National opamp inflation

Tolu

Member
2007-03-27 12:40 pm
Hi

I am a little bit confused about the new product range of National. Regarding the use in high-end preamps there are now at least 4 opamps that seems to be interesting.

LME49720 (LM4562), LME49722, LME49725, LME49713

But where are the significant technical and audible differences?

The datasheets are in some respects very covered! Why don't they have some sample applications for line drivers in their data sheets like other companies?

Can anyone tell me more?
 
The LME49713 can't be put in the same basket as the first three because it's a current feedback design and the others are voltage feedback.

Looking at the specs for the other three, you can see there are various differences (or trade-offs). Take the LME49722 vs LME49720 for instance. The LME49722 has slightly better distorion specs and better channel separation, but this comes with higher input bias current, input offset current, and quiescent current.

Pick the one with the specs that matter the most to your application?
 

audioman54

Member
2008-06-18 2:58 am
Lme49713

Hi Everyone,

I have designed a D/A box that used both parts. The LME49713 and LME49710. However I was laid off two months ago and I did not have enough time to publish the circuits.

To answer the questions though the LME49713 CFB is a slightly better sounding part than the LME49710 VFB but they are both better than any other opamp on the market at this time. The THD+N spec of 0.00005% or so is REAL! But the process the parts were built on and the engineer who designed them is what sets them apart. (I specified the LME49713) These will be the reference opamps for audio for many years to come...and this is coming from someone who is out of work because of National and wondering where I will end up?

In my D/A design I use the metal can LME49713's in most places but I do use the LME49710 metal can in one place where VFB opamps work better than CFB ones. By the way the metal can parts sound better than the dip parts but measure the same on the AP2 Cascade (192).

Best Regards Everyone... and if anyone knows an analog/audio company that needs a semiconductor audio applications / audio equipment design engineer please let me know.

Mark / Audioman54 at yahoo dot com
 

audioman54

Member
2008-06-18 2:58 am
Hi Tibi,

No, I am not a chip designer; I am an analog audio circuit and high-end audio/consumer audio equipment designer. I worked at National up until 7 weeks ago as a Principal Applications Engineer in the Audio Group for the past 10 years. I was part of a team that specified the LM4562/LME49720/10. I personally specified the LME49713CFB opamp as well as the LME49811 mono power amplifier driver parts which are my favorite parts sonically in the entire lineup. I also was the guy who pushed hard for the metal can packages which do sound better than the identical die in the plastic dip and SO packages. Bob Pease and I were going to try and find out just why that was but we never got the chance to do that and now I am gone and trying to enjoy some time off...while looking full time for a new job in the worst job market in decades!

The chip designer who did design those parts to our team’s audio specs is now also "retired" in Japan.

I am glad you like the parts as 5 years of work by a whole team of outstanding people went into getting those opamps, power amp drivers and buffers (LME49600) into the market place.

Mark / audioman54

(PS- Hi Eric)
 

KLe

Banned
2005-07-15 1:26 am
Brisbane
Re: Lme49713

audioman54 said:
Hi Everyone,

I have designed a D/A box that used both parts. The LME49713 and LME49710. However I was laid off two months ago and I did not have enough time to publish the circuits.

To answer the questions though the LME49713 CFB is a slightly better sounding part than the LME49710 VFB but they are both better than any other opamp on the market at this time. The THD+N spec of 0.00005% or so is REAL! But the process the parts were built on and the engineer who designed them is what sets them apart. (I specified the LME49713) These will be the reference opamps for audio for many years to come...and this is coming from someone who is out of work because of National and wondering where I will end up?

In my D/A design I use the metal can LME49713's in most places but I do use the LME49710 metal can in one place where VFB opamps work better than CFB ones. By the way the metal can parts sound better than the dip parts but measure the same on the AP2 Cascade (192).

Best Regards Everyone... and if anyone knows an analog/audio company that needs a semiconductor audio applications / audio equipment design engineer please let me know.
Mark / Audioman54 at yahoo dot com

Hi Mark, firstly, sorry to hear about that :(
... and, secondly, did you have anything to do with the LME49810?
... and what do you think of it?
thanks
:)
 
My favourite is http://www.national.com/pf/LM/LME49870.html
This has got higher voltage supply: 2x22V (absolute max 2x23).
LME49710 max 2x17V

LME49860 is the dual version of LME49870. Of course a dual OP can only dissipate 50% power heat per channel, compared to single channel opamp in one chip package.

