Objective Reviews & Commentary - An Engineer's Perspective

August 18, 2011

Op Amp Measurements





















GIANT KILLER: The following op amp deserves its own category:







  • 4558 – Same as above



  • NJM2068 – Cheap and Cheerful
  • NE5532 – The reasonably priced objective benchmark
  • OPA2134 – A mainstream audiophile favorite
  • LM4562 – An audiophile favorite (NJM4562 stocked at Mouser)

















































  1. Wednesdays can't come fast enough! Thanks for making my afternoon at the office pass by a little quicker.

    How often do you suspect the higher end op amp being forced to work under less than optimal conditions creates an audible difference? I tend to believe placebo plays a bigger role, but it's an interesting prospect.

  2. Yep, I think this article is more my style than the last one. Great article again!

    One question: you mentioned 24/96 slew rates and then implied that SACD would require a higher slew rate than that... why is that?

  3. Thanks b0ck3n, I didn't make Wednesday even in my time zone this time. The article was another late night "rush job".

    In a Cmoy, or other application, where the op amp is driving headphones directly nearly all of them are working under stressful conditions. I've also seen examples of where someone removes a relatively slow op amp from a piece of gear and replaces it with a much faster op amp thinking it's an upgrade. But the new fast part is unhappy in a PC board and circuit designed for a much slower part.

    The result might have poor transient response as it's now under-compensated. Or it might be borderline unstable with ultrasonic ringing or even oscillation. Any of those can make it sound different.

    And subjective bias being what it is, many who just got done de-soldering a $0.50 part and replacing it with a $5+ part will assume what they're hearing must be better sound as the new op is supposedly so much better. They think: "Ah! That's how my gear is supposed to sound if the manufacture hadn't used that cheap crappy op amp!" and they run off to their PC and give the swap a rave review on Head-Fi assuring others propagate the myth and degrade their gear in the same way.

    That's what happens when people who don't fully understand the engineering start messing with parts that have response out into the tens or hundreds of Megahertz. They have no way to test they got it right. Even RMAA can't do it as soundcards are blind to most of the frequencies where the instabilities show up. Not to mention few know how to even use RMAA properly.

    Evaluating only by ear, when they hear differences, they're strongly biased to perceive them as improvements. And, as you say, even when there are not differences, the placebo effect usually assures people still hear a difference.

  4. SpaceTimeMorph, 24/96 can only reproduce a signal up to about 45 Khz (48 in theory). A DSD SACD, in theory, can reproduce a 100 Khz signal although there seems to be debate on if that's actually even possible with any real world SACD player. But, at least on paper, DSD was designed to compete with 24/192 which cuts off around 90 Khz.

  5. Who needs that when you can get the TakeT super-tweeter? ... *shrug*

  6. OK, at least we know you don't work for TI, National or AD :-)

    It is unfortunate that for the longest time seeing a 5532 opamp it some audio gear, it would automatically devalue it.

    Perhaps the dip requirement should be "lifted". I am not very good at soldering but if the carrier board has long traces, one can heat the traces (instead of the pin) and easily solder an SOIC device

    Thanks for another great article

  7. Another nice write-up!

    I'm a big fan of Samuel Groner and Daniel Weiss' work. I'm not saying their units sound any better than any number of other DACs that measure well beyond the "it matters" point, but their heroic engineering and Swiss precision are worth the price in the same sense that a Patek justifies a premium over a Rolex.

    I'll kick in some bux for a blind test reward if you can get His Royal High-ness from AMB to balls-up and agree to one... :-)

    I guarantee, you'll have no takers - I offered a huge amount to one of the hoity-toity audio snob magazines some time ago, they get the money if they pass, I get to just publish the results if they didn't. Still silent.

    The million dollar speaker cable challenge shows best that the audio emperors have no clothes.


  8. Throw some clipping tests especially at 10khz, 20khz, and 45khz with a capacitive+resistive load attached.

    Another stringiest test would be configure the opamp into highpass or lowpass sallen & key filter with gain 3 and then over drive the inputs and watch for phase reversal at outputs. NE5532 will excel here.

  9. Will you be able to talk a little more about the alternative buffer opamps? I am especially interested about the performance of OPA551 and TLE2062.

    If stability with OPA551 is an issue, one idea is to wrap the output resistor inside the feedback loop to reduce output resistance, fa-schmidt at headwize reported good results using a 47 Ohm resistor, however I am not too sure how the math translates into the actual output impedance seen by the headphones.

