What are the good general purpose audio op-amps these days? - Page 1
Forum section: electronics / projects

author: Unknown
author_rank: Unknown
timestamp: May 24, 2015, 04:17:14 am
content: As the title says: What are the good general purpose audio op-amps these days? Last time I did anything audio-related I would've reached for the NE5532 & friends, but I assume better devices have appeared in the last 20+ yearsI'm toying with the idea of building a couple of custom small audio mixers for basic sound reinforcement / recording use by a local non-profit organisation (they have their own building with a few presentation/conference rooms; sessions may be per-room, piped across a couple of rooms, or even broadcast over the building PA, & are often audio/video recorded for sale or lending). Inputs will be balanced or unbalanced line level, though I'll probably include the option of dynamic mics & phantom powering on at least a couple of inputs.So high input impedance/bandwidth/slew rate aren't particularly necessary (I can use something more suitable for the input stages if necessary); low V/I noise, unity gain stability, & good CMRR are. Price & current/future availability too.While I'm digging through the manufacturer parametrics & datasheets myself, do you guys have any suggestions?

author: Richard Crowley
author_rank: Super Contributor
timestamp: May 24, 2015, 04:48:32 am
content: THAT makes many special audio chips including several mic preamp chips, balanced line drivers and receivers, dynamics processors, VCAs, etc.http://www.thatcorp.com/Datasheets.shtmlAnd TI have bought out National Semiconductor and Solid-State Music and Burr-Brown so they are the other major source of 21st-century audio chips like:http://www.ti.com/lsds/ti/analog/audio/audio_overview.pagehttp://www.ti.com/product/ina217http://www.ti.com/product/pga2500http://www.ti.com/product/lme49724http://www.ti.com/product/lme49710and several moreAnd the 5532 is still widely used as well.

author: moffy
author_rank: Super Contributor
timestamp: May 24, 2015, 05:03:35 am
content: The LM833 is a great low distortion audio op amp.

author: Zero999
author_rank: Super Contributor
timestamp: May 24, 2015, 08:23:05 am
content: It depends on what you want to do.The NE5532 is still good enough for most applications. Plenty of new audio equipment still uses old op-amps such as the NE5532 and TL072 because anything better is overkill and not cost effective.

author: dom0
author_rank: Super Contributor
timestamp: May 24, 2015, 09:37:21 am
content: The NE5532 is sufficient for systems with SNR in excess of 90-100 dB, so it's still 'good enough' for audio and the like. It is also very cheap and besides the NJR (2068, 4556) there are few parts in the same price range with overall similar performance.The LM833 is only slightly better in some specs than the NE5532 (notably it has a bit more phase margin at unity gain, the '5532 has only like 45° or so PM which leads to overshoot and poor stability with capacitive loading in follower applications). They are overall very similar chips and should, in most cases, be interchangeable without much difference. The 833 doesn't really perform better in terms of THD or noise, they are nearly indistinguishable.The newer LM4562/LME49720 series improves on many parameters at once cf. NE5532, e.g. noise, bandwidth, THD and output current. They have, however, higher current noise andcost ten times as much. They were designed for systems with 120+ dB SNR. Note the high bandwidth of these devices (which leads to high open loop gain at audio frequencies, which in turn increases feedback and thus reduces THD, which is how they achieve the extremely low THD of these devices - high feedback and a very linear op amp to start with), which means that you need excellent bypassing and careful layout ; these are "high speed devices" and somewhat prone to oscillation by insufficient bypassing or too high feedback network resistances (which create too much phase shift with parasitic capacitances).There are some other contenders, but most have, in usual applications, one or more (important) disadvantages over the 5532. So for the great majority of applications the 5532 is just fine, but as a bipolar op amp it's not well suited for high source impedances (JFET territory).All in all your circuit and it's layout and environment will matter much more than the specific choice of op amp, be it 5532 or 2068 or 4562. Mind you, be aware that you often can't just swap op amps, especially against faster ones, without adjusting the circuit.

author: blackdog
author_rank: Frequent Contributor
timestamp: May 24, 2015, 10:58:53 am
content: Hi,I totally agree with dom0 comments...Thre is at least one way to make the NE5532A en de 5534A (Yes Always use the A version) and that is take the load of the opamp.Use a buffer between de output af te opamp en the fedback resitors/Load.Thre are several types of buffers, a famous one is the BUF634, LT1010 enz, Yes more expensive than de opamp itself :-)With a buffer, you can use lower values your feedback resistors, this gives less noise and you also have less trouble with parasitic capacitances.What you will use depends on whether you can pay the price of the buffer and the need for your design?There are so many ways to make it better if you want to get the last bit out of it.Intelligent design, does more than expensive and opampKind regarts,Blackdog

author: dom0
author_rank: Super Contributor
timestamp: May 24, 2015, 11:10:59 am
content: For the 5532 you actually don't need the fancy super-fast integrated buffers, a couple of transistors get the job done, too, with hardly any difference.

