Does Op-amp Rolling Work?

[Whatsthephuss]

The entire industry is permeated with scammers scamming the employees and some as we know scam the customers too… The entire mass of people involved is permeated with fictional beliefs, half truths and using the convenient facts while ignoring the inconvenient facts that do not prop up the various peoples' agendas. The manufacturers are comprised of as I mentioned various agendas too.

Sad but very true! I appreciate you sharing your perspective and experience. I don’t have a horse in the op amp race but I do have to admit I’ve bought a few to experiment with and I’m genuinely just confused by the whole experience. I would like to believe that companies like ESS (DAC chips) and TI (op amps) are releasing new products pushing the limits of low distortion circuitry for a reason other than money, but I can understand if that’s all it is at the end of the day.

I’ve been following this site for years and have always tried to support companies that actually publish honest measurement specs because I believed that it could be translated to a higher fidelity experience…. or at least a more accurate one. But this sentiment can also be exploited nowadays to charge a premium for “flagship” specs.

Coming back to op amps, I have been doing a blind side by side of two Fosi ZH3 with different op amps and wish I didn’t but I’m pretty sure I can hear a difference. I don’t have a super well trained ear but to me it sounds like there is a difference in transient decay (like how tight a kick drum hits). Maybe I’m overdriving one of them or it isn’t designed for the circuit, idk, but it seems to me like there should be a measureable metric for something I can hear. That’s why I brought it up here, but I hear what you’re saying and if the physics be what they be then maybe it’s just human psychology (me) that’s fvcked.

 

[JSmith]

80dbSINAD is inaudible so a waste of money

Price is rarely correlated to performance in the DAC space... wouldn't you prefer to have a 120dB SINAD DAC than an 80dB SINAD DAC, simply on the basis of great measured performance and thus excellent implementation/engineering design? I'd rather not have a DAC where they haven't bothered to optimise it as it's "good enough", rather than excellent.


JSmith

 

[Whatsthephuss]

Price is rarely correlated to performance in the DAC space... wouldn't you prefer to have a 120dB SINAD DAC than an 80dB SINAD DAC, simply on the basis of great measured performance and thus excellent implementation/engineering design? I'd rather not have a DAC where they haven't bothered to optimise it as it's "good enough", rather than excellent.


JSmith

Funny you mention that, as I did recently buy a 120db SINAD DAC (Topping DX5II) simply for its excellent engineering and impressive price to performance. To me it’s incredible how far some of this technology has come - even just 5years ago something like the DX5II would cost 5-10X as much as it does now…

I also own a Qudelix 5k with ~82db SINAD, but the SINAD doesn’t detract from the incredible piece of engineering that it is. I would like to believe that I can hear a difference between the two units with the Topping having greater clarity, and I’d absolutely buy another Qudelix unit if they released one with newer chips & better specs. But in some ways I respect them even more for continuing to sell the same 5k even if it does just measure “good enough.”

 

[Doodski]

Sad but very true! I appreciate you sharing your perspective and experience. I don’t have a horse in the op amp race but I do have to admit I’ve bought a few to experiment with and I’m genuinely just confused by the whole experience. I would like to believe that companies like ESS (DAC chips) and TI (op amps) are releasing new products pushing the limits of low distortion circuitry for a reason other than money, but I can understand if that’s all it is at the end of the day.

I’ve been following this site for years and have always tried to support companies that actually publish honest measurement specs because I believed that it could be translated to a higher fidelity experience…. or at least a more accurate one. But this sentiment can also be exploited nowadays to charge a premium for “flagship” specs.

Coming back to op amps, I have been doing a blind side by side of two Fosi ZH3 with different op amps and wish I didn’t but I’m pretty sure I can hear a difference. I don’t have a super well trained ear but to me it sounds like there is a difference in transient decay (like how tight a kick drum hits). Maybe I’m overdriving one of them or it isn’t designed for the circuit, idk, but it seems to me like there should be a measureable metric for something I can hear. That’s why I brought it up here, but I hear what you’re saying and if the physics be what they be then maybe it’s just human psychology (me) that’s fvcked.

