Quad to 2Ch

Ramlee · 6th January 2012, 05:55 AM

Hi DIY friends,

I recently got my hands on (don't ask how) a SANYO LA4645N power amp chip. I was able to download a datasheet for the LA4645 (in Japanese) where I discovered on page1. could be configured to a BTL 2Ch 18W X 2 power amp. I though Great! and scrolled down to see the appropriate test circuit which....wasn't there. The quad configuration is provided and I'm guessing that the 2Ch config. is not a radical departure from the quad. SANYO refuse to help me as the chip is out of production. Can anyone give me any suggestions regarding the 2Ch configuration??...for example, what additional components should be included/excluded to get this thing pumping in stereo.

AndrewT · 6th January 2012, 10:39 AM

The rule for bridging (BTL) is that the bridged circuit gives double the power into double the impedance compared to the single channel amplifier.

If the BTL specification says 18W, then the mono single channel will be 9W.
But at what operating conditions does it produce 18W?
Is it closer to a real 10W or 12W? Meaning you end up with 4 mono channels of about 5W to 6W for each.

Ramlee · 6th January 2012, 02:53 PM

That's exactly right Andrew. The incomplete data sheet says the chip can provide quad 4 x 6W into 4 ohm loads or BTL 2 x 18W into 4 ohm loads. I can send over some information of you have time to take a look.

AndrewT · 7th January 2012, 09:25 AM

No.
You have misinterpreted the datasheet.
18W into 4ohms from the bridged pair is equivalent to 9W into 2r0.
Using this figure, expect >~4.5W into 4r0
But this is still based on the ridiculously distorted waveform. The truth for real maximum Power output will be much less.
That 5W to 6W of real power output is into 2r0, since it is extracted from the 18W into 4r0 bridged pair.

GloBug · 7th January 2012, 12:44 PM

How did you recently get your hands on a Sanyo LA4645N?

Th3 uN1Qu3 · 7th January 2012, 01:29 PM

Probably jacked it from a boombox or something.

Ramlee · 7th January 2012, 02:31 PM

Quote:

Originally Posted by GloBug

How did you recently get your hands on a Sanyo LA4645N?

Truth be told, I found it in a cereal box.

GloBug · 7th January 2012, 04:46 PM

Sweet, I have to get me some cereal with electronic prizes.

6th January 2012, 05:55 AM	#1
Ramlee diyAudio Member Join Date: Nov 2011 Location: the big island	Quad to 2Ch Hi DIY friends, I recently got my hands on (don't ask how) a SANYO LA4645N power amp chip. I was able to download a datasheet for the LA4645 (in Japanese) where I discovered on page1. could be configured to a BTL 2Ch 18W X 2 power amp. I though Great! and scrolled down to see the appropriate test circuit which....wasn't there. The quad configuration is provided and I'm guessing that the 2Ch config. is not a radical departure from the quad. SANYO refuse to help me as the chip is out of production. Can anyone give me any suggestions regarding the 2Ch configuration??...for example, what additional components should be included/excluded to get this thing pumping in stereo.

6th January 2012, 10:39 AM	#2
AndrewT diyAudio Member Join Date: Jul 2004 Location: Scottish Borders	The rule for bridging (BTL) is that the bridged circuit gives double the power into double the impedance compared to the single channel amplifier. If the BTL specification says 18W, then the mono single channel will be 9W. But at what operating conditions does it produce 18W? Is it closer to a real 10W or 12W? Meaning you end up with 4 mono channels of about 5W to 6W for each. __________________ regards Andrew T.

7th January 2012, 09:25 AM	#4
AndrewT diyAudio Member Join Date: Jul 2004 Location: Scottish Borders	No. You have misinterpreted the datasheet. 18W into 4ohms from the bridged pair is equivalent to 9W into 2r0. Using this figure, expect >~4.5W into 4r0 But this is still based on the ridiculously distorted waveform. The truth for real maximum Power output will be much less. That 5W to 6W of real power output is into 2r0, since it is extracted from the 18W into 4r0 bridged pair. __________________ regards Andrew T.

7th January 2012, 01:29 PM	#6
Th3 uN1Qu3 diyAudio Member Join Date: Feb 2010 Location: Bucharest	Probably jacked it from a boombox or something. __________________ "Audio grade" components simply means that they failed at a more critical job.

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6th January 2012, 02:53 PM	#3
Ramlee diyAudio Member Join Date: Nov 2011 Location: the big island	That's exactly right Andrew. The incomplete data sheet says the chip can provide quad 4 x 6W into 4 ohm loads or BTL 2 x 18W into 4 ohm loads. I can send over some information of you have time to take a look.

7th January 2012, 12:44 PM	#5
GloBug Banned Join Date: Jun 2011	How did you recently get your hands on a Sanyo LA4645N?

7th January 2012, 04:46 PM	#8
GloBug Banned Join Date: Jun 2011	Sweet, I have to get me some cereal with electronic prizes.

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