National LME49713 CFB Audio Op Amp

GroupDIY Audio Forum

Help Support GroupDIY Audio Forum:

This site may earn a commission from merchant affiliate links, including eBay, Amazon, and others.

bcarso

Well-known member
Joined
Feb 20, 2005
Messages
4,055
Location
San Fernando Valley, Los Angeles
Looks interesting. I wonder about the output current capability with that package (note that dissipation is internally limited). The current noise is high, in keeping with rich bias on the input bipolars, which makes it questionable somewhat for one of their listed apps, phono preamps (at least MM, and the voltage noise is not SOTA for MC).

Also, I can't reconcile their FFT data with the stated quad nought eight (0.8 ppm) distortion claim: look at the first graph, with 2nd at -108dB and 3rd at -107dB. But maybe those are really dBu and not dBr (perverse if so). Even if dBu that's more than 4uV against the stated 3V rms.

But, undoubtedly could be a useful part. CF amps are tricky to use but can be fun. At least no one is going to complain about slew rate limiting for audio.

National is taking audio quite seriously these days. I just read an article in which Don Tuite went to their listening room and talked with an audio app guy, and was impressed that he could hear how high quality the system was. He had anticipated that with his old impaired ears he'd be unable to discern quality differences. They did have some fancy Wilson Audio speakers in the setup, which featured signal chains full of the new NS chips. They stated that their aim was to finally get all of the discrete part electronics holdouts to move to their ICs. Good luck.
 
I just noticed that some of the other graphs have appreciably better distortion performance, at 4V rms. Maybe the first few are wrong.

I doubt we will see those parts in DIP or TO-99, because of lead inductance issues.
 
Maybe the first few are wrong.
I wouldn't be surprised, some of the positive PSRR graphs in the LME49860 datasheet look wrong as well. BTW, I've measured this opamp (the LME49860) and it's not as good as one might think from reading the numbers shown. It's a clear progress over the NE5532, about as good as a LT1469 but still behind the AD797.

Samuel
 
Distortion is relatively sensitive to loading, with an indication of thermal effects as there is a slight increase below 100 Hz, and more of that with heavier loading. But the real issue is the CM performance with almost an order of magnitude increased distortion down to 10 Hz (and not just at the upper end of the audio range as with most opamps).

For the price it's probably the best you can get (though I haven't checked that price range carefully), but just not the best at any cost as I've felt it has been advertised and hyped in the forums.

Samuel
 

Latest posts

Back
Top