  10. Thanks Heycarnut! I'd love to have Mr AMB step up to a blind test! But, the fact is, he won't even post in the official O2 threads where there can be an open discussion. So it doesn't seem likely he would ever agree to put any of his amps on the line where they could be judged fairly in a blind test even by his own ears.

    Anon - I talk about both the OPA551 and TLE2062 in the O2 Design Process article. The TLE2062 is the op amp I chose for the long battery life version of the O2.

    The OPA551 is harder to stabilize without using series resistance or an output inductor. And, perhaps even more significantly, it doesn't offer much benefit over paralleling the much cheaper and more stable NJM4556 when used as a buffer.

    Putting a resistor in the feedback loop actually makes stability worse than no resistor at all. With reactive loads, the voltage drop across the resistor will be out of phase with the output of the amplifier. That creates unwelcome phase shift in the feedback signal. And that's all that separates an amplifier from an oscillator. It's generally poor engineering practice unless the resistor is absolutely required for some other reason or only pure resistive loads are used (which rules out nearly all headphones).

    The resistor also tends to increase distortion into low impedance loads as it's creating relatively massive feedback error signals under those conditions.

    AMB tried the resistor-in-the-feedback-loop trick with the Mini3 and the high-strung AD8397. And the Mini3 is borderline unstable as can be seen with the 4 Mhz ringing in my scope captures. It also has very high distortion into 32 ohms--especially at high frequencies--although at least some of that is the OPA690 "third channel".

    But, all that said, with enough time and patience it might still be possible to tame the OPA551 for headphone duty without any significant compromises. It looks great on paper, but ultimately, I'll put a paralleled NJM4556 up against it in a blind test any day. They both have the same power dissipation which is ultimately the limiting factor for power output. And the NJM4556 can deliver 200 mA of peak current (as shown in my O2 Headphone Amp article.

  11. Its nice that you've put some effort into this and I found it quite interesting interesting.

    Unfortunately, as you mentioned, these sorts of ideas never rest in peace no matter how much evidence stacks up against them. A lot of the people you'd argue about this sort of thing with will tell you that THD is a worthless spec anyway. Of course even if you measured everything else under the sun they'd still tell you either that something else mystical and unmeasurable was causing the differences they can only hear sighted or that the high-speed opamp they put in a circuit that makes it unstable is more actually "musical".

    For the most part you're doing a thankless job but I'd like to chime in and give you at least one thanks for another interesting article.

  12. Thanks Maverick. The "specs don't matter" crowd is why I put the $500 challenge in this article. And apparently heycarnut is willing to raise the prize money even further.

    Anyone who argues the specs don't matter is welcome to step up and take the challenge with their own ears, their own headphones, and their own music. I mean, according to all the stuff they post with such definitive authority, how hard can it be to hear the difference between say the $0.69 NE5532 and a $24 pair of OPA627s?

  13. NwAvGuy - Love your articles =) huge fan!

  14. Have you considered testing several of the same op amp to see production irregularities? I had a tube of 100 ne4556 and half of them had high dc offset compared to the rest.

  15. Anon, I don't know anything about the NE4556, which as far as I know, isn't even available. Was that an old Signetics part? And you seriously hand tested 100 of them? Also, only 50 fit in a tube.

    I have tested a total of a dozen NJM4556 ICs from five different date codes and all are under 4 mV offset at unity gain (which is how they're used in the O2). They've been very consistent in every other way as well.

    Grado used the NJM4556 in their nearly $350 RA-1 headphone amp and I've not heard of any DC offset problems with it.

  16. *** Grado used the NJM4556 in their nearly $350 RA-1 headphone amp ***

    IIRC that amp was "outed" a few years ago.

  17. What does that have to do with offset problems? My point was I've not seen any evidence, even in a mass produced product using the NJM4556, that it's a problem.

  18. Aaah, I didn't know about PSRR. It (well, it's rejection by some groups of people) explains a lot, thanks!

  19. You can partly blame the Difet process for the OPA627's high price. The main advantage of the process is low input bias current (see OPA129) which isn't really a huge concern in this application. How the OPA627 became a designer opamp for audio applications is a mystery to me. Luckily process advancements have provided alternatives to the Difet process and there are now opamps with comparable input bias specs at a fraction of the cost (see OPA140).