author: Unknown
author_rank: Unknown
timestamp: May 24, 2015, 11:42:53 am
content: Wow - I came back to comment on the earlier replies & what I dug up, but dom0's pretty much nailed it.Looking around there's more practical options than I remember (e.g. the Burr-Brown TI parts are now (a) available & (b) affordable!; LT & NJR have some interesting parts, etc), but nothing that stands out as massively better than the NE5532 for the price. The LM833 is, IIRC, another one from the same era as the NE5532, and looking at the specs it's not too different.IIRC - and I'll have to double-check this - the main contributor to the NE5532's low phase margin is the compromise of internal compensation, correct? Again, I'll have to run the numbers, but I suspect the NE5534 + external compensation can be made better in that respect. On the other hand, while I remember I had to be a little careful with the NE5532 in the past, I dont recall anything that couldn't be overcome with careful design & layout. Hopefully all will come back to me when I start playing with one again...And yeah, blackdog, the A version. I'd forgotten about the buffer trick too, even though I've used it in the past.(Aside: I knew that op-amp swapping was a bit of an audiophool thing - but by God there's a lot of wankery about it out there!)Quote from: Richard Crowley on May 24, 2015, 04:48:32 amThanks - nothing in the way of op-amps I can see, but it reminded me to look at options like that for balanced line receivers.Thanks for the info everyone. I'll keep looking tomorrow, but welcome any further thoughts in the meantime.

author: Zero999
author_rank: Super Contributor
timestamp: May 24, 2015, 12:07:09 pm
content: Quote from: dom0 on May 24, 2015, 09:37:21 amThe TL072 is still good enough if high impedance input/low bias currents are required but it's more noisy than the NE5532 and has a high output impedance - it's all a compromised between cost, noise and input impedance.Another solution is to add a source follower stage to the NE5532 but the offset voltage will be compromised, although that's not normally a problem with audio.

author: Kleinstein
author_rank: Super Contributor
timestamp: May 24, 2015, 12:22:51 pm
content: While the NE5532 is still competitive today, there are better FET based alternatives to the TL07x series:OPAx134 and several similar ones with about halve the noise and still not that expensive.

author: Zero999
author_rank: Super Contributor
timestamp: May 24, 2015, 01:05:42 pm
content: Quote from: Kleinstein on May 24, 2015, 12:22:51 pmNot that expensive. Are you joking? The OPA2134 is over ten times the price of the TL072! It's better but, like I said it's a compromise between cost, as well as other factors.Quote from: blueskull on May 24, 2015, 12:35:05 pmAt a price.

author: Richard Crowley
author_rank: Super Contributor
timestamp: May 24, 2015, 01:43:51 pm
content: IME building microphone preamps with "discrete components" is no longer necessary here in the 21st century when we have specialty ICs like THAT 1510/12 and INA217 et.al. And, for that matter, THAT 1646 for balanced line driving. There are better things to do with your time than fooling around building previous-century mic preamp circuits.Otherwise, I agree that the modern variations of the 5532 are widely-applicable and inexpensive.

author: dom0
author_rank: Super Contributor
timestamp: May 24, 2015, 01:49:00 pm
content: Quote from: blueskull on May 24, 2015, 12:35:05 pmUntil your source impedance exceeds a few kOhm, then it gets quickly beaten by parts with a fraction of the cost...

author: linux-works
author_rank: Super Contributor
timestamp: May 24, 2015, 01:53:07 pm
content: opa2132 and 2134 are good and not expensive. I prefer fet-opamps due to low dc offset.you can google 'tangentsoft' and read up on his views on OA's for audio. make your own decision if that info is useful or just 'lore'.for me, once things get good enough, I can't hear any diff. so the 2134 is fine for me. if money does not matter, the very low noise opa627 and 637 are hard to beat but were $20 last time I looked ;(

author: Unknown
author_rank: Unknown
timestamp: May 25, 2015, 04:52:31 am
content: Quote from: Richard Crowley on May 24, 2015, 01:43:51 pmAgreed (and I never had any real intention of doing otherwise) - though I'm more inclined to roll something with an instrumentation amp like the INA217 than a THAT1510/12, simply because it's a known quantity with a better chance of future availability/substitution. Although they (and the SSM2019) are pin-compatible?, and should only need minor circuit changes between them.For the main guts (i.e. not input / output), it's basically looking like:NE5532A / LM4562 / NJM2068 / NJM4562 - Barely anything between them; nothing that can't be dealt with by attention to design. The choice will come down to any difficulties with that, and price/availability.All the others e.g. OPAanything - 3x the price and upwards, for only marginal improvement.I'm not after world-class performance. This isn't for a recording studio; it's for day-to-day PA use, with a sideline in semi-semi-pro A/V recording. I don't need to eke out the last noise-free dB at any expense.Quote from: linux-works on May 24, 2015, 01:53:07 pmCall me a cloth-eared philistine if you like*, but I have an automatic bias against evaluations which use terms like 'impactful', 'mellow', 'smoothness', 'aggressive', 'analytical', 'laid back', or even 'tubby', in lieu of any objective measurements beyond clipping...Personally, I foundNWAvGuy's comparisonto be a useful starting point for getting back up to speed on what's current these days.(* "Hey, Tex! You're a cloth-eared philistine!")

