tapped cathode resistor for partial bypassing.

Magnet wire resistors, enough to make any engineer scream.
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dave slagle
Posts: 2022
Joined: Sat Jan 22, 2005 3:54 am
Location: NYC

tapped cathode resistor for partial bypassing.

Post by dave slagle »

had a request for a tapped cathode resistor for partial bypassing of the cathode. I decided to wind them as two discret resistors on a common teflon tube and they were to be 260 and 20 ohms for a total Rk of 280R which 260R will be bypassed with a cap.

the 20C resistances were about 246 and 19 ohms to account for temp rise and as an added "bonus" i added a third resistor wound with Alloy 60 resistance wire. Alloy 60 is a non-magnetic copper nickel alloy with 6X the resistance of copper. The alloy 60 winding consists of