    It would have been nice to see how the OPA1612 and OPA1642 measure up but they only come in surface mount packages. Gotta love those SOIC to DIP adapters!

  20. I will confess to being quite interested to see how well the OPA627 performs vs the other OpAmps in the article...

    But according to your text the OPA627 should annihilate other OpAmps in a well implemented circuit, then?

  21. Anon, while the OPA627 looks good on paper, what I tried to say was in most audio applications the OPA627 offers no meaningful advantages over even $1 op amps--no matter how well implemented.

  22. (Pardon the Anon status, I'm browsing over a public terminal and the usual cautiousness applies...)

    I'm curious though, is this possibly why 'companies' like RSA file away the OpAmp markings on their products. More food for thought on my side, I guess...

    Anticipating the probably upcoming O2DAC... ;)

  23. Removing op amp part numbers creates "mystique", makes it harder for someone to clone your design and sell it on eBay, and may be to hide using inexpensive parts. In reality, in most headphone gear, there are lots of op amps that will perform nearly identically as long as they're used correctly. So it really doesn't matter much.

  24. Look what I found, some more test data on opamp headphone driving capabilities (from back in 2005/2006, it seems).
    A '072 expectedly sucks, as do all the 4558s. The difference between NE5532 and NJM5532 is interesting.

    The 4556 gives the best result short of a dedicates headphone driver.

  25. Thanks Stephan. I'm not surprised the NJM4556 came out on top. With 12 volt supply rails (as used in the O2) the 4580 beats the NE5532 which is also consistent with my measurements. After the TLE2062, the 4580 is my third choice for a DIP8 dual headphone op amp.

    I never compared the NJM5532 to the NE5532 driving headphones. I only compared them in the O2's gain stage where they performed very similarly.

  26. I can only disagree with one thing:

    A Ferrari 458 Italia is way more raw, engaging, and fun to drive than any BMW, even an M3. I would rather drive a 458 to the supermarket.

    Actually I'd rather drive a 911 GT3 to the supermarket but that's besides the point.

  27. In my city, JRC4556 in only available in SMD package (Power dissipation 250mW against 700mW for a DIP). I’ve built a basic CMOYs (gain 4X & also 0 gain) with “real ground”. At +-15V to +-12 V the SMDs would get uncomfortably hot (with / without load), at +-9V SMDs get slightly warm(With 60 Ohms) but still would get hot if I use 32 Ohms or less h/p. My question is
    1. Can I get max. power output (comparable to DIP’s peak current capabilities 70mA.Operating voltage +-9V to +-12V) by using proper heatsink?
    2. Does running them on +-5V has any disadvantages for h/p under 60 Ohms as this makes the SMDs work cooler.

  28. +/- 5V would be OK if you don't need much voltage swing on the output. And running the two sections in parallel, as in the O2, doubles the dissipation but don't try to parallel even more op amps unless you use larger isolation resistors.

    It's hard to heat sink SOIC8 packages unless they're designed with some of their pins attached to the die directly internally which is unlikely with the 4556. So it all comes down to the load, type of music, and supply rails. The dissipation goes up with the square of the supply voltage. +/- 10V has four times the dissipation of +/- 5V.

    If you haven't read it, there's a dissipation section in the O2 Details article Circuit Description that might provide some more info.

  29. NwAvGuy, TYSM for putting together your blog. It has been a pure delight reading from beginning to end. All the H-F EE flunkies out there have nothing better to do but throw stones when they should be diligently improving their own inferior product(s). Don't worry about your detractors a bit. The Objective₂ will stand and shine on it's own merits.

    Since I missed the boat on the GB so I am having to purchase boards from JDS, oh well. I am building several for friends and family and look forward to "un-hearing" them, lol. Soon, the Objective₂ will be "Unheard in the best places".

    Ok, now a question. What are the effects of reducing the isolation resistors to .5Ω values? Do the 4556's really need 1Ω to keep from killing each other? I wonder because it seems that the .5Ω output impedance is simply half of the 1Ω value of the 4 resistors. The IEMs I mainly use are really 13Ω, not your measurement standard of 16 Ohms. Do you think that a 3Ω difference will be of any significance?

    BTW, I pronounce your handle as 'EnWaveGuy' as I have seen several ask how you are supposed to say it. Cheers!

