Burr Brown OPA 2143 vs NJM2068

Joaco - TL081 is a single amp. It is very old and very cheap amp designed as a improvement over 741 type (one of the first op-amps). It is not an audio amp. LM4562 comes in single version with completely different number starting with LME.... - I have to check again.

Generally, not a good sub. OPA2134 is FET-input (higher noise voltage, lower noise current) and NJM2068 is bipolar (higher noise current, lower noise voltage). This means that they're optimized for different circuit impedances.

What's wrong with using the original part?

What's wrong with using the original part? - without going into technical stuff let just say that Texas Instr. introduced this part in October 1976 and LM4562 was introduced around 2006. Not only 30 years difference but also TL081 was design as universal amp while LM4562 was designed specifically as an audio amp (with incredible DC spects).

I was referring to the original poster's question - the OPA134 family is excellent, and I can see no reason to sub . . . other than the convienence of what parts one has lying around.

While I don't think the reason of "it's newer!" is in and of itself a valid reason for swapping opamps around, I am also very much NOT a fan of the TL0xx devices - they have an internal resistor in series with the output that can in many applications severely affect phase margin. But it's still a good idea to consider why they were chosen for the original design - and the same reasoning applies to the TL0xx opamps - they're FET-input, and the LM4562 is . . . not. So the current noise for an LM4562 will be MUCH higher than the TL0. A much better choice would be something like an AD845.

Also, with single opamps you generally have to be more careful with subbing - because of those extra pins. In the case of the TL071, it's still internally compensated, and the extra pins are just offset null or something - almost always unused in an audio application. But the PCB designer may still have routed a trace across an NC pin that's not NC on your sub, so you still need to check before you swap.

And something like the 5534 (unlike its dual-opamp brother, the 5532) has external compensation, so you DON'T want to sub around willy-nilly in this case - that and the 5534, despite its age, is still an outstanding opamp.

I was refering to Joaco post about power amp that has TL081. As for 5532, it depends - if it's thin sounding Philips amp I would replace it, but if it is TI amp I would leave it. But if your amp has 5532 it probably has output capacitor (like Benchmark DAC1). Change to LM4562 and you might be able to remove this cap.

Joaco - AD818 is a video amp. It could be used in audio applications (Rowland uses video amps in Capri preamp) but care must be taken. Pinout of the NULL pins is different so verify if NULL feature is used. In addition bias current is much higer. 100MHz bandwidth in not always a blessing. Wide bandwidth amps can often oscillate since small circuit capacitance at 100MHz can "eat out" phase margin.