Does Op-amp Rolling Work?

[solderdude]

It's because tubes physically roll.

Almost correct... the more correct answer is in post #431

Your answer had me rolling across the floor.... while shouting; 'I'm not crazy ...I am a vacuum tube'

 

[NTTY]

And about random OPA rolling and impact on FR, I found 5min to overslay 12 of the 90+ measurements I performed some time ago (with different combinations of OPA):

That was not in an amplifier, I must say, but in a low price DAC (OPA rolling possible in the I/V and LPF slots).
Bandwidth was not flat, stock, but none of the OPAamps had an influence on it (plot at 1k).

THD vs Frequency (@-12dBFS) showed some differences though:

Plot at 1k to read the THD in the legend for each combination of OPA.

Now you can argue that the device was of too low quality for comparison. Maybe, but hey, I've been told that it's easy to hear a difference between two OPAs. Nobody told me that I had to use a 120dB SINAD capable DAC
BTW I also gave to friends, family and audiophiles a recording of music for each, together with the original WAV file. Nobody was able to provide a result anywhere close to valid: ie everything sounded the same. All of that took quite some time.

I did some mistakes too. At the end, the socket was worn and I had false (negative) results, as in super high levels of distortion. So the real interesting discovery (for me) was not to do OPamp rolling too much. Not doing at all, because it's useless, was the real conclusion

 

[T&T]

So different part, different voltage, different gain, different built, different materials and they all sound the same...Bahhh

 

[ckernel8]

Almost correct... the more correct answer is in post #431

Your answer had me rolling across the floor.... while shouting; 'I'm not crazy ...I am a vacuum tube'

I am ashamed. I knew this.

 

[Gorgonzola]

Bit of an exercise in futility doing it all again then

Still - why let that stop you.

Point is "purely subjective" findings can only be of interest to the subjective listener. They cannot inform anyone else about what they might perceive in the sound from a piece of gear. (by the very definition of the word subjective). No-one knows if your "impressions" come from the sound, or from your unconscious brain.

It therefore makes it pretty pointless reporting on them. Here, at least.

Frankly neither do I . Feel free to totally ignore my conclusions. Meanwhile I'll continue to enjoy the Sparkos SS3602's on my VTV buffers.

 

[pma]

Linear small signal amplifier with 30dB gain, measured with 3 opamps: LT1028, AD829 and uA748. Are we still saying that "opamp rolling" does not make sense? To me, laymen addressed threads like this one do not make sense. Output voltage is 1.5Vrms.

 

[solderdude]

yeah ... the 741 ... as if anyone currently alive and in a somewhat sane state would ever consider using one of those to improve sound quality
And distortion below 0.0003% is that really audible ? In the discussed amp it would be masked by the 0.003% THD of the output stage anyway.
Besides ... those op-amps in the discussed amplifiers will have a gain of max. 3x or so and not 30x.
Nah ... we get your point that not all op-amps are the same and in certain applications they matter.
The thing is in the discussed amp ... with the suggested op-amps would 'rolling' make sense.

 

[Buckeye Amps]

Nah ... we get your point that not all op-amps are the same and in certain applications they matter.
The thing is in the discussed amp ... with the suggested op-amps would 'rolling' make sense.

This is typically what happens with threads where Amir or someone else shows data that "x" doesn't change the audible sound: some people take it as a personal challenge to either widen the goal posts or move the game to a completely different sport just to prove a point (or stroke their ego).

In a recent "Power Cords don't change the sound" thread, there was a poster who spent pages arguing that they do if there is a grounding issue that is audible as ground hum in the signal.

I guess it needs to be explicitly spelled out in bold words in the top of the OP that the discussion is dealing with OP amps (or power cords, or RCA cables, etc) that do not degrade the baseline sound/performance (whether intentionally or because of poor designs). Even though nearly all of us know this is implied...

 

[levimax]

Almost correct... the more correct answer is in post #431

Your answer had me rolling across the floor.... while shouting; 'I'm not crazy ...I am a vacuum tube'

I always thought the term was derived from "Roll your own" as in cigarettes or joints.

 

[pma]

And distortion below 0.0003% is that really audible ?