  30. @FLAudioGuy - it's Northwest AV Guy but that's quite a mouthful. Sadly, all the decent .com domain names are long gone so one has to take what they can get. Thanks for the kind words.

    Your post would be better in one of the O2 articles, but to answer your question I wouldn't lower the resistors and I don't think the 0.5 ohm output impedance of the O2 is a problem for your IEMs.

    I do the math in the February output impedance article and ,as long as the output impedance is less than 1/8th the headphone impedance, life is good. So your IEMs need < 1.6 ohm output impedance and the O2 is already about 3 times better than that.

    The reason you don't want to go smaller with the resistors is differences in DC offset voltage (which varies between samples of op amps) create a constant DC current between the op amps. That current, besides draining the batteries a bit faster, also shifts the DC bias point of the output stage in the 4556. If you shift it too far, the distortion goes up. I did lots of tests with different samples of the 4556 and different value resistors to arrive at the optimal 1 ohm value.

    I think it's discussed a bit more O2 Details Circuit Description.

  31. Great info! Thanks!
    Just one question - some time ago I came across the NJM4580 in the DigiKey catalog, and the description said "noiseless". We know there is no such thing, so far. So, you did not mention testing the 4580 as a gain stage, but you did reject it as an output stage. Did you consider it as a gain stage?

  32. Gotta love those noiseless op amps! My perpetual motion machine uses one. ;)

    The 4580 has higher noise and higher distortion compared to the NJM2068. So it's an inferior choice for a gain stage. It does, however, have vastly better low impedance drive capability which might be useful in some rare applications. But, generally, the 5532 or LM4562 would be a better choice for such applications if the higher cost is not an issue.

  33. NwAvGuy,

    This blog is great. I remember reading the tangentsoft site where they compare op amps with "aggressive" or "laid back" sounds. WTF is that?

    As a student of EE, I respect and welcome your objective contribution to the DIY audio community. I started reading about headphone amps with the intent to build my own. With the R&D put into the O2 and the testing done on it to prove the design, I'll probably pick up a PCB and build my own.

    Thanks for bringing a grain of truth to the beach of BS.

  34. I regards to Soundshui's question about supply voltage I also had to buy SMD JRC4556 parts from RS Components in UK. The package was even smaller than SOIC so I had to bend the legs to fit the carriers.

    I put one in the headphone amp at +-8V in my CD player with 32ohm headphones. It plays plenty loud enough and gets only a little warm. I have another JRC4556 as the output driver running off +-12V and this gets warmer but not too bad. I put a JRC4556 in my preamp and used it to drive headphones through 1ohm resistors. The sound was unbelievably transparent (maybe that should be believably transparent). Unfortunately with +-18V rails the quiescent dissipation exceeded the 255mW and the light has now gone out on my preamp suggesting the device has expired and taken down the power supply. Looks like I will have to bite the bullet and get some DIPs from Mouser - I just did not want to pay 12GBP shipping on a few 0.50GBP parts - and fit some 9V regulators for safety.

  35. Are you sure the dissipation goes up as the square of the voltage? I would have thought that most of the current goes through constant current sources (P=I*V) rather than resistors (P=I2R). The spec shows operating current only increases from 8mA at +-4V to 9mA at +-18V. Sorry to be picky especially as I made my temperature measurements with the tip of a pinky.

  36. @Steve, the dissipation you have to worry about in the 4556 isn't the quiescent current but in the output stage when the amp is driving headphones. I agree constant current sources keep the quiescent current relatively constant. But the "V*I" losses in the output stage are typically an order of magnitude, or more, greater and they do go up as the square of supply voltage.

    There's a section in the O2 Details article Circuit Description that talks about power dissipation. The easy way to measure it is to record the DC power being consumed and subtract the AC audio power being delivered to the load. The difference is all dissipated as heat.

    Sorry to hear some are suffering with surface mount parts. Have you looked on eBay? The 4556, in DIP8, is often available there with very inexpensive shipping for just a few dollars.

  37. I have now dropped the rails to +-9 and the 4556 is running much cooler now. With this driving the pre to power amp cables, the improvements at all frequencies over the OPA2134 are not subtle.

    Are the LM4562 and the JRC4562 the same animal? The spec sheet says that the NMJ4562 is compensated for gains of 10 and above whereas the LM4562 is unity gain compensated? Does your amp design compensate for lower gains? I would also quite like JRC4562 for I-V conversion in place of an OPA275 (now OPA2134). If I order 4556s from Mouser then I could get a couple of these too.

