I'm sure this is absolutely true, unless a designer moves with some IP snuck under his jacket
I saw this only recently in a badly-designed op-amp circuit, a TI TL064 (the standard used on 1000's of production units) was perfectly stable yet an alternative '064 was not, and would occasionally oscillate. This was due to bad design in that a cap load had not been decoupled from the op-amp output; it clearly demonstrated the difference between the two devices in terms of phase margin, and no doubt that the internal circuitry, or maybe just the compensation, was different.
In this case an easy fix, but audio apps are often a different kettle of fish...
Andy.
Andy:
I have noted similar effects, and I will add that the oscillation may manifest itself only under certain conditions. Sometimes it appears to be a specific combination of cable load and immediate RF conditions that triggers the oscillation in one opamp - but not another "identical" one.
I suppose that to be _proper_ about these things, one really should carry out a full battery of measurements each and every time we use our equipment (particularly if something changes, be it the cables, operating location, or the chance presence of a police car with radio transmitter turned on), because at times the behaviour of some equipment will be measureably affected.
Incidentally, in my experience, 317 and 337 3-terminal regulators from various companies can also sound differently, behave differently and measure differently.
regards, jonathan carr
I have noted similar effects, and I will add that the oscillation may manifest itself only under certain conditions. Sometimes it appears to be a specific combination of cable load and immediate RF conditions that triggers the oscillation in one opamp - but not another "identical" one.
I suppose that to be _proper_ about these things, one really should carry out a full battery of measurements each and every time we use our equipment (particularly if something changes, be it the cables, operating location, or the chance presence of a police car with radio transmitter turned on), because at times the behaviour of some equipment will be measureably affected.
Incidentally, in my experience, 317 and 337 3-terminal regulators from various companies can also sound differently, behave differently and measure differently.
regards, jonathan carr
I compared 3 different Philips NE5532Ns using a CD player, all sound different. Two from 2 CD players, The other was bought recently. One marked Thailand on the top across between pin 1 and 8, one has a solid white bar and the other has a white bar not in solid form. (I have taken pic only 33kb but have problem in attaching it.)
John
John
Hello everyone.
I'm new to this forum so first I'd like to say how much I've enjoyed reading this all.
This thread caught my eye because I have some good old SE5532s and was thinking of building a really low-budget guitar-to-headphones adapter for a friend. Inexpensive is the main consideration.
Anyhow, after reading all of this, I can't help but to notice something.
I see where many people (myself included) would just like to know what the best Op Amp for all audio applications is. It would be so nice to have it carved in granite that this one particular amplifier IC would work the best in any audio circuit. That way, we could all just stock up on these miracle ICs and use them for everything. But the unfortunate thing is that an Op Amp is a reasonably complex device which cannot just be substituted randomly into any Op Amp socket and be expected to perform at its best or get the best out of the rest of the circuit.
All Op Amps have different designs which interact with the rest of the circuit into which they are "inserted".
A complete circuit design must take into account so many variables which are unique to each Op Amp's own internal design that it makes it impossible to have a single test circuit into which a person can substitute Op Amps until they find that one magic "best" amplifier IC.
This makes it very difficult to quickly judge Op Amps in a general way. The only fair way to judge any Op Amp is to carefully design a circuit with the characteristics of that particular Op Amp taken into account. But then you can’t just swap amplifier ICs so you end up not knowing any more than you did when you started.
I guess the point is that we can’t really get the one single easy answer we want. An Op Amp is not a magic device that does not interact with its surroundings.
This same problem holds for various complete audio devices such as a complete phono preamplifier or CD player, etc. They too will interact with the attached equipment and will behave “better” in some circumstances than they do in others.
This is not at all what I or most of us would wish for, but it’s the reality of the situation. We cannot ever say with certainty that any given IC or piece of equipment will be the best in all situations.
