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Old 26th February 2010, 06:52 PM   #1
maurycy is offline maurycy  United States
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Default Stay with current trafo or add another one?

I am currently running my LM3875 gainclone on small 42VCT 80VA trafo (one trafo and one PSU board). Would I benefit on adding another 42VCT 80VA trafo and additional PSU board to have one trafo for each amp board?

Or should I just go with another trafo all together. I also have dual 21.5V 2.7A available.

Thanks.
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Old 26th February 2010, 07:26 PM   #2
AndrewT is online now AndrewT  Scotland
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since you already have the 21.5Vac 100VA, try adding rectifier and smoothing to that and hear what a monoblock can sound like.
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Old 26th February 2010, 07:37 PM   #3
maurycy is offline maurycy  United States
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Andrew, if I understand you correctly, I should drop the 42VCT I am using and replace it with the 21.5V 2.7A trafo (dual secondaries)? I only have one of those so wouldn't it be the same as adding another 42VCT trafo?
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Old 26th February 2010, 07:49 PM   #4
AndrewT is online now AndrewT  Scotland
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Hi,
you asked about adding a second transformer and PSU to your chipamp.
I presumed you had two channels on the original PSU, since you stated one transformer and one PSU.

My reply suggests separating the two channels and powering each channel as a monoblock.

If you only have one channel, then I think simply doubling up the PSU components will be a waste of resource.
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Old 26th February 2010, 09:32 PM   #5
maurycy is offline maurycy  United States
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Thanks for explanation Andrew. Yes, currently I have two channels, one PSU and one trafo. I will add another trafo and PSU board.

What's the amp wattage is going to be with 21V 80VA supply for each channel with my LM3875?
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Old 26th February 2010, 10:00 PM   #6
AndrewT is online now AndrewT  Scotland
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the datasheet tells you.
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Old 27th February 2010, 02:26 AM   #7
Kinnja is offline Kinnja  United States
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Quote:
Originally Posted by maurycy View Post
Thanks for explanation Andrew. Yes, currently I have two channels, one PSU and one trafo. I will add another trafo and PSU board.

What's the amp wattage is going to be with 21V 80VA supply for each channel with my LM3875?
There is a table on the data sheet "Output Power vs Supply Voltage".

It depends on the speaker impedance.

You will need to figure out what your voltage will be after its been rectified.

Last edited by Kinnja; 27th February 2010 at 02:33 AM. Reason: correction
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