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| OK audio gurus: What are the highly regarded FET-input op amps these days? |
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| SiliconWizard:
--- Quote from: cvanc on December 07, 2018, 02:42:59 pm ---They are OPA2134PA and OPA2134PAG4. The 'G4' is never explained in the datasheet. Any idea what it all means? And thanks again. --- End quote --- See here: https://forum.digikey.com/t/texas-instruments-e4-g4-suffix-information/95 It's related to the lead finish and apparently parts with and without G4 are now equivalent (G4 used to be the "green" finish - lead free - but they are all "CU NIPDAU" now as you can see in the datasheet.) Due to stock reasons, you will find that there can be significant price difference between the two, whereas they are basically the same AFAIK. |
| cvanc:
--- Quote from: SiliconWizard on December 07, 2018, 04:25:58 pm --- --- Quote from: cvanc on December 07, 2018, 02:42:59 pm ---They are OPA2134PA and OPA2134PAG4. The 'G4' is never explained in the datasheet. Any idea what it all means? And thanks again. --- End quote --- See here: https://forum.digikey.com/t/texas-instruments-e4-g4-suffix-information/95 It's related to the lead finish and apparently parts with and without G4 are now equivalent (G4 used to be the "green" finish - lead free - but they are all "CU NIPDAU" now as you can see in the datasheet.) Due to stock reasons, you will find that there can be significant price difference between the two, whereas they are basically the same AFAIK. --- End quote --- Hey, thank you! Clears things right up. |
| Zero999:
--- Quote from: Kleinstein on December 07, 2018, 11:49:17 am ---It depends very much on the circuit if a faster OP can be used. If there are more complicated parts (especially active parts) in the FB path, a faster OP can be a problem. However typical preamplifier circuits with just some gain or filtering may very well work with an faste OP too. --- End quote --- I agree, if it's a basic op-amp circuit, then it should generally be OK, even with a faster op-amp. The main risk is the board layout and decoupling might be insufficient for a fast op-amp, but as long as you don't go crazy, it should be fine. --- Quote from: cvanc on December 07, 2018, 02:42:59 pm ---Thanks everyone for your input and suggestions, they are always appreciated. I'm going to sidetrack my own thread and ask a question now about the various versions of OPA2134. They look nice to me, but Digi-Key stocks 2 slightly different part numbers. Here's the kicker: As far as I can see even the T.I. datasheet (link below) doesn't explain what the difference is. The 2 part numbers read identically in all specifications. They are OPA2134PA and OPA2134PAG4. The 'G4' is never explained in the datasheet. Any idea what it all means? And thanks again. http://www.ti.com/lit/ds/symlink/opa134.pdf --- End quote --- You've not said what the piece of equipment is or what op-amps were originally used? If it's replacing something like the LF351, then the OPA134 is only a little faster so shouldn't cause any problems, unless there are other gain stages in the feedback loop, but if it's something really slow and low power, such as the TL061, it becomes more of a risk and the power consumption will be a higher too. Will you notice any difference in sound quality? Probably not. The only way to tell honestly is by conducting a blind test, to eliminate any cognitive bias you may have. Fit sockets to the PCB, cover the part numbers on the ICs and randomly swap them around to see if you can tell the difference. |
| floobydust:
OP, with audio op-amps most EE's are datasheet designers- using a few listed numbers to compare parts. In that regard, a 5532 is all you'll ever need as Douglas Self proclaims. Going beyond the datasheets, even as far back as 1987 it was known op-amps have many important traits not characterised on their datasheets. Input, output and transfer non-linearity, common-mode slew rate etc. Example graphs of LF351 and LF356 from Audio IC Op-Amp Applications by Walter Jung. I have more but it's to see THD can be up there, for different reasons. I don't think you can "get into it" here, it quickly degrades to psychoacoustics and audiophoolery compared to science. The diyaudio forum might be better suited for posing the question. You can dig on the Internet and find modern op-amp test results, but it quickly crosses over into sonic character and subjective opinion. They'll say the OPA2134 "sounds dark" for example. There have been audio op-amp distortion measurements and comparisons with double-blind listening tests. Paid access: http://www.aes.org/e-lib/browse.cfm?elib=16029 |
| Zero999:
The NE5532 is all you'll ever need? I don't know about that. It's not very good in applications which require a high input impedance, where a J-FET input op-amp is pretty much essential, although I suppose one could add a discrete J-FET input stage to the NE5532, for those applications. And what about low voltage applications? Old op-amps such as the NE5532 and LF353 are marginal for even 9V applications, let alone V or 3V, then there's the really crappy LM358 with horrific crossover distortion. Valid comparisons between amplifiers can only be made by a double blind test. Decent quality audio amplifiers all sound the same anyway, as long as they're not driven towards the point of clipping. Over 40 years ago a double blind test was done on three amplifier designs: one thermionic and two solid state, with golden eared audiophiles and they couldn't tell the difference! http://www.keith-snook.info/wireless-world-magazine/Wireless-World-1978/Valves%20versus%20Transistors%20DCD.pdf |
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