I see people swapping Op Amps in and out of pieces of equipment to find which one sounds the best to them. That’s great and when you find one that works the best in that particular circuit, then you have learned something. But you have not learned which Op Amp is the best overall. You’ve just found one that happens to work well (to your ears) in that particular circuit. And that is valuable.
I see people building so-called passive preamplifiers and then raving about the relative merits of different volume control pots, etc. But when they test the different pots, they aren’t even the same resistance! It seems to me that in a passive preamp, the pot resistance would have such a profound effect on the loading of the previous device and the “driving” of the cable and next device that you, again, wouldn’t have learned anything with such a non-scientific experiment – except again, you’ve found the one pot which sounds the best to your ears in that particular exact setting.
Remember that "scientific method" requires that you must limit the experiment to a single variable and then make your observations. Unfortunately, that is virtually impossible in many cases.
Woe to all of us audio enthusiasts (including me, of course) who just want a simple answer.
Now this does not mean that everyone’s contributions and observations here are of no value. Quite the opposite. I’ve learned a lot by just reading this one thread. And I consider everyone’s observations to be valuable and helpful and in no case a waste of time. After all, we’re all trying to figure out what will work the best for our individual applications, and the more information, the better.
And this also does not mean that we cannot draw some general conclusions and narrow down the list of amplifier ICs that we’d prefer for various applications. But we all need to keep in mind how complex each of these ICs really is and be sure that when we apply them, we try to get the best out of each of them by taking those differences into consideration when we design the rest of the circuit.
I’ve wasted lots of space with this and probably have not said anything that most of you didn’t already know so I’ll shut up now.
But will one of you, please, just tell me what the best Op Amp for all circuits is so I can order some of them up and get on with my projects!
I'm new to this forum so first I'd like to say how much I've enjoyed reading this all.
This thread caught my eye because I have some good old SE5532s and was thinking of building a really low-budget guitar-to-headphones adapter for a friend. Inexpensive is the main consideration.
Anyhow, after reading all of this, I can't help but to notice something.
I see where many people (myself included) would just like to know what the best Op Amp for all audio applications is. It would be so nice to have it carved in granite that this one particular amplifier IC would work the best in any audio circuit. That way, we could all just stock up on these miracle ICs and use them for everything. But the unfortunate thing is that an Op Amp is a reasonably complex device which cannot just be substituted randomly into any Op Amp socket and be expected to perform at its best or get the best out of the rest of the circuit.
All Op Amps have different designs which interact with the rest of the circuit into which they are "inserted".
A complete circuit design must take into account so many variables which are unique to each Op Amp's own internal design that it makes it impossible to have a single test circuit into which a person can substitute Op Amps until they find that one magic "best" amplifier IC.
This makes it very difficult to quickly judge Op Amps in a general way. The only fair way to judge any Op Amp is to carefully design a circuit with the characteristics of that particular Op Amp taken into account. But then you can’t just swap amplifier ICs so you end up not knowing any more than you did when you started.
I guess the point is that we can’t really get the one single easy answer we want. An Op Amp is not a magic device that does not interact with its surroundings.
This same problem holds for various complete audio devices such as a complete phono preamplifier or CD player, etc. They too will interact with the attached equipment and will behave “better” in some circumstances than they do in others.
This is not at all what I or most of us would wish for, but it’s the reality of the situation. We cannot ever say with certainty that any given IC or piece of equipment will be the best in all situations.
I see people swapping Op Amps in and out of pieces of equipment to find which one sounds the best to them. That’s great and when you find one that works the best in that particular circuit, then you have learned something. But you have not learned which Op Amp is the best overall. You’ve just found one that happens to work well (to your ears) in that particular circuit. And that is valuable.
I see people building so-called passive preamplifiers and then raving about the relative merits of different volume control pots, etc. But when they test the different pots, they aren’t even the same resistance! It seems to me that in a passive preamp, the pot resistance would have such a profound effect on the loading of the previous device and the “driving” of the cable and next device that you, again, wouldn’t have learned anything with such a non-scientific experiment – except again, you’ve found the one pot which sounds the best to your ears in that particular exact setting.
