OPA627BP or OPA637BP for preamp?

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I once built a headphone amplifier which used the 627, followed by a 634 buffer. Swapping the 637 for the 627 resulted in a much more rounded, natural sound to my ears. Both sound great. Just note that the 637 is not unity gain stable and needs a gain of at least 5.
 
once built a headphone amplifier which used the 627, followed by a 634 buffer. Swapping the 637 for the 627 resulted in a much more rounded, natural sound to my ears

Impression seconded in a phono stage. What i really don't get though is why JoeBob is lazy to compare them himself. Too much work?
 
I did compare, I just wanted to see what other peoples opinions were on these parts.

I tried them and my preferance was the 637, gave better sound in my opinion. I liked it alot more, not just a small preferance. But for unity gain, I tried the 627, but in this place I liked a monolythic buffer more ( I used the EL2001).
 
Does anyone know how the 627/637 compare with the regular OP-27/37?

Are the 627/637 quite different internal architectures but designed to do (essentially) the same job as OP-27/37, i.e a pin-for-pin replacement in the appropriate circuit but with "improved" performance?
 
PGW said:
Does anyone know how the 627/637 compare with the regular OP-27/37?

Are the 627/637 quite different internal architectures but designed to do (essentially) the same job as OP-27/37, i.e a pin-for-pin replacement in the appropriate circuit but with "improved" performance?

You will find the differences in the datasheets (www.ti.com and www.analog.com).

For integrators - use OP27
For audio amplifiers - use OPA627

They are pin compatible, except for external trimpot offset pins (usually not needed).
 
PGW said:
Does anyone know how the 627/637 compare with the regular OP-27/37?

Are the 627/637 quite different internal architectures but designed to do (essentially) the same job as OP-27/37, i.e a pin-for-pin replacement in the appropriate circuit but with "improved" performance?
The two products are totally different and has nothing to with each other.

OPA6x7 is a precision JFET type with rather low noise

OPx7 is a bipolar type with low noise type and also MUCH cheaper.
 
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