Better audio op-amp than NJM2060 - Page 1
Forum section: electronics / repair

author: MathWizard
author_rank: Super Contributor
timestamp: February 10, 2021, 08:24:36 am
content: I have a cheap stereo, and it uses these old NJM2060 quad BJT op-amps, with 0-18V rails in the stereohttps://www.njr.com/electronic_device/PDF/NJM2060_E.pdfI'm wondering (if my stereo's circuit is generic enough, or with a silght mod), what would be some simlar BJT biased type op-amps, that are better. I'm ordering some other parts real soon, so I'd get something if I knew what to try.

author: NOON Design
author_rank: Contributor
timestamp: February 10, 2021, 09:35:03 am
content: The NJM stuff is generally pretty competent for audio and this looks like a decent chip, it's certainly no 741. Changing opamps isn't likely to make a significant difference, it's more likely the overall circuit design and other cheap components like caps that are compromising performance.

author: Zero999
author_rank: Super Contributor
timestamp: February 10, 2021, 09:40:31 am
content: There's nothing wrong with the NJM2060. Changing the op-amps for something faster will most likely bugger it up.Swapping op-amps, for "better ones" in consumer equipment is audiophoolery.It's also highly likely there's nothing wrong with the cheap stereo. If it sounds cheap, it will be because of the crappy speakers, room acoustics, or it's purely psychological i.e. it's in your head: you got it cheap, so it will sound cheap to you.

author: Kleinstein
author_rank: Super Contributor
timestamp: February 10, 2021, 09:53:47 am
content: There are not that many quad audio OPs. Most of them come as duals only, especially the lower noise ones as they tend to use quite some power.I don't know a BJT base alternative. The OPA1679 may be worth a look - it is JFET based and a little faster (16 MHz), so it depends on the circuit if it would be an upgrade or not or even oscillate. At least from the DS it still looks lower noise, but the data-sheet for the NJM2060 is a little odd: The RIAA curve RMS noise looks much better than the noise density curve. So not sure which part is right.For a noise comparison also keep in mind than BJT based OPs have quite some current noise - so expect the total noise of a BJT based OP to be some 40% higher. This is the number if they have the source impedance for the lowest noise figure. It can be less than 40% extra with very low impedance source and can be a lot worse with a high impedance source (e.g. many pots).I agree that just changing the OPs would likely not make a big difference, and it can cause other trouble.

author: floobydust
author_rank: Super Contributor
timestamp: February 10, 2021, 06:36:25 pm
content: New Japan Radio makes some cheap low end stuff i.e. NJM4558, NJM4559 that ended up in a lot of consumer gear.OP yes you can upgrade the op-amps for sonic benefits, but also need awareness of what the circuit is and needs. i.e. DAC reconstruction filters, phono preamp, mic preamp, EQ - all are examples of functions with vastly different requirements for op-amps.I've done upgrades in recording studios, in the consoles and it can be night/day for lower distortion, noise and better bandwidth.That notion is not really supported here, go thediyAudio forumsfor that. But they suffer the other extreme - have some a religious following for some boutique op-amps, blanket statements that "X part is the best", and the usual voodoo can be found instead of a little science.I don't know model number or schematic of what yourNJM2060is in. Quads usually are in EQ's.Sometimes putting in the wrong op-amp causes damage or side effects - i.e. offset voltage changes polarity which is not good for the electrolytic coupling caps.I would look at putting in a DIP socket, and considerLM837orOPA4132.

author: coppice
author_rank: Super Contributor
timestamp: February 10, 2021, 06:40:37 pm
content: Quote from: Zero999 on February 10, 2021, 09:40:31 amSometimes it is. Sometimes it isn't. I thought a friend was being an idiot swapping the op-amps that drove the headphone sockets in his top of the range Sony LD and CD players. The result actually transformed their performance. Nothing subtle and debatable about it. The result was dramatic. Its not so rare to find high end consumer equipment being compromised by one or two poor performance parts in an otherwise top of the line signal chain.