It's a big blue pill or maybe the red pill is better situation. I was an technically uneducated subjective listener for many years before I admitted to myself that the majority of the gear sounded the better electronics gear/CD/amps etc sounded the same and bucked everybody around me that said the gear sounded different. I could not hear a difference between the better amps excluding the cheap STK chip/IC amps that where obviously bad sounding and failed/blew up when pushed. For at least the first 4-5 years when working in the small sales and service mom and pop audio stores and then especially when I first got to the big store with many good brand names & over a dozen+ great speaker lines with all the models in store, the entire full line models of everything displayed and ready in the warehouse for sale with multiple sound rooms. We had several big 40 source and 40 speaker switchboxes and we had 40+ CD players, 40+ cassette decks, at least 90 amp models all good brands etc. For many displays we mounted like 40-50 models of the source gear on the slat wall shelves tightly packed together so one could see it all right there and hear it all very easy. I was all over that gear & I was determined to hear a difference. I tried over and over and over again and the result was the CD players all sounded the same with speakers or headphones, the amps once into the better Japanese and up quality amps all sounded the same unless the speakers where terribly demanding difficult loads, the cassette decks did sound different and more money almost always meant better this or that or better all that, turntables was a matter of I was in the transition zone where they where not really in demand but we carried Dual anyway and sold a small amount but it was not my thing to sell them and most customers where either getting away from them or not getting into them and starting out in CD.

We had the very good big power gobbling power block amps with massive output and they where used on the big Kappa models or the Matrix etc and yes they where better for that but for midrange speaker pairs @ $400-$3000 for Euro or American speakers the big amps could not be differentiated from the big Japanese integrated amps or the mid and big receivers. I had to admit to myself that this was reality and no fictions allowed because everything I did and sold had to be actually and factually demonstrably better if I was to get the customers to expense themselves for the gear. I had a bazillion repeat customers, their relatives, their friends, their work mates all referred to me and the reason was simple. I only sold what was good and what was not fictions and dreams. If it was better I had to be able to demonstrate that and show it to be fact. The good customers love that, they respect that and they open their wallets when they get the truth and get the facts and see somebody who takes the time, makes the time and does what is necessary.

After 9 years of audio sales I returned to post secondary study for the second time, became a technician and learned all about the actual science facts and why etc. The facts of the sales techniques that I eventually used where closely aligned with the physics of the science but that was not by my design and it was simple common sense and admitting the truth to myself after years of subjective garbage and then working in the big store with huge traffic flow and huge dollars passing hands and the money I was making was substantial and the only way to do that was to be honest because the bad sales people lasted 3 months and maybe 6. The OP amps when using common sense listening say they are so close as to be imagined as different and it's all subjective brain dishonesty/fooling with oneself and then when using the science facts the same is said because they are so amazingly good for the low cost that to translate that into the actual physics of sound waves and into the ear's accuracy it is very obvious that OP amp rolling is near 100% subjective gobbledygook and people using garbage science to prop it up. When I started studying OP amps I was for sure 100% deluded and biased against OP amps and then when the electron physics study of them went on and on and on and on and I was really into the deep operation and proving it all with the calculations it was very obvious what their facts, science and abilities are all about.

They are very very special application incredibly optimized sophisticated super accurate incredibly refined tuned designs that are fully and completely optimized to do what they are so very good at. They simply obliterated every thing technology wise that came before them and they still do that to this very day. Even the cheap old models of OP amps are still very good at audio applications and the really amazing OP amps are for applications that far exceed audio applications and using these super good OP amps for audio is simply a situation of diminished returns because the basic OP amps are already so good for simple audio applications that the better ones are simply overkill for audio frequencies. When OP amp rolling is done the entire matter is using junk science. There is no calibration gear, no test gear, no measurements and the OP amps are simply swapped out for a different make and model. In electronics without an actual measurement using highly sophisticated and super accurate metering the entire operation is done totally blind, all guesswork and subjective junk science. Sometimes the new OP amp swapped in the circuit oscillates and can cause horrific circuit damage or even system damage as in the speakers getting it if the system has enough power and the conditions are just right. Anybody that knows electronics does not pretend, act randomly, act subjectively or use fiction to estimate part models or circuit parameters and topology and those that do cause issues that the real actually knowledgeable people end up fixing. OP amp rolling is hopes and dreams and not for reality seekers that use actual science and make proper good circuitry.