These LME49870/60 have same good specs as LME49710/20, but can work at and output higher voltage.
Max rec Supply voltages are 44 vs. 34 VDC. = 10 extra volts :cool:

Link to list with National Performance Audio opamps:
http://www.national.com/cat/index.cgi?i=i//305
 

audioman55

Disabled Account
2008-06-28 2:13 am
To answer the last two posts...

300 people were laid off from National in November and I was part of that. Our great economy is part of the problem and also since I am over 50 my days were numbered. We are not all just leaving...we are being asked to leave, along with a lot of other engineers in the valley from other companies too!

and...
The LME49810 was designed as higher output current driver for live music amplifiers and has 50 ma of output current. To get the extra output current (the LME49811 has 7ma) an A/B output stage was added to that part (the 811 has a class A output stage). There were also some minor changes made to the input stage on the LME49811 (one was a suggestion by Bob Pease which is a great story I might tell everyone sometime). I prefer the sound of the LME49811 to the 810 (I did listen to both parts on the same circuit board with minor changes) but they are very close to each other. If you need more than 300w I would use the 810. For 300w or less the 811 is the way to go.

Mark / Audioman54 or 55 depending on which addr they let me on with?
 
Hi Mark,

I was laid off from HP a couple of months ago here in the valley as well. 2000 of us were the first wave of over 30,000. Everyone in my group was over 43, except for one person. The average age was close to 50.

On a brighter topic.... These opamps look very interesting. I ordered a handful of LME49720's to play around with as unity gain buffers and perhaps I/V converters.

We should get together sometime for lunch, since we are both in the valley and looking.

-David
 
Hi Mark - sorry to hear that you are on the street and hope that maybe someone here can provide you with some contact info. What I would be interested in finding out is - - - What do (or were) you using for speakers that would allow you to hear the difference between these devices? That has to be some kind of super speaker!!! :bigeyes:

Next question - got any ideas on a DIY version! :D :D :D
 

audioman54

Member
2008-06-18 2:58 am
To answer the last two posts...

300 people were laid off from National in November and I was part of that. Our great economy is part of the problem and also since I am over 50 my days were numbered. We are not all just leaving...we are being asked to leave, along with a lot of other engineers in the valley from other companies too!

and...
The LME49810 was designed as higher output current driver for live music amplifiers and has 50 ma of output current. To get the extra output current (the LME49811 has 7ma) an A/B output stage was added to that part (the 811 has a class A output stage). There were also some minor changes made to the input stage on the LME49811 (one was a suggestion by Bob Pease which is a great story I might tell everyone sometime). I prefer the sound of the LME49811 to the 810 (I did listen to both parts on the same circuit board with minor changes) but they are very close to each other. If you need more than 300w I would use the 810. For 300w or less the 811 is the way to go.

Mark / Audioman54
 
c2cthomas said:
What do (or were) you using for speakers that would allow you to hear the difference between these devices? That has to be some kind of super speaker!!! :bigeyes:


I can offer an assist here. The National sound room has authentic (not "clones") Wilson Watt Puppies and B&W 800 (?) series speakers. For the signal amps, Mark also uses high end Grado Headphones.
 

audioman54

Member
2008-06-18 2:58 am
Benchtester,

Thanks for covering for me! National's Watt Puppies were model 7's and we also had a set of b&W 802D's as well.

They were all driven by a set of LME49811 power amps I designed (and benchtester and I built together) and a D/A preamp I also designed. You can search National Semiconductor Sound Room / for more info on the room (and me)...

or here are a few web references on the National Room and other LME parts info.

http://electronicdesign.com/Articles/ArticleID/16804/16804.html
or
http://www.edn.com/blog/1700000170/post/790011279.html?q=LME49860
or
http://www.eetimes.com/news/semi/showArticle.jhtml?articleID=202401094

Too bad I can't use the room anymore. Although right now I miss the AP2/192 more! Anyone know where I can find a used AP2 Cascade 192 for a reasonable price? Of course even at a reasonable price being out of work means I probably can't afford it!

Looks like they posted my replies under both names. I am going to stick with audioman54 from now on.

c2cThomas,

Do you want a DIY Speaker design? If so maybe Dave Wilson can help us all with that!

hifimaker,

Sounds good! HP was right up the street from National and I drove by it every day for 10 years. Now there are a lot of us in the valley on extended vacation right now!...and most of us are over 50!

