Upgrade for NE5532

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I don't think that a lot of people over here will agree, but I prefer high slew-rate opamps with a large open-loop bandwidth (> 10Khz), such as the AD826. Why?

- The high slew-rate (350V/us) enables them to cope with very fast signals. Also a good choise for a DAC I/V.
- The slightly higher noise figures (18nV/Hz) do not affect the results too much. Resistors contribute more to noise figures than the opamp.
- The open-loop bandwidth reduces the need for NFB, as well as the distortion figures in the higher audio bandwidth.

Further: the AD826 sounds very good and involving.
350V/uS: Non sense.
Two good questions are not answered .....:rolleyes::rolleyes:
 
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I don't see ANY difference between the LM4562 and the LME49720 on the datasheets. The latter is ~ 15¢ cheaper @ Mouser.

Thanks for the confirmation/crosscheck! I think I still cannot believe that they are the same :xfingers: But whatever, I cannot trust most products circulated in the market in my country. Everything looks fake nowadays :redhot:

I think you're lucky if you find LME cheaper there. Here LM is a lot cheaper but I had a feeling that LME is better.
 
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1. Don't use FET op amps for audio! --> Non linearity!
2. NE5532/34 is the best op amp for audio.
3. LM4... is even better in THD, but shows signs of instabilities. Be careful! And its far more expensive. N.B. The LM4... from National has reached end of life. Many thanks to Texas Instruments!
 
JFET input need an input resistance of loweer than 2kOhm. Otherwise distortion will occur.

In general, JFET input has high impedance. Easy to drive.

Regardless the input type, each opamps have specifications. Bipolar JRC2068 needs source impedance lower than 2k and needs load impedance higher than 2k to get the optimum result. JFET LF353 can drive 10k with less than 0.02%.

1. Don't use FET op amps for audio! --> Non linearity!

You meant MOSFET. OPA2604 is JFET-input suitable for audio.

2. NE5532/34 is the best op amp for audio.

Spec sheet doesn't say so. As long as you pay attention to the gain, input and output impedance requirements, JRC2068 will outperform NE5532 in every aspects in most audio implementations.
 
As long as you pay attention to the gain, input and output impedance requirements, JRC2068 will outperform NE5532 in every aspects in most audio implementations.
Almost. NE5532 has a higher slew rate (9v/uSec vs, 6). 2068 voltage noise IS lower than the 5532, but I cannot find a spec on current noise for the 2068---which the 5532 is particularly LOW in, even lower than the mighty LM4562. This makes the NE5532 especially good for higher source impedance circuits.
 
Before you replace the NE5532, you need to analyze the schematics.
JFET input need an input resistance of loweer than 2kOhm.
Otherwise distortion will occur.

Have a good read of the OPA164x series, OPA627 or anyone else with a dielectric isolation JFET-input opamp.

1. Don't use FET op amps for audio! --> Non linearity!
2. NE5532/34 is the best op amp for audio.
3. LM4... is even better in THD, but shows signs of instabilities. Be careful! And its far more expensive. N.B. The LM4... from National has reached end of life. Many thanks to Texas Instruments!

NE5532 is a great opamp, but, what?!
 
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- The open-loop bandwidth reduces the need for NFB, as well as the distortion figures in the higher audio bandwidth.
.

I don't think that is true in general. Wide open loop opamps in general have lower open loop gain in much of the audio band. So they actually would need more feedback to become totally transparent. At the same time, the low open loop gain means that less is available for feedback.
You lose on both sides.

Jan
 
Two questions.

1. What do you mean by "very fast signals"?
2. Is the NE5532 (or NE5534) unable to cope with "very fast" audio signals?
The engineers at National Semiconductor designed the NE5532 for ultra low noise application with a slew rate (5 V/µs) which is much improved over the then standard 741 family of opamp. That makes NE5532 very good for low cost phono amp, but not necessarily everything.

Nelson Pass had a very insightful interview on the subject slew rate on Stereophile where he concluded that a slew rate of 50V/µs is sufficient for audio applications.

