U5 and U1 OpAmp

Hi, for U1 you can use a TL072 op-amp, no problem with that.

For U5 (The op-amp that makes the current sink for the PT2399) you NEED a rail to rail op-amp, the MCP6002 is perfect (the TL972 does not sound good). The thing with this op-amp is that its output needs to go very low, almost to 0V, that's why you need a rail to tail (and U5 is powered at 5V).

I end up using 2xMCP6002 instead of TL072 + MCP6002 because for the end user it's easier to source one op-amp that 2 different models. I know that you are abusing the supply on U1, but we have been doing it for a long time in other projects without problems.

Why do you have the MCP6002 in the BOM instead of the TL072 like you have in the schematic?

Sorry for the confusion, I am updating all the schematics now with the same parts as the BOM.

also the GBW is bigger in the TL072 and has less noise voltage density.

You are totally right, the TL072 is Vn = 18 nV/√Hz (Typical) which is great. I am thinking that for now on I am going to use a TL072 + MCP6002 in the kits and update the assembly manual.
Thanks for the heads up.

EDIT: I have been doing some listening tests and rewrite this post.

Thanks for the feedback, I am updating now the schematic, BOM, manual, etc to include the TL072 option. I will have a look at the Analysis too. Thanks.