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Old 24th January 2013, 07:01 PM   #31
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I don't want to have to use heat sinks, so multiple OpAmps is the way forward for me I think. As for buying the PCB, I much prefer to make my own. As I said in a previous post, I will use prototype board, populate them with OpAmps and then stack the boards using stackable headers. This means I can try each board and add to them easily.

Thanks for the eBay link to the NE5532s Counter Culture'
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Old 26th January 2013, 01:51 PM   #32
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I've ordered a few bits and pieces and come up with a design. The prototype PCBs I found on eBay have a nice layout which works well when laying out the board, not too many cuts and jumpers needed:

Copper Prototype PCB Stripboard/ Printed Circuit Board/Strip/Vero Board | eBay

The amp boards and the input boards are stackable using stackable headers. Here is the layout done in DIYLC:

Click the image to open in full size.

The boards will have a little cut off each edge as indicated on the drawing with the black vertical lines. The grey link wires represent connections on the bottom of the boards. There are also 2 jumpers on each amp board to allow you to disconnect the input and output of the board.

By making the boards stackable, you can simply keep adding boards until you have enough current output. It works out pretty cheap to make each board as all the components can be bought in bulk. Maybe as cheap as £4 a board.

I think I will make up for the cost of parts in the cost of time


I'll make an input board and a couple of amp boards and test. If successful, I will make another input board and eventually have 6 amp boards per channel. This will give me 96 OpAmps per channel and if we say each one can run comfortably at 25mA, then I will have 2.3A output capacity on each channel.
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Last edited by portreathbeach; 26th January 2013 at 01:56 PM.
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Old 26th January 2013, 02:30 PM   #33
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The short coloured wires shown of the boards above are just an indication of what each pin of the headers are. Only the input board has any wires actually attached to it. The amp boards get there power and signal via the 8 pin stackable headers (represented on the drawing as black circles). The output from each board connects via the 3 pin stackable header at the top.

Using stackable headers means that you only have to fix the bottom board to the chassis, the rest will support themselves.
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Old 26th January 2013, 02:43 PM   #34
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I started to make an op-amp "power amp" a couple years ago but got bored (overwhelmed?) will all my projects so it never got finished.

The original plan was 20x opa2134 per channel configured as unity buffers. In the pic I had one "PowerTower™" completed. The cardboard was intended as spacers to make an airflow gap between each op-amp. You can also see local ceramic decoupling caps and 10R output resistors on each output.

I think I just threw the whole thing in the trash a couple weeks ago.
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Old 26th January 2013, 04:22 PM   #35
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That's a shame, did you ever try it out?
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Old 26th January 2013, 04:44 PM   #36
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No, that channel still needed the driving op-amp installed for gain and feedback. I actually just found the stack broken in half in the trash bag I threw it in. Was cleaning up my junk room but the trash bag never actually made it to the curb (winter lazyness). Maybe I'll turn it into a headphone amp some day.

I have a couple hundred SOIC and TO-220 BUF634 that would probably be better suited for the task of a power amp anyway.
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Old 26th January 2013, 07:52 PM   #37
ahaja is offline ahaja  Poland
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2 weeks ago I made for fun p2p headphone amp with multi opamps.
One channel:
Buffer - ne5532
Gain stage - op27 (AD)
Output stage - njm4556 x5

schematic

inputs and buffers

alps pot

gain stage and output buffers

Works very good.
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Last edited by ahaja; 26th January 2013 at 07:55 PM.
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Old 27th January 2013, 09:08 AM   #38
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Nice. Hopefully mine will sound good
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Old 28th December 2013, 08:52 PM   #39
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Any progress on this OP?
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Old 30th December 2013, 05:57 AM   #40
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I have to admit, id love to try this with the dozen or so LT1115/LME49710 i have lying around...
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