Choosing of best sounding OP AMPs for the lowest possible THD+N -really the best Way?

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#448
skitron said:
I'm definitely not going to claim it's the best I've found, but for cheap, I'm having good luck using tips I fabricate into a hammerhead shark shape that spans 4 pins. (made by hammering out the end of a copper tip [that has been cutoff square] into a flat "platter" and then cut/file perpendicular to the tip shaft to create the hammerhead shark shape) Then flow enough solder on the hammerhead to ensure good thermal conduction to all 4 pins simultaneously. I use a jeweler's screwdriver ground concave on one of the flat sides to create a sharpened tip as a lifting tool. Then lift a single side via the end of the opamp while heating 4 pins (which slightly bends the pins on the non-heated side in the process). Then ensure no solder bridges from the lifted pins to the pads below. Once clear, apply the hammerhead to the other 4 pins and simply slide the opamp off the pads while grasping opamp with small forceps. I'm usually able to do a pull in 60-120 seconds. I had one near disaster with a pad from not getting good enough thermal contact on one of the pins, but recently modified the tip a little to ensure all 4 are fully contacted in the same portion of the pin bend...plus using a bit more solder on the hammerhead and not worrying about cleaning up some bridged pads after the pull. I've done about 150 pulls of 8 pin SOIC and all the pulls survived and only one pad separation that fortunately did not break from the trace, so was able to solder in a new opamp with no problems. That episode led to tweaking the tip shape for better assurance all 4 pins getting equal heat...
Click to expand...

this seems like a LOT of trouble to avoid using hot air and a $10 USB hotplate ...
 
#449
Well, given one cannot listen before purchasing the parts and implementing them in your design; is there any other way to choose, other than by specification? I would say that listening to them in someone else's design, would make for an utterly useless datapoint for your own design.

I certainly choose based on the needs of the project and the datasheet, to select for a certain bandwidth, performance, power supply voltage and budget. Although in the case of opamps, budget doesnt really come into it for me. even the most expensive IC cost fades by comparison t the rest of the BOM, unless its for a multichannel, composite multiloop design I guess. but even then, if you need, say 30 parts, the most you will be out is a few hundred bucks and you can spend that on a pair of tubes, so spending 100 for cheap chips, or 300 for what is ideal... I generally take the latter; as its not a commercial endeavor.
 
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