Remember that "scientific method" requires that you must limit the experiment to a single variable and then make your observations. Unfortunately, that is virtually impossible in many cases.
Woe to all of us audio enthusiasts (including me, of course) who just want a simple answer.
Now this does not mean that everyone’s contributions and observations here are of no value. Quite the opposite. I’ve learned a lot by just reading this one thread. And I consider everyone’s observations to be valuable and helpful and in no case a waste of time. After all, we’re all trying to figure out what will work the best for our individual applications, and the more information, the better.
And this also does not mean that we cannot draw some general conclusions and narrow down the list of amplifier ICs that we’d prefer for various applications. But we all need to keep in mind how complex each of these ICs really is and be sure that when we apply them, we try to get the best out of each of them by taking those differences into consideration when we design the rest of the circuit.
I’ve wasted lots of space with this and probably have not said anything that most of you didn’t already know so I’ll shut up now.
But will one of you, please, just tell me what the best Op Amp for all circuits is so I can order some of them up and get on with my projects!
What you say is not without merit but to find the best opamp is not that hard.
Just put together a simple amp with a gain of 10 followed by a resistive divider to equalise the gain back to unity. As long as the loading is kept constant and hi, you'll be able to hear the intrinsic 'tone' of the opamp, either compared to a direct connection or to other opamps. Practically any opamp will function well under these easy conditions. This experiment won't tell you how the opamp works in capacitive load or when real current is called for, but you may still get a good insight of how much the opamp will colour the sound under 'ideal' conditions.
You may be surprised how big are the differences.
jcarr said:Andy:
I have noted similar effects, and I will add that the oscillation may manifest itself only under certain conditions. Sometimes it appears to be a specific combination of cable load and immediate RF conditions that triggers the oscillation in one opamp - but not another "identical" one.
------------------------------------------------------------------------------------
I was pleasantly surprised by two discoveries. First the LM6171 can be made to sound nice (and lush) by using an npo .1 uF across the rail. All other trials over a long period with different configurations without this produce a thinnish sound. instantly disliked.
Also an Alesis Masterlink recorder stuffed with NE5532s but quite well designed sounds rather good. This is inspite of a dirty switching PS! Improving the PS to eliminate hf hash results in a better sound still. This computer based stuff is rather sonically dodgey even though the measured results in terms of distortion etc are good
Usually pro stuff with NE5532 and 5534s sound 1D and upfront to me.
Is this amp inverting or non-inverting? What are the input and feedback impedances? 553x amps don't have the best reputation for CMRR (common mode rejection ratio).
Unfortunately most audio op amp applications use non-inverting circuits where CMRR affects performance, and this is probably why OPA627/637 and AD8610 with their cascode input stages are preferred over 553x.
Some more comments -
OPA627 and AD8610 use JFET as well as cascode input stage, I guess that most users are interested in the JFET and may not be aware of the CMRR benefit of the cascode.
Does anyone know of an audio op amp with a bipolar cascode input stage?
I used NE5534s in non-inverting op-amp based MM phono and line preamps for awhile, then learned about substituting a cascode JFET input for the on-chip bipolar inputfrom an old Siliconix app note, a real improvement in clarity and smoothness, most recently tried AD8610 and LM6171 with class-A output stage biasing.
Unfortunately all of these seem dull and uninvolving compared to circuits with tube or discrete transistor input stages.
OPA627 and AD8610 use JFET as well as cascode input stage, I guess that most users are interested in the JFET and may not be aware of the CMRR benefit of the cascode.
Does anyone know of an audio op amp with a bipolar cascode input stage?
I used NE5534s in non-inverting op-amp based MM phono and line preamps for awhile, then learned about substituting a cascode JFET input for the on-chip bipolar inputfrom an old Siliconix app note, a real improvement in clarity and smoothness, most recently tried AD8610 and LM6171 with class-A output stage biasing.