author: MathWizard
author_rank: Super Contributor
timestamp: February 10, 2021, 07:03:26 pm
content: So they're not terrible, and other things can make it sound "cheap" too. I' have some other NJM chips on a good quality sound card, the 4558's or , IDK, I'll order a few of them anyways, if they have them in quads, and try it........but yeah it's not like a guitar pedal with 1 op-amp.Someday I should just get better PC speakers, it's just never been a priority, even using a singlr speaker playing FPS online games, but for the fun of it, I'll try another op-amp

author: magic
author_rank: Super Contributor
timestamp: February 11, 2021, 06:04:31 pm
content: Per the datasheet it's a quad 4560, which is a slightly faster 4559 which is a slightly faster 4558. Probably good enough if the circuit is designed right, and certainly not some LM358 rubbish. Chinese AliBay vendors sell 4558 rebadged as various audio opamps and gather plenty of positive feedbackIf you find an upgrade, try it without knowing which is which and see if the difference still persists

author: drussell
author_rank: Super Contributor
timestamp: February 11, 2021, 06:32:29 pm
content: You can always make your own break-out to replace a quad with two duals if you want to upgrade in an audio application. Sometimes itcanmake a serious improvement in some audio situations to do things like replace a couple strategic OP amps, especially if the originals are noisy, especially if there are many in a signal chain like in a mixing console or something, etc.On cheap gear, though, there's probably a point of serious point of diminishing returns so putting some $20 OP amps in is not likely to produce a reasonable cost:performance ratio result...Perhaps, though, something newer and audio-specific like from the NJM8xxx series, like maybe a couple ofNJM8068orNJM8080or something could be interesting for you to play with as an experiment. They're cheap enough yet specifically designed for audio and include rather clever RFI suppression circuitry that makes them a nice engineering aid in many applications for helping reject things like cell phone interference in the audio chain when it wasn't the best and quietest in the originally engineered design.YMMV

author: thm_w
author_rank: Super Contributor
timestamp: February 12, 2021, 12:37:02 am
content: Quote from: MathWizard on February 10, 2021, 07:03:26 pmIf you are using PC specific speakers, then, 90% chance you can get some bookshelf set off craigslist for <$100 that will be a big upgrade.

author: SilverSolder
author_rank: Super Contributor
timestamp: February 12, 2021, 02:19:27 am
content: Quote from: floobydust on February 10, 2021, 06:36:25 pmThere is an OPA4134 quad as well, I have been looking at it for an active filter upgrade project - do you think it would be a reasonable choice for a good audio quad?

author: floobydust
author_rank: Super Contributor
timestamp: February 12, 2021, 06:13:09 am
content: TL074would be lowest cost, it's been updated to the TL074Hfor better EMI rejection. Can be unstable in some filters due to the CM voltage making gain non-linear see 9.3.2OPA4134is much better but not available in DIP-14 package. Audio quad op-amps are harder to find because of their high power dissipation with Class AB bias, around 0.5W total for the OAP4134. It's a fair bit of heat at +/-15V.

author: drussell
author_rank: Super Contributor
timestamp: February 12, 2021, 06:43:25 am
content: Quote from: SilverSolder on February 12, 2021, 02:19:27 amThe OPAx132 and OPAx134 are certainly good audio OP amps in the right circuit situations, and they are available in DIP (though I don't think they make the quad in DIP anymore,) sure, but now you're getting into the silly level of pricing for OP amps ($5, $10, even $15 per dual) in most places in typical consumer-level gear compared to something like the NJM8068 or NJM8080 ($0.75 - $1 per dual.)Or, at least that's likemy opinion, man... YMMV

author: drussell
author_rank: Super Contributor
timestamp: February 12, 2021, 06:51:13 am
content: Quote from: floobydust on February 12, 2021, 06:13:09 amA TL07x isn't really an audio OP amp, even though they are often used as such.Of course, this is how you go down that rabbit hole. Install some sockets in the device in question then start trying various OP amps.Once you have sockets installed, it is easy to try various choices and you can easily make little plug-in modules for parts that are only available in SMT. In the case of mounting a single SMT in a single socket, a dual in a dual or quad in a quad you don't even really need much of an "adapter", you can easily just solder them onto the top of another decent quality socket to turn them into DIPs so you can just stick them right in your board's socket and play around to your heart's content.Soon you'll be well on your way to audio lunacy like the rest of us.

author: magic
author_rank: Super Contributor
timestamp: February 12, 2021, 09:15:40 am
content: Quote from: SilverSolder on February 12, 2021, 02:19:27 amIt's a quad OPA2134 so same thing as OPAx132 but with lesser DC specs. Theoretically there might be some correlation of DC offset with nonlinearity because input pair imbalance contributes to both, but dunno if anyone has ever investigated this thoroughly in opamp ICs. I'm also not sure how the sort of DC trimming techniques that they use to reduce offset in opamps affect linearity. Some audiophools swear by the 2132, but other designers say you can just save money with the 2134 if its DC precision is satisfactory for the application. Anyway, these are decent opamps except for a somewhat high voltage noise.There appears to be some LME49743 as well, SMD only and no idea what it is.Quote from: floobydust on February 12, 2021, 06:13:09 amThat's interesting. Makes me wonder what's insideeditAm I reading right, 37nV/rtHz noise density at 1kHz?