    1. You're correct, the JRC4562 is not a plug and play replacement for the LM4562. I should probably clarify that in my article. The JRC4562 is stable in the gain stage of the O2 at 2.5X gain due to the added compensation in the O2 design but I think the LM4562 is a better, and safer, option for only a dollar or two more.

      If you want a Mouser stocked "upgrade" for the O2 gain stage the OPA2227 is a proven option. Mouser doesn't sell National Semi op amps.

  38. Sorry if this is a dumb question, but what about the LME49860? You said you tested it, but you didn't publish the results. You don't have to go to the trouble of publishing the results, but I just want to know how good is it compared to the mainstream LME49860? Is it a clear upgrade in every category, or is it better in some things and worse at others?

    1. The LME49860 is a higher voltage version of the LM4562. They perform similarly. Generally you should only use the LME49860 if you need a higher supply voltage than +/- 15V (30 volts).

  39. Great article NwAvGuy.

    When it comes down to it which would you choose, the OPA2227 or LM4562? Yes, I just happen to have these two Op Amps in front of me.


  40. Awesome work!
    I just finished my O2 and I´m test driving it as I type...sweet sweet performance. Very happy! thank you for for developing this killer amp. Can´t wait for the ODAC!

    I´m tempted to try a AD712 that I have on U1, would like to know your thoughts on the matter and how do you think this will work with the O2


    1. I'm glad you like your O2 but I'm wondering if you read the article above and my Op Amp Myths article? Unless you have your O2 configured for freakishly high gain, the output op amps dominate the distortion in the amplifier. Using a more expensive op amp in the gain stage won't help anything. In fact, it may degrade the performance because the O2's transient response (compensation) has been optimized for the NJM2903.

      Op Amp rolling is 99% myth. When real differences are heard between op amps it's because one or more of the op amps are being used incorrectly. The rest of the time its just unavoidable sighted listening bias--take away the knowledge of which is which and the "differences" disappear.

  41. Hey there NwAvGuy. There's an old audiophile's tale (like a wive's tale) that OpAmps in a TO-99 package sound better than the same OpAmp in a DIP/SOIC package. The only theory I've heard to explain this is that the metal can package rejects RFI better. So what I want to know is:

    1.) Have measured any objective differences between TO-99 OpAmps and their equivalent in a DIP/SOIC package?
    2.) Have you observed (heard) any differences between the different OpAmp packages? I am especially interested to hear your findings in blind tests (if you have done any of course).

    This is slightly unrelated but I read your newest article (Apr. 1) and the ODAC sounds (err... measures) incredible. I bought an X-Fi Titanium HD to hold me over until the ODAC + O2 (or maybe the ODA) comes out.

    Thanks for all that you are doing for the audiophile community, and take care. :-)

    1. You might look up what's significant about April 1st... (if you missed that detail).

      There's the RFI issue as a very weak possibility. It's far more likely RFI will be a problem in the much larger surrounding circuitry and components that with the very tiny silicon die inside an op amp. Shielding just the die is like putting a postage stamp on a badly leaking roof.

      But there's a more likely explanation and perhaps grain of truth to the claim: Thermal issues. If an op amp is driving a challenging load playing music the instantaneous temperature of the tiny silicon die is constantly changing. If the op amp's key parameters fluctuate significantly with temperature changes you can get some degradation in the performance from thermal modulation. And, sometimes even worse, in a dual op amp servicing both channels the music in one channel modulates the thermal performance of the other channel. In that circumstance a metal package tends to keep the die at a more constant temperature and you might get slightly better performance.

      I've met and talked with one of National Semi's former audio application engineers about this very issue and his view was it's much more a problem with poorly designed op amps or op amps being used in the wrong application. I agree with him. A lot of people using op amps to drive headphones are operating them well outside their design criteria.

      The critical gain stage of the O2 amp runs at a constant temperature so thermal issues are not an issue. The output stages are much less critical as unity gain buffers. The parameters that may drift slightly with temperature are unlikely to be an issue in such a buffer stage with relatively high signal levels. Plus the O2 uses a separate device for each channel which not only doubles the output dissipation lowering the temperature of each device but also prevents one channel from thermally modulating the performance of the other.

