LM338 regulated snubberized PSU for audio amplifiers

[carlosfm]

Here it is.
Results are impressive, this elevates the chipamp to a league of it's own.

Notice that I recommend 1,000~2,200uf caps on the chips, snubberized.
I'm using 2,200uf.

This regulated PSU is good for two chips (LM3886, etc.).

As a side note, this is not only a PSU for chip amps.
There are discrete class-A amps around that use the LM338 regs.
These amps will also benefit from the snubber.
No, let me put it this way: every regulated PSU benefits from a snubber.

The values for the snubber were calculated for the LM338's output impedance. Don't ask me how, I won't reveal it.

Enjoy.

 

[homer09]

I knew you wouldnt resist sharing your most recent recipe

how does this supply compare to non-regulated high-cap snubbed PSU?

Is this the new chip amp PSU king ?

 

[cjd]

Now, if I could run four chips off this... X-GC using a pair of LM4780's per side, you know? (the chips showed up today in the mail finally!)

Wonder what the flavor of the month will be next month. Discrete?

C

 

[carlosfm]

I knew you wouldnt resist sharing your most recent recipe
how does this supply compare to non-regulated high-cap snubbed PSU?
Is this the new chip amp PSU king ?

This is it.
I couldn't help but sharing...

Now, if I could run four chips off this... X-GC using a pair of LM4780's per side, you know? (the chips showed up today in the mail finally!)
Wonder what the flavor of the month will be next month. Discrete?
C

I was thinking in paralleling, but results are so impressive with this PSU and single chips that I'm not doing it.
Deam it, this stereo power amp sounds better with my speakers than a Krell integrated (used as a power amp) I had at home last week.
What's on my plans for soon is to make two small monoblocks with two chips each for bi-amping my Epos ES11 speakers.

 

[XELB]

I will tell a friend to try it on a stereo bridged LM4780 amp.
(my PSU is not regulated)

I hope to have news tomorrow.
Since you don't tell the miraculous formula, I will tell him to buy thousands of caps and resistors to find out the best combination LOL

 

[carlosfm]

I will tell a friend to try it on a stereo bridged LM4780 amp.
(my PSU is not regulated)

I hope to have news tomorrow.
Since you don't tell the miraculous formula, I will tell him to buy thousands of caps and resistors to find out the best combination LOL

You have a complete PSU schematic with the right values.
What do you want more?

 

[homer09]

You have a complete PSU schematic with the right values.
What do you want more?

i think he wants to check your math

 

[XELB]

You got me... I was with hope that you would tell! LOL

[inocent] [/inocent]




If you say that this one is much better, I will give it a try but I only have 8,600uF caps.


What electronic House you recommend in Lisboa ?
I will have to buy some parts.

 

[mateo88]

The values for the snubber were calculated for the LM338's output impedance. Don't ask me how, I won't reveal it.

[/B]

If you pretend the power supply is a speaker and calculate a zobel for it, that gets you in the general ballpark. Mess around with the values a little to see what works best.

 

[carlosfm]

If you say that this one is much better, I will give it a try but I only have 8,600uF caps.

That's not important, those are fine.
On this PSU you should have around 10V more voltage before the regs, so there's plenty of voltage to sag.
After the regs, the voltage is steady as a rock, of course.
Big capacitance is not needed, 4,700uf is fine, or up to 10,000uf.

What electronic House you recommend in Lisboa ?
I will have to buy some parts.

In Lisboa you have Dimofel and some others, but not too good for decent parts. Sometimes you find them, but you have to search.
There's a guy in Cacem that has Philips caps is almost all values, and 1% film resistors.
It's on the main street, on the Bons Amigos (I think it's called this way) shopping center.

 

[carlosfm]

Re: Re: LM338 regulated snubberized PSU for audio amplifiers

If you pretend the power supply is a speaker and calculate a zobel for it, that gets you in the general ballpark. Mess around with the values a little to see what works best.

I don't feel like messing around, it's fine as it is.
Try it with these values.
Then you can try other values, but I doubt you can improve this...

 

[mateo88]

I'm not saying the values aren't great as they are, I'm just saying that's how you can calculate the values. I don't know if you tried these values yet, but 1 ohm and .1 uf look like good values to correct the impedance issues above 1 mhz.

 

[XELB]

In Lisboa you have Dimofel and some others, but not too good for decent parts. Sometimes you find them, but you have to search.
There's a guy in Cacem that has Philips caps is almost all values, and 1% film resistors.
It's on the main street, on the Bons Amigos (I think it's called this way) shopping center.

At the beginning, I went to Dimofel but know I go to a small store between Areeiro and Alameda. They sell 4,700uF NA caps, 2.50€ each. ( I don't know if it's a nice price)

LM3886 costs 5€.

But the last time I went there I bought 6,800uF caps

 

[carlosfm]

I'm not saying the values aren't great as they are, I'm just saying that's how you can calculate the values. I don't know if you tried these values yet, but 1 ohm and .1 uf look like good values to correct the impedance issues above 1 mhz.

I'm lowering the impedance at a much lower frequency.
1R+100nf is what I recommended for the unregulated PSU, and it's fine for that.

 

[carlosfm]

They sell 4,700uF NA caps, 2.50€ each. ( I don't know if it's a nice price)

Nice price, but toilet caps.

LM3886 costs 5€.

Do they sell them?

 

[mateo88]

That's cool, I'm not trying to say that you're wrong or anything. I'm just trying to say that you can calculate the snubber by calculating a zobel network based on the output impedance of a power supply.

Just letting people know how to calculate the snubber so they can do it on their own and experiment with values that their ears agree with.

 

[XELB]

Do they sell them?

Yes.
And normally they have a few different LM models in stock



This store was recommended form a friend specialized in electronic and HIFI techniques. ( He is now creating an High End HIFI chip (maximum THD 0,003%)
I have shared your snubber technique with him...

 

[carlosfm]

Just letting people know how to calculate the snubber so they can do it on their own and experiment with values that their ears agree with.

Just try different cap values and keep the resistor at 0.47R.
But why bother?
Try this first, you will not want to touch it.

 

[metalman]

Hmmm ... Thanks for sharing Carlos. This should be pretty easy to add to my current PS setup (only missing the snubber caps and resistors). Let me see if the XGC likes it!

Cheers, Terry

 

[carlosfm]

Hmmm ... Thanks for sharing Carlos. This should be pretty easy to add to my current PS setup (only missing the snubber caps and resistors). Let me see if the XGC likes it!

Cheers, Terry

Do that, try it.