diode bridge

laki101 · 20th January 2010, 05:08 PM

Making my first amp ever its an IC lm3886
now I am currently doing the power supply a have a 2x25v 250VA torus trafo and I need to make it DC of course

Now in the original plans (which are a bit weird) it says to use mur860 but cause my trafo has a bit too many volts I was suggested to use some oder diodes and condensers in parallel to the diodes.
I have 2 250v 25A grez bridges so could I use them and what condensers to use?

Joshua_G · 20th January 2010, 05:29 PM

The MUR860 diodes are ultra fast recovery ones, therefore highly recommended over conventional diodes or bridge rectifiers. If you need to drop only few volts, the best solution will be to use the MUR860 diodes for rectification and following it few conventional diodes in series. Conventional power diodes drop about 0.6 – 0.7 volt each. Choose diodes appropriate for the peak current consumption of your amplifier.

woody · 20th January 2010, 06:49 PM

Why do you say your transformer has to many volts? A transformer with 2 25V windings will let you have about 33V + and - after the bridge rectifier and filter caps. Isn't that about perfect for the gainclone?

laki101 · 20th January 2010, 07:15 PM

well I am new here so I was told it would be a bit too much for the lm3886 but cause I will make the amp with 2 parallel IC for better sound I am not sure now

so cause I alredy bought 4 mur 880 (there just a bit stronger then 860) I will probably make just the +, see how much power it makes and then decide on what to do

AndrewT · 07:30 PM

Quote:

Originally Posted by laki101

.....I was told it would be a bit too much for the lm3886 but cause I will make the amp with 2 parallel IC for better sound ................

Laki, you have misunderstood the advice and the reasons given in that other thread.

Quote:

was suggested to use some older diodes and condensers in parallel to the diodes.

who said this? It's sounds familiar and misleading.

laki101 · 21st January 2010, 05:30 PM

made first half and tested it works and I have exactly 35V so will this do for PA100(2x2 lm3886)

Joshua_G · 21st January 2010, 07:14 PM

According to the manufacturer, the supply range is 20V - 94V: LM3886 - High-Performance 68W Audio Power Amplifier with Mute so there's no problem with 35 Volt.
When paralleling ICs, there's no change in supply voltage, only in the supply current.
Make sure you know how to parallel ICs, or have a known schematic showing how to do it.

laki101 · 22nd January 2010, 09:17 AM

I have an schematic for audio input and as I understand I just do the power supply part like I would with one IC for every IC so just double it

Joshua_G · 22nd January 2010, 02:17 PM

With 2 ICs you need the same amount of voltage and double the amount of current than with 1 IC.

20th January 2010, 05:08 PM	#1
laki101 diyAudio Member Join Date: Dec 2009	diode bridge Making my first amp ever its an IC lm3886 now I am currently doing the power supply a have a 2x25v 250VA torus trafo and I need to make it DC of course Now in the original plans (which are a bit weird) it says to use mur860 but cause my trafo has a bit too many volts I was suggested to use some oder diodes and condensers in parallel to the diodes. I have 2 250v 25A grez bridges so could I use them and what condensers to use?

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20th January 2010, 05:29 PM	#2
Joshua_G diyAudio Member Join Date: Nov 2008 Location: Israel	The MUR860 diodes are ultra fast recovery ones, therefore highly recommended over conventional diodes or bridge rectifiers. If you need to drop only few volts, the best solution will be to use the MUR860 diodes for rectification and following it few conventional diodes in series. Conventional power diodes drop about 0.6 – 0.7 volt each. Choose diodes appropriate for the peak current consumption of your amplifier.

20th January 2010, 06:49 PM	#3
woody diyAudio Member Join Date: Jan 2002 Location: Tyrone Ga. U.S.A.	Why do you say your transformer has to many volts? A transformer with 2 25V windings will let you have about 33V + and - after the bridge rectifier and filter caps. Isn't that about perfect for the gainclone?

20th January 2010, 07:15 PM	#4
laki101 diyAudio Member Join Date: Dec 2009	well I am new here so I was told it would be a bit too much for the lm3886 but cause I will make the amp with 2 parallel IC for better sound I am not sure now so cause I alredy bought 4 mur 880 (there just a bit stronger then 860) I will probably make just the +, see how much power it makes and then decide on what to do

21st January 2010, 05:30 PM	#6
laki101 diyAudio Member Join Date: Dec 2009	made first half and tested it works and I have exactly 35V so will this do for PA100(2x2 lm3886)

21st January 2010, 07:14 PM	#7
Joshua_G diyAudio Member Join Date: Nov 2008 Location: Israel	According to the manufacturer, the supply range is 20V - 94V: LM3886 - High-Performance 68W Audio Power Amplifier with Mute so there's no problem with 35 Volt. When paralleling ICs, there's no change in supply voltage, only in the supply current. Make sure you know how to parallel ICs, or have a known schematic showing how to do it.

22nd January 2010, 09:17 AM	#8
laki101 diyAudio Member Join Date: Dec 2009	I have an schematic for audio input and as I understand I just do the power supply part like I would with one IC for every IC so just double it

22nd January 2010, 02:17 PM	#9
Joshua_G diyAudio Member Join Date: Nov 2008 Location: Israel	With 2 ICs you need the same amount of voltage and double the amount of current than with 1 IC.

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