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
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
Pah, I turn my back for five minutes and you're already chasing other PCB designers... MEN! You're all the same! 
😉
😉
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.
Mark
Mark
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.
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.
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
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
pinkmouse said: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.
An externally hosted image should be here but it was not working when we last tested it.
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.
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
Mark A. Gulbrandsen said:
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
I_Forgot said:
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.
Thanks Alex for those Gerbers!! I believe I will give this a try. What I will more than likely do is modify it so the DRV134 is right on the board.
Mark
Mark
Mark A. Gulbrandsen said:
The DRV134's DC offset can be as high as 20mV, so I have to use the input cap to block the DC.
An alternate solution would be the Jeff Rowland way - to use a input transformer to split the input signal to normal phase and reversed phase. The advantage is that you can save the DRV134 and related curcuit. Also the transformer can block all the DC.
Disadvantage is that a good audio transformer is very expensive (e.g. Jensen), and its distortion is much higher than DRV134.
Mark A. Gulbrandsen said:
Please feel free to use it or improve it! Please note that the capacitor 47pF printed on the PCB is the old value, now I use 8pF instead.
47pF rolled off the high frequency a bit too early.
me32dc said:
They are from a Taiwan DIY order site :
http://www.my3c.net/product/default.asp?gid=116
You may need a Chinese friend to help if you want to place an order 🙂
alexw88 said:
Superb looking cases ... can anyone do an English translation, such as prices for the cases, postage etc. ?
i know this is an old thread but i must say that you did a great job...
i checked out that link and it appears one of those cases will cost around $70Canadian shipped...
heh...anyone selling bpa300 pcb's yet?
i checked out that link and it appears one of those cases will cost around $70Canadian shipped...
heh...anyone selling bpa300 pcb's yet?