      You can measure THD+N at 5hz or 10hz driving the desired load at various output levels and usually see clear signs of any thermal modulation issues. A sine wave at those frequencies typically creates even greater thermal swings than most music does. The O2 passes the test with flying colors. But a single stage amp, like the Mini3 or a Cmoy, may not. It depends on the thermal characteristics of the op amp used.

      So, to summarize, if you're using an op amp within its design criteria, and it's designed for high performance audio use, and especially if you're not sharing channels within an op amp, it's unlikely the package will make any measurable or audible difference. If you're using say a video buffer op amp in an audio application, or using a load impedance lower than recommended, you need to test for thermal modulation.

  42. What do you think of the NJM2114D as a buffering OpAmp? My hypothesis is that it's a pretty good OpAmp, because both the Titanium HD by Creative and the Xonar STX by Asus use it for buffering. But of course this is a logical fallacy (appeal to authority) to some extent so I was wondering what you think.

    BTW thanks for your response about TO-99 OpAmps, very informative. :) My Titanium HD uses two single OpAmps so I guess temperature is not going to be a big issue.

    Thanks again. :-)

  43. The NJM2114D is similar to the 5532 so it should make a fine buffer. You could use either one.

  44. Hello, I've been looking around for a good opamp or opamp+buffer option for a portable SMD amp I'm planning. Reading through your articles I see you've chosen the 2277 and the 2062 as an opamp and buffer. If I were to design an amp around these, would it be necessary to use two 2062s for output buffering? Would using only one defeat the purpose of a buffer? (Something about unity gain allowing for better current amplification compared to having both in one opemp?) - Planning to use the amp for DT880/600s and RE0 64 ohm IEMs but I may want to release it for public use once finished.

    I don't want to go into too many details about the amp design here, but I might PM more info if you were interested.

    Thanks for the great articles!

    1. If you haven't already, you might want to read up on my comments in the O2 Design and O2 Details articles on the 2062. It performs notably worse in every way than NJM4556 (except power consumption). Into the 600 ohm DT880 I might be more tempted to use a 5532 if you can't get the NJM4556. And because the RE0 shouldn't need much output, and the 880/600 doesn't need much current, you can live with a single output buffer per channel.

      The O2 Design article also explains the many benefits of a two stage design.

    2. My main reason for choosing the 2277 and 2062 were for the much lower current usage. Since this is project is aimed for portability and low power consumption, the less current it draws, the better. As you said though, the noise is still better than almost all amps (esp. in a portable amp. The only concern is the increasing THD with low impedance, which I can't really visualize because your graph only graphs 15ohm and 150ohm, which have a 10x difference; pretty substantial.

      It'd be great to go with the NJM4556, but running from a 3.7v/1400mAh (Li-Ion) battery boosted to +/-7v with a LM3471 that has ~75% compounded efficiency isn't going to leave me with much power leeway.


    This is not entirely correct in the article, since the analog signal is not reconstructed by connecting the samples with straight lines. The worst case slew rate of a pure sine wave (at the zero crossings) is π * Vpp * f, or 3.14159 * 20 Vpp * 0.02205 MHz = 1.385 V/us with CD format audio and "ideal" DAC filtering.

  46. Thanks. You're correct. I was trying to keep the math simple ;) But the rules of thumb for slew rate still apply, and those who think 30 V/uS will sound better and "faster" than 5 V/uS are still just as mistaken when their music can't slew faster than 1.4 V/uS and, in reality, even that value is extremely unlikely (a 0 dBFS 22Khz signal).

  47. Any thoughs on OPA 2111, I'd like to try it on mCmoy v2.03

  48. Hi NwAvGuy,

    What Op Amp is suitable for i/v conversion?


    1. There are many. I would suggest using the op amp the DAC manufacture suggests or uses in their reference design.

  49. Would have liked to have seen the specs for, say OPA 627's

    1. The point of the article was to show how similar many op amps are, when properly used, and how other aspects of the complete design can mask differences (in this case the output stage of the O2).

      Many have some favorite op amp they think magically sounds better, but, used properly, they all sound the same. The OPA627 is obscenely expensive, yet in 99% of properly designed audio applications, will sound exactly the same as the 5532 in blind testing.

      If you're going to chain together 50 op amps in series then the OPA627 *might* sound better than a cheap 5532. Otherwise forget it.