author: Kleinstein
author_rank: Super Contributor
timestamp: February 12, 2021, 09:43:50 am
content: The LME49743 is a low noise BJT based OP and thus has relatively high current noise. So it is low overall noise only, if the impedance is quite low (e.g. less than 2 K).The OPA1679 is kind of a modern improved (in most aspects) version of the OPA4134 - not available in DIP, but lower noise, lower current consumption and lower cost.

author: magic
author_rank: Super Contributor
timestamp: February 12, 2021, 09:58:16 am
content: This chip is a bit weird because its noise voltage is rated the same as NE5534 but noise current is much worse and input bias is only 50% of NE5534. Does it mean it has (a very lousy) bias cancellation?Well, if it's anything like the "higher end" LME49720/LM4562 it will have weird problems with increasing bias current and phase reversal if the inputs are taken to the negative rail but should be OK otherwise.

author: Kleinstein
author_rank: Super Contributor
timestamp: February 12, 2021, 10:47:33 am
content: Relatively low bias and high current noise for the LME49743 point toward some bias compensation. AFAIK the NE5534 like many other audio OP use no bias compensation to avoid the extra current noise that comes with this. Anyway one has to be a little careful with the current noise specs - this is just 1 number, but there are 2 inputs and the current noise can have correlated and non correlated parts. Some data-sheets give only the non correlated part. So real life noise can be higher.The LME49743 data-sheet is odd with the sample circuits: many of the later circuits use a rather high input impedance and would thus be relatively noisy.

author: magic
author_rank: Super Contributor
timestamp: February 12, 2021, 11:28:56 am
content: Yes, NE553x have no bias cancellation.But what I'm saying is that LME49743 actually hashighinput bias for its voltage noise level, only half of NE5534. That kind of difference couldperhapsbe achieved with improvement in hFE alone. And it would be pretty poor result for a bias-cancelled opamp - LM4562 achieves 10nA typical and still has less voltage noise.Quote from: Kleinstein on February 12, 2021, 10:47:33 amIf you mean LT1028, it's even worse.AFAIK the usual convention is to give noise current per one input pin (including or excluding the correlated part which may or may not be mentioned), but what Linear's datasheet gives is 1/sqrt(2) of uncorrelated noise per one pin, a fact easily seen by analyzing the specified test circuit.Marketing must have worked really hard on that one

author: Kleinstein
author_rank: Super Contributor
timestamp: February 12, 2021, 02:43:40 pm
content: I did not know the LT1028 data-sheet was specific on how the number is to understand. This way it makes sense that the actual current noise often turns out higher.I though about some precision OPs (e.g. OPA177), were they assume same resistance at both inputs and thus give the rather optimistic 1/sqrt(2) the uncorrelated part. For low noise it is often not a real option to add extra resistance, just to get better balance, as the resistor adds more noise.Given that one has to add current noise the noise of the LME49743 does not look that good anymore. Add some 40% for the current noise and one is at 5 nV/sqrt(Hz), which is higher than good JFET types.

author: magic
author_rank: Super Contributor
timestamp: February 12, 2021, 03:27:26 pm
content: OPA177 uses a simpler bias cancellation scheme borrowed from OP07 and its noise is uncorrelated. The datasheet recommends against adding unnecessary resistors to balance source impedance andthe noise spec is pretty high, so probably legitimate.there is no current noise spectral density specification, but it has to be pretty low given other specs.OP27, OPA227, LT1007 and the likes use the correlated scheme and creative specmanship is a risk.

author: SilverSolder
author_rank: Super Contributor
timestamp: February 12, 2021, 03:27:43 pm
content: Quote from: Kleinstein on February 12, 2021, 09:43:50 amMore distortion, slightly less gain? But lower noise.

author: magic
author_rank: Super Contributor
timestamp: February 12, 2021, 03:50:32 pm
content: OPA1679 has more gain. Open loop gain specs are meaningless for AC above a few hertz. GBW is what you should compare, although there are traps because it isn't always linear. NE5534 has 60MHz GBW at audio frequencies and only 10MHz unity gain bandwidth.

