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New LME Design -bridged / balanced inputs
New LME Design -bridged / balanced inputs
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Old 2nd April 2009, 01:01 PM   #1
AudioGrade is offline AudioGrade  Germany
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Question New LME Design -bridged / balanced inputs

Hi,

I want to design a 150W amp with the LME 49830 / IRFP240 for an active speaker (SMD).

But Ive a problem to find an nice symmetrical design for such an amp for a bridged applikation which should be controlled by a balanced input.

Does anyone use the LME in inverted mode?
Ok, I could use the standard-application for each side, but I think it must be possible to use a symetrical design for a perfect performance?!

Does any user has done this before or any experience with such a design?

Thanks and regards,

Wolfram
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Old 3rd April 2009, 08:50 PM   #2
qsa is offline qsa  Germany
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You should use Quasi symetrical design for mosfet amplifier with LME..., performance and sound will be excellent compare to than IRFP9240 / IRFP240.

IRFP9240 / IRFP240 looks symmetrical but they are not symmetrical. If you want symmetrical design you should use IRFP310 for IRFP240.

I had build many years before symmetrical mosfet amplifier with IRFP9240 / IRFP240 devices, performance in sound was worse...


Check schematic from Quasi member for Quasi symetrical mosfet design

Next time i will designing Quasi symmetrical mosfet design with LME
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Old 3rd April 2009, 08:58 PM   #3
ostripper is offline ostripper  United States
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IRFP310 ?? google says it is discontinued.
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Old 3rd April 2009, 11:38 PM   #4
Nelson Pass is offline Nelson Pass  United States
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New LME Design -bridged / balanced inputs
Quote:
Originally posted by qsa
I had build many years before symmetrical mosfet amplifier with IRFP9240 / IRFP240 devices, performance in sound was worse...
The IR version of the P channel parts have a known flaw in which
the transconductance "shelves" to a lower figure in the mid-band.

This makes them even less of a match for the N channel parts, and
you want to consider that when designing with them.

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Old 5th April 2009, 02:27 PM   #5
AudioGrade is offline AudioGrade  Germany
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Hi,

thanks for the answers. The module should be a part of a new acitve speaker electronics as shown:

An externally hosted image should be here but it no longer works. Please upload images instead of linking to them to prevent this.


In this picture is only one LME placed, so Ive to update it soon.

Here is my sheet for the first, with no values and a bit drawn "quick and dirty":

An externally hosted image should be here but it no longer works. Please upload images instead of linking to them to prevent this.


Here is the seen the beginning of the pcb-placement for this sheet:

An externally hosted image should be here but it no longer works. Please upload images instead of linking to them to prevent this.


So it will be a very tiny amplifier module, I hope

Because the SK1530/SJ201 are very difficult to buy here in Germany I want to use the IRFPs.

@Nelson:

Im having no much experience in matching FETs. Do you advice the SK1530 or to match the IRFPs?

Thanks and regards

Wolfram
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Old 5th April 2009, 04:35 PM   #6
AudioGrade is offline AudioGrade  Germany
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Ups, just seen that the embedded screens arent really good read ..

Here are the attached ones...

Regards,

Wolfram
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File Type: png be200-sch.png (31.7 KB, 187 views)
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