Burr Brown OPA 2143 vs NJM2068

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.

Typical bias current for LM4562 is 10nA. Taking into account possible unbalance of 10k we get 0.1mV unbalance.

LM4562 has excellent AC characteristics but the sound is what matters. Benchmark uses it as a driver for XLR outputs because of the ability to drive 600 ohm (not necessarily because of sound). Getting rid of output cap would be a good thing but my Benchmark is still under warranty. NE5532 has bad rap on DIY forum - perhaps because it is so cheap. Somebody tried already replace NJM2068 with OP2132 and complained about metallic sound.

I do not have experience with LM4562 so I would not push for replacement of OPA627 or OPA2134 but original question was about replacement for NJM2068 - pretty old dual amp. Bias current runs here 150nA typ. and 1000nA max (it doesn't get much worse than that) - LM4562 is good candidate here.

Typical bias current for LM4562 is 10nA. Taking into account possible unbalance of 10k we get 0.1mV unbalance.

Good, keep going. Calculate the effect of the input offset current based on the higher of the two source impedances, and add that. Then add the input offset voltage. Then multiply by the the sum by the DC gain of the circuit . . . you now have the number you're after. A mV or two of offset gets pretty scratchy-clackety on the source-selector and volume controls of a following preamp (provided they're DC coupled).

Again, it COULD work fine if you change to DC output coupling to accompany your opamp sub (10nA is pretty low for a bipolar opamp) . . . but like any modification, a full analysis of the particular circuit as it pertains to your particular mod is required if you want to be confident of a positive outcome.