 

[RexrothPigeon]

It's a big blue pill or maybe the red pill is better situation. I was an technically uneducated subjective listener for many years before I admitted to myself that the majority of the gear sounded the better electronics gear/CD/amps etc sounded the same and bucked everybody around me that said the gear sounded different. I could not hear a difference between the better amps excluding the cheap STK chip/IC amps that where obviously bad sounding and failed/blew up when pushed. For at least the first 4-5 years when working in the small sales and service mom and pop audio stores and then especially when I first got to the big store with many good brand names & over a dozen+ great speaker lines with all the models in store, the entire full line models of everything displayed and ready in the warehouse for sale with multiple sound rooms. We had several big 40 source and 40 speaker switchboxes and we had 40+ CD players, 40+ cassette decks, at least 90 amp models all good brands etc. For many displays we mounted like 40-50 models of the source gear on the slat wall shelves tightly packed together so one could see it all right there and hear it all very easy. I was all over that gear & I was determined to hear a difference. I tried over and over and over again and the result was the CD players all sounded the same with speakers or headphones, the amps once into the better Japanese and up quality amps all sounded the same unless the speakers where terribly demanding difficult loads, the cassette decks did sound different and more money almost always meant better this or that or better all that, turntables was a matter of I was in the transition zone where they where not really in demand but we carried Dual anyway and sold a small amount but it was not my thing to sell them and most customers where either getting away from them or not getting into them and starting out in CD. We had the very good big power gobbling power block amps with massive output and they where used on the big Kappa models or the Matrix etc and yes they where better for that but for midrange speaker pairs @ $400-$3000 for Euro or American speakers the big amps could not be differentiated from the big Japanese integrated amps or the mid and big receivers. I had to admit to myself that this was reality and no fictions allowed because everything I did and sold had to be actually and factually demonstrably better if I was to get the customers to expense themselves for the gear. I had a bazillion repeat customers, their relatives, their friends, their work mates all referred to me and the reason was simple. I only sold what was good and what was not fictions and dreams. If it was better I had to be able to demonstrate that and show it to be fact. The good customers love that, they respect that and they open their wallets when they get the truth and get the facts and see somebody who takes the time, makes the time and does what is necessary. After 9 years of audio sales I returned to post secondary study for the second time, became a technician and learned all about the actual science facts and why etc. The facts of the sales techniques that I eventually used where closely aligned with the physics of the science but that was not by my design and it was simple common sense and admitting the truth to myself after years of subjective garbage and then working in the big store with huge traffic flow and huge dollars passing hands and the money I was making was substantial and the only way to do that was to be honest because the bad sales people lasted 3 months and maybe 6. The OP amps when using common sense listening say they are so close as to be imagined as different and it's all subjective brain dishonesty/fooling with oneself and then when using the science facts the same is said because they are so amazingly good for the low cost that to translate that into the actual physics of sound waves and into the ear's accuracy it is very obvious that OP amp rolling is near 100% subjective gobbledygook and people using garbage science to prop it up. When I started studying OP amps I was for sure 100% deluded and biased against OP amps and then when the electron physics study of them went on and on and on and on and I was really into the deep operation and proving it all with the calculations it was very obvious what their facts, science and abilities are all about. They are very very special application incredibly optimized sophisticated super accurate incredibly refined tuned designs that are fully and completely optimized to do what they are so very good at. They simply obliterated every thing technology wise that came before them and they still do that to this very day. Even the cheap old models of OP amps are still very good at audio applications and the really amazing OP amps are for applications that far exceed audio applications and using these super good OP amps for audio is simply a situation of diminished returns because the basic OP amps are already so good for simple audio applications that the better ones are simply overkill for audio frequencies. When OP amp rolling is done the entire matter is using junk science. There is no calibration gear, no test gear, no measurements and the OP amps are simply swapped out for a different make and model. In electronics without an actual measurement using highly sophisticated and super accurate metering the entire operation is done totally blind, all guesswork and subjective junk science. Sometimes the new OP amp swapped in the circuit oscillates and can cause horrific circuit damage or even system damage as in the speakers getting it if the system has enough power and the conditions are just right. Anybody that knows electronics does not pretend, act randomly, act subjectively or use fiction to estimate part models or circuit parameters and topology and those that do cause issues that the real actually knowledgeable people end up fixing. OP amp rolling is hopes and dreams and not for reality seekers that use actual science and make proper good circuitry.

paragraph breaks, I beg you

 

[Doodski]

paragraph breaks, I beg you

Yes, I will go back and chop it up a bit.

