Did I read that right? Slew rate is critical for a phono preamp? Just how much gain are you thinking?!
Yes, it is. RIAA feedback loops are quite hard on an opamp.
It's also critical for a power amp, where you should have at least 1v/us/peak volt output. A good rule is 60 v/us minimum for a power amp, which takes you up to 225 watts. "Transient Intermodulation Distortion" is a fancy made up word for slew induced distortion.
I have an engineering degree. I'm pretty good at this stuff.
Before you guys get carried away that application uses the null pins as inputs with the input devices disabled, there are no modern op-amps with that feature. There are numerous choices for phono pre-amps today with lower noise than the LM394 which for MM was never the best choice in the first place.
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Yes, I agree with you that the LM5534 is a dated design and there are much lower noise choices such as AD797, LT1115. It is from the same era of the LM318, but a much improved opamp for audio from 30 years ago than LM318.
The LM5534 has a 5V/uS slew rate which is more than adequate for phono stage. Do not confuse slew rate requirement for power amplifier with a line level/impedance output.
The problem of LM318 is easily audible. It is easily visible when you feed it a 10KHz square wave. The LM318 rings after the rising and the falling edge, making it unsuitable for audio application.
It appears to me that marklawrence is new to this forum. He is confusing power amp with line level amp. Hopefully, he will find the posts by Nelson Pass and others on this subject.
IMHO, LM5534 / 2, while it may not be the very best opamp available, is fine for an MM preamp in most systems. I'm using 2 stages of NE5532 in my own preamp (based on Rod Elliot design) and the noise is barely audible. When nothing is playing - even with the volume all the way up - there is almost no difference in noise c/w a dead shorted preamp input on my system (you can hear sounds from the room being picked up by the cart, though!)
I am new to this forum.
I routinely make crossovers that Nelson Pass says are impossible to realize with passive components.
I'm not confusing anything. I'm quite well trained and have quite good experience. For example, in 1977 I build an 18 bit 56khz A to D, which was the fastest and most precise in the world at the time. Of course by today's standards it's a done with a single cheap chip, but at the time it required hand made .003% resistors. 56 khz sounds slow, but just for example the sample and hold had to switch in 1/2 nano second. 2Ghz. I got those speeds out of 3905s and 2222s - cheap 30Mhz transistors.
And yes, slew rate is critical for a phono preamp. The demands on the feedback loop are enormous.
I routinely make crossovers that Nelson Pass says are impossible to realize with passive components.
I'm not confusing anything. I'm quite well trained and have quite good experience. For example, in 1977 I build an 18 bit 56khz A to D, which was the fastest and most precise in the world at the time. Of course by today's standards it's a done with a single cheap chip, but at the time it required hand made .003% resistors. 56 khz sounds slow, but just for example the sample and hold had to switch in 1/2 nano second. 2Ghz. I got those speeds out of 3905s and 2222s - cheap 30Mhz transistors.
And yes, slew rate is critical for a phono preamp. The demands on the feedback loop are enormous.
It is nice to welcome an expert that is more qualified than Nelson Pass to this forum.
If you have any simulation or test results on your phono stage response claim, please, share them here. Or provide a link to them.
I agree with you that the LM5534/2 is sufficiently good for MM phono preamp and line amp. I still prefer the LME49720 for a better margin in open loop gain. But the difference is hardly audible.
On the other hand, LM318 is a poor choice in noise and in transient response.
The fact TI don't even bother to specify THD or input noise in the spec sheet is a bit of a giveaway.
The LM318 is a fast Opamp for instrumentation with a small signal bandwidth of 15MHz. It is NOT meant for audio use. Noise or THD are not critical in general application Opamp. National Semiconductor designed the LM5534/5532 series for audio which was very successful, but has since been superseded by better Opamp.
You can find information on measuring and reducing noise for LM318 in this old National Semiconductor application note that TI re-published.
http://www.ti.com/lit/an/snla206a/snla206a.pdf
There were many good discussion on high end, Opamp based phono stage in this forum. They are wonderful reading for those who are interested in learning the subject.
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In a MM amp, as frequency rises, the noise contribution from the source resistance and the 47k load resistor quickly dominate and swamp the noise of the opamp when the amplifier noise current is factored in.
The NE5534 was way ahead of anything on that score when it was released in the late 1970's. The noise voltage is commendably low, but for a bipolar opamp, so is the noise current. The result is in an MM amp you have an almost perfect balance of specs FOR THE MONEY. Given that you can get these for about 40c from Mouser or RS, nothing comes close - 'bang for the buck' it punches way above its cost in the MM application.
Low voltage noise JFET input opamps can best it because they combine low noise voltage with negligible noise current, but very few of these are cheap. An excellent candidate is the AD743/AD745 family but they are about $10 in the UK (£8).
The NE5534 was way ahead of anything on that score when it was released in the late 1970's. The noise voltage is commendably low, but for a bipolar opamp, so is the noise current. The result is in an MM amp you have an almost perfect balance of specs FOR THE MONEY. Given that you can get these for about 40c from Mouser or RS, nothing comes close - 'bang for the buck' it punches way above its cost in the MM application.
Low voltage noise JFET input opamps can best it because they combine low noise voltage with negligible noise current, but very few of these are cheap. An excellent candidate is the AD743/AD745 family but they are about $10 in the UK (£8).
I think it was Signetics that brought out the TDA1034/NE5534 parts many years ago.
Others (Motorola, TI, etc.) eventually became 2nd sources, but some wonder is the 2nd source parts are actually using the same internal schematic.
And I agree, one could do a lot worse than use the NE5534 in MM RIAA preamps.
mlloyd1
Others (Motorola, TI, etc.) eventually became 2nd sources, but some wonder is the 2nd source parts are actually using the same internal schematic.
And I agree, one could do a lot worse than use the NE5534 in MM RIAA preamps.
mlloyd1
The '318 was a fast (for the time) opamp for instrumentation. The audio market for chips was teeny, and cost-driven ('318 was not cheap when new). No reason to spec noise or THD.
The '5532 amps, as mlloyd1 says, are derived from '1034, another instrumentation opamp. It "failed" in its intended market, but some audio guys used it, and it was re-born with minor changes and a new number.
The '5532 amps, as mlloyd1 says, are derived from '1034, another instrumentation opamp. It "failed" in its intended market, but some audio guys used it, and it was re-born with minor changes and a new number.
I stand corrected. For many years in the professional audio field, the 5532/5534 series were "the standard audio op amp to which others are compared". It was a huge improvement over the 741 type operational amplifier at that time.
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In the application cited by the OP, the 318s input stage was nulled out and bypassed, resulting in a noise figure of 1.8nV / root(hz). Considerably better than your dream chip, the 5534.
You're out of your playpen, Dr.BoeingFellow.
As of today (2019), my choice for RIAA circuit opamp is the Linear Technology LT1115.
LT1115 Spec Sheet said:
If I travel back in time for 30 years, I still will pick the NE5534 over the LM318 any day. Today, I select the LT1115 for its ready availability and low price in the US. Other candidates worth consideration for RIAA phono stage are AD797, OPA627, LME49710 and many others.
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High Speed IC Op Amps
Some perspectives on High Speed IC Op-Amp from the history of development. Please, note that we are very lucky to have Scott Wurcer and Wyn Palmer frequently participate here. They are the history maker in the earlier IC development days.
OP AMP APPLICATIONS Analogue Devices 2005 page_H.66 said:
Some perspectives on High Speed IC Op-Amp from the history of development. Please, note that we are very lucky to have Scott Wurcer and Wyn Palmer frequently participate here. They are the history maker in the earlier IC development days.
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