Time flies! It’s been almost 4 years since I last updated this Op Amp Shootout page. Now It’s 2017, and this page is still our top hitter. I guess that only means that people find this page helpful. And I am always happy to share information. I’ve updated the page to reflect recent developments. I always have a keen eye for new Op Amps and the new additions were taken straight from my notebook.
Question: What’s a good Op Amp for audio? The answer: depends. There are many factors to consider and there’s no single best answer. There was a time when I was quite happy with the cheap and simple TL072 for most tasks. If I needed something better, then there’s the more expensive (at the time) 5532. It’s notable that after all these years, these critters are still quite capable. I did some research and bumped into this series of articles: Op amps in small-signal audio design (part1, part2, part3, part4) by Douglas Self (EE Times). The article was written in 2011 and yet still mainly talks about the TL072 and the 5532 plus a little bit about a couple of newer designs later on.
I’d wish more space were given for modern Op Amps in the article. There’s a bewildering plethora of Op Amps out there from the most generic to all sorts of highly specialized designs. So, I went on and scoured the web searching for nice “modern” candidates. The basic requirements are:
- Low noise
- Low THD+N
- Good response (slew rate)
- Low power
Those are somewhat conflicting requirements. Typically, low power Op Amps have dismal noise and THD specs. I need to find the right balance. So here’s my mini Op Amp shootout. The table below compares the basic audio-performance specs that I am interested with. For the benchmark, we have the 5532 and the TL072. Performance-wise, I consider anything on a par with or better than the 5532 suitable. It might even make sense to sacrifice a bit on one or two aspects. For instance, do we really need a vanishingly low THD+N? For the hex pickup preamp, perhaps not.
The requirement for low power is in the list, but that requirement is now somewhat relaxed. It is still in the list because we want to be as general purpose as possible. However, if other subsystems such as MCUs or DSP processors consume a lot more power and will easily drain AAA batteries anyway, it makes sense to consider higher powered candidates with exceptional noise figures. These may be a good choice for port (e.g. USB) powered electronics or designs using heftier rechargeable (e.g. Li-ion) batteries. Come to think of it, is this the norm in this day and age of smart phones?
The benchmark 5532 (and its sibling, the 5534) and the TL072 are highlighted in yellow. I also highlighted the 4558 in yellow due to its popularity. The LMH6629 Ultra-Low Noise, High-Speed Operational Amplifier is most impressive, with a vanishingly low distortion specified as HD2/HD3 = −90 dBc/−94 dBc (where HD2 and HD3 are the 2nd and 3rd Order harmonic distortion, respectively). It is seconded by the LMH6624 with HD2/HD3 = −60 dBc/−76 dBc and 0.92 nV/√Hz at 1kHz noise figure —still outstanding. The OPA1611, with 0.000015% THD and 1.1 nV/vHz noise figure—is still outstanding, but with a more reasonable power requirement, consuming 3.6 mA per amplifier.
What started out as a blog entry became a rather unending search for the right Op Amp. My current favorites have changed since then, partly due to shifting requirements. Now, there are more choices, highlighted in red, blue, light-green and dark-green, sorted from highest performance and highest power, to moderate performance and low power. For preamplifiers, the ones that are highlighted in blue are my current favorites with good overall balance. Ultra low noise is necessary for preamplifiers keeping in mind that later stages (e.g. compressors, overdrives and distortions) along the signal path will amplify any noise present in that stage. This noise will end up as annoying hiss in subsequent stages, masking low-level details in the sound. Such details will end up being thrown away by the noise gate.
It is now 2017 and there are some interesting additions such as the OPA188 with a wide supply range of 2V to 18V, and very low 500μA current consumption. I also added a bunch of very Op Amps from Japan with rather respectable specs. Check out the NJ series Op Amps from JRC New Japan Radio Co., LTD. I found out about these cool Op Amps from studying Roland schematics. Have a look at the NJU77806, for example, with a noise figure of 5.5 nV/√Hz at 1kHz while consuming only 500μA.
Cost, is also a concern. Higher performance devices, obviously cost a lot more. You might want to scroll to the right to see the price of each Op Amp (see note a1 and a2). Again, engineering is always a balance. For example, later stages in the signal chain need not require the utmost noise performance and the lower power, and more cost-effective candidates would certainly be smart choices.
|Price per Op Amp; January 2017 Mouser 100pcs.||a1|
|Price per Op Amp; January 2017 Mouser 1000pcs.||a2|
|JFET input stage||e|
|Low offset voltage||g|
|Overture Series (E-Series Ultra-low Distortion, Ultra-low Noise)||h|
|New design (2011)||k|
|integrate RF/EMI rejection filter||l|
|BiCom-3x (SiGe complimentary bipolar) process||n|
|Distortion specified as (HD2/HD3 = −90 dBc/−94 dBc)||o|
|Distortion specified as (HD2/HD3 = −60 dBc/−76 dBc)||p|