 

[MaxwellsEq]

All analog components have limited bandwidth, so in theory that would put a bandpass “filter” on the impulse sent through op amps, would it not? My point using DA filters was an exaggeration but not exactly irrelevant.

I feel that you need to learn a lot more about the theory. You seem to know some basics but only have sufficient knowledge to get some of the application of this knowledge wrong.

Admittedly, getting your head around time domain and phase stuff is tricky. You are partially right - anything that has roll-off at some frequency has a time-domain/phase impact at that point. Here's a critical thing to grasp - your physical/brain hearing is one such band-pass system and so has time-domain/phase impacts close to 20Hz and wherever your hearing rolls off (20kHz if you are a child, lower if you are an adult).

You were implying that impulse graphs when applied to different Nyquist filters have some relevance to amplifiers. But amplifiers, as a rule NEVER need or have brick wall type filters in them. There IS quite a skill in ensuring that the high frequency rolloff does not result in resonances and instability with real loads, but that's quite different from attempting to attenuate by 80dB over a couple of kHz!

 

[Whatsthephuss]

I feel that you need to learn a lot more about the theory. You seem to know some basics but only have sufficient knowledge to get some of the application of this knowledge wrong.

alright then. I am just looking for an explanation for something I am hearing - that’s the only reason I commented. Thanks for correcting my insane theory

 

[Whatsthephuss]

In electronics without an actual measurement using highly sophisticated and super accurate metering the entire operation is done totally blind, all guesswork and subjective junk science.

Unfortunately I’m only adding to the gobblygook with my junk observations, but you’re right I have no idea without an actual measurement. I posted here hoping that others who have done the work could answer my questions about how op amps affect impulse response, and I haven’t been disappointed with the answers I’ve gotten. Thank you all

 

[DVDdoug]

I have been doing a blind side by side of two Fosi ZH3 with different op amps and wish I didn’t but I’m pretty sure I can hear a difference.

A proper ABX test includes multiple trials and statistical analysis to get a statistical probably instead of being "pretty sure". i.e. If you identify X correctly 10 out of 10 times, there is less than a 0.10% chance that you are "guessing correctly" or "getting lucky". If you get it correct 7 out of 10 times there is a 17% that you are guessing.

And as a practical matter, if you can't hear a difference 100% of the time with careful listening, does it really matter? Our auditory memory is short so if there's no obvious difference, you what know which one you are listening to the next day or the next week.

Also see Controlled Audio Blind Listening Tests.

 

[MAB]

alright then. I am just looking for an explanation for something I am hearing - that’s the only reason I commented. Thanks for correcting my insane theory

I hear differences that I want to explain all the time. Our hearing isn't helpful in determining differences, it just isn't unless the circumstances are controlled, and even then the ability to hear small frequency response deviations or distortion is extremely limited. People forced to try to hear differences in identical sounds fail to hear the similarity, like the famous Sapphire Group listening test:

Audio Listening Test That Fooled the Hollywood Sapphire Group

Some of the most highly trained audiophiles in the industry were asked to do a blind “A-B” listening comparison test of two audio circuits. Were they able to hear a difference, or were they fooled?

www.audioholics.com

We are all fools for sound.

Unfortunately I’m only adding to the gobblygook with my junk observations, but you’re right I have no idea without an actual measurement. I posted here hoping that others who have done the work could answer my questions about how op amps affect impulse response, and I haven’t been disappointed with the answers I’ve gotten. Thank you all

I've posted a number of tests including in this thread, and some others, and a test with many including some hacked dual OpAmps to try to help members out with their imagination. And for sure, we have imagination... All of the tests do show that OpAmps and the circuitry that surrounds them change the signal but by parts per million. For instance, if we were able to hear the difference between 0.0001% and 0.0002% 3rd HD, then OpAmp swapping might be audible. But we can't, 0.1% to 0.15% is more like the limit of most people's ability to hear distortion, so 3 orders of magnitude below audibility. So someone would need to put in a really odd OpAmp that is unsuited to the application to create a circuit that has audible degradation.

