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Old 11th May 2004, 02:57 AM   #1
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Default Feeler Wiki up - paralleled 4780 board bulk-buy

Hey mod team, if this needs to be over in another section, please feel free to throw it there.



A BUNCH of folks have been following my LM4780 paralleled amp project, and I've gotten a number of E-mails asking about buying boards.

I mean, a NUMBER of E-mails.

I'm an old hand with bulk-buys, having orchestrated the moving of several thousand white LEDs direct from Nichia Chemical Corp. in Japan (and correspondingly several thousand dollars from about a hundred people), so I'm debating another bulk-buy - this one of PC boards of my paralleled LM4780 design.


The board will be double-sided with plated holes and vias, full solder masks and silkscreened parts locations. Each board will be 3.8" by 2.5" and will contain TWO AMPLIFIER BOARDS, panellized. These can be hooked up in parallel to double output power or run separately for stereo. With a supply voltage of 60 volts rail-to-rail the amps should hit 120W RMS into an 8-ohm load.

The board design includes integrades close-to-chip decoupler cap mounting points as well as integrated thumpless mute. The design has thus far proven itself surprisingly immune to noise and hum. You'll need to provide appropriate supply filtration and run the mute connect points to some form of SPDT switch or relay. Additionally, the board is designed first and foremost to be compact - its connect points are for soldered wire, not terminals or connectors. It's not meant for temporary installation.


I don't do bulk-buys until I do a feeler, as standard policy. To that end I have posted a feeler page in the Wiki for everyone interested to post their desired quantity of boards. The more the cheaper, and price per board is posted in the Wiki page.

Wiki paralleled-LM4780 board feeler page


Pics of the prototypes will come shortly.

oO
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Old 11th May 2004, 03:02 AM   #2
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Prototype boards, and a couple LM4780s:

Click the image to open in full size.



Prototype populated with parts:

Click the image to open in full size.



Prototype built:

Click the image to open in full size.



Prototype being tested:

Click the image to open in full size.

oO
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Old 15th May 2004, 03:07 PM   #3
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A quick bump...

oO
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Old 17th May 2004, 02:12 AM   #4
jhead is offline jhead  United States
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How might your board design differ from Brian's and Peter's would you se yours haveing a advantage
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Old 17th May 2004, 02:43 AM   #5
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Quote:
Originally posted by jhead
How might your board design differ from Brian's and Peter's would you se yours haveing a advantage
Only size. Mine's about the smallest of the designs. Since all of us are working off the datasheet's schematic the circuits will all be about the same.

That's the downside to having several people come up with working board designs at the same time - it's almost an eeny-meeny-miney-moe type thing to choose a board!

oO
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Old 17th May 2004, 03:55 AM   #6
jhead is offline jhead  United States
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Then I guess it might also come down to the end price to purchase as well as ease to build and aquire parts
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Old 17th May 2004, 05:20 AM   #7
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Quote:
Originally posted by OddOne


Only size. Mine's about the smallest of the designs.
I guess, you mean the smallest PS caps? What is the size of your board? I'm in an inquiring mood tonight

BTW, you use Zobel, right?
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Old 17th May 2004, 04:39 PM   #8
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Quote:
Originally posted by Peter Daniel


I guess, you mean the smallest PS caps? What is the size of your board? I'm in an inquiring mood tonight

BTW, you use Zobel, right?
1.75" x 2.5" with the chip along the narrow end. I figure if I mount 'em like blade computers I could stuff probably sixteen into a 2U rack chassis. (Picture that kind of a setup, muahahahahah! )

No Zobel, unless you count the load-balancers the chip calls for in parallel as they sure look like Zobels to me.


Personally I think the three of us with 4780 boards should swap a board with each other and then come up with a single design that kicks the most backside. But, that's just me.

oO
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Old 17th May 2004, 04:44 PM   #9
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The PS caps seem to be rather small, what dia. are those?
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Old 18th May 2004, 05:59 PM   #10
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Quote:
Originally posted by Peter Daniel
The PS caps seem to be rather small, what dia. are those?
They are small, as the board design moves all supply-rail filter capacitance off the main amp board. All that's on the board are local filters and decouplers.

Something has to give in order to provide for a small footprint - in this case the supply-rail filters are off-board.

Seems to work rather well in my tests though.

oO
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