And you would still need to test in circuit. The offset spec may be lower on paper, but that doesn’t mean the more modern part will be happy in the circuit as a whole and you may see a dramatic rise in offset when installed.
And +1 in general to the reply above…there isn’t a way to know of compatibility without trying it out…it’s a bit of a crap-shoot whether or not JFET-based parts can be swapped in for BJT-based parts and vice-versa…it all depends on the parts and overarching circuit design. I’m sure people much smarter than I could look at the schematic and data sheets and make an informed prediction, but commoners like me “get out the hammer” and just measure, swap in the replacement part and measure again; offset, distortion, square wave response, and most importantly, ears. Always helpful if there are multiple channels with the same circuit so you can A/B and compare stock vs modified in real time. The majority of the time, not vast majority but a majority, I end up preferring the stock circuit. I find better gains in (if we are talking about 30-40 year old gear) a recap with modern parts including the power supply; often better noise floor gains and better clarity gains depending on the age of the device and quality of the caps than changing opamps…YMMV. But often times the “faster” parts sound more harsh or sharp to me. And we talk an awful lot about the slew rate for a given opamp, but we never talk about the system slew…how responsive the entire signal path is from input to output and to your ears. That’s what you really hear. So a faster opamp here and there is going to have diminishing impact on the system slew. So this is all a mix of factual information and my own opinions and preferences, and, again, YMMV…your ears are different than mine. But I can affirmatively speak to my own experiences messing with opamp changes in a variety of devices and stations in a signal path, and, again, the majority of the time I prefer the stock component. And measuring is crucial. I have done this in circumstances where a certain change was highly recommended…reported to sound “awesome” etc., but there was no quantitative analysis. And I measured and found the output offset of the substitute opamp was 200mV vs the stock part at 20mV in circuit, which is still a bit on the high side but not unusual. But 10x that? No. The part is not happy. Unsuccessful modification.
So…there’s more that nobody asked for. I just think it’s wise to be mindful and intentional when “chasin’ them there waterfalls.”
I still maintain the 553x opamp is still decent on paper, and, generally-speaking, “musical” in circuit. It is the choice in high-zoot designs spanning well into the 2000s by very respected companies. PDG for a part originally released in 1979! My Studer console uses them in the hybrid opamp/transformer output stages (which sound *great*), and the 5534 is used in the mic amp. Neither the mic amp or output drivers are anything akin to garden variety. And my console was introduced in the mid-late 1990s and production ran into the early 2000s…maybe 2003? Other parts used include 33078, DRV134, and SSM2142…these are not cheap parts. They also used the humble TL072, which is maybe one of the most highly utilized audio ICs. Why? It does a good job, and is so popular it is cheap. But it does a good job especially in a well-designed circuit. So what I see in my Studer console is strategic use of particular parts for particular stages…very mindful design…and a low-compromise commitment to quality. And these humble parts (5532/5534, TL072), are used right alongside hi-pro parts. So you have to ask yourself is it more important to have $$$ parts everywhere, or to know where they are necessary/most beneficial?
Things to think about.