Thanks everyone,

Mark / audioman54
 
benchtester said:

I can offer an assist here. The National sound room has authentic (not "clones") Wilson Watt Puppies and B&W 800 (?) series speakers. For the signal amps, Mark also uses high end Grado Headphones.


Hi benchtester - thanks for the info. Those babies are juuust a few grand out of my budget. :bawling:
Guess I'll keep working on my OB project using ESS AMT1's with a Fostex 107's for mid's and some Eminence Alpha 15 woofers.

Hey - I was 53 when the door hit my rear end. This allowed me the privilege to obtain a nice title at a company that I sank a lot of $$$ into. That one was Ok - I waked away ahead of the game. The second try - well that one still owes me! :dead:

It's a beach trying to get good employment after 50. I don't give a hoot what people say about age discrimination - it's here - and it's real. Bottom line - the young guns will do your job for half the pay - and if they are working overseas they'll do it for 10% of your pay.
 
Re: Lme49713

audioman54 said:
Hi Everyone,

I have designed a D/A box that used both parts. The LME49713 and LME49710. However I was laid off two months ago and I did not have enough time to publish the circuits.

To answer the questions though the LME49713 CFB is a slightly better sounding part than the LME49710 VFB but they are both better than any other opamp on the market at this time. The THD+N spec of 0.00005% or so is REAL! But the process the parts were built on and the engineer who designed them is what sets them apart. (I specified the LME49713) These will be the reference opamps for audio for many years to come...and this is coming from someone who is out of work because of National and wondering where I will end up?

In my D/A design I use the metal can LME49713's in most places but I do use the LME49710 metal can in one place where VFB opamps work better than CFB ones. By the way the metal can parts sound better than the dip parts but measure the same on the AP2 Cascade (192).

Best Regards Everyone... and if anyone knows an analog/audio company that needs a semiconductor audio applications / audio equipment design engineer please let me know.

Mark / Audioman54 at yahoo dot com


Hey Mark,

This is a bigtime bummer to hear. You helped put National back at the top of the heap in high-quality audio, both from a technical point of view and a credibility point of view. It has never been easy to get big semiconductor houses to take high-quality audio seriously. National was also very wise to have experienced high-end audio people like yourself involved in their efforts. I hope that these parts are selling well so that National will realize that there is a worthwhile market for such high quality devices. I'm really sorry to hear about the layoff.

BTW, I expect to be out at ISSCC in February.

Send me an email when you have a chance.

Best,
Bob
 
Audioman54

With your references you will not stay long unemployed.!

May I take the ( sad) opportunity to ask some questions I have on the LME serie.

First when you mention that the lme49811 is better sounding that the LME49810, was it with the same ouput power stage and bjt or mos ?

It looks to me that the lme49811 is more or less the mono version of the 4702.
Reading the specs, the LME49811 and 49810 are very close with one exception: the open loop dominant pole is larger for the 49811/4702 than the 49810 Is this the reason of sound difference?

Is the baker clamp usefull from a sound quality point of view?

In the system I am designing ( 10 amplifiers to be used in the Orion Linkwitz speaker), the amplifers are monitored by a pic controller. The dc on ouput, fsoa and short circuit detect are monitored by the pic that will shutdown the chip. Can we consider the mute input on the LME49810 as having the same performances as the shutdown pin in the LME489811 for this use.
In other words can we use the mute input as an efficient shutdown to be used as output protection in case of short circuit.

In the application note you wrote on the use of the 4702, you mentionned the bad effect of the input coupling capacitor, is this a major effect or a subtle one?

Can you describe the output stage of the LME 49811, the one of the LME49810 has been given. As I understand, it is the same as the 4702, a VAS stage current source loaded.
I am using the LME49810 with a T ouput stage triple ( Locanthi/Leach). I use the output stage of the LME49810 as first driver of the triple with thermaltracks as ouput. Do you think that it would be worth to use the LME49811 instead and use a discrete out of chip first driver stage.
As a side comment, it is a pitty that two ouput diodes where included on the chip to compensate for the vbe drops of the ouput buffer. Without them, we would have more headroom in the design of the Vbe multiplier. multiplication factor. This is important if we use the thermaltracks and if we intend to adjust the thermal tracking of the diodes.

A last and very important question: is the output current seen on the bias pins very stable in operation such that the biasing can be done with a potentiometer and diodes without Vbe multiplier.
Do you expect some degradation by bringing the Vas collector signal far away from the chip in the diodes of the thermatrack transistors. Will a shunting capacitor help there?

A lot of questions sorry, but thanks in advance for your comments


JPV