Sometime in the late 90’s to early 2000’s, depending on the manufacturer, the LM308N was discontinued. The good news is the current replacement OpAmp OP07 is a great replacement. The issue is not whether the OP07 sounds the same as the LM308N, the issue is that the market has been flooded with fake LM308N chips.
How is this happening? When the OP07 chips are being created a few of them are sold before they are branded and then branded as LM308N instead of OP07. Or .. The chips have the top sanded and someone prints LM308N on the top. Either way it’s not hard to re-badge a chip and the LM308N is not the only chip that is counterfeited.
So why does this matter? Well it’s fraud. If you pay $10+ for an “authentic” LM308N chip or pay the up-charge for a pedal with the chip in it, then you should get what you pay for. The OP07 chip that is in modern Rat pedals only costs about $1.00 or maybe less if you buy in bulk. You may find this hard to believe, but I have found fake LM308N chips on very reputable sites located in the USA.
The good news is I have created a solid method of testing chips. They occasionally pop up in various places and I buy a sample lot and test them. If they check out then I buy all of them. I, of course, test every LM308N I have ever purchased and only put authentic chips in pedals advertised as having an LM308N chip.
Here is one way to test for a real LM308. As you can see from the picture below the authentic LM308 has very different resistance values.
As an additional test you can pull the compensation capacitor. If the LM308 is authentic the circuit will start squealing or make some other kind of odd noise.