Unfortunately all of these seem dull and uninvolving compared to circuits with tube or discrete transistor input stages.
-----------------------------------------------------------------------------------nuvistor said:Some more comments -
Unfortunately all of these seem dull and uninvolving compared to circuits with tube or discrete transistor input stages.
Worth trying:
AD825 with fet class A biasing to 3-4 mA
LM6171 with npo .1 uF across rail. The type of cap affects the sound a lot!!
A very good question. The 5534 IME sounds incredibly better inverted with equalised source impedances on both inputs.
I have the feeling that most people simply won't put up with the inconvenience of inverted operation.
Could you tell us more about it?
Indeed they do. The lower the input voltage ranges, the worse the seem to perform.
analog_sa said:
Hello all. Please excuse this long diatribe again.
I’m really no expert in Op Amps or audio circuits, and I do believe that you could learn something from an experiment such as you describe. But I disagree about your experiment helping you find “the best Op Amp”. It could only help you choose an Op Amp that you like when used in that or a similar circuit.
Here is just one simplified example:
Let’s say I build a simple gain-of-ten amplifier circuit into which I can plug various Op Amps to be tested. I set this circuit up as a non-inverting amplifier and I decide to use relatively low values for the feedback resistors to keep noise low, but the source impedance happens to be quite high.
Now everything seems ok, especially if I’m going to use JFET input Op Amps because their input resistance is so high that there won’t be any problem with increased offset from the imbalance in the input circuit impedances.
So I begin my testing of Op Amps and I first insert an Op Amp which has input JFETs with very low gate junction capacitances. The circuit will probably sound fairly good.
Next, I insert an Op Amp who’s input JFETs have larger input junction capacitances. This Op Amp will probably display a much higher level of harmonic distortion than the first one did.
The mechanism for this is explained very well by Walt Jung in this article:
http://www.elecdesign.com/Globals/PlanetEE/Content/1518.html
My test might lead me to believe that the first Op Amp (with the low input junction capacitances) is “better” than the second Op Amp (with the larger input junction capacitances). But in reality it is only because the surrounding circuit was not optimized for the Op Amp with the large gate capacitances that it ended up sounding worse than the one with the smaller gate capacitances.
If I were to use the “bad” Op Amp in an inverting circuit, or if I were to balance the source impedances seen by the inverting and non-inverting inputs, I might well prefer the sound of the Op Amp with the larger input device gate capacitances.
And of course, the reverse would also be true. If I designed the circuit to minimize or eliminate the effects of large input JFET gate capacitances, I might end up thinking that the Op Amp with the large input capacitances was “better” than the other one. But again, it wouldn’t be a fair test and certainly wouldn’t prove that one Op Amp was better than the other in every application.
Thus, by using this type of general experiment, I would have fooled myself into believing that one Op Amp was inherently worse than another when in fact, it had just been misapplied – a victim of a circuit which brought out its worst characteristics.
This is just one example. There may be as many examples for how the surrounding circuit might favor one Op Amp over another as there are different Op Amps.
I’m not trying to say that all Op Amps will make good audio circuits. And I, like all of us, want to find the ones that have the most potential for my projects. I certainly won’t be using a 741 or a 1448 in any serious audio circuits. And I would look for faster Op Amps than the 5532 or 5534 for a new high quality design. But those faster amplifiers will require that I do other things in their surrounding circuitry to bring out their best. If I plug a 2500V/uS Op Amp into a socket where I just pulled out a 5534 in some old piece of equipment, I’d lay even money that it will oscillate and sound really nasty. It darn sure won’t perform up to its potential. But again, that doesn’t mean that the 2500V/uS Op Amp is inherently bad. Again, it’s just misapplied.
So my point is that we need to be careful not to draw false and illogical conclusions based on invalid or unfair tests. Op Amps do not behave independently of their surrounding circuitry. Any test circuit can only test the Op Amp’s performance in that test circuit. We can draw inferences about how it’ll behave in similar circuits, but nothing more. You can’t separate the Op Amp from its surrounding circuit – no matter how generic and “ideal” you believe that test circuit to be.
