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
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.
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
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.
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:
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
Superb looking cases ... can anyone do an English translation, such as prices for the cases, postage etc. ?