Simple Chip Amp for P to P wiring

[danielwritesbac]

Originally Posted by AndrewT

. . .A pair of 3886 chip will perform better than a 4780.

BPA200 with LM3886's and 4 ohm woofers is difficult to heatsink, but I can do it.

LM4780 isn't suited for that application, because of heat pooling and the slower thermal interface.

[coldcathode]

I have been looking all over the net for more ideas regarding this project.

I have found a project that seems to be known as PA150 by Alex88?

It uses 3 Lm3886's in parallel then bridged with another 3 in parallel. Very similar to what I want to do.

He then tried it with a Lundahl transformer with some success.

Do you think this could be done in a Point to Point configuration?

The wiring would be a GIANT PITA, but I think it could be done.

I do have the PS with 23AMPS @ about 24 Volts so I think I have the current needed.

The most difficult part of the project would be the PS capacitors that really need to be at the Terminals of the Chip.

Has anyone used the Laser Printer method of etching PC boards? I think the board would be fairly easy to make myself?

I happen to have a very good electronics store about 45 minutes away that sells the Double sided board and etching supplies.

[danielwritesbac]

Originally Posted by coldcathode

I have been looking all over the net for more ideas regarding this project.

I have found a project that seems to be known as PA150 by Alex88?

It uses 3 Lm3886's in parallel then bridged with another 3 in parallel. Very similar to what I want to do.

He then tried it with a Lundahl transformer with some success.

Do you think this could be done in a Point to Point configuration?

The wiring would be a GIANT PITA, but I think it could be done.

I do have the PS with 23AMPS @ about 24 Volts so I think I have the current needed.

The most difficult part of the project would be the PS capacitors that really need to be at the Terminals of the Chip.

Has anyone used the Laser Printer method of etching PC boards? I think the board would be fairly easy to make myself?

I happen to have a very good electronics store about 45 minutes away that sells the Double sided board and etching supplies.

Well, this is quite easy to point-to-point wire. The local power caps per each chip would be 100uF to make for 300uF (right on the mark) per each rail of PA150. A circuit board would actually increase the difficulty.

To get the BPA300 stereo/dualmono, its just four of PA150 and two transmitter size heatsinks (about $40 or less for a pair).

For triple parallel, its crucial to avoid a difference in DC offset!! Any difference in DC offset and it will play its own tune that sounds like: "chunka, chunka, chunka, flippy, flippy, doo."

Perhaps, an easy helper is to have a single signal star ground per each PA150, and therefore the groundlift resistor (or thin solid core cable, or trace) that creates the signal star ground isn't different.
Each chip does seem to require its own dividers for NFB and the individual feedback resistors needs to be 1% tolerance matched.

Question: Can a single NFB cap operate all 3 chips in a PA150?

Question: Is this right--in non-inverting LM3886 PA150, a 100k feedback resistor per chip should have unified 300k input impedance; and, likewise, a 50k feedback resistor per chip in PA150 should have unified 150k input impedance?

P.S. Standing by, with the soldering irons hot.

[danielwritesbac]

Oops! Gotta run for this weekend. Darnit!

Oh, but anyway, the easy way to make the board is to use the special pen and just draw on it instead of those hours wasted at the computer software, trying to convince it to draw a line where you want. Does your store have that pen (protects copper from etchant, wherever you draw)?