Big test of DIP dual op-amps for audio: LM4562, NE5532, OPA2134, TL072 and LM1458

[pma]

There are questions if it matters which type of op-amp is used in the audio amplifier and my answer is that it depends on circuit schematics and op-amp parameters. Some of those parameters are obvious from datasheets, but others may be quite hidden and not clear from the first view. For the test I have chosen well known dual op-amps LM4562, NE5532, LM1458 (bipolar input) and OPA2134, TL 072 (JFET input).
LM1458 is one of the first op-amps usable for audio and it is dated at sixties of the previous century. NE5532 was then a big big improvement in audio op-amps, introduced by Signetics company in 1979. LM4562 appeared in 2006 as an improvement in noise and supposed to have lower distortion than NE5532.
OPA2134 was introduced by Burr-Brown in the nineties as a lower noise and lower distortion improvement of TL072.
As far the datasheet and popular info.

When making a choice of the op-amp, we always need to know the application circuit. For the test I have chosen quite common non-inverting amplifier circuit with +6dB gain and 10k feedback resistors.

The test rig is driven from a DAC with low, 20 ohm output impedance, and loaded with 1 kohm ADC input impedance. This is quite difficult load, but as the output voltage did not exceed 3V, all the op-amps are deep in the area of allowed output current.

Measurements

For the start, I have chosen measurements of THD vs. output voltage at 1kHz and 10kHz and measurements of 13+14kHz CCIF IMD vs. output voltage. The plots are shown below:

We can see that the LM1458 is simply unusable for audio, even at low output voltage and that we can assume it will have its own sound signature. Both JFET opamps, OPA2134 and TL072 have higher distortion than LM4562 and NE5532, in all 3 tests. The result of the old NE5532, that is slightly better than LM4562, is a small surprise to me, I have expected the opposite result.

In all cases, I have tested at least two samples of each op-amp type, to prevent random results. All the samples of the same types behaved identically within the measurement repeatability.

More tests can be done, suggestions welcome. But I will wait for the forum feedback.

All the measurements done with 96kHz sampling and 45kHz effective bandwidth.

Note: for loopback test please go to post #33

 

[Scrivs]

Thanks Pavel

 

[Grotti]

Thank you, Pavel! Is there a reason, why every device produced after the 5532 shows the increase of distortion above about 0.2 Volt?

 

[Jon L]

So, the much-maligned NE5532 redeems itself.
Do you have access to much-touted discrete opamps, e.g. Sparkos, Burson, Sonic Imagery?

 

[pma]

Thank you, Pavel! Is there a reason, why every device produced after the 5532 shows the increase of distortion above about 0.2 Volt?

Usually input stage linearity, cm distortion and output stage distortion.

So, the much-maligned NE5532 redeems itself.
Do you have access to much-touted discrete opamps, e.g. Sparkos, Burson, Sonic Imagery?

No, unfortunately not, but have no expectations after checking the datasheets.

 

[Joe Smith]

Well, this makes me feel good that I stuck with the 5532 and 4562 chips for my little class D amps, and did not go down the "discrete" train.

Burson had sent me some free ones (v5 and v6 ones), but I really could not hear any difference with them.

 

[EERecordist]

Thanks, great contribution.

What power supply voltage have you standardized on using? Gain compression would be a useful measurement.

The NE5532 was designed into the Focusrite Studio Console by Rupert Neve and was popular with many other professional recording equipment makers.

It would be fun to test some of the boutique op amps, though they may have problems with part-to-part variation. Your test may be the first proper test that part has experienced. It would also be fun to test a 741.

 

[KL....]

So, the much-maligned NE5532 redeems itself.
Do you have access to much-touted discrete opamps, e.g. Sparkos, Burson, Sonic Imagery?

Usually input stage linearity, cm distortion and output stage distortion.

No, unfortunately not, but have no expectations after checking the datasheets.

@pma, thank you for testing, nice surprise with the NE5532, isn't it?
From these tests, do you expect the discrete opamps (Sparkos, Burson, Sonic Imagery) to have lower performance than the NE5532?

I highlighted Sparkos only because that was the one that fellow in the video kept suggesting (literally, raveing about it) was the best in the Douk A5. Perhaps the NE5532 performs to well in the Douk A5 (was the LME49720 tested, I cannot remember, I will need to check) and the Sonic Imagery was even worse. Perhaps (even) the NE5532 (or LME49720 or Sonic Imagery) is too fast/swamping the Douk A5 class-D output circuit causing compatiblety/synchronousity issues (to timing/overlaying, filtering, PFFB application, etc) but the discrete Sparkos (perhaps) does not (is more compatable), is this possible? I have asked this before but it is on my mind, so I ask again.... thanks :=)

 

[Cbdb2]

Thank you PMA, always good to have more proof of what you already know.

So, the much-maligned NE5532 redeems itself.
Do you have access to much-touted discrete opamps, e.g. Sparkos, Burson, Sonic Imagery?

Amir tested a sonic imagery discrete in a device.

No difference, except 100 times more expensive!

 

[solderdude]

There are questions if it matters which type of op-amp is used in the audio amplifier and my answer is that it depends on circuit schematics and op-amp parameters. Some of those parameters are obvious from datasheets, but others may be quite hidden and not clear from the first view. For the test I have chosen well known dual op-amps LM4562, NE5532, LM1458 (bipolar input) and OPA2134, TL 072 (JFET input).
LM1458 is one of the first op-amps usable for audio and it is dated at sixties of the previous century. NE5532 was then a big big improvement in audio op-amps, introduced by Signetics company in 1979. LM4562 appeared in 2006 as an improvement in noise and supposed to have lower distortion than NE5532.
OPA2134 was introduced by Burr-Brown in the nineties as a lower noise and lower distortion improvement of TL072.
As far the datasheet and popular info.

When making a choice of the op-amp, we always need to know the application circuit. For the test I have chosen quite common non-inverting amplifier circuit with +6dB gain and 10k feedback resistors.

View attachment 438490

The test rig is driven from a DAC with low, 20 ohm output impedance, and loaded with 1 kohm ADC input impedance. This is quite difficult load, but as the output voltage did not exceed 3V, all the op-amps are deep in the area of allowed output current.

Measurements

For the start, I have chosen measurements of THD vs. output voltage at 1kHz and 10kHz and measurements of 13+14kHz CCIF IMD vs. output voltage. The plots are shown below:

View attachment 438493

View attachment 438494

View attachment 438495



We can see that the LM1458 is simply unusable for audio, even at low output voltage and that we can assume it will have its own sound signature. Both JFET opamps, OPA2134 and TL072 have higher distortion than LM4562 and NE5532, in all 3 tests. The result of the old NE5532, that is slightly better than LM4562, is a small surprise to me, I have expected the opposite result.

In all cases, I have tested at least two samples of each op-amp type, to prevent random results. All the samples of the same types behaved identically within the measurement repeatability.

More tests can be done, suggestions welcome. But I will wait for the forum feedback.

Can you show a loopback ... to get a feel of the measurement floor. ?

 

[solderdude]

Thank you PMA, always good to have more proof of what you already know.


Amir tested a sonic imagery discrete in a device.

View attachment 438542

No difference, except 100 times more expensive!

The point here is that
A: differences seen could be channel differences. For science sake the op-amps should have been measured twice but in the other channel to eliminate possible channel differences.
B: the op-amp distortion, very likely, is 'masked' by higher distortion of the output stage.

 

[Zek]

@pma can you find an old version of the NE5532, some swear it's the right version for audio applications.
Something like this - Signetics

 

[amirm]

A: differences seen could be channel differences. For science sake the op-amps should have been measured twice but in the other channel to eliminate possible channel differences.

The amplifier did not have consistent enough performance to show comparable results there. As temps varied, so would level of noise and distortion. Swings were as much as 5 dB so no way to get anything out of shutting down, switching op-amps and then testing again.

 

[solderdude]

Such is the burden of measuring near performance limits.

 

[Cbdb2]

The point here is that
A: differences seen could be channel differences. For science sake the op-amps should have been measured twice but in the other channel to eliminate possible channel differences.
B: the op-amp distortion, very likely, is 'masked' by higher distortion of the output stage.

I thought the point was to show that swapping the OAs in a device like this was pointless.

 

[solderdude]

That is the point of the Douk thread.
However, the test here is about measuring performance limits in simple audio circuits using some well known op-amps.

Most 'audiophiles' don't care about performance and want to hear recordings of op-amps.
The possible snags here are used DAC/ADC quality and music for the test files and the actual performance of gear used to compare the test files at home.
If the quality is lower than that of the test files what is one actually comparing when the technical differences (that are guaranteed to exist) are masked by lesser reproduction gear.

My opinion for testing with music is that it would have to be done in lab conditions and controlled with suitable gear.

For technical measurements the whole ear and reproduction gear is not needed but that's what audiophiles are more interested in.

 

[restorer-john]

Well done Pavel.

Results are THD only. How about absolute noise figures for each device (20-20k WTD or UNWTD)?

 

[Salt]

The amplifier did not have consistent enough performance to show comparable results there. As temps varied, so would level of noise and distortion. Swings were as much as 5 dB so no way to get anything out of shutting down, switching op-amps and then testing again.

He measured two samples of each OPA, and ambient temperature should not be a problem for OPA designed for home use, not?

 

[audio_tony]

Some years ago I carried out similar tests but all at 1kHz and into a 2.7k load. I still have most of the ICs so I can carry out the same measurements as PMA (although possibly my ADC might be a limiting factor.)
I also have the Signetics opamps as mentioned by @Zek

OPAMP tests into a 2k7 load

OPAMP tests into a 2k7 load

gtkc.net

 

[solderdude]

He measured two samples of each OPA, and ambient temperature should not be a problem for OPA designed for home use, not?

The problem Amir described is not caused by the op-amp used but rather the entire amp and the limits of the entire circuit.
Especially switching devices (like class-D) can easily have/cause measurement errors when looking in the microvolts and volts levels of measurement signals happening at the same time.