Dual discrete opamp PCB in DIP8 - Page 2 - diyAudio
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Old 13th April 2004, 01:44 AM   #11
tiroth is offline tiroth  United States
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Okay! This is much cleaner. Thanks again to moamps and millwood.

This can be used as a 6-pin SIP with ground, or two together can be linked by the pads on the left side and plug into a standard dual opamp pad.

For use as DIP8, the left half would use leads from 'O'ut through 'N'egative. The right half would use 'P'lus through -IN. Ground could be left unconnected if R10 were soldered to the PCB.

Any comments? BDP, where do you want the adjustable resistor?
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Old 13th April 2004, 02:16 AM   #12
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Quote:
Originally posted by tiroth
Any comments?

it looks great.

One quick suggestion: you may want to drill a "hole" in the middle of the board. You can then tie the two modules togather using a screw through an insulation spacer (between the two modules). and the final module can be inserted into a dip8 socket directly.
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Old 13th April 2004, 03:54 AM   #13
BDP is offline BDP  United States
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Tiroth

The pot. would be used in place of fixed resistor R3 or R4. Since they are in parallel it doesn't matter which one. In MOAMPS parts list the value is listed as 3.9K. The parallel value of 3.9K and 392 equals 357 ohms and I see MOAMPS has a 360 ohm value placed in the circuit previously posted.

BDP
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Old 13th April 2004, 06:56 AM   #14
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Well, one stays away for a couple of days and here what pops up!

Great work, I appreciate a lot the possibility to break the board in half and use it separately.

Cheers

Andrea
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Old 13th April 2004, 12:20 PM   #15
tiroth is offline tiroth  United States
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Thanks for the feedback! I will try to incorporate both suggestions. The screw idea will take up some considerable real estate because of the lateral offset between the boards, but it is a good idea and I'll try to fit it in.
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Old 13th April 2004, 02:50 PM   #16
MBK is offline MBK  Singapore
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Tiroth,

the order of standard DIP 8 op amp pins is different from your PCB, it is "out, (-)in, (+)in", see pic.

I am not sure if it's a good idea to break up the board. As a drop in for dual op amps, it's unnecessarily complicated - better have just one board. And a drop in for a *single* op amp package would still have to be DIP 8, but with conflicting pin arrangements (dual DIP 8 op amps DIL's are not just two opposing single op amp SIL's).

So, I think it's most useful if it's either a drop in for dual op amps, pin compatible, therefore w/o the offset adjust *or* two additional pins, or as a drop in for single op amp (but still in DIP 8). Advantage of the single solution is the smaller board real estate (you don't get such big "wings" to the sides), and offset adjust capability in DIP 8. I wonder though how much offset you would get anyway with a FET input design...
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Old 13th April 2004, 02:51 PM   #17
MBK is offline MBK  Singapore
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Here the single op amp pin layout.
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Old 13th April 2004, 03:47 PM   #18
tiroth is offline tiroth  United States
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Quote:
Originally posted by MBK
the order of standard DIP 8 op amp pins is different from your PCB, it is "out, (-)in, (+)in", see pic.
Ouch, that is what you get for rushing at night. An easy fix. Thanks!

Quote:
I am not sure if it's a good idea to break up the board.
Actually, I think it is simpler routing broken up. And it has a smaller footprint at the expense of vertical height...which means it is more likely to fit into pre-existing designs.

Quote:
And a drop in for a *single* op amp package would still have to be DIP 8
Well, it was never intended to be a DIP8 single opamp replacement. The idea was more that DIYers could feel free to, like moamps, design their boards around the SIP6 form factor if they wanted single discrete opamps.

Quote:
I wonder though how much offset you would get anyway with a FET input design
Virtually none, I think, with 2SK389. The offset adjust trimmer should come in handy for designs using standard (single) JFETs.

Thanks for your input.
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Old 14th April 2004, 01:41 AM   #19
tiroth is offline tiroth  United States
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Updated PCB, with trimmer and screw pads.

The screw pads accommadate a 2-56 screw with 5/32" diameter spacer. R8 was moved to the back, and if you use the optional screw attachment R9 moves the back on the left half and must be soldered after the screw is attached on the right. Pretty easy. I didn't want to increase the board size (and cost) to those who don't need it.

If you are interested in these PCBs, please sign up! I am close to having enough commits to lower the price from 8 for $9 to 8 for $6.
http://www.diyaudio.com/wiki/index.php?page=Moxbuy
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Old 14th April 2004, 03:25 PM   #20
tiroth is offline tiroth  United States
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The price dropped to 8 for $6
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