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-   -   no spike protection allowed (http://www.diyaudio.com/forums/chip-amps/101737-no-spike-protection-allowed.html)

tryonziess 11th May 2007 04:58 PM

no spike protection allowed
 
is there a good quality high powered chip amp without internal spike protection which i could use in a 250 watt output project.

drummer_Dave 11th May 2007 05:29 PM

I'm not trying to be rude or anything, but what is your reasoning for not wanting spike protection? you could use several lm3886 or lm4780 in bridge and or series configurations to get up to your power requirements, but they still have spike protection. I am very interested to find out what you are planning here.

here's a link to a very nice project

http://www.diyaudio.com/forums/showt...threadid=90864

good luck

jackinnj 11th May 2007 06:47 PM

OPA549 from Texas Instruments -- bridge two of these -- note that most chipamps have some kind of current protection -- amplifier chips want good heatsinking.

you could also use an LM4702 and parallel some HexFETs -- but you need to get the bias up to a couple of volts (or use Lateral MOSFETs) -- somewhere I posted a schematic from an article that Borbely wrote up for audio amateur.

BWRX 11th May 2007 07:07 PM

Quote:

Originally posted by drummer_Dave
here's a link to a very nice project

http://www.diyaudio.com/forums/showt...threadid=90864

It has potential to be a nice project. There were a lot of problems with the first design posted by DJexprice.

tryonziess 12th May 2007 09:24 PM

why no spike
 
i have noticed fluctuations on the scope when certain low frequency music is playing are similar to the fluctuations when the 3886 is clipping. i just wanted to rule out the possibility that spike might be coming on when it is not needed to protect the chip. i do not know enough about this subject to explain this phenomenon other than trial and error. substituting and observing are my best methods at this time

jackinnj 13th May 2007 01:33 PM

Re: why no spike
 
Quote:

Originally posted by tryonziess
i have noticed fluctuations on the scope when certain low frequency music is playing are similar to the fluctuations when the 3886 is clipping. i just wanted to rule out the possibility that spike might be coming on when it is not needed to protect the chip. i do not know enough about this subject to explain this phenomenon other than trial and error. substituting and observing are my best methods at this time
What was the thermal impedance of the heat sink you were using? (or can you give us an idea of its approximate surface area).

tryonziess 13th May 2007 05:52 PM

the area of copper was 5x12 inches 1/2 inch thick with 11 5x1 fins. the sink temperature never reached 100 f. the only fluctuations occured at roughly 80hz and below into a 12 inch woofer. actual volume was quite "loud". no more specifics since i would not no what to look for. i am only following a hunch that spike might be a little hasty in its activation. it could be something else, but i have good clean response until these parameters come together. this is a new endeavor and i am learning as i go.


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