I've taken a bunch of blind tests with files recorded through different OpAmps, I can't tell the difference. Which is good since the majority of music I listen to has been through hundreds of NE5532 during the production phase, so it is reassuring that none of this is even close to audibility. It's also good from a human livability perspective, if we could hear -120dB the world would be an overwhelming cacophony of sound, and we would need to have developed filters to avoid listening to air molecules battering membranes in our ears and distracting sounds from miles away.

 

[Whatsthephuss]

A proper ABX test includes multiple trials and statistical analysis to get a statistical probably instead of being "pretty sure". i.e. If you identify X correctly 10 out of 10 times, there is less than a 0.10% chance that you are "guessing correctly" or "getting lucky". If you get it correct 7 out of 10 times there is a 17% that you are guessing.

And as a practical matter, if you can't hear a difference 100% of the time with careful listening, does it really matter? Our auditory memory is short so if there's no obvious difference, you what know which one you are listening to the next day or the next week.

Also see Controlled Audio Blind Listening Tests.

Thanks for the tips. I’ve done double blind tests (I know which ZH3 has which op amp but the person routing the RCAs doesn’t) but only with two options, so no ABX. I’ll have to set that up and do a statistical analysis

 

[Whatsthephuss]

I hear differences that I want to explain all the time. Our hearing isn't helpful in determining differences, it just isn't unless the circumstances are controlled, and even then the ability to hear small frequency response deviations or distortion is extremely limited. People forced to try to hear differences in identical sounds fail to hear the similarity, like the famous Sapphire Group listening test:

Audio Listening Test That Fooled the Hollywood Sapphire Group

Some of the most highly trained audiophiles in the industry were asked to do a blind “A-B” listening comparison test of two audio circuits. Were they able to hear a difference, or were they fooled?

www.audioholics.com

We are all fools for sound.


I've posted a number of tests including in this thread, and some others, and a test with many including some hacked dual OpAmps to try to help members out with their imagination. And for sure, we have imagination... All of the tests do show that OpAmps and the circuitry that surrounds them change the signal but by parts per million. For instance, if we were able to hear the difference between 0.0001% and 0.0002% 3rd HD, then OpAmp swapping might be audible. But we can't, 0.1% to 0.15% is more like the limit of most people's ability to hear distortion, so 3 orders of magnitude below audibility. So someone would need to put in a really odd OpAmp that is unsuited to the application to create a circuit that has audible degradation.

I've taken a bunch of blind tests with files recorded through different OpAmps, I can't tell the difference. Which is good since the majority of music I listen to has been through hundreds of NE5532 during the production phase, so it is reassuring that none of this is even close to audibility. It's also good from a human livability perspective, if we could hear -120dB the world would be an overwhelming cacophony of sound, and we would need to have developed filters to avoid listening to air molecules battering membranes in our ears and distracting sounds from miles away.

I appreciate your response and also find it reassuring to know that op amps are not a limiting factor in the signal chain.

I guess my question then should be rephrased to “could discrete op amps be designed to degrade the signal enough to be audible?”

I haven’t seen any measurements of the Burson or Muse op amps but if a circuit designer *wanted* to use op amps to degrade the sound, would that even be possible, or would the surrounding circuitry still be the deciding factor?

 

[MaxwellsEq]

Thanks for the tips. I’ve done double blind tests (I know which ZH3 has which op amp but the person routing the RCAs doesn’t) but only with two options, so no ABX. I’ll have to set that up and do a statistical analysis

It's absolutely essential to ensure levels are exactly matched, using an AC voltmeter. Even 0.01V difference (which will sound audibly just as loud) can be a "tell".

 

[Doodski]

I appreciate your response and also find it reassuring to know that op amps are not a limiting factor in the signal chain.

I guess my question then should be rephrased to “could discrete op amps be designed to degrade the signal enough to be audible?”

I haven’t seen any measurements of the Burson or Muse op amps but if a circuit designer *wanted* to use op amps to degrade the sound, would that even be possible, or would the surrounding circuitry still be the deciding factor?

Remember when I commented that OP amps ICs are optimized, specialized and highly tuned circuits? They are very optimized for temperature, distortion, frequency response and on and on and it is all able to be done by controlling every aspect of the design. The design size, integrity, circuit layout, distance between components and temperature operational matters are all optimized by the OP amp IC designers making many adjustments and stuff to reach the final layout and design and putting it into the OP amp IC. By making a OP amp discreet circuitry all that optimization and the repeatability of that optimization is lost because discreet circuitry cannot be optimized like a OP amp IC can be optimized and then totally controlled in all aspects the way a IC OP amp is manufactured to such incredibly accurate repeatable specification.

