Massively parallel LME49990 headamp

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#21
flux isnt good for you either, I would avoid deliberately using my finger with it. the problem with the frypan method is youve kinda gotta be standing there looking down at it. flux fumes can cause pulmonary problems over time and I reckon youde be getting a good dose doing it that way.

I use toaster oven reflow and paste, with arduino reflow controller
 
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#22
agdr said:
... Parallel op amps are the wrong thing for speakers. For headphones at least the load is more in the ballpark, if narrowed down to the 2/3-or-so of cans that don't have huge current or high(er) voltage requirements.
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A single high-performance opamp, with a discrete output-current booster, will suffice for just about any normal headphone load.

Check this topology and implementation out, which should work with the LME49990 (I simulated it with the LME49860, and actually built it with the venerable LM318M - it works fine in both cases):

http://www.diyaudio.com/forums/anal...-like-buffer-current-booster.html#post3582199
 
#23
linuxguru - I've been wondering if anyone had tried bolting a discrete buffer onto an LME49990! Nice looking circuit and layout. It would be really interesting to have that measured on an AP or dScope. One handy thing about chips end-to-end is their distortion and other AC parameters are all right there on the datasheet.
 
#24
agdr said:
It would be really interesting to have that measured on an AP or dScope. One handy thing about chips end-to-end is their distortion and other AC parameters are all right there on the datasheet.
Click to expand...

If you have access to test equipment, I can send you a few partially assembled boards for testing, for a nominal cost + shipping. I don't have the LME49990, but have everything else. You'll have to mount the LME (or any other single opamp worth testing) on the reverse, and solder the pins - both relatively easy. PM me to work out the details.
 
#25
linuxguru - unfortunately I don't have an AP or dScope. One of these days I may eventually get one though, I'm seeing more of the usefulness all the time. It would be really handy if some company out there with a dScope or AP would start offering a for-pay testing service to the DIY community! I'll bet they would get a lot of business.
 
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