And, as has been pointed out as the basis for this thread, even the much maligned 5534 can sound quite good in the right circuit. Just because I may have heard a circuit where it sounded bad doesn't make the chip inherently bad. Of course, it doesn't make it good either
Sigmo,
I expect you are correct, an op-amp must surely interact with its surrounding circuit. However I have had very similar subjective results from various op-amps in three different circuits, I/V conversion, a balanced to unbalanced converter and a power amplifier voltage gain stage. In these circuits each op-amp displays a strong resemblance to its own sound in the other two circuits. From this I conclude that the circuit complexities within each op-amp impart a sonic signature that dwarfs (at least in the above mentioned circuits) the effects of the surrounding circuit.
I suspect the greatest variable of all is human. Just as our eyesight is different we surely have ears that differ too, leading to pronounced differences in the signals from ear to brain. At first thought this would perhaps explain much about how our perception of good seems to differ, however we experience the same real-world sounds as each other and therefore the brain should ‘know’ what is real and what is not, so perhaps it ‘adjusts’ to the ears own peculiar response unconsciously.
So where does this leave us? I am not convinced that overall system balance is necessarily the overriding influence over what makes one op-amp sound good in one system and bad in another, though it must surely have large significance (I dislike the idea of ‘correcting’ a frequency response anomaly in a loud-speaker – brightness, for example - by selecting the op-amp which sounds least bright. The op-amp probably has a similarly flat response to its counterparts and therefore is probably the wrong 'tool' for the job) and there are certainly large differences between the way different rooms and speakers interact.
So I wonder if the greatest and most significant variable is not the human ear, nor system balance, but human perception - the way we listen to, and what we expect from, music.
Tim.
I expect you are correct, an op-amp must surely interact with its surrounding circuit. However I have had very similar subjective results from various op-amps in three different circuits, I/V conversion, a balanced to unbalanced converter and a power amplifier voltage gain stage. In these circuits each op-amp displays a strong resemblance to its own sound in the other two circuits. From this I conclude that the circuit complexities within each op-amp impart a sonic signature that dwarfs (at least in the above mentioned circuits) the effects of the surrounding circuit.
I suspect the greatest variable of all is human. Just as our eyesight is different we surely have ears that differ too, leading to pronounced differences in the signals from ear to brain. At first thought this would perhaps explain much about how our perception of good seems to differ, however we experience the same real-world sounds as each other and therefore the brain should ‘know’ what is real and what is not, so perhaps it ‘adjusts’ to the ears own peculiar response unconsciously.
So where does this leave us? I am not convinced that overall system balance is necessarily the overriding influence over what makes one op-amp sound good in one system and bad in another, though it must surely have large significance (I dislike the idea of ‘correcting’ a frequency response anomaly in a loud-speaker – brightness, for example - by selecting the op-amp which sounds least bright. The op-amp probably has a similarly flat response to its counterparts and therefore is probably the wrong 'tool' for the job) and there are certainly large differences between the way different rooms and speakers interact.
So I wonder if the greatest and most significant variable is not the human ear, nor system balance, but human perception - the way we listen to, and what we expect from, music.
Tim.
Someone put it best earlier in the thread with "There's no accounting for taste." i.e. personal preferences are not up for debate.
Though the NE5534 doesn't fit my tastes exactly, it obviously suits others just fine. We all hear things differently and certainly focus on different aspects of the sound, no matter how objective we try to be.
I have found many times that an op-amp may perform extremely well in some circuits, and not so well in others. Therefore, I believe it is important to evaluate each situation objectively and not discount one op-amp or another based on previous experience in a completely different circuit.
Happy experimenting! It is good to know that some people actually listen to their circuits and are not exclusively concerned with test specifications.
Though the NE5534 doesn't fit my tastes exactly, it obviously suits others just fine. We all hear things differently and certainly focus on different aspects of the sound, no matter how objective we try to be.