author: Kleinstein
author_rank: Super Contributor
timestamp: February 12, 2021, 04:20:06 pm
content: For an AC application the DC gain does not matter very. It is more he GBW that sets how much feedback is available to cut down on the THD. Here the newer OPA1678/9 is about 2 times faster and accordingly the THD specs in the DS are slightly better. At that level the typical THD curves are always a little tricky one is often quite close to the noise limit and the exact conditions can matter. So the OPA134 with 2 K load is a little lower distortion than the OPA1678 with 600 Ohms load.One problem with many JFET based types is that the input capacitance changes with common mode voltage - this can be a problem with relatively high impedance circuits. Some types (e.g. OPA1642) avoid this to a large part. With a relatively low impedance circuit build to work with a BJT based OP the input capacitance should not be that critical.For the OPA177 I would not count on the current noise being uncorrelated: at least the part from the current source to the input differential stage is correlated. Another point is noise in the input current mirror - this also results in current noise, this time correlated with negative sign. For me it is hard to tell which noise source would dominate.

author: floobydust
author_rank: Super Contributor
timestamp: February 12, 2021, 06:32:00 pm
content: It's been a long time since I've seen a properly done audio op-amp shootout.It started withWalter Jung's"Audio IC Op-Amp Applications" old work showing the differences between parts, distortions and non-linearities between inverting and non-inverting configurations for example. All stuff beyond the datasheets. Post here:https://www.eevblog.com/forum/projects/ok-audio-gurus-what-are-the-highly-regarded-fet-input-op-amps-these-days/msg2021749/#msg2021749Operational Amplifier DistortionSamuel Groner Oct. 2009 436pgs. is a continuation and I don't know of anything newer.This is interesting work, comparing many newer op-amps using some science AP1 THD+N for transfer, common-mode, output non-linearity and input impedance linearity.All measurements not in EE school or textbooks.edit: I can't find a mirror for Walt Jung's website, I guess it was abandoned in 2018.

author: SilverSolder
author_rank: Super Contributor
timestamp: February 12, 2021, 07:04:17 pm
content: Quote from: floobydust on February 12, 2021, 06:32:00 pmApparently he has a new site:http://waltjung.orgI agree it would be cool with a proper audio op amp "shootout"!

author: Zero999
author_rank: Super Contributor
timestamp: February 12, 2021, 08:42:09 pm
content: I would strongly advise against fast op-amps such as the LME49743 and LM837, which are highly likely to cause oscillation, in a circuit/layout not designed for fast op-amps.I didn't know about the NJM2060. It looks quite good. I might use one in a design when I need four audio op-amps and don't want to use two duals due to space restraints and save power.New Japan radio make some nice op-amps.Quote from: coppice on February 10, 2021, 06:40:37 pmIt making a difference in a headphone amplifier is more plausible, because the ear is in the near field region so as long as the head set isn't total crap, acoustics and distortion from speakers are less of an issue.Three possibilities:1) Placebo effect.2) The replacement, higher speed op-amp was introducing an artefact such as ringing/boosting a treble frequency, making it sound "brighter".3) The original design was really crappy, just some junk with a high price tag and he just paid for the name.Did you conduct any objective measurements, or blind tests?

author: coppice
author_rank: Super Contributor
timestamp: February 12, 2021, 09:57:26 pm
content: Quote from: Zero999 on February 12, 2021, 08:42:09 pmAs I said before, we made similar changes to a Sony CD player and a Sony LD player. We didn't make any measurements. In each case we just replaced one op-amp with a high performance pin-compatible op-amp and tried the machine. There was a massive difference in the sound from the left and right channels. So much so that I thought we had done something wrong when we modified the first machine. When we replaced the second op-amp the two channels balanced up. So, there was no question that a change of op-amps made a huge difference. The final result sounded great. Things sounded pretty dull before. This was nearly 30 years ago, and I can't remember which op-amps were used. Working in a semiconductor company, we just picked the best thing the company made that was in the same package and pin-out as replacements. It seemed like Sony had just used such crappy op-amps for the headphone output, that were incapable of giving a flat response. This was hilarious, as the boards were very complex. The LD player was about $2000, and it seemed no-expensive had been spared anywhere else. So, don't just assume people are idiots when they change op-amps. There is a lot of crappy equipment out there. Especially when you look at parts of the design that are not in the main signal path, and probably won't get tested by reviewers.

