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Resistors


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4/25/2000 8:52 PM
SA
Resistors
What is the difference in metal oxide and metal film resistors. Whaich one is more preferrable to use in amp building.  
Thanks, SA
 
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4/25/2000 9:41 PM
Carl Z

SA;  
 
Man, you're opening a can of worms on this one! Go over to Randall Aiken's site and read up on the differences between the two. It's a good informative article! The jist of it is that metal films are quietest followed by metal oxide.  
 
There's a thing or two that isn't mentioned there that might come into play. First, high voltage ratings on metal films are a mutha to get hold of! 350 volt stuff is the norm and 500 volt resistors are typically special order. 5% 500 volt metal oxides are much easier to get hold of so that's a consideration.  
 
Second thing is that the reason these are getting used is primarily for noise reduction and component accuracy. Carbon comp resistors are very noisy and drift like crazy! Lose them at all cost!  
 
In the case of noise going from carbon comp to carbon film is a big reduction. Then from carbon film to metal will yeild a reduction but it isn't an obvious sort of change. Between metal film and metal oxide there's not going to be much difference at all. You'll be hard pressed to hear it!  
 
 
So, with the consideration of all the above, as well as the idea of diminishing returns, here's what I'd recommend. 1 watt metal oxide 5% on the plates. 5% accuracy is jut fine here, but you may stumble across some 2% resistors which may be about the same price. Use 1/2 watt 1% metal films on all the grid and cathodes.
 
4/25/2000 9:57 PM
SA

I was just curious and did read the article over on the Aiken site after i posted. Very informative.  
Thanks , SA
 

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