author: linux-works
author_rank: Super Contributor
timestamp: May 25, 2015, 05:36:32 am
content: nwav guy - lol! whatever happened to him? came, make a big stir and then left just as fast. very suspicious.I don't speak audiophile, but the tangentsoft guy does do real engineering work. you have to decide which things are more subjective vs objective, but I find the list of op-amps there a good starting point. I would buy samples, test them and keep the lowest cost one that does what I want.

author: Unknown
author_rank: Unknown
timestamp: May 25, 2015, 06:16:22 am
content: Quote from: linux-works on May 25, 2015, 05:36:32 amNo idea. Note, I didn't say NWAvGuy's site was good - for a start, I have some minor issues with e.g. his methodology - but rather a useful starting point for me to catch up after 20 years of basically ignoring audio.Quote from: linux-works on May 25, 2015, 05:36:32 amFair enough. It'd be useful if he posted some of it on his website...Quote from: linux-works on May 25, 2015, 05:36:32 amWhich is what I intend to do.edit: Ah, now I see - NWAvGuy is famous in audiophile / headfi circles for arguing that sensible by-the-book design beats common knowledge & folklore, making his point with a couple of examples, then doing a disappearing act. Didn't know that at all.

author: Armxnian
author_rank: Regular Contributor
timestamp: May 25, 2015, 06:17:15 am
content: Quote from: linux-works on May 25, 2015, 05:36:32 amNo one knows, but he did put out two good products and created an informative site.The o2 uses the JRC 4556AD and it sounds great. I ended up frying mine after an hour of full power sine wave testing but they only cost $.73 to replace.

author: Zero999
author_rank: Super Contributor
timestamp: May 25, 2015, 05:52:27 pm
content: Quote from: linux-works on May 24, 2015, 01:53:07 pmWhere do you buy them from?Everywhere I look the OPA2132 is considerably more than the NE5532. I'd consider it too expensive to prototype with and risk blowing up.The OP37 costs less (still wouldn't say it's cheap though), is very good but it's undercompensated and single channel only.

author: Kleinstein
author_rank: Super Contributor
timestamp: May 25, 2015, 06:49:26 pm
content: If you can use a bipolar OP, the NE5532 is usually the better choice than a JFET OPA2132 / OPA2134. The OPA2134 is more a better replacement for the TL072 when you need a FET type. This may be the case with low frequency filters.The OPAx132 is the slightly better version for DC critical applications. Normal audio can use the cheaper OPA2134. At something like $2 for the dual version its not as cheap as the TL072 but still affordable.The OP27/OP37 or similar may be attractive if a lower bias is needed for some reason. Otherwise there is little advantage over an NE5532, LM833 and similar.

author: jaxbird
author_rank: Frequent Contributor
timestamp: May 25, 2015, 08:40:06 pm
content: The old ne5532/4 is still very respectable in performance.The opa2132/4 are great and not that expensive while maintaining excellent specs.But even better are LME49710/20 (old LM4562) or the LME49990, incredibly low noise and distortion. Really only matters if you are doing 24 or 32 bit designs for specs only.I doubt anyone would ever be able to hear the difference between any of these in a blind test.

author: mzzj
author_rank: Super Contributor
timestamp: May 25, 2015, 10:39:00 pm
content: Quote from: Hero999 on May 25, 2015, 05:52:27 pmNot all of OP37's from different manufacturers are the same. I did try out some of them in a modified low distortion wien bridge and there was some differences between manufacturers.

author: macboy
author_rank: Super Contributor
timestamp: May 27, 2015, 02:40:49 pm
content: Quote from: dom0 on May 24, 2015, 09:37:21 amListen to this man, he knows what he is talking about.I would throw the NJM4580 (JRC4580, RC4580) in as a contender, but only as a rough equivalent to NE5532 or LM833. It is about the same spec-wise and you will find it in many mid to high end Japanese Hi-Fi. I bought a bunch for ~$0.20 each (TI made RC4580) to replace some much noisier spec Mitsubishi M5218 op-amps in a AVR maybe 12 years ago. I was quite pleased with the result.

author: Pjotr
author_rank: Frequent Contributor
timestamp: May 27, 2015, 03:23:28 pm
content: Quote from: jaxbird on May 25, 2015, 08:40:06 pmHold on, the old NE5532/4 are of a different league than the modern LM4562 etc. The old ones use medium speed transistors and junction isolation. The modern LM ones more linear 5 GHz transistors and capacitive isolation. That gives them a much higher GBP, so the loop gain can be much higher at audio frequencies. If you can hear this sound-wise is questionable, I agree.You can however measure the difference. My 24/192 sound card had the standard 3532A's on board. I replaced them with LM4562's (and did some extra PSU filtering). Overall distortion dropped about 12 dB in a loop back measurement (DA_out--> AD_in of the card).It also depends largely you design for. The low cost NE5532/4 suffice in almost any case but the LME49710 now has gained some mythic aura in high-end circles. And that has its ownmarketingvalue