author: magic
author_rank: Super Contributor
timestamp: February 12, 2021, 10:48:45 pm
content: Quote from: Kleinstein on February 12, 2021, 04:20:06 pmI don't think contribution from internal input stage currents is very significant. Those noises are likely about sqrt(β) times higher than noise in base currents of the input devices, but only 1/β of their magnitude appears externally as variations in Ib. That's -20dB difference with just a modest β of 100. It seems base current noise of the input devices is the dominant source, plus base current of the cascodes (I refer to OP07/OPA177 specifically now) which is mirrored into the input pins for cancellation of the former. Also those mirrors add some noise, but not as much IIRC.Quote from: Zero999 on February 12, 2021, 08:42:09 pmIs this likely though? I know that one anonymous audio blogger who shall remain nameless loved to rant about it on every occasion, but IME when audio opamps ring or oscillate, it's not at a frequency you are likely to hear. Maybe if you are lucky, it may throw the opamp out of its normal operating points and cause increased distortion within the audio band. Maybe. Self says it sometimes happens to poorly decoupled 553x, though I don't remember him stating that the effect is audible rather than measurable.I tend to blame most audiophoolery on placebo. It's quite eye opening to see people rave about the wonderful sound of chips they bought on some auction site which you are 100% sure must have been some NE5532, if not RC4558, with fake markings

author: SilverSolder
author_rank: Super Contributor
timestamp: February 12, 2021, 11:01:50 pm
content: Quote from: magic on February 12, 2021, 10:48:45 pmNE5532 is a "charmed" design, though - it hit the ball out of the park. And, no matter what you listen to, it probably passed through one or more of them on its way to you! Maybe we are now at the point where anything else sounds "unnatural"!

author: ve7xen
author_rank: Super Contributor
timestamp: February 13, 2021, 01:32:44 am
content: Quote from: floobydust on February 12, 2021, 06:32:00 pmNot all that comprehensive, but this guy nwavguy did a series of posts on a properly engineered opamp-based headphone amplifier way back in 2011. One of them included some discussion and audio analyzer measurements of several opamps that might be of interest. His general conclusion that is apparent across this project is that once you move beyond TL072 into audio-specific chips, there's not much in it, and probably nothing audible. I found the series of posts had some good insight on common 'gotchas' in audio design and what to pay attention to.http://nwavguy.blogspot.com/2011/08/op-amp-measurements.html

author: magic
author_rank: Super Contributor
timestamp: February 13, 2021, 08:49:03 am
content: Oh yes, the anonymous audio bloggerWell, problem is, he only tested very few chips and only in one particular application and made no effort to produce data that would generalize to other applications (higher gain, different output loading, common mode input swing, source impedance, etc). This is nothing compared to the materials linked by floobydust.Furthermore, his noise measurements (and the accompanying commentary) make me doubt if he understands the distinction between current noise and voltage noise and certainly the concept of noise spectral density. At any rate, his noise vs frequency plots are quite useless, because he never scaled them properly on the vertical axis.Oh, and the LM4562 which he tested is a Texas Instruments NE5532 with fake markingsAnd since I'm ranting about the AAB, I might also mention that NJM4562 isabsolutely nota substitute for LM4562 and that all of the chips he ended up using in the O2 after discarding TL072 due to phase reversal (among other reasons) also have phase reversal, a fact he never detected because he didn't know how to test for it, apparently.There might be other things I forgot

author: SilverSolder
author_rank: Super Contributor
timestamp: February 13, 2021, 03:26:45 pm
content: Quote from: magic on February 13, 2021, 08:49:03 amLooking at the specs, NJM4562 doesn't look too bad - what do you see as less good about it?

author: magic
author_rank: Super Contributor
timestamp: February 13, 2021, 04:31:24 pm
content: Let's see...QuoteThat's for starters. Then the fact that NJM4562 (which appears to actually be a second source of Raytheon RC4562) is an ancient dinosaur from the '80s with 8MHz unity gain bandwidth while LM4562 is made on a modern complementary process and hits 50MHz.Then you have some THD plots in both datasheets to look at and noise voltage specs to compare.Input bias current certainly is not cancelled so it will be higher, I can't even be bothered to look it up. On the upside, the NJM likely has less current noise. OTOH, I speculate that good (accurate) bias cancellation may actually reduce distortion from high source impedances due to Ib variation with collector voltage of input devices. Dynamic cascoding is another solution commonly employed in modern high end opamps which simply stabilizes said collector voltage, forget it in old chips. Long story short, it will probably have more common mode distortion in noninverting stages.Quote from: magic on February 13, 2021, 08:49:03 amBTW, on second thought, I think it's not a TI because TI wouldn't have that notch at the top end of the pacakage.That being said, I can't imagine how a genuine LM4562 would produce that kind of noise in the O2 so it had to be fake. Either some other NE5532 or maybe an opamp with similar noise level, like LM833 or whatever.

