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Old 11th December 2005, 04:18 PM   #21
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Nice amp! I would be interested in building the BPA300 for sure. Finally a chip amp that is useful!! Is the board your design or one that is commercially available from Hong Kong? Anyone here in for a group buy on this sort of board. Since Pinkmouse is pretty burried with other PCB requests I could ask a friend over at GE Medical that designs their PCB's to do this for us. He is has been itching for something like this do to on the side.....

If this board is not commercially available then we could just copy it for the most part. If anyone would like to give any input as to modifications or changes please feel free to do so.

Mark
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Old 11th December 2005, 04:50 PM   #22
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Pah, I turn my back for five minutes and you're already chasing other PCB designers... MEN! You're all the same!


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Old 11th December 2005, 04:59 PM   #23
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No, not really but you were the one that listed all the PCB's that you have to do.... excluding the GG of course. I would much prefer that you do it but do really you have the time???? I think this would be a very worthwhile project but I would probably do it with the servo as reccomended by National Semi. We could eliminate the input caps. I am in the middle of reading the N.S. paper and the servo is not that big of deal.

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Old 11th December 2005, 05:08 PM   #24
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S'alright Mark, I forgive you!

I have been tempted by the BPA style designs before, but I was going to use the OPA chips, as I still have a good few to use up in something or other. That PCB design does look good at a glance, and if your mate's up for it then with the help of the schema you should be able to do a reasonable clone.
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Old 11th December 2005, 06:13 PM   #25
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It looks like a really nicely made amp! Well done!

How are you getting the heat out of the box? I see holes in the top, but none in the bottom, and the heatsinks don't look very big for a 300W amp, even if it is class B. Have you monitored the heatsink temperature?

I_F
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Old 11th December 2005, 06:15 PM   #26
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Quote:
Originally posted by pinkmouse
S'alright Mark, I forgive you!

I have been tempted by the BPA style designs before, but I was going to use the OPA chips, as I still have a good few to use up in something or other. That PCB design does look good at a glance, and if your mate's up for it then with the help of the schema you should be able to do a reasonable clone.
If you take two or 3 "bridge boards" and parallel them with the LM4780 you will, equivalently, have 4 or 6 LM3886's -- but you have to be very careful about selecting resistors if you go servo-less.

Click the image to open in full size.

since I have the Gerber file already, I was thinking of incorporating the servo -- as you can see there is plenty of real-estate on the board for a dual opamp, associated components and localized V+ - regulators. I would prefer to do it in surface mount, however.

the OPA's would make a great buffer but there seems little point incorporating them on the amplifier board.
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Old 11th December 2005, 06:23 PM   #27
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very nice and clean work
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Old 11th December 2005, 08:23 PM   #28
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Quote:
If you take two or 3 "bridge boards" and parallel them with the LM4780 you will, equivalently, have 4 or 6 LM3886's -- but you have to be very careful about selecting resistors if you go servo-less.
It would seem to me though that more LM3886's(or4780's for that matter) paralleled would allow a considerably lower output impedence than the lower count 4780 route. I think that was one of the main reasons that Rowland went this route.... if that be true then that would certianly pose a big advantage over a lower chip count. Aside from the several dollars of extra parts I can't see why not servoing them would be a big deal. I would definately want to get rid of the input cap.

Mark
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Old 12th December 2005, 12:55 AM   #29
alexw88 is offline alexw88  Hong Kong
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Quote:
Originally posted by Mark A. Gulbrandsen
Is the board your design or one that is commercially available from Hong Kong? Anyone here in for a group buy on this sort of board.

If this board is not commercially available then we could just copy it for the most part. If anyone would like to give any input as to modifications or changes please feel free to do so.

Mark

Mark, I am not selling these boards but if you like you can use my gerber files to order some.

Attached are the gerber files for the PA150 board, but you still have to make your own DRV134 board because I get mine from a Taiwan web site : www.my3c.net
Attached Files
File Type: zip pa150.zip (66.5 KB, 1234 views)
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Old 12th December 2005, 01:00 AM   #30
alexw88 is offline alexw88  Hong Kong
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Quote:
Originally posted by I_Forgot
How are you getting the heat out of the box? I see holes in the top, but none in the bottom, and the heatsinks don't look very big for a 300W amp, even if it is class B. Have you monitored the heatsink temperature?

I_F

If you look at post #4, you will see threr are holes at the side of the case.

When Idle, the heatsinks are just warm to touch. At full load, the heatsinks gets very hot, but I can still leave my hand on it, so I think the temp. at full load is about 80 degree C.
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