Why do OpAmps sound different? - Page 2  

If you do a search on Digikey, you'll get something like this to help narrow down the many pages of results:

That is not an insignificant number of things to choose from. It seems natural to me that choosing an opamp with different specs should result in some tangible differences. Otherwise why do they bother to make so many types? It's not like Texas Instruments and Linear Technology are part of a snake oil opamp industry leeching off the wallets of audiophiles.

Different types of opamps interact differently with different circuits. The audible differences are subtle compared to differences between headphones. But they tend to be exaggerated when described because the differences were what the listener was focusing on.

Like with everything else in audio, placebo is also a factor. But I would hesitate to say it is the only factor in this case.

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Originally Posted by 9pintube 

So you ask about the real question, what causes 0p-amps to sound different, fair enough!  But when you say is it the op-amp itself or the listener and their biases and expectations, that's implying one can't hear the difference.... I know several of listeners and myself who listened with me while changing OP-A sets in my DAC that couldn't believe the difference in the sounds of these different OP-A sets!  We all heard a night and day difference in the sound of different Op-amp sets... Read this link if I can post it.   By the way I'm not trying to start an argument with you or any other member of this post, but I hope most of you guys CAN hear a difference in most of these changes in our equipment..http://sound.westhost.com/dwopa.htm#rules
 

 

I wish we could get away from that supposed implication. I am sorry if you thought that and I will word future posts differently.

For the record, people do hear differences, I do not dispute that, I only ask why. One of the possible answers to why is indeed biases, user expectation, placebo, whatever you want to call it. But there are other possibilities, primarily an undiscovered electrical property that only works with some people some of the time.

Sadly even asking why and pointing out the possible answers that can get you abuse and bans from hifi forums.

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Originally Posted by Prog Rock Man 

I wish we could get away from that supposed implication. I am sorry if you thought that and I will word future posts differently.

 

For the record, people do hear differences, I do not dispute that, I only ask why. One of the possible answers to why is indeed biases, user expectation, placebo, whatever you want to call it. But there are other possibilities, primarily an undiscovered electrical property that only works with some people some of the time.

 

Sadly even asking why and pointing out the possible answers that can get you abuse and bans from hifi forums.

 

RMAA something like an Audio-gd Fun with different OPAMPs. I recall graphs showing the stereo crosstalk in some being far from flat, showing why there were distinct differences in their overall tonal balance. There are a couple of papers out there where someone measured a couple of dozen different OPAMPs and showed their differences. One, whose original URL I don't have handy, is called opamp_distortion.pdf.  Some of it would have to do with the circuit they are installed into, which is explained in the papers as well IIRC.

As for bans, that is what happens when you break the rules, and/or basically go around trolling the same thing all over the place in an annoying and unhelpful manner, regardless of topic. 

http://www.sg-acoustics.ch/analogue_audio/ic_opamps/pdf/opamp_distortion.pdf

Originally Posted by Currawong 

RMAA something like an Audio-gd Fun with different OPAMPs. I recall graphs showing the stereo crosstalk in some being far from flat, showing why there were distinct differences in their overall tonal balance

here: http://audio.an-pan-man.com/files/rmaa/earth_vs_moon_vs_sunv2_vs_lt1469.htm

Originally Posted by Willakan 

99% of opamp comments make no sense at all. For example, many will tell you that the OPA627AP is nothing compared with the OPA627BP, despite the only difference being that the latter has better DC specs - they measure identically as applicable to audio.

Higher grade means tighter specs, and also for AC of course: http://focus.ti.com/lit/ds/symlink/opa627.pdf

I've personally compared AD797AN/BN, LT1028CN8/ACN8 and so...and yes, higher grade chips always sounded "better". Rolling opamps blindly is not a very good idea to begin w/, as you want the layout to be optimized for that specific opamp....so higher grade chips always come to the rescue IME(and others).

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Quote:

Originally Posted by Currawong 

RMAA something like an Audio-gd Fun with different OPAMPs. I recall graphs showing the stereo crosstalk in some being far from flat, showing why there were distinct differences in their overall tonal balance.

 

Originally Posted by leeperry 
here: http://audio.an-pan-man.com/files/rmaa/earth_vs_moon_vs_sunv2_vs_lt1469.htm

But there is nothing in those graphs that point to (or can explain) any audible differences.

The only thing you can tell from them is that the DAC is subpar (regardless of OP-amp) by modern standards.

Quote:

Originally Posted by D. Lundberg 

But there is nothing in those graphs that point to (or can explain) any audible differences.

The only thing you can tell from them is that the DAC is subpar (regardless of OP-amp) by modern standards.

On the contrary, the stereo crosstalk graph at the bottom very clearly shows exactly what I thought I heard when I tried the Moon HDAM.  It'd take me forever to dig out the post, but I said I thought the mids sounded recessed, or the bass and treble were stronger (depending on perspective).  Now can you see the green line (for the Moon) with around 10dB of higher crosstalk in the bass and treble regions?  It was deliberately designed this way (to sound "tube-like" if you're wondering why). The designer said to the effect that he could design an amplification circuit to sound any way he wanted (tonally) by the way he constructed the circuit. Ask him about it if you like. 

Quote:

Originally Posted by Currawong 

On the contrary, the stereo crosstalk graph at the bottom very clearly shows exactly what I thought I heard when I tried the Moon HDAM.  It'd take me forever to dig out the post, but I said I thought the mids sounded recessed, or the bass and treble were stronger (depending on perspective).  Now can you see the green line (for the Moon) with around 10dB of higher crosstalk in the bass and treble regions?

The crosstalk measurment only tells you how strongly the channels are separated. If the channel separation is poor they will start to "bleed" into each other, and if it gets really poor you'll be listening to mono instead of stereo (or you may get stereo widening).

In this case the crosstalk is nowhere near where it starts to be audible, but I assume the measurments are for the line outputs and not the headphone output?

The headphone output will probably tell a completely different story (at least if it's poorly designed) when it comes to crosstalk, frequency response and distortion.

http://en.wikipedia.org/wiki/Crosstalk_measurement

@Leeperry - Tangent's website, with his influential (around here, anyway) breakdown of opamp sound signatures says the following "I see no reason to pay extra for the "B" grade in an audio application." This coming from someone who actually believes wholeheartedly in opamp sound signatures.

@Currawong - If you look at the SG-Acoustics measurements, you'll see that the real reason for the strange sound of the Moon discrete opamp is absolutely atrocious distortion measurements - from "high to very high" in the words of the writer. This distortion, aside from being gigantic, also varies with frequency. -70db vs -80db of crosstalk is extremely unlikely to be the factor causing the sound signature you commented on IMO.

Doesn't exactly fill you with faith regarding AudioGd's engineering prowess, looking at their opamp measurements. A Burson opamp (unsure if the same model as used in their recent products) is also tested - the author proclaims surprise after noting it appears to be identical to the AudioGD Earth discrete opamp, which boasts poor linearity performance "with every respect" and similar distortion as the other AudioGd opamp.

Originally Posted by Willakan 

Tangent's website, with his influential (around here, anyway) breakdown of opamp sound signatures says the following "I see no reason to pay extra for the "B" grade in an audio application." This coming from someone who actually believes wholeheartedly in opamp sound signatures.

And what do *YOU* think? Have you compared several chips in lower and higher grade and listen to them with your very own ears? There used to be a time on head-fi when one's was only allowed to talk about gear he had actually heard himself.

I haven't bothered with OPA627, but the SQ improvement when going LT1028CN8>LT1028ACN8 or AD797AN>AD797BN is very real. Several friends of mine have heard it too, and so did majkel: http://www.head-fi.org/forum/thread/397691/audio-gd-discrete-op-amps-reviewed-opa-earth-opa-moon-opa-sun-v-2

I'm entirely willing to believe that we're all a bunch of crazy loons and that all opamps sound the same..sure thing. That's a possibility

Here are some more opamps RMAA/oscilloscope measurements results: http://www.jensign.com/RMAA/RMAAOpAmpTests.html

There are many more things going on in an opamp than we'd all ever be able to understand...and those things can easily oscillate like hell if there are no decoupling caps and/or an incompatible layout(too high/low gain). As much as I love LT1028, it oscillates in the MHz range in my Firestone Spitfire DAC and makes nasty glitches when my refrigerator motor turns on, so I'm forced to use "unity gain stable" chips instead.

Another issue is that dual opamps sound too colored and boxy/plasticky, even TI acknowledges it: http://focus.ti.com/docs/prod/folders/print/opa1612.html

TBH I still find two OPA1611 to sound better than one OPA1612, and so did 12bass: http://www.head-fi.org/forum/thread/473867/2x-to99-to-dip-8-adapters/15#post_6423431

Going LT1364>2*LT1363 or OPA1642>2*OPA1641 is a clear step ahead SQ-wise. The most prestigious opamps for audio applications don't even come in dual form anymore(ADA4627-1BRZ, LT1028, AD797, OPA827, etc). So when I see the Benchmark-1 full of LM4562 and NE5532, I'm a bit like .

I think ppl interested in opamps should start doing their homework...as already been said several times, talking about music is like dancing about architecture. So fire up your favorite CD, roll opamps like there's no tomorrow and you shall see what the fuss is all about. If not, that's cool too...at least you tried. Basing your beliefs on other ppl's real world experiences hardly ever works IME.

I gave an example from someone who held the opinion that opamps had sound signatures, who is also well-respected due to his work in designing DIY audio stuff, in a effort to demonstrate that DC specs really, really are not applicable. I assumed you would find this more persuasive than a purely scientific proof.

Nobody is saying that ALL opamps sound the same, but if someone claims to hear differences between two opamps which both measure far into the realm of inaudibility, I call BS until they can demonstrate that decision was not affected by bias. It's like having two objects which you have measured as identical in form, mass, density, appearance and so on to within an insignificant fraction of the relevant unit - then someone declares that one is slightly more purple-coloured than the other. You can either cast all your measurements out of the window straight away, or you can ask them to verify that they can detect differences in a formal, fair test before you disregard a fair chunk of modern science.

Also, interpreting TI saying that single-channel opamps offer lower crosstalk and general interaction between channels as an admission that dual opamps sound "coloured and plasticy" is a rather liberal interpretation, to say the least. Additionally, the reason Benchmark used those "inferior" opamps is that as implemented in their product, they felt that they did the job very well - this is reflected in the measurements.

Whilst you may view the opinion of people who have not "heard it for themselves" as invalid or of less value, other people who may not share your views on the validity of opinions, especially when the arguments used to justify the opinions in question do not require "hearing it for yourself", may disagree.

Quote:

Originally Posted by leeperry 

Basing your beliefs on other ppl's real world experiences hardly ever works IME.

I guess you should never use anything you haven't completely designed yourself then.  Every time you drive a car, get on a plane, or take public transportation you are literally puting your life in the hands of what other people think about safety.

Why is it that the smaller the stakes the more people complain...

Originally Posted by maverickronin 

I guess you should never use anything you haven't completely designed yourself then.

I was mostly referring to the hearsay of self-proclaimed experts you can read on internet boards...where ppl tend to depict real world experiences as hard "facts". So before quoting someone on his personal perception of audio equipment, hear it for yourself. I'm sure everyone here has already bought audio gear based on raving reviews, and ended up falling flat on his face(for me, it'd be the Pro750 and the Musiland 02US...and I know several ppl who still wonder what the TP hype is all about). We do all hear differently, and have different expectations too.

Simple solution: Buy no equipment based on the opinion of others, except when objective measurements for the type of product (eg headphones) of the correct nature and applicability are extremely hard to come by (in that case amalgamate as many opinions as humanly possible, weighting by reliability, and observe general trends...bit OTT but hey...)

I stopped reading "reviews" after I conclusively proved that a popular DAC was simultaneously worse and better than another popular DAC.