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Dual mono = dual transformer?

Started by joecool85, January 13, 2007, 11:31:23 AM

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joecool85

I know normally when you do a dual mono you would do two transformers, one for each PSU board...but I have a 330VA transformer running my mono LM3886 and want to add another channel.  I have the stuff for a dual mono, or I could just build the amp board and use the existing PSU board.  Would it better to use the existing PSU board to run both LM3886 amp channels, or build another PSU board and split the power from the transformer to both boards?  This is going to be for a bass rig btw.
Life is what you make it.
Still rockin' the Dean Markley K-20X
thatraymond.com

zyggurat


LM3886 is a 70W amplifier IC, am I right?
So that means you need approximately 140VA transformer to run it , that´s for dual mono 2x140VA=280VA of power altogether. So you can split that power among 2 amps, on both amps there ´ll be same supply voltage in both amps as in the PSU , but  it´ll drain double current from the PSU. So it´s unnecessary to use 2 transformers when that one is powerful enough.

Sorry for my bad english, I still study it  0:)
By the way this forum is great, long time I looked for something like this...

teemuk

I agree with Zyggurat, there is no good reason why the amps could not share the same transformer. The post of Joecool85 is quite old and I once thought about answering it but forgot it then. Anyway, If you use separate power supply (in this case separate rectifiers and filters) for each amp unit each supply has to handle only the current of their corresponding amp. This means decreased (waste) power dissipation per board (thus more durability and longer lifetime) and likely better channel separation between the two amps since loading of one module should not effect the other through power supply sag as much. If you think of it, this should have been pretty obvious in the first place.

joecool85

So you can split the transformer to run two amp PSU boards?
Life is what you make it.
Still rockin' the Dean Markley K-20X
thatraymond.com

teemuk


joecool85

Quote from: teemuk on February 06, 2007, 07:13:04 AM
See the first figure in the article.
http://sound.westhost.com/project04.htm

Sweet, thats exactly what I needed to know.  I'll probably do that basically.  When it's done I'll get some pics up in here, its going to be pretty wicked.
Life is what you make it.
Still rockin' the Dean Markley K-20X
thatraymond.com

zyggurat

Quote from: teemuk on February 06, 2007, 07:13:04 AM
See the first figure in the article.
http://sound.westhost.com/project04.htm

I think there is no need to use two rectifiers and double amount of filter caps, you only have to use caps with double rate of cappacitance and only one rectifier, but  with double current rate , so fo example if you use 3A rectifier and caps with total amount of capacitance 20000uF, for dual amp you´ve got to use at least 6A rectifier and total of 40000uF capacitance for filtering...
Good luck  ;)