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odysseybmx414 10th December 2005 03:59 PM

paralleling chips
ok maybe this is a stupid question or maybe not

ive always wondered why each chip has to have its own parts and why you cant just put one chip on top of the other(connect the inverting input to the other chips inverting input etc instead of having to use 2X as many resistors etc. if anybody has an answer to this please let me know as im very curious. i have never tried this before as in i have no speakers i am willing to blow to test this. but if anybody tried it let me know the results.


tiltedhalo 10th December 2005 05:18 PM

paralleling chips??
Let me get this straight, you mean paralleling the chips and useing a global feed back loop for all parallel chips, same with input net works and output also???

tiltedhalo 10th December 2005 05:22 PM

parralleing chips
Sorry didnt read the post close enough! these chip are not unity gain stable, boostrapping wont work

odysseybmx414 10th December 2005 06:16 PM

opa549 is unity gain stable so would it work

and jus to make sure what i mean i mean just connecting all the pins from one chip directly to the other chip and just using one fb, input resistor, etc.

tool49 10th December 2005 06:39 PM

Due to difference in chips, doing so would cause imbalance. You would to the very least need to have a current sharing method to insure that they're all working to the same degree.

Hope this helps!

odysseybmx414 10th December 2005 07:30 PM

ive decided im going to try it with 2 opa549's i will repost later

tiltedhalo 10th December 2005 11:26 PM

paralleling chips
Holy chip, it works! I tried it with two LM3875,S I had laying around. Split the input with 2 1K resistors and 1 22K to ground used a common feed back loop with a 22.1K .1%, 47uf tantalum cap, and a 1k .1% to ground fed the outputs to two .15 ohm 1% soldered directly two the pins and took the feedback of the combination of outputs. Might have to take a closer look at this! I got the least amount of DC offset of any chip amp Ive made!! :bigeyes:

troystg 10th December 2005 11:38 PM


Picture please.....

neutron7 11th December 2005 01:20 AM

i know you can do it with BUF634 for headphone amps etc.

tiltedhalo can you try it without the tantalum cap? lots of GCs dont use a cap in the feedback.

tiltedhalo 11th December 2005 03:44 AM

cap removal
The tantalum should not be removed for DC offset, you also need current resistors, but you can use a common feed back network. I would post pics but my wife is out of town and has the digital camera.
I had this strange idea of potting the hole thing in epoxy and soldering the chip to a piece of copper and basically building a parallel module:xeye:

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