 

[MAB]

I appreciate your response and also find it reassuring to know that op amps are not a limiting factor in the signal chain.

I guess my question then should be rephrased to “could discrete op amps be designed to degrade the signal enough to be audible?”

I haven’t seen any measurements of the Burson or Muse op amps but if a circuit designer *wanted* to use op amps to degrade the sound, would that even be possible, or would the surrounding circuitry still be the deciding factor?

The Burson and Muse are fine OpAmps, inaudible. Even the OPA2228 which is self-oscillating due to it's high bandwidth isn't audibly different (yellow trace in this test). Some ultra-high bandwidth OpAmps will likely become audible in certain circuits that don't specifically limit the bandwidth. Some don't behave well used in unity-gain applications, others not good with high gain. The Burson and Muse are not in these categories, and can be used in most common audio applications. Applications like certain high-gain MC phono preamp could uncover differences in noise. But those are corner cases, important for some applications where care needs to be taken in layout and the circuitry around the OpAmp.

 

[Yourtaer]

OK.... this has been a long-running thread with recurring questions and answers, mostly revolving around audibility thresholds (-80, -90, or even -120dB) and SINAD measurements. But as hard as the "tech side" hammers down those SINAD graphs, the audiophile camp retorts with "I hear what I hear." Conversely, when engineers claim to optimize and control every detail through rigorous testing, they often fail to provide the actual graphs or measurements to back it up, dismissing them as "industrial secrets." No personal intent, but without backup science and explanation, just a few posts back, this "They are very optimized for temperature, distortion, frequency response and on and on and it is all able to be done by controlling every aspect of the design. The design size, integrity, circuit layout, distance between components and temperature operational matters are all optimized by the OP amp IC designers making many adjustments and stuff to reach the final layout and design and putting it into the OP amp IC. By making a OP amp discreet circuitry all that optimization and the repeatability of that optimization is lost because discreet circuitry cannot be optimized like a OP amp IC can be optimized and then totally controlled in all aspects the way a IC OP amp is manufactured to such incredibly accurate repeatable specification." has the same vibe as any audiophile mumbo jumbo, not? From a scientific point of view, I’d like to offer some insight/questions into this impasse.

Basically, the discussion often misses the mark because we’re talking past each other: it’s 'scientific measurements' versus 'subjective hearing and feeling.' In my view, the best approach is to flip the script and use science to challenge those same arguments. Imagine two people watching cars pass by on a highway. One might scientifically conclude that they are all traveling at 120 km/h with a variance of less than 0.5%, meaning there is no 'scientific' difference between them. Meanwhile, the other person waxes lyrical about the smooth, quiet ride of a high-end Mercedes or BMW, or the instantaneous throttle response of a Ferrari.

The only thing they might agree on is that an old Fiat Panda is clearly struggling to maintain that 120 km/h: it’s probably running hot, burning a bit of oil, and screaming at high RPMs. But their consensus ends there: for one, anything from a Volkswagen Golf upwards is identical because they all hit 120 km/h... period.

Right, now let’s translate that to the world of audio, and specifically op-amp rolling in the Fosi ZD3. While I appreciate the "crisp and clear" signature of discrete options like the Sparkos 3602 or Burson Vivids, I wanted to try a different path. The LMs in the Fosi units (like my V3 Monos) also belong to that same clean, clinical school of thought. So, just for the sake of it, I ordered a set of OPA2604s for very little money to try out in my Fosi ZD3.

The ZD3 feeds my ZP3 through both XLR and RCA, creating a sort of "hybrid op-rolled" preamp setup. This allows me to switch between op-amps on the fly—rolling the XLR path while keeping the RCA stock, and then vice versa. In my experience, op-amps seem to have a much greater impact in preamps than they do in power amps.

While I do believe in measurements and agree that distortions below -70dB are generally inaudible in a vacuum, I don't believe a single-tone waveform can compete with the complex signal-splitting job our brains perform. You cannot ignore the fact that while a single 2kHz tone may look identical on two different graphs, actual music will show slight variations. Specifically, how a component handles the timing and integration of harmonics under load is where the real differences lie.