I have found many times that an op-amp may perform extremely well in some circuits, and not so well in others. Therefore, I believe it is important to evaluate each situation objectively and not discount one op-amp or another based on previous experience in a completely different circuit.
Happy experimenting! It is good to know that some people actually listen to their circuits and are not exclusively concerned with test specifications.
Sigmo
Again, i mostly agree with your views. My point was slightly different - that opamps, same as everything else, have their own, inherent sound which you simply can't avoid, no matter how well you meet their specific requirements.
Last time i did a straight wire test with a 5534 was almost 20 years ago. Even under ideal conditions it did something bad to the highs - reduced decay, flattening of perspectives, generally lowered subjective resolution. Under less than ideal conditions and especially in non-inerting mode it scored a lot worse.
More recently i've repeated this experiment with a 627 and buf634. Arguably better than the 5534, both these devices, alone or together, add a distinctive sonic imprint on all music passing through them. The 627 may well score better than a 5534 under real world conditions but is just as easy to spot against a 'straight wire' (what a term
)More recently i've repeated this experiment with a 627 and buf634. Arguably better than the 5534, both these devices, alone or together, add a distinctive sonic imprint on all music passing through them. The 627 may well score better than a 5534 under real world conditions but is just as easy to spot against a 'straight wire' (what a term ) [/B][/QUOTE]
-----------------------------------------------------------------------------------
I agree with you about 627/634. Detailed, hifi sound asnd don't understand why people go ga ga about the 627 (I have 12 that I have taken out and replaced with AD825/LM6171/OPA132
etc that sound much better.
) [/B][/QUOTE]-----------------------------------------------------------------------------------
I agree with you about 627/634. Detailed, hifi sound asnd don't understand why people go ga ga about the 627 (I have 12 that I have taken out and replaced with AD825/LM6171/OPA132
etc that sound much better.
analog_sa -
I have not tried 5534 in inverting circuit with balanced source impedances, but I have found that solid-state power amps sound cleaner and more detailed with such a circuit as long as the preamp can drive the lower input impedance (I use 1k input). I sometimes wonder how inverting bipolar input op amp circuits with JFET input buffers would sound, I find buffers with cascode NJFET followed by NPN with constant current sink to be essentially transparent if not loaded too heavily.
"Composite Op Amp for High Performance" in the 1986 Silliconix FET databook is the app note I referred to. This is long out of print and I have not see it on line, but it's prettty simple:
5534 pins 2,3 are connected to 4, this turns off its input stage. A 2N5912 dual JFET as differential pair is cascoded by another 2N5912 dual, gate of cascode pair tied to source of diff pair. Drains of cascode pair are connected to 5534 pins 1,8. 1.37k resistors from drains to V+ are in parallel with the 5534's 13k collector resistors, 2.5V is expected across the drain resistor. A 4mA "ring of two" constant current sink with 162 ohm b-e resistor completes the circuit.
In my builds, I used high Vp FETs for the cascodes like 2N4392, they don't need close matching, and for the diff pair, medium gm duals like U401, about 1mA drain current . A modern high gm dual like 2SK369 would probably work well but I haven't tried this. A 2 - 4mA current sink on the output gives a smoother sound.
The Nat Semi app note AN-222 has a MM RIAA preamp using LM394 and LM318 using the same idea of turning off the op amp input stage and connecting an external diff pair, but the Siliconix circuit is a better design.
fmak -
LM6171 were harsh sounding in my first use, a 5mA current sink helped some, and a cap right on the DIP package (I used 18nF NPO) pretty much removes the harshness, these are fast amps and in audio layouts may have stability problems without very close bypassing, my guess is that 100nF isn't much different with close lead dress.
Sigmo -
Agreed, the op amp and its application circuit must be considered together, general statements about superiority of one chip over another may not take this into account.