author: Rasz
author_rank: Super Contributor
timestamp: February 13, 2021, 06:52:10 pm
content: Quote from: coppice on February 12, 2021, 09:57:26 pmthis is normal and expectedQuote from: coppice on February 12, 2021, 09:57:26 pmand this is you deciding what is better based mostly on loudness, overall or of particular bandsQuote from: coppice on February 12, 2021, 09:57:26 pmyou mean neutral? the way they were meant to sound?Quote from: coppice on February 12, 2021, 09:57:26 pmok then ;-)

author: coppice
author_rank: Super Contributor
timestamp: February 14, 2021, 01:20:56 am
content: Quote from: Rasz on February 13, 2021, 06:52:10 pmReally? Why would that be? One adequate op-amp being replaced with a superior one should give no discernible difference. An op-amp with inadequate GBP replaced with a better one will clean up the top end.Quote from: Rasz on February 13, 2021, 06:52:10 pmDo you know what an op-amp is? How would changing an op-amp affect the volume, other than an op-amp with inadequate GBP rolling off the top end?

author: drussell
author_rank: Super Contributor
timestamp: February 14, 2021, 01:43:20 am
content: Quote from: coppice on February 14, 2021, 01:20:56 amExactly....Or having inadequate drive capability driving a low impedance, or unable to do full voltage swing on higher impedance headphone loads. Of course the OP amp can make a difference, especially on something like a headphone jack.

author: coppice
author_rank: Super Contributor
timestamp: February 14, 2021, 03:09:11 am
content: Quote from: drussell on February 14, 2021, 01:43:20 amA lot of headphone outputs on phones and notebooks are driven by really unstable amps. One high quality pair of headphones might sound great when plugged in, while another model destabilises the amp and sounds awful.

author: floobydust
author_rank: Super Contributor
timestamp: February 14, 2021, 03:18:41 am
content: It is usually theperceivedvolume changing, due to a change in harmonics.Vout is precisely controlled by NFB, so it's rare to have a real amplitude change between parts.An op-amp with higher THD- due to it's design or a circuit flaw (such as fluctuating rails or dynamic instability) will "sound louder".I use 600 ohm headphones to do listening tests, most op-amps can drive that directly.

author: magic
author_rank: Super Contributor
timestamp: February 14, 2021, 07:18:48 am
content: Quote from: coppice on February 14, 2021, 03:09:11 amThat sounds like audiophool lore. Any measurements of the effect (not necessarily by you, a link is OK)?I would expect output impedance (by means of series R and C, not amplifies themselves) and maybe output loading distortion to be the first culprit behind any (non-imagined) differences between that sort of devices, and also dependent on load.

author: Kleinstein
author_rank: Super Contributor
timestamp: February 14, 2021, 09:43:27 am
content: It is essentially impossible to hear the small differences in distortion between different reasonable OPs (e.g. nealy everthing better than LM358). In critical circuit one can heat a difference in the noise level. However not all OPs are really noise sensitive and with modern parts it is not so uncommon that the main noise source is not an OP but a resistor.There are a few cases of poor design. One such scenario is an OP at the edge of instability, so that external capacitance can make it oscillate and the capacitance of the ear phone can make a difference. In rare cases the replacement OP may be more tolerant to capacitive loading. Another not so uncommon design error is ignoring the current noise when used with high impedance sources - this can lead to audible noise, despite of using OPs that look low noise on paper (if one does not look at the fine print). With modern speakers that have high efficiency this can be an issue, as noise gets audible that was not with older speakers.When it comes to THD the cheap NJM2060 is usually well good enough (unless used with high gain combined with extra nonlinearity in the loop).If the amplifier does not show an audible problem (especially noise) there is no reason to expect to solve a problem that is not there.

author: Zero999
author_rank: Super Contributor
timestamp: February 14, 2021, 10:47:51 am
content: Low impedance headphones are quite common, so using an op-amp to directly drive a headphone socket is bad practise. If 32 Ohm headphones are used and the device used an ordinary op-amp to directly drive the headphone socket, it would current limit, clip and sound terrible. Replacing it with an op-amp with a higher current capability would help a lot.Noise is a factor, but only when the op-amp is used with a low-level signal such as a microphone. I have both measured and heard the difference between the NE5532 and TL072, when used as a dynamic microphone amplifier. The NE5532 is definitely much better, than the TL072, with low input impedances.Unless there's something wrong with the design, an op-amp is overloaded, or too noisy, for the application, there's no point in replacing it.

