The (high-cap.) unregulated PSU for chipamps - Page 51

carlosfm · 17th September 2005, 02:35 PM

Quote:

Originally posted by Aghead
So if one wanted to use a pair of say, 25000uf caps i happen to have in place of C3 to C6, does that change everything or is it a reasonable substitution?

That's fine, you can use them without any other change.

XELB · 17th September 2005, 07:38 PM

I just got a new trafo, 20-0-20 650VA.
This will give me 16,25A.....

I was thinking to use the MUR860 as you, Carlos, use on you unregulated PSU.
But, I am affraid that the MUR860 could burn

with such amount of current

Any advise ?

Thanks.

carlosfm · 17th September 2005, 09:18 PM

Quote:

Originally posted by XELB
Any advise ?

I have used the MBR16100 on one PSU.
You can also try the MSR1560.

MikeLewis · 19th September 2005, 05:59 PM

I haven't done extensive load testing on it yet, but I used MUR1560's and they seem to be holding up fine on a 650VA, 50,000uf per rail snubbered PSU. I'll let you know hot hot they're getting once I start to push it.

Mike

XELB · 19th September 2005, 06:21 PM

Thanks Mike.

I will use the 650VA trafo in a PSU with ~70.000uF p/ rail.
This will feed four LM3886 chips bridged, two for each channel.

If you don't have problems, I think that I will not have

Mick_F · 26th September 2005, 11:56 AM

This surely is the king of faq, but nevertheless I'd like to ask: Does the power rating of the 0R47 and 0R1 snubber resistors really need to be that high (2W and 1W, respectively)?
Estimating the dissipation in these resistors I arrive at values of the order of microwatts. Even with very generous assumptions for the values involved, shouldn't ratings of the order of 1/4 be plenty?

I am asking because I am close to finishing the supply, but I have only access to wirewound resistors with high power rating. Since these (potentially) possess a high inductance, I'd prefer not to use them.

Mick

jackinnj · 26th September 2005, 12:53 PM

Quote:

Originally posted by Mick_F
This surely is the king of faq, but nevertheless I'd like to ask: Does the power rating of the 0R47 and 0R1 snubber resistors really need to be that high (2W and 1W, respectively)?
Estimating the dissipation in these resistors I arrive at values of the order of microwatts. Even with very generous assumptions for the values involved, shouldn't ratings of the order of 1/4 be plenty?

I am asking because I am close to finishing the supply, but I have only access to wirewound resistors with high power rating. Since these (potentially) possess a high inductance, I'd prefer not to use them.

Mick

Shhhh, it's a secret -- once the power supply is "loaded" with a real amplifier the snubber RC network performs only a decorative function.

Mick_F · 26th September 2005, 01:57 PM

Cmon. I'd really like to know

jackinnj · 26th September 2005, 02:09 PM

the amount of energy stored by the capacitor (then dissipated by the resistor) is given by the equation:

P = C * F * (V^2) where V is the ripple voltage.

Mick_F · 26th September 2005, 02:24 PM

Quote:

the amount of energy stored by the capacitor (then dissipated by the resistor) is given by the equation:

I know, this is how I made my estimate of the power dissipation (and arrived at some milliwatts).

17th September 2005, 07:38 PM	#502
XELB diyAudio Member Join Date: Dec 2004 Location: Lisboa	I just got a new trafo, 20-0-20 650VA. This will give me 16,25A..... I was thinking to use the MUR860 as you, Carlos, use on you unregulated PSU. But, I am affraid that the MUR860 could burn with such amount of current Any advise ? Thanks. __________________ If you want power you must add control

19th September 2005, 06:21 PM	#505
XELB diyAudio Member Join Date: Dec 2004 Location: Lisboa	Thanks Mike. I will use the 650VA trafo in a PSU with ~70.000uF p/ rail. This will feed four LM3886 chips bridged, two for each channel. If you don't have problems, I think that I will not have __________________ If you want power you must add control

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19th September 2005, 05:59 PM	#504
MikeLewis diyAudio Member Join Date: Aug 2005	I haven't done extensive load testing on it yet, but I used MUR1560's and they seem to be holding up fine on a 650VA, 50,000uf per rail snubbered PSU. I'll let you know hot hot they're getting once I start to push it. Mike

26th September 2005, 11:56 AM	#506
Mick_F diyAudio Member Join Date: Jun 2005 Location: Cologne	This surely is the king of faq, but nevertheless I'd like to ask: Does the power rating of the 0R47 and 0R1 snubber resistors really need to be that high (2W and 1W, respectively)? Estimating the dissipation in these resistors I arrive at values of the order of microwatts. Even with very generous assumptions for the values involved, shouldn't ratings of the order of 1/4 be plenty? I am asking because I am close to finishing the supply, but I have only access to wirewound resistors with high power rating. Since these (potentially) possess a high inductance, I'd prefer not to use them. Mick

26th September 2005, 01:57 PM	#508
Mick_F diyAudio Member Join Date: Jun 2005 Location: Cologne	Cmon. I'd really like to know

26th September 2005, 02:09 PM	#509
jackinnj diyAudio Member Join Date: Apr 2002 Location: Llanddewi Brefi, NJ	the amount of energy stored by the capacitor (then dissipated by the resistor) is given by the equation: P = C * F * (V^2) where V is the ripple voltage.

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