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Help! Parallel 2x 3875 per channel design - please advise.
Help! Parallel 2x 3875 per channel design - please advise.
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Old 17th March 2004, 08:24 PM   #21
azira is offline azira  United States
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Originally posted by Rudy
maybe so, but have you actually tried it, i think not ...
Yeah, actually I have. I use 5% resistors 'cause they are availible at radioshack in kit packs and don't cost $200 for a kit. They can measure similarly but only because you've got a <3% margin that they are going to fall into.


I measured some resistors on a tape, infact, many values on many tapes, and whilst the ones next to each other were often the same as measured by my cheap DMM, there is always a point (maybe after 2, 5, or 8 in a row) where they will measure different. So if my meter measures consistently, it shows just taking them off a tape does not gurantee they'll be the same

(these were all 1% tol. metal film 1/4w)
The problem with this is that your cheap DMM isn't able to get a good measurement better than 3 significant figures and you've already got the values nailed down to 3 sig figs. So, of course you're going to see a lot of "matches" which could be up to .5% off. Which in my book is great but not for this application.
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Old 17th March 2004, 10:20 PM   #22
SimontY is offline SimontY  United Kingdom
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Originally posted by azira

Which in my book is great but not for this application.
Sadly, I wasn't offering a solution! Just saying that if a cheap DMM can consistently measure one resistor as different from another, you can't assume two next to each other on a tape reel will be a close match.
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Old 17th March 2004, 10:33 PM   #23
BrianGT is offline BrianGT  United States
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I have a reel of 1% metal film resistors sitting here, and while the resistors aren't 0.1% of the intended value, they are generally less than 0.1% of each other, for the random samples that I took, sequentially on the reel. My resistors in the 5% reel are also quite close to each other.

I am using a fairly accurate fluke multimeter.

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Old 3rd April 2004, 10:08 PM   #24
metha is offline metha  Thailand
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Default Parallel LM3875 for AV system

I've got may spare LM2875 it might be good to use them for a high power amp for AV system.

After reading & apply all comments above in condition that using all 1% res, how about this one?
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