Tim A -
The multi-bit DAC I/V application is at audio frequencies probably one of the better circuits for 5534 since it is inverting with low source impedances, but bipolar input stages can have slew-related problems due to the step transistions at the DAC current output, this can be mitigated by adding the right cap values between DAC current output and ground and across op amp feedback resistor as described by Scott Wurcer in the AD744 data sheet (Scott where are you?
)
I have not tried 5534 in inverting circuit with balanced source impedances, but I have found that solid-state power amps sound cleaner and more detailed with such a circuit as long as the preamp can drive the lower input impedance (I use 1k input). I sometimes wonder how inverting bipolar input op amp circuits with JFET input buffers would sound, I find buffers with cascode NJFET followed by NPN with constant current sink to be essentially transparent if not loaded too heavily.
"Composite Op Amp for High Performance" in the 1986 Silliconix FET databook is the app note I referred to. This is long out of print and I have not see it on line, but it's prettty simple:
5534 pins 2,3 are connected to 4, this turns off its input stage. A 2N5912 dual JFET as differential pair is cascoded by another 2N5912 dual, gate of cascode pair tied to source of diff pair. Drains of cascode pair are connected to 5534 pins 1,8. 1.37k resistors from drains to V+ are in parallel with the 5534's 13k collector resistors, 2.5V is expected across the drain resistor. A 4mA "ring of two" constant current sink with 162 ohm b-e resistor completes the circuit.
In my builds, I used high Vp FETs for the cascodes like 2N4392, they don't need close matching, and for the diff pair, medium gm duals like U401, about 1mA drain current . A modern high gm dual like 2SK369 would probably work well but I haven't tried this. A 2 - 4mA current sink on the output gives a smoother sound.
The Nat Semi app note AN-222 has a MM RIAA preamp using LM394 and LM318 using the same idea of turning off the op amp input stage and connecting an external diff pair, but the Siliconix circuit is a better design.
fmak -
LM6171 were harsh sounding in my first use, a 5mA current sink helped some, and a cap right on the DIP package (I used 18nF NPO) pretty much removes the harshness, these are fast amps and in audio layouts may have stability problems without very close bypassing, my guess is that 100nF isn't much different with close lead dress.
Sigmo -
Agreed, the op amp and its application circuit must be considered together, general statements about superiority of one chip over another may not take this into account.
Tim A -
The multi-bit DAC I/V application is at audio frequencies probably one of the better circuits for 5534 since it is inverting with low source impedances, but bipolar input stages can have slew-related problems due to the step transistions at the DAC current output, this can be mitigated by adding the right cap values between DAC current output and ground and across op amp feedback resistor as described by Scott Wurcer in the AD744 data sheet (Scott where are you?
)
Hello all,
This is a really great forum. My thanks go out to everyone for all of their insight and willingness to share.
I found this forum while searching for exactly this sort of information. It’s been a while since I built any good audio projects, so I’ve been rooting around for information on what Op Amps I should consider.
Despite the main point of my previous posts to this thread, I really do hope, and fully expect that I will find a couple of Op Amps that sound good to me and which I can use as the basis for some new projects.
Being able to read about which ones sound good to all of you is very helpful in narrowing down the field. The IC manufacturers rarely see high-end audio as a large part of their potential market so you don’t often see high quality audio applications in their data sheets. Of course, there are exceptions. I’ve still got about 20 AD846s that I bought years ago. The ADI databook at that time actually showed an audio preamp schematic as one of the applications in that IC’s datasheet.
From what I’ve read, I really wish that the AD825 were available in a DIP package. It might compromise the operation to put it in a different package, though. But from reading what others have written, and from looking at the data sheet, it seems like a very promising IC. Probably worth the effort to deal with the SO package.
Has anyone played with ADI’s OP275? This is touted as being an “audio op amp” by ADI. It’s a dual, so it might just plug right into many existing circuits for a quick, easy upgrade. I know, I know, I do remember what I’ve said about doing that, but hey, I’m always up for an easy way to make a crummy CD player sound better too!