author: coppice
author_rank: Super Contributor
timestamp: February 14, 2021, 03:05:49 pm
content: Quote from: magic on February 14, 2021, 07:18:48 amWhy do some people on this forum have "audiophool" Tourettes? Lots of equipment has real performance issues. Not every complaint about equipment problems is by an idiot, and many of the knee jerk responses are.

author: coppice
author_rank: Super Contributor
timestamp: February 14, 2021, 03:12:53 pm
content: Quote from: Zero999 on February 14, 2021, 10:47:51 amI find it strange that the headphone industry has never settled around well defined impedances. Dynamic headphones can be from a few ohms to several hundred ohms, yet we expect them all to plug into the same headphone socket, even though their voltage vs current needs are very different. The headphones I use most of the time are AKG712s. They are large, and you might expect them to be 8 or 16 ohms, since most larger heapdphones are low impedance. Nope. These are actually 62 ohms. So, when plugged into many headphone sockets you can't get enough voltage to achieve high volume. You need to find an amp that will pair well with them. They are great headphones, but the impedance choice is just stupid.

author: SilverSolder
author_rank: Super Contributor
timestamp: February 14, 2021, 03:36:48 pm
content: I can see how driving a lower impedance than designed for might be a challenge, but why would it ever be difficult to drive a higher impedance?

author: madires
author_rank: Super Contributor
timestamp: February 14, 2021, 03:52:42 pm
content: Too many people with golden ears!Sometimes it's reasonable to replace cheap op-amps with better ones. Sometimes it's simply a poor circuit design, PCB layout or PSU. Anyhow, beyond NE5532 or similar you'll enter the realm of cognitive dissonance.

author: coppice
author_rank: Super Contributor
timestamp: February 14, 2021, 03:56:02 pm
content: Quote from: SilverSolder on February 14, 2021, 03:36:48 pmIts not difficult to driver a higher impedance load, but you need more voltage to get the same power, and hence volume. If you design to get enough voltage swing for a high impedance load you might blow up a low impedance load when the volume control goes above 2.

author: drussell
author_rank: Super Contributor
timestamp: February 14, 2021, 04:03:29 pm
content: Quote from: SilverSolder on February 14, 2021, 03:36:48 pmInsufficient voltage swing.My 600Ω Sennheisers often receive insufficient drive voltage for the levels I'd like when attempting to run them from most "modern" headphone jacks.

author: drussell
author_rank: Super Contributor
timestamp: February 14, 2021, 04:05:54 pm
content: Quote from: coppice on February 14, 2021, 03:56:02 pmThat's why most headphone outputs that can do reasonable voltage levels have some significant series resistance to cut it down with low impedance loads while still having less of an effect on the total voltage swing available for driving high impedance headphones. Most "modern" circuitry just dispenses with being able to drive anything much above about 32Ω at all with reasonable total power.

author: magic
author_rank: Super Contributor
timestamp: February 14, 2021, 04:09:53 pm
content: Quote from: coppice on February 14, 2021, 03:05:49 pmYou made a very specific and testable claim ("A lot of headphone outputs on phones and notebooks are driven by really unstable amps.") which doesn't appear to be widely known and accepted as fact, without any backing evidence. That's audiophoolery

author: floobydust
author_rank: Super Contributor
timestamp: February 14, 2021, 07:26:37 pm
content: The eyes and ears are excellent sensors. But you still require a trained mind to see/hear subtleties. And the mind can and does fool.A recording engineer uses his/her ears like a microscope and they can spot minor noise/distortion easily. I've been called in to do repairs and have to translate what they are hearing down to the component level to do the repair. Lesser distortions show up as a smearing or masking of details within a mix or for a particular instrument, dynamic distortions make something like a snare or high-hat sound trashy during the transient. You have to have experience with live music to know what it's supposed to sound like, pure.One big console was sounding terrible (poor clarity, gritty, "it sounds shitty") and when I poked around I found the main mixing buses, which are the (-) input on inverting summation op-amp, the virtual ground- had AM radio on it. It's a long 2m run ribbon cables connecting the 36 channels, in a metal enclosure. These consoles are 6-10ft wide. I have no idea how AM radio is getting inside the console. I added ferrite-beads and the problem vanished. Most of the time, it's everything surrounding the op-amp (clean power, no RF or out of band signals, proper compensation and not overloading the output) that affects their performance.The majority of people are content listening to mp3's and hear no difference between mid and high-end recordings or equipment.I was going to compare what some people say here about op-amps to Stradivarius wasting time taking so long making violins. Then I checked on Wikipedia and in double-blind listening tests, we have psycho-acoustics where the mind thinks the $2M 1711 violin sounds better, butmost preferred were new violins."It" sounds better because it's old, hand crafted, worth million$, has history etc. where the mind can and does have bias.