Nelson Pass said:
the idea being that high-speed signals would somehow confuse an amplifier. People began building fast amplifiers and, lo and behold, quite a few of those fast amplifiers sounded significantly better. The interesting thing was that in order to achieve that higher speed, they had to make the circuits simpler. I don't think it was actually a cause-and-effect relationship. I think that for the most part the higher-speed circuits sounded better because it took simpler circuits to get high speed with stability.
However, there were some examples of very high-speed circuits out of some companies—who shall remain nameless—where they were doing 1000V/µs but everybody thought they sounded pretty bad.
............................
One of the most fascinating tests I ever ran was one of those "let's go see how many teeth the horse really has," as opposed to discussing it, kind of things. By the way, Peter Walker of Quad did exactly the same thing at the same time—two minds, at least, thinking alike. We decided to find out in real life what kind of slew rates were really occurring. Then, operating off that basis, you can come up with your 10:1 figure that you need to achieve. So I built a differentiating circuit—this was pre-digital--and using a very high-quality moving-coil cartridge and step-up system that was certainly not compromised with regards to bandwidth, I simply played music into loudspeakers near the capacity of the amplifier, which was 200Wpc on various types of recorded material.
On record ticks and pops I could register slew rates as high as 20–30V/µs—real signals that were being processed through the differentiating network and then onto a storage 'scope. So it came time to play some music. Again, if you clipped the amplifier you could see 40 and 50V/µs recovery; that is to say, the amplifier, in catching up from clipping to get to where the signal was, would travel that fast to catch up. So clearly the system—the amplifier and the measuring system—were capable of resolving 40 and 50V/µs transients. In playing music we were looking at piano, cymbals, violins—a large range of instruments all played loud, near the power capacity of the amplifier. And we were getting values like 0.1V/µs, 0.5V/µs. In fact, at that time in that series of tests, the highest transient we were able to achieve was about 1V/µs. So the 10:1 ratio would dictate that you would need at least 10V/µs performance. That was somewhat faster than some of the slow amps that were being criticized at that time, which were in the 4 and 5V/µs range. But clearly, I didn't see where slew was overloading them as such.
Norton: You mention that the slew rate of record ticks and pops was quite a bit faster. Was their level so low that it didn't cause problems?
Pass: No, it was a factor. Subsequent to that, though, the Sheffield Drum Record was used in a test and we started getting figures into the 5V/µs ballpark. And those were rim shots. In fact, as far as I can make out, rim shots present the fastest transient that I've seen on a recording. The Sheffield Drum Record was the fastest example that stands out. I haven't seen anything like it since. But given that you're on the 5V/µs rate, we ultimately settled on approximately 50V/µs as a speed beyond which was fine, but it became a minimal figure that we deal with in our designs.

Read more at Nelson Pass: Simple Sounds Better Page 4 | Stereophile.com

Read more at Nelson Pass: Simple Sounds Better Page 3 | Stereophile.com
 
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The engineers at National Semiconductor designed the NE5532 for ultra low noise application with a slew rate (5 V/µs) which is much improved over the then standard 741 family of opamp. That makes NE5532 very good for low cost phono amp, but not necessarily everything.

Nelson Pass had a very insightful interview on the subject slew rate on Stereophile where he concluded that a slew rate of 50V/µs is sufficient for audio applications.

That was about power amps with a gain of anywhere of 10 to 30. So opamps in preamps need at the very most 1 or 2V/uS, add a safety factor and you're at 5V/uS.
The NE5534 is specced at 13V/uS, the NE5532 is 9V/uS, not 5V/uS.

Jan
 
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The engineers at National Semiconductor designed the NE5532 for ultra low noise application with a slew rate (5 V/µs) which is much improved over the then standard 741 family of opamp. That makes NE5532 very good for low cost phono amp, but not necessarily everything.
Datasheet shows 9v/uSec for NE5532; but certainly not the BEST for phono amp application----about 5 db noisier than an LM4562/LME49720, but definitely less $$--about 1/3rd the cost. The BEST, IMNHO, for phono is the OPA1612---another 7 db quieter than the 4562, and faster----at a cost, though--more than 2x the 4562.
 
And NE5532 isn't originally a National product (Signetics). ;)

Anyhow, one must mind the current noise, too, so it really depends on the network impedances at hand. One could use a OPA1644 as 4 parallel inputs (thus halving its E_n) and still have essentially zero current noise for a phono preamp, giving it a lower total noise than many/all of the bjt-input opamps with their respectively "high" current noise. Or a ADA4898, or ...
 
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