It does seem as though the semiconductor manufacturers could create, if they wanted, a really great – and somewhat universal – audio Op Amp. The OP275 is the one I see as being ADI’s premier offering in this area. ADI’s data sheet for the OP275 says that its 22V/uS slew rate “is the fastest of any standard audio amplifier”. Now if I recall correctly, the NE5534 is about half this fast, and the gain-bandwidth product of the OP275 is 9MHz. That’s exactly the same as the old NE5532s that I’ve got!
So on the surface, it seems like this state of the art “audio Op Amp” may not be a significant improvement over the NE5532. But I’ll bet that it sounds a whole lot better due to its totally different input architecture. Still, I wonder how it sounds compared to the “non audio” types that we all seem to recruit into audio duty when designing a high-end audio device.
Thanks again for all of your opinions and experiences with this. I’m itching to order some parts and get going with a few new projects here.
This is a really great forum. My thanks go out to everyone for all of their insight and willingness to share.
I found this forum while searching for exactly this sort of information. It’s been a while since I built any good audio projects, so I’ve been rooting around for information on what Op Amps I should consider.
Despite the main point of my previous posts to this thread, I really do hope, and fully expect that I will find a couple of Op Amps that sound good to me and which I can use as the basis for some new projects.
Being able to read about which ones sound good to all of you is very helpful in narrowing down the field. The IC manufacturers rarely see high-end audio as a large part of their potential market so you don’t often see high quality audio applications in their data sheets. Of course, there are exceptions. I’ve still got about 20 AD846s that I bought years ago. The ADI databook at that time actually showed an audio preamp schematic as one of the applications in that IC’s datasheet.
From what I’ve read, I really wish that the AD825 were available in a DIP package. It might compromise the operation to put it in a different package, though. But from reading what others have written, and from looking at the data sheet, it seems like a very promising IC. Probably worth the effort to deal with the SO package.
Has anyone played with ADI’s OP275? This is touted as being an “audio op amp” by ADI. It’s a dual, so it might just plug right into many existing circuits for a quick, easy upgrade. I know, I know, I do remember what I’ve said about doing that, but hey, I’m always up for an easy way to make a crummy CD player sound better too!
It does seem as though the semiconductor manufacturers could create, if they wanted, a really great – and somewhat universal – audio Op Amp. The OP275 is the one I see as being ADI’s premier offering in this area. ADI’s data sheet for the OP275 says that its 22V/uS slew rate “is the fastest of any standard audio amplifier”. Now if I recall correctly, the NE5534 is about half this fast, and the gain-bandwidth product of the OP275 is 9MHz. That’s exactly the same as the old NE5532s that I’ve got!
So on the surface, it seems like this state of the art “audio Op Amp” may not be a significant improvement over the NE5532. But I’ll bet that it sounds a whole lot better due to its totally different input architecture. Still, I wonder how it sounds compared to the “non audio” types that we all seem to recruit into audio duty when designing a high-end audio device.
Thanks again for all of your opinions and experiences with this. I’m itching to order some parts and get going with a few new projects here.
fmak -
LM6171 were harsh sounding in my first use, a 5mA current sink helped some, and a cap right on the DIP package (I used 18nF NPO) pretty much removes the harshness, these are fast amps and in audio layouts may have stability problems without very close bypassing, my guess is that 100nF isn't much different with close lead dress.
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The 100nF fits exactly on top. You will find that the type nand value of the caps makes a difference to the sound. With 100nF npo, the sound changes tohints of lushness even!
LM6171 were harsh sounding in my first use, a 5mA current sink helped some, and a cap right on the DIP package (I used 18nF NPO) pretty much removes the harshness, these are fast amps and in audio layouts may have stability problems without very close bypassing, my guess is that 100nF isn't much different with close lead dress.
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The 100nF fits exactly on top. You will find that the type nand value of the caps makes a difference to the sound. With 100nF npo, the sound changes tohints of lushness even!
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