author: Zero999
author_rank: Super Contributor
timestamp: February 14, 2021, 07:58:35 pm
content: Well of course relying on one's ears to find faults is good and often the easiest and quickest way, but modern test equipment is much more sensitive than the ears and is the only way to prove whether amplifier x is objectively better, than amplifier y, assuming they're both half-decent designs. In reality psycho-acoustics dominate, which is why brand, aesthetics and marketing are much more important, than specifications of modern audio equipment. Yes, compressed audio formats such as mp3 often have audible artefacts, but uncompressed digital audio doesn't and is much lower, noise, distortion and higher dynamic range than the old analogue technologies such as real to real tape and vinyl.The audio amplifier is something which has been solved for many decades now. Recent developments have been about increasing the efficiency and more compact design, rather than distortion and noise, which have been over an order of magnitude below the perceivable level for many years now. How about when the amplifier is driven into clipping and the nasty sound that make, some might say? Well that doesn't count, since a Hi-Fi amplifier should never be run into clipping. Old vacuum state technology is still there for guitar amplifiers but they're being replaced by modelling amplifiers. which are supposed to emulate them quite well, although I don't pretend to know anything about that. I suspect people will still like to have the old valve amplifiers for many years to come, as there are still plenty of steam enthusiasts around, even though we've had diesel and electric locomotives for over a century now.

author: SilverSolder
author_rank: Super Contributor
timestamp: February 14, 2021, 09:56:43 pm
content: Valve amps are interesting in the IC age just like there is still something cool about an unhomogenized V8 musclecar in the era of EVs. Old stuff can be entertaining! - we still admire hundreds or even thousands of years old art...

author: coppice
author_rank: Super Contributor
timestamp: February 20, 2021, 10:54:19 pm
content: Quote from: floobydust on February 14, 2021, 07:26:37 pmThe eyes and ears are highly variable sensors, depending on your mood, level of tiredness and other factors. If you use, say, a piano regularly it never seems to sound quite the same on any two days. Yet, it can only be varying slowly with the seasons, as temperature and humidity change. The way some people try to compare what they are hearing and seeing with an experience they had somewhere else, some time ago, as if they had absolute sensing, can be really annoying.

author: coppice
author_rank: Super Contributor
timestamp: February 20, 2021, 10:59:15 pm
content: Quote from: magic on February 14, 2021, 04:09:53 pmThe last time I tried this was about 5 or 6 years ago. Things may have improved with the increasing use of tiny class D amps in mobile devices. We took a number of notebooks in the office, from Dell, HP and Lenovo (Thinkpads), and several pairs of headphones from Sennheiser, AKG and probably one or two others. We played the same music video on various combinations of headphone and notebook. All the headphone could sound OK with some of the notebooks, and some had the gurgling bass of an unstable amp. All the notebooks could sound OK with some of the headphones. You don't need to use instrumentation to detect when an unstable amp is gurgling. There is nothing subtle about these issues.

author: coppice
author_rank: Super Contributor
timestamp: February 20, 2021, 11:09:37 pm
content: Quote from: Zero999 on February 14, 2021, 07:58:35 pmThe best early transistor amp designs of the 1960s sound about the same as the best amps now, except for a higher noise floor on the older amps. However, many amps have been produced over those decades that have serious problems, and they are still being produced. Its still quite common to find an amp sound horrible as you turn up the volume, because any minute overload shifts bias points in the amp that take some time to settle, so an almost imperceptible clipping turns in to a major nasty noise. Its still quite common to hear amps that test really well for THD on a single continuous tone and IMD on multiple continuous tones, to sound poor on music because they behave poorly under dynamic conditions. Idiots indignantly say if you can't measure it, you aren't really hearing it. Of course that is true, but its irrelevant. The real question is whether you are making the right measurements. You can measure weird dynamic behaviours, like transient IMD, without much difficulty, but when did you last see a reviewer perform testing like that?