The core of the debate is that we are often looking at the wrong domains. A SINAD figure derived from a constant 1 kHz sine wave tells us about baseline quality, but almost nothing about how a component reacts to the complex, non-periodic signals of music. Here is why the standard FFT might be missing the mark:

The Failure of Static FFT with Transients (Settling Time): Standard FFT measurements are steady-state. Music is a succession of impulses. An op-amp with a narrow Phase Margin or a sub-optimal feedback loop exhibits "ringing" and overshoot following a steep transient. You won't see this on a static FFT because the error is in the time domain and Vaak ultrasonic. In a Null Test, need these op-amps reveal a distinct spike in the residual signal at every transient, affecting timing precision and soundstage focus—elements to which our hearing is extremely sensitive via the Precedence (Haas) Effect.

Thermal Tail (Thermal Memory): Transistors on the silicon die change temperature with every current spike, modifying bias and gain-factors in real-time. An Audio Precision sweep is too slow to capture this; by the time the sweep registers, the chip has reached thermal equilibrium. This results in signal-dependent modulation perceived as a lack of micro-dynamics—a dynamic non-linearity that static THD measurements simply mask.

RFI/EMI Rectification and Input-Stage Behavior: Op-amp input stages (JFET vs. Bipolar) react differently to high-frequency interference from DAC clocks and switching power supplies. Some op-amps "rectify" or demodulate this ultrasonic garbage into the audible band. This doesn't appear as a distinct peak on an FFT but rather as a subtle elevation of the noise floor during playback, impacting the "black background" and perceived depth.

IMD in the Ultrasonic Domain and Load Interaction: Standard analysis stops at 20 kHz, but DACs produce significant artifacts above that. An op-amp with a lower Slew Rate or higher high-frequency distortion can modulate these ultrasonic tones back into the audible range via Intermodulation Distortion (IMD). Furthermore, real-world loads (cables, traces) are capacitive and inductive, not just resistive. The stability of the feedback loop under these dynamic loads is crucial for transparency.

Low distortion is a prerequisite for good audio, but not a guarantee of transparency. Relying solely on the FFT is like looking at a still photograph of a race to conclude who has the fastest sprint. The truth lies in the time domain and dynamic stability.

 

[oleg87]

more LLM slop?
can we ban this crap already?

 

[Mort]

more LLM slop?
can we ban this crap already?

Simple policy to make, hard to enforce.

 

[Yourtaer]

I've taken a bunch of blind tests with files recorded through different OpAmps, I can't tell the difference. Which is good since the majority of music I listen to has been through hundreds of NE5532 during the production phase, so it is reassuring that none of this is even close to audibility. It's also good from a human livability perspective, if we could hear -120dB the world would be an overwhelming cacophony of sound, and we would need to have developed filters to avoid listening to air molecules battering membranes in our ears and distracting sounds from miles away.

I appreciate your perspective on blind tests, but there’s a fundamental methodological flaw in that logic. Recording a file through various op-amps and then playing them back through the same output stage is not the same as comparing the output stages themselves.

The discussion here isn't about how a file 'captures' an op-amp's signature; it's about how the final output stage—the actual gatekeeper—interacts with the complex, dynamic load of the rest of the chain. When you're rolling op-amps in a preamp, you’re changing that final interface.

Referring to the hundreds of NE5532s in the production phase is a common argument, but it ignores the fact that those chips operate in a highly buffered, internal environment. The op-amp in your DAC or Preamp, however, has to deal with high-frequency DAC noise, RFI, and varying cable capacitances in real-time.

And I’ll raise you a '100 times' test, which creates a perfect Catch-22: if we ran a signal through an op-amp path 100 times and there’s no difference, you’d say it’s inaudible. But if there is a difference after 100 passes, you’ll just argue that we’ve simply amplified cumulative signal degradation and noise floor issues, rather than the op-amp's character itself.

Lastly, the '-120dB air molecule' analogy misses the mark. We aren't claiming to hear a -120dB floor; we are discussing how non-linearities in the time domain (like ringing or settling time) affect the clarity and timing of the transients at 85dB. It’s not about volume; it’s about signal integrity under dynamic load.