chokdee.

Ok, so what 'bad' effects are those please?

I have read this many times here and yet there is no hard evidence to support this. Some have done listening tests but has anyone done proper AB tests using remote controlled switching from the listening position ?

I have done extensive listening tests today with a 3886 amp which has different smoothing capacitors switched by a relay.
This relay is operated from the listening position.

Using many different types of music and two different sets of loudspeakers in turn, I could not detect any change in the "top end" when switching from 2200uF to 10000uF. (for the stereo pair of amps)
Absolutley none ! Bass yes, treble no change.
If I had detected a change, I was going to do the same with and without snubbers but there is absolutley no point.
I think the whole thing is just a case of "The Emperors new chipamp".

Certainly, my new 3way active filtered system will just be using capacitor values that agree with the laws of Physics and no snubbers.

Frank

 

[Nuuk]

Using many different types of music and two different sets of loudspeakers in turn, I could not detect any change in the "top end" when switching from 2200uF to 10000uF. (for the stereo pair of amps)

Frank, I had a hi-fi like that once - bl**dy awful!

Seriously, the snubber debate has already caused more than enough ill-feeling on this forum and we really don't want to go over old ground again. If it doesn't work for you then don't use it! At least you have the satisfaction of knowing that it is not for you!

I don't use it because I prefer the SMPS for my GC PSU but that's no reason to argue against anybody else going with a linear supply and if they want to snubber it, where's the harm?

 

[jackinnj]

So, we don't want to hurt anyone's feelings discussing Snubbers and LM338's

Let's make an assumption that you have about 4 inches (10cm) of trace from power supply to load, that your transformer has a pretty low leakage inductance of 1uH and you only use one MUR860 (about 400pF JCO) -- not unreasonable assumptions -- here's a simmed example of what happens if you use no diode snubber or Carlosfm snubber:

as you should expect there is a nice peak, about which the diode/transformer circuit rings --

An externally hosted image should be here but it was not working when we last tested it.

 

[jackinnj]

put in the last CarlosFM snubber (you can correct me if I have the values wrong and I will redo the sim) --

An externally hosted image should be here but it was not working when we last tested it.

 

[jackinnj]

but if you do the math and place the RC network across the diode (as the doctor recommended):

An externally hosted image should be here but it was not working when we last tested it.

 

[poobah]

The PIctures look identical Jack...

 

[pinkmouse]

Have you been on the Wookie Juice? The last sim looks way different to me.

 

[jackinnj]

probably posted before I got it up (premature ejac-u-posting). In fairness to the banned Carlos, the 47n/0.4R will round off the edges a bit) -- here's a sim with it disconnected).

An externally hosted image should be here but it was not working when we last tested it.

 

[poobah]

Sorry Pink,

In fact, the opposite is true... Mrs. poo is mixing up my medication right now.

 

[jackinnj]

speaking of medication -- Jacques Pepin was "profiled" in the Sunday New York Times Magazine -- here's how he starts his evening: "At 5:00 I have a scotch and select two bottles of wine for dinner".

 

[poobah]

My kinda guy...

 

[mateo88]

I'm not trying to start an argument or anything (hell, I don't even use snubbers in my amp), but isn't the point of the snubber to reduce the impedance of the power supply? Certainly this is visible in the second graph you posted, jackinnj. Granted, the peak isn't taken care of at all, but isn't that peak far out of the audio spectrum? Surely lowering the impedance of the power supply in any amount would make it "better," right?