what is the best metal/alloy for DIY wire resistors ?

[mikelm]

Having just discovered that constantan wire sounds seriously better than thick film resistors and is also much cheaper I am interested to find out what is the best choice of wire to make the very best wire resistors.

I have found this UK website that has a pretty good range

http://www.wires.co.uk/

does anyone have any specialist knowledge in this area ?

thanks

mike

[Sch3mat1c]

Seems to me scandium would work the best.

[mikelm]

OK - could enlighten us a little more - what is your reasoning for this choice

I get the feeling that scandium is probably horribly expensive

I was rather thinking of the best commonly available resistance wire.

thanks

mike

[wrenchone]

What sort of resistance range are you considering? For low value resistors I have used stuff like alloy 180, which is copper alloyed with a bit of nickel to bring its resistance up. It's not the most stable resistance alloy in terms of temperature coefficient, but it's very solderable.

[mikelm]

this sounds like a variation on constantan which so far I am very pleased with.

I can get 44swg @ 95 ohms / meter
and 33swg @ 10 ohms / meter

this gives be a practical range from 0.1 to 10 ohms using uninsulated wire and avoiding winding it into coils

If there is a wire that sounds good, can be soldered and goes to 1000 ohms / meter that would give me a nice range before I have to start buying expensive NI WW ready made resistors.

the only one I know about is nichrome. Is this commonly used in WW resistors ?

mike

[Sch3mat1c]

Originally posted by mikelm
I get the feeling that scandium is probably horribly expensive

[1audio]

The best wire for resistors if you are after accuracy would be Evenohm an alloy designed for ultrastable standard resistors. It has essentially no temperature co-efficient . I'm told that the wire is passing into history, the metalurgists that made it have all retired and the demand is very small. The NIST standards were made in the '20s and are still in use and accurate. This is a market that has really saturated.

The problem with copper alloys is a high temerature co-efficient meaning its restance changes a lot. And it changes pretty fast. This same phenomena is the primary cause of power compression in speakers.

I have done similar experiments with the same resistors and arrived at very different conclusions. Its unlikely that the Caddocks or Vishays are distorting but its possible that the resistance wire is complementing something in the speaker. Perhaps changing the value of the resistance wire to give the same sound as the suspect resistors will shed some light on what's happening.

-Demian