Once again, I am saying nothing about audibility. However, if it is legal to have a SINAD chart competition in this forum, with the audience waiting for new winners, is it illegal to show that opamps, depending on the application, do make a difference as well and may contribute to those SINAD charts wars?? What is the difference? The same approach.

 

[jan.didden]

I've been distained a good many times for reporting my purely subjective and impressionistic findings, so I'm used to the abuse. I've rolled op amps a few times and have found subtle differences.

Most striking was my recent experience with my VTV Purifi 1ET400A stereo amp. Originally I ordered this from VTV with the Hypex Eval I/O buffer. Immediately and spontaneously I was disappointed with at least one aspect of the sound versus my previous Hypex NC252MP amp; the top end, especially and higher volumes, was "screamy" and unnatural. Almost right away I ordered VTV's own I/O buffers with Sparkos SS3602 (discrete) dual op amps. The VTV buffers that accommodate 8 pin DIPs and larger form factor "pro" op amps.

With the VTV buffer with the SS3602's the sound was improved in that top end respect: "screaminess" gone. However I proceeded to try several other op amps I had lying around from previous experimentation, including OP2134, the venerable OPA247, the Burson V6 Vivid discrete, plus I ordered the OPA1612.

My personal, subjective conclusion after much swapping back & forth was that I preferred the Sparkos SS3602's for having the nicest transparency and natural top end. Runner up was probably the OPA1612. It's worth mentioning that the VTV buffer was designed by the same designer as the Sparkos op amps, (which I didn't know at the time), so the fact might have optimized the buffer and op amp combination.

But I note & emphasize that difference among these op amps were extremely subtle excepting for the Hypex buffer that was distinctly awful in context of my VTV Purifi amp. (I knew but now don't recall the surface mount op amp used in the Hypex.)

No disrespect intended, but if this is 'My personal, subjective conclusion' from 'purely subjective and impressionistic findings', why should that be of any interest to any if us?

Jan

 

[pma]

This is typically what happens with threads where Amir or someone else shows data that "x" doesn't change the audible sound:

In case you stick with audibility, almost nothing matters, talking about contemporary DACs and amplifiers, except for power and complex load drive ability.

 

[Buckeye Amps]

In case you stick with audibility, almost nothing matters, talking about contemporary DACs and amplifiers, except for power and complex load drive ability.

Yes, that's where we are at now a days with performance of most components.

 

[EERecordist]

One thing I would add is what do we know about quality testing of the boutique op amp makers?

There are many, just from a quick search: Muse, Sparkos, Orange, Red, Burston, GAR, NewClassD, FiveFish, VTV, Whistle Rock, Elise Audio, Eisen Audio, Audioscape, Hairball Audio JE-990 DIY kit* and many China-originated makers like LME, LHY, Shenzhen Taida Century - Taidacent, and others on eBay and other channels.

How well controlled are the parts which make up these small PCBs?

On the DIY audio forums, there is a lot of discussion, schematics, and kits.

We are in an irrational new market entrant and over production period of boutique op amps now. The margins must be good, the going rate seems to be about $US 60.

One of my early jobs was testing high speed memory chips. Analog testing is less demanding. If you look at a TI or Analog Devices data sheet, all those parameters would be tested at some point, and then perhaps if your manufacturing was under good statistical process control, you could sample the in-control parameters, knowing the root cause of any deviations. TI, AD, OnSemi, STM, Toshiba, and the like would have high volume automated testing. Mature manufacturers would also do accelerated testing at overvoltage, temperature extremes, humidity, and possibly vibration.

What quality testing are the boutiquers doing? What is their fail rate for the testing they do? What is their part-to-part variation?

It has been discussed many times on ASR, everything on one chip produces better element control and temperature tracking. The reason the early op amps were discrete, the Jensen 990, Melcor, and API2520 was because monolithic op amps were not available with the needed specs.

*At least Hairball uses a matched Analog Devices transistor pair on the input.

Walter Jung at Analog Devices has a very readable paper on the history and applications of op amps. There was early work at Bell Labs which was classified because op amps were used in analog computers which were then used in military applications. Maybe vacuum tube op amps will come back in audio!

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www.analog.com

Jung's books explain the data sheet parameters of op amps and their impact on the end system performance.

