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Old 3rd November 2008, 12:05 PM   #1
Tolu is offline Tolu  Germany
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Question National opamp inflation

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?
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Old 3rd November 2008, 12:48 PM   #2
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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?
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Old 4th November 2008, 07:37 AM   #3
Tolu is offline Tolu  Germany
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My ear is my best measure instrument! I think the amount of zeros behind the comma will not only influence the sound.

Anyone tried the ADA4898-1? Nice distortion and DC offset!
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Old 8th January 2009, 03:46 AM   #4
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Default 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
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Old 8th January 2009, 12:22 PM   #5
tvicol is offline tvicol  Romania
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Mark,

Are you the engineer who designed these outstanding opamps (LME49710 / LME49713) ?

Regards,
Tibi
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Old 8th January 2009, 11:31 PM   #6
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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)
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Old 9th January 2009, 12:38 AM   #7
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Quote:
The chip designer who did design those parts to our team’s audio specs is now also "retired" in Japan.
Is there a problem? Why is everyone leaving the company?
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Old 9th January 2009, 12:47 AM   #8
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Default Re: Lme49713

Quote:
Originally posted by audioman54
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
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Old 9th January 2009, 12:52 AM   #9
lineup is offline lineup  Sweden
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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

Link to list with National Performance Audio opamps:
http://www.national.com/cat/index.cgi?i=i//305
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Old 9th January 2009, 01:34 AM   #10
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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?
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