LM338 regulated snubberized PSU for audio amplifiers

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carlosfm

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homer09 said:
I think XLEB was asking about max current handling, not max voltage handling. Yes the LM388T could handle 35VAC * 1.41 = ~50VDC.
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And I answered that the rectifiers don't have problems with a 340VA trafo, at 2x35V.
This was his question.:D
I know, it sounds funny, but it was his question.:clown:

homer09 said:
LM388T can handle continuous up to 5A and peak at 7A. So this means you will reach your trafo's max before you reach the LM338T's limit. As for heat, i have no idea.
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It can handle 12A peak, with a voltage differential between input and output at around 10V.
More than this, it will have lower peak current, and it will also dissipate more heat.:hot:
At a voltage differential or around 10V it doesn't get hot, doesn't need big heatsinks.
Check this graph:
 

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carlosfm

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Joined 2003
XELB said:
That's why you buy them so cheap.
The LM338 STEEL costs 3 times more ;)
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Of course, the K version is much more expensive.
If you don't mind paying the extra, you can make something pretty.
I love TO3 devices, and they deserve to be shown to the outside world.;)

Take a look at these TO3 chips, at $80 each, for quantities of 1,000.:eek:
 

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XELB

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Joined 2004
homer09 said:



I think XLEB was asking about max current handling, not max voltage handling. Yes the LM388T could handle 35VAC * 1.41 = ~50VDC.

But the question is, could it handle all the current that that the trafo is capable of sending its way?

35 x 2 secondaries means: 340VA/(2*35) = ~4.85 A (same result that XLEB got)

LM388T can handle continuous up to 5A and peak at 7A. So this means you will reach your trafo's max before you reach the LM338T's limit. As for heat, i have no idea.
Click to expand...

At least, some one that can understand me :D LOL :D
(next time I will say that it's 2x35) :p


Thanks for the info!



[inocent] What is a TRAFO ? [/inocent] :angel:
Abreviation of Transformer ?



PS: Next time I will make the calculations for the babies :dead: :clown:
 
X

XELB

Member
Joined 2004
BTW with your trafo I would regulate for at least 35V.
You are hitting 50V DC out of it, and regulating for 30V will dissipate lots of heat.
And less current out of the LM338 regs.
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The problem is that my actual chip can only handle 42V :bawling:

Quote from the datasheet:
Maximum supply voltage
VCC max ± 42 V
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Maybe this is my confusion! Max VCC is max DC voltage, correct ?


If so, 35V * 1,41 = 49,35V DC

With 30V I will cross the line.... but I think that will have no problem. ( 30V*1,41= 42,3V DC)
 
homer09

homer09

Member
Joined 2004
carlosfm said:


And I answered that the rectifiers don't have problems with a 340VA trafo, at 2x35V.
This was his question.:D
I know, it sounds funny, but it was his question.:clown:

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carlos, what im starting to see is that you often answer the questions people should be asking, or will be asking and rarely give direct answers (unless they are asking the right question of course). you are always one question ahead, i think thats where a lot of the arguements get fired up and why people dont always understand your answers. (because they are one step behind. :clown: )

maybe you should start your posts with: "i think you should be asking me this .... And the answer to that question is ...."

just my 2 cents on your way of giving yours :D

heck, as long as i could keep up with you, i have a great source of knowledge ;)
 
X

XELB

Member
Joined 2004
I love TO3 devices, and they deserve to be shown to the outside world.

Take a look at these TO3 chips, at $80 each, for quantities of 1,000
Click to expand...




When hot, they seem great to make same sardines
An externally hosted image should be here but it was not working when we last tested it.





Yes, they are nice
An externally hosted image should be here but it was not working when we last tested it.
 
C

carlosfm

Banned
Joined 2003
homer09 said:
carlos, what im starting to see is that you often answer the questions people should be asking, or will be asking and rarely give direct answers...
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I was confused with the question, and I thought he was worried about the rectifiers, even if it doesn't make sense, but who knows?;)

homer09 said:
... (unless they are asking the right question of course).
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That would be good.:xeye:
 
neutron7

neutron7

Member
Joined 2003
diyti.com
2 bits of metal welded together cost at least 3 cents (TO3). after the middlemen thats worth 5 DOLLAH! /joke

Well actually its more because they cant just buy a to3 package and put the chip in it. they have to weld the can head to the metal after the chip is mounted to it.

With a 220, they just have to mount it on a pre-cut peice of aluminium and then encapsulate it or whatever they do with the plastic used on all the other chips they make zillions of.

Some places may not even be able to make TO3 any more. so they have to send out their chips to be TO3ed. How many TO3 packages do you see in new electronics these days? they are almost as rare as tubes.
 
N

nina

Member
Joined 2005
carlosfm said:
Here it is.
Results are impressive, this elevates the chipamp to a league of it's own.:cool:

:att'n: Notice that I recommend 1,000~2,200uf caps on the chips, snubberized.:att'n:
I'm using 2,200uf.
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Just curious what the cap you using on the ships are? Do it still need those good quality cap (e.g. FC, BG, Nichicon, low impedence XXX brand) on chips ... or just NORMAL xxx-brand cap with snubber are fine?


:confused:
 
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carlosfm

Banned
Joined 2003
Re: Re: LM338 regulated snubberized PSU for audio amplifiers

nina said:
Just curious what the cap you using on the ships are?
Click to expand...

I used Jamicon 2,200uf caps on the chips, on this amp.
On another amp I'm updating I'm using Philips caps.

nina said:
... or just NORMAL xxx-brand cap with snubber are fine?
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"Normal" caps are fine, as long as you don't use too "normal" ones from unknown or dubious brands.
The snubber makes it's role there.
 
N

NealG

Member
Joined 2003
Carlos, many thanks for this idea. It works really well a big :up: from me. :drink: !

I had to change the caps at the chips to 2200µF (Pan FC) from 100µF then add the 330nF as recommended.

The amp has improved across the board, most noticeably in the HF then the midrange. The best ‘gainclone’ sound I have heard to-date, thankyou!
 
Idefixes

Idefixes

Member
Joined 2003
audiyofield.wifeo.com/index.php
Heres my interpretation of Carlos (thanks for all sharing) PSU Schematic. Larges Cap are Mallory 22.000mF/40V I have instock.

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


This psu will go with a XGC that had the snubber section on his Bord.

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


There could be mistake in the bord i have to check them one more.

Marc
 
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