 

[Multicore]

The problem here is that they have already 'proven' that the differences exist and have confirmation from the manufacturer and countless people.
Then we ask them to doubt that what they 'know to be true' and have to prove that they are right to a bunch of tech guys that only measure gear.

The procedure indeed is not that difficult, doing it properly is though and involves other people to assist which cannot give any 'hints'.
Doing this 'long term' (as that always seems to be the counter argument) takes months to complete.
Besides ... what IF these tech guys were right and it turns out statistically they cannot clearly identify that what they always could.
Are these people 'open' enough to accept that testing methods is what is paramount to perceive differences.

Never going to happen (well maybe a handful) so the 'opposing views' will continue and nothing would change.

You're right. For these and other reasons (commercial, for example) the overall configuration is stable.

But as we see here, the conversation is not useless.

 

[Sokel]

This is typically what happens with threads where Amir or someone else shows data that "x" doesn't change the audible sound: some people take it as a personal challenge to either widen the goal posts or move the game to a completely different sport just to prove a point (or stroke their ego).

In a recent "Power Cords don't change the sound" thread, there was a poster who spent pages arguing that they do if there is a grounding issue that is audible as ground hum in the signal.

I guess it needs to be explicitly spelled out in bold words in the top of the OP that the discussion is dealing with OP amps (or power cords, or RCA cables, etc) that do not degrade the baseline sound/performance (whether intentionally or because of poor designs). Even though nearly all of us know this is implied...

You 're probably not very involved so you're excused but @solderdude is not.
Why? Because he knows damn well (from diyaudio and the rest of the suspects) that people go to such lengths as to pay (not much, we're talking hundreds but still pay) for 50's stuff, like oil Russian caps or in general use whatever would differentiate them from the rest as long as it hides some short of mystical "aura" in it.
And that goes around to non-diyers at the end and so on.

The note you want to explicitly spelled out is in reality what really happens. Chances are things go south and mess things big time.
But unless you measure (with fancy APs as reviewers and you companies do, or with silly interfaces as we hobbyists do) you never know unless something is so wrong that dies a glorious death taking some other gear with it.

That's what the responsible ones should note: the dangers.

 

[solderdude]

Once again, I am saying nothing about audibility. However, if it is legal to have a SINAD chart competition in this forum, with the audience waiting for new winners, is it illegal to show that opamps, depending on the application, do make a difference as well and may contribute to those SINAD charts wars?? What is the difference? The same approach.

The difference is that in this particular amplifier the differences between op-amps don't really matter as the class-D stage is what determines the final result.
I admit... it would be fun to put a 741 in one of these amps and 'market' the higher distortion as 'tube sound'.

I get that what you really are against is the SINAD race ... and I agree above a certain point and taking into considerations other factors than SINAD then we know good is good enough. In this case a half decent op-amp is already good enough and even the best of the best won't improve the amp's performance even one iota.

 

[Sokel]

I did some mistakes too. At the end, the socket was worn and I had false (negative) results, as in super high levels of distortion. So the real interesting discovery (for me) was not to do that too much. Not doing at all, because it's useless, was the real conclusion

Now that you said "sockets", we know that some OPAs need their caps as close as possible right,like just on their leg.
Adding a socket kisses goodbye that proximitty.
Adding a socket and another socket and an adaptor to it (as some OPAs are sold like this after market for the bold ones) what exactly does?

(and that's where I start to question even the pro-audio 0.1% THD+N limit, it must be even lower )

 

[pma]

Yeah. Sockets and adapters may matter a lot. And opamp “rolling” made by unqualified person, without stability check, without stability criteria checked, makes no sense. This debate with contributions of mostly laymen audience is totally pointless. Debates are pointless, so are the discussion forums. Disappointment.

 

[Heinrich]

... then we know good is good enough. ...

Thanks for making me read this platinum note.

Debates are pointless, so are the discussion forums. Disappointment.

They are not. Remember the discussion regarding noise in vinyl context, great contributions that are for sure going somewhere. But on opamp rolling the board routinely chases its tail. The 'subjectivist's' perspective cannot be challenged by engineering. It is designed this way. It may appear plain impractical to more sophisticated folks, but so it is.
Best tactics to 'win': depart from audio, generalize the 'subjectivist' approach, find a counter example in some other field.