Whats the deal with non inductive ww resistors?

[Eric]

OK, now I'm experience enough in the field of audio to know that things don't always sound like they measure, nor do the measure like they sound...

With that in mind, I recently received some Mills non-inductive wire wound resistors. Out of curiosity, I compared their inductance to standard sand-cast white rectangular wire wound resistors that I got from Radio Shack for a fraction of the price. The result is that BOTH have EXACTLY THE SAME inductance (3.4 uH) What gives? Are the ones from Radio Shack secretly non-inductive, or are the ones from Mills really NOT non-inductive?

Just seemed sorta strange to me

 

[joeblutz]

Are you measuring the inductance of your test leads? Straight wire should yield about 0.02 uH per inch. Depending upon the diameter of the loop you form between the bridge and the resistor, your results will be somewhat higher.

LOL

Joe

 

[harvardian]

Hi,

I measured my Mills resistors versus sandcast with a LCR bridge and found that the Mills were indeed lower. Don't remember exact values, but it was significant.

Dale

 

[peranders]

Non-inductive ww restors doesn't exist but bifilar (bifilärt in swedish, not sure the english word) wounded resistors have less inductance than a regaular one wich is a coil. If you are after power resistors with good HF-properties, check the one from Caddock, very expensive but also really good.

BTW: 3.4 µH is rather much. Compare with a regular coil in a output filter for power amps. 10 mm diam and 15-20 turns = 0,5-1 µH.

If you shall use the resistors as emitter resistances you should have as low inductance as possible.

 

[Eric]

I am planning to use these resistors on the emitters of my a40 amp.

Joe: I suppose the leads could have contributed to the inductance - they are 3 inches long, but I used the leads when measuring both types of resistors, so the additive inductance would be the same in both cases.

I had just assumed the Mills 5w resistors would be very different from the Radio Shack ones and was surprised to find no difference in measurement.