So if lower value resistors load down the IC and higher value resistors are noisy, where is the happy medium...4K, 5K, 10K?
I'm referring to voltage-feedback op-amps.
On an other way, i found some OPAs to sound a little 'inconsistant' if not loaded enough.
I remember, some decades ago, to had changed all OPAs in a big Calrec 48 tracks mixing desk. With long blind listening comparisons. While, on each slice, the change was not so obvious, in the bus mixing stage (inverting configuration), it was day and night. We had chosen OP260, a 1000V/µs current feedback witch run with a relatively high feedback impedance we can use in Audio. Sadly obsolete, now.
With all the VFAs we tried, the problem was this one. With few slices plugged in, it was OK. But, more slices in, and the dynamic and ease to separate instruments gone away. While the sound remained unchanged with the CFA, between 1 and 48 slices in (noise apart).
I believe it is bandwidth and IM related.
While the bandwidth decrease with the VFAs when the gain increase, it stay unchanged with the CFAs.
Oh, we had to change the power supplies because those OPAs were hotter. More class A was part of the game ?
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My rule is, load the IC with about 10% of it's capability, that is a significant load but not real heavy (as a rule of thumb). Earlier I did say that for the line driver amp I use 1k, the amp is LME49710 and has a capability of 50mA, so applying my 'rule of thump' that gives me 5V V(out) nominal where normal line levels are 1.4V and there will be enough spare current for full rail to rail output swing.
One word about blind tests.
I always found that the way some organize their AB listening comparison kinda strange.
They insist on the instant switch, witch is not so important if you have some listening accuracy and habit, and a memory better than a goldfish one.
But they listen to a record, so they compare different samples of music. Apples and orange.
I always prepare little samples of music that you can loop in a musical way (twelve-bar blues as an example). Each one chosen for something you want to focus on. Dynamic on piano, drums, attack of guitars, ease of separation of each instruments (doubled voices can be useful too for this), little details of a low level instrument behind a big wall of sound, sound stage and reverberation decrease, space localisation, natural of cymbals reproduction, presence of the voices etc...
Then i switch from A to B at the end of the samples. In rhythm if i can, for it is more agreeable and less disturbing.
And, most of all, several times. At various levels and listening conditions. Sometimes, it can help to listen from outside of the room, or focusing on something else, like reading some paper etc...
Well, in fact, if it is difficult for me to figure out a difference, if i'm unsure, not able to say instant witch is A and witch is B, i consider there is no interesting difference. Because it will be less than my subjective feeling one day from an other, or the ones that will happen with a difference of temperature in the room or humidity, or AC changes in outlets etc...
In fact, i don't care too much if it is *blind* or not. Who want to fool himself, apart an audiophile under a guru influence ?
But it is absolutely necessary i can know which one between A and B is playing. I need my eyes to focus and remember, and I can close them if i want to be blind.
With experience, if you use always the same samples that you know perfectly, you can reject in few minutes an amp or any gear some provider want to sell-you, and bring in your studio for testing. Or found in love for it. It helps me a lot, on the bench, when i have to take a decision about some change in one of my designs.
Oh, btw, if it is about an electronic component, i use both speakers and headphones to figure out the differences. They bring a very different perspective.
I always found that the way some organize their AB listening comparison kinda strange.
They insist on the instant switch, witch is not so important if you have some listening accuracy and habit, and a memory better than a goldfish one.
But they listen to a record, so they compare different samples of music. Apples and orange.
I always prepare little samples of music that you can loop in a musical way (twelve-bar blues as an example). Each one chosen for something you want to focus on. Dynamic on piano, drums, attack of guitars, ease of separation of each instruments (doubled voices can be useful too for this), little details of a low level instrument behind a big wall of sound, sound stage and reverberation decrease, space localisation, natural of cymbals reproduction, presence of the voices etc...
Then i switch from A to B at the end of the samples. In rhythm if i can, for it is more agreeable and less disturbing.
And, most of all, several times. At various levels and listening conditions. Sometimes, it can help to listen from outside of the room, or focusing on something else, like reading some paper etc...
Well, in fact, if it is difficult for me to figure out a difference, if i'm unsure, not able to say instant witch is A and witch is B, i consider there is no interesting difference. Because it will be less than my subjective feeling one day from an other, or the ones that will happen with a difference of temperature in the room or humidity, or AC changes in outlets etc...
In fact, i don't care too much if it is *blind* or not. Who want to fool himself, apart an audiophile under a guru influence ?
But it is absolutely necessary i can know which one between A and B is playing. I need my eyes to focus and remember, and I can close them if i want to be blind.
With experience, if you use always the same samples that you know perfectly, you can reject in few minutes an amp or any gear some provider want to sell-you, and bring in your studio for testing. Or found in love for it. It helps me a lot, on the bench, when i have to take a decision about some change in one of my designs.
Oh, btw, if it is about an electronic component, i use both speakers and headphones to figure out the differences. They bring a very different perspective.
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"Want" has nothing to do with it.
Not understanding the basics of perception and not understanding how to set up a test for audibility is the more serious issue for you here.
May-be you are right, and it should be a pity after all a life in the recording business. You know, the ones who created the records you love to listen to, painting with their 'perceptions' ?
Or, may-be, you generalize your own psychological character and listening accuracy ? (witch is mostly based on experience)
Do-you think a professional wine tester can be fooled by the label on a bottle, or the price of it ?
Or do-you think i'm just stupid, like this nice way to answer me seems to indicate ?
May-be you can consider that, for a producer or a sound engineer, any 'perception' mistake can have huge consequences for his living. So, we use to be very suspicious about them. And, in the same time, we have to be fast in our instinctive decisions. Just think about this.
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Absolutely, which is why serious evaluation is done blind. Likewise, the evaluations needed for that professional to achieve certifications (CET, MW, MSom...).
SY, let-me tell-you a story.
In France, we used, in movie mixing studios, to provide a normalized acoustic level for 0 dB vu (85 dBSPL with pink noise).
One night, in the middle of a film mixing period, we made the usual nightly maintenance and verified this level. Found something like 1 dB of error, and fixed-it.
Next morning, the sound mixer arrived to continue his work. After some minutes of work, he asked-us: "Did something has changed since yesterday in the listening chain ?".
It is hard for me, even today, to believe-it, but it happened ! I was the technical manager of this facility at this time.
About wine tester, we had one candy cameras program where some wine testers were invited to a dinner. The program producers had changed the content of one bottle of wine. Same 'cepage', different year. The first one who drink his glass, in the middle of a conversation, immediately took the bottle to look at the label with a suspicious expression on his face.
Do-you think you and i should had noticed anything in those both situations ? We have all different accuracies, knowledge and experiences.
On my side, i don't see the difference, comparing two OPAs, if they are named OP260 and AD815, or A and B. Just names or label. And i'm sure to be not influenced at all by the reputation, prestige, prices or famous names and even personal previous experiences in an other situation.
In France, we used, in movie mixing studios, to provide a normalized acoustic level for 0 dB vu (85 dBSPL with pink noise).
One night, in the middle of a film mixing period, we made the usual nightly maintenance and verified this level. Found something like 1 dB of error, and fixed-it.
Next morning, the sound mixer arrived to continue his work. After some minutes of work, he asked-us: "Did something has changed since yesterday in the listening chain ?".
It is hard for me, even today, to believe-it, but it happened ! I was the technical manager of this facility at this time.
About wine tester, we had one candy cameras program where some wine testers were invited to a dinner. The program producers had changed the content of one bottle of wine. Same 'cepage', different year. The first one who drink his glass, in the middle of a conversation, immediately took the bottle to look at the label with a suspicious expression on his face.
Do-you think you and i should had noticed anything in those both situations ? We have all different accuracies, knowledge and experiences.
On my side, i don't see the difference, comparing two OPAs, if they are named OP260 and AD815, or A and B. Just names or label. And i'm sure to be not influenced at all by the reputation, prestige, prices or famous names and even personal previous experiences in an other situation.
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It must be a curious thing being a robot person, totally subservient to criteria such as label, and price. When my wife and I visited the largish wine store up the road a couple of days ago, and sampled a couple of reds at the mini wine tasting, by the maker of Grange, and very pricey by Oz standards, the two of us, plus the chap pouring the stuff agreed that one had good fruit still, but the other was certainly well past it, had been opened too long - the brand, and the mighty price did zero to make us think otherwise ... I would hate to be so muddle headed that I was always a victim of trivial aspects of the situation ...
I would assume you could do the same with two pairs of speakers one with blown tweeters.
I think the idea is take a random bunch of people and unflawed bottles of Grange and Greg Norman Shiraz. Been there. Once a particularly obnoxious British wine snob shared our table tasting 6 California vs. 6 French chardonnays, I ID'd all 12 as to origin and identified the most expensive French wine as the oxidized and flawed one while he picked the best US wine as "obviously the Batard Montrachet" and carried on waxing about it. Until the unveiling...
Pretty obvious why folks avoid blind tests.
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LOL.
MOTS: don't make pronouncements unless you are in total command of the facts.
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