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Does Op-amp Rolling Work?

Rate this article on opamp rolling:

  • 1. Terrible. Didn't learn anything

    Votes: 9 3.5%
  • 2. Kind of useful but I am still not convinced

    Votes: 17 6.6%
  • 3. I learned some and agree with conclusions

    Votes: 53 20.5%
  • 4. Wonderful to have data and proof that such "upgrades" don't work

    Votes: 179 69.4%

  • Total voters
    258

amirm

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When I post my last video on review of Douk A5 amplifier, I mentioned that rolling (changing) op-amp ICs in there is fruitless. I got have a dozen comments under that video in youtube asking why so I thought I experiment again with the A5. Note that I have done the same testing with both DACs and Power Amplifiers and found the change to not make a difference. But let's see if the results are different this time.

Op-amp rolling amplifier 994Enh-Ticha Sonic Imagery Labs NE5532P TI Testing Douk A5 Stereo Aud...jpg

The Douk A5 makes this job both easy and hard. It is easy because you can just lift the plexiglass and replace the op-amps. The difficulty was replacing the standard TI NE5532P opamp with the discrete Sonic Imagery Labs as it was too larger to fit in there. I pushed the adjacent caps more than I was comfortable with to get it to fit. Fortunately it worked.

There is a massive cost difference with the stock NE5532P costing US 57 cents in single quantity compared to minimum of $49 I found for the Sonic Imagery 994Enh-Ticha dual opamp. You would need two of them for stereo operation which would represent a premium that matches that of the amplifier itself! Here is a close up shot the 994Enh-Ticha:

index.php


As you see in the above picture, i decided to replace the right channel (Ch 2 below) and left left channel (Ch 1) the same. That way we can compare the two channels simultaneously under the same environmental situation. Amplifiers are temperature sensitive and shutting down to replace the opamp and powering back up would have created another variable. Alas, there is also channel to channel variations so the testing is not 100% exact but very close as you see below.

Opamp Rolling Measurements
Here is our usual dashboard:

Op-amp rolling amplifier 994Enh-Ticha Sonic Imagery Labs NE5532P TI Measurement.png

As we see the performance is the same with SINAD which sums noise and distortion. This is of course at one power level so let's sweep the input voltage and measure at all power levels up to clipping:
Op-amp rolling amplifier 994Enh-Ticha Sonic Imagery Labs NE5532P TI Power 4 ohm Measurement.png

There is the tiniest gap between the two but that may just be variations between channels. Even if it weren't so, it is a miniscule difference.

Maybe the differences becomes more visible if we use other frequencies than 1 kHz represented above:
Op-amp rolling amplifier 994Enh-Ticha Sonic Imagery Labs NE5532P TI Power 4 ohm vs frequency M...png


I have zoomed into this graph to make differences larger. Dashed line is the Sonic Imagery discrete op-amp. We see that both at 15 kHz and at less than 500 Hz, the discrete amplifier is actually worse! But again, that could be variations between channels.

I wanted to investigate that a bit more so ran a couple of FFTs at both 100 Hz and 1 kHz:
Op-amp rolling amplifier 994Enh-Ticha Sonic Imagery Labs NE5532P TI 1 kHz FF Measurement.png





Op-amp rolling amplifier 994Enh-Ticha Sonic Imagery Labs NE5532P TI 100 Hz FF Measurement.png

The profile of distortion changes but not the high-order message that any difference is relegated to high order harmonics that are at or below threshold of hearing.

Discussion And Conclusions
It is natural to assume that the much more expensive, larger and fancier hand-made opamp IC would do better. All is not as it seems. An integrated circuit (IC) benefits from high precision components and even components that cannot be instantiated using discrete parts. Path lengths are also shorter allowing for better optimization of the design. Mass production using automated systems follows up by sharply reducing its cost.

On the other hand ICs can be subject to thermal coupling where rise in temperature in one part of the IC can negatively impact the performance of the rest of the IC. This doesn't apply here because the opamp is used at the front-end of the amplifier that is not attempting to produce power (only acts as a buffer and/or gain stage). Importantly, there is feedback that is used to correct the non-linearities in the op-amp. This correction highly linearizes both discrete and integrated op-amps as to almost erase any signature of the original part. This is why we don't see much difference in measurements.

People report improvements in sound and with it justify the upgrade. As members of this forum well know, such listening tests are improper. Testing must be controlled to exclude all extraneous (non audible) factors. When done, the measurements powerfully predict no audible difference. Indeed, I only know of one research paper that dug into sonic differences in op-amps and that only happened when the opamp was vastly overdriven.

Finally, I am not saying that all opamps are the same. There are countless ones for a reason. But unless you have instrumentation such as I am using, you have no prayer of knowing if a change improves anything. Or worse yet, made things worse. Here are the results form the DAC test:
index.php

There we do see a bit of differentiation but not enough to bother with any of this.

Net, net, leave the engineering to well, engineers! :) But a performant audio product and use it as is. Don't risk damaging and spend money on something that has essentially no chance of doing you any good.

Video version available as well:

EDIT: Part 2 with Sparkos SS3602 and Fosi V3 Mono amplifier posted as well: https://www.audiosciencereview.com/...-rolling-using-sparkos-on-fosi-v3-mono.61903/
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As always, questions, comments, recommendations, etc. are welcome.

Any donations are much appreciated using: https://www.audiosciencereview.com/forum/index.php?threads/how-to-support-audio-science-review.8150/
 
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Thanks! I was finishing my schooling when op amps became common and affordable. Op amps were also used in analog computers and analog synths. I met Walter Jung at AES and worked with Neil Muncy's early Melcor op amp module-based mixers, then on to using API mixers built around their own API 2520 op amp module. Jung's books are a great source for DIY electronics. In the audio world at that time transformers could provide gain. In professional audio I think some of the designs are for deliberate compression and harmonics. Hopefully that is all done for the creator artistic purposes. Then I prefer an unadulterated version.
 
maybe im missing something after reading through the initial post, but this 'only' seems like a Sonic Imagery 994Enh-Ticha review, instead of answering the question at hand.
Finally, I am not saying that all opamps are the same. There are countless ones for a reason.
what are they then? im into really interested in magic audiophilia dust blessing from boutique brands, im interested in getting to know more about this topic, which often[and feels like yet again] goes into the conclusion of 'there are many different opamps for good reasons' and 'its pointless swapping opamps' at the same time.
 
Not sure what the purpose of this thread is, other than to stir the pot even more on opamp rolling. Maybe start an argument to get engagement?

The power stage is the limiting factor here, not the opamps.

On another note, the 994enh SI opamps run hot and can pull quite a bit of current. I've got a few cooked ones here.
 
Maybe same testing but using SOTA DAC instead of Douk-class amp could reveal something more substantial.
With all honesty I barely imagine a person who a) buys such amp for serious listening and b) at the same time values op-amp switching and invests into it.
 
what are they then?
There are many applications for them that require different designs. An "instrumentation" op-amp for example produces least amount of DC offset. A "video" one has very high bandwidth. Some come with one or man op-amps in one package. Some cost more than the others. And yes, there are performance differences between them.
 
The power stage is the limiting factor here, not the opamps.
So you think someone who has built a state of the art power stage, left room on the table on the front-end buffer/gain stage?
 
But you didn't listen to it, the drawn curtains, the PRAT, the microplankton, the distance from your lap to Diana Krall... /s
yup...yup...one...to..bind...them...one...to...rule...them...all...
 
Ok, let's say ypu have a phonostage with mm and mc inputs. One requires the lowest current noise, the other the lowest voltage noise. Choosing the same op amp for both inputs will be suboptimal.

Now consider the complexity of all gain/ comparator circuits and you have the reason for the huge spread of op amps. Sometimes you need slew rate, sometimes dc offset, sometimes a jfet input, sometimes cmos...

It's highly unlikely that any designer has chosen the wrong opamp, so you can usually only make things worse, and where better is possible it's likely inaudible anyway, though not always, but certainly in 99.9999% of cases.
 
There are many applications for them that require different designs. An "instrumentation" op-amp for example produces least amount of DC offset. A "video" one has very high bandwidth. Some come with one or man op-amps in one package. Some cost more than the others. And yes, there are performance differences between them.
so would that then mean, that for given workload, like audio dac, there would be a virtually 'one-size-fits-all' opamp design? and other design exist for the purpose of different workloads, like the one for "video"? that sounds like it make sense
 
so would that then mean, that for given workload, like audio dac, there would be a virtually 'one-size-fits-all' opamp design?
There is competition in the market so there won't always be a single solution.
 
And I saw that which is why I commented here, but you responded, not Amir. He only dropped the one line and didn't go into detail... ;)
Wish granted. :cool:
Not sure what the purpose of this thread is
Just a lot of new and other members have been asking about opamp rolling recently, so we ended up with this combined discussion thread and now this test/video thread;
Some companies have been promoting the practice too, even suggesting different opamps are needed for specific genres of music.


JSmith
 
So you think someone who has built a state of the art power stage, left room on the table on the front-end buffer/gain stage?

There's nothing "state of the art" about the Douk A5.

Exactly what do you think plugging an alternative opamp into a cheap class D amplifier with ordinary performance and then running a few tests proves about either opamp specifically?

Nothing to see here.
 
what are they then?
Some have lower noise, but that's not much of an issue with line-level signals, especially line-level buffers which are about the easiest thing thing to build with an op-amp. It's hard to make a "bad" one.

With microphone preamps, you might have gain of 60dB or more and any internal noise gets amplified so it's a bigger concern.

I was also around in the early days and some op-amps had slew rate limitations and some weren't stable at low gains (they would oscillate if not properly "compensated"). I think those problems are gone. I once built a preamp that turned-out to be an RF oscillator and it fried one channel in my power amp! Luckily, my tweeters survived. Probably because of the voice coil inductance at MHz frequencies.
 
There's nothing "state of the art" about the Douk A5.
There isn't. I was addressing your comment that this amp's output state is not good enough to show the difference.
 
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