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Old 26th April 2005, 01:29 AM   #11
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Default Re: Re: LM338 regulated snubberized PSU for audio amplifiers

Quote:
Originally posted by mateo88
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...
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Old 26th April 2005, 01:35 AM   #12
mateo88 is offline mateo88  United States
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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.
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Old 26th April 2005, 01:44 AM   #13
XELB is offline XELB  Portugal
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Quote:
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
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Old 26th April 2005, 01:48 AM   #14
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Quote:
Originally posted by 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.
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.
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Old 26th April 2005, 01:52 AM   #15
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Quote:
Originally posted by XELB
They sell 4,700uF NA caps, 2.50 each. ( I don't know if it's a nice price)
Nice price, but toilet caps.

Quote:
Originally posted by XELB
LM3886 costs 5.
Do they sell them?
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Old 26th April 2005, 01:55 AM   #16
mateo88 is offline mateo88  United States
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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.
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Old 26th April 2005, 02:00 AM   #17
XELB is offline XELB  Portugal
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Quote:
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...
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Old 26th April 2005, 02:05 AM   #18
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Quote:
Originally posted by mateo88
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.
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Old 26th April 2005, 02:07 AM   #19
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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
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Old 26th April 2005, 02:09 AM   #20
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Quote:
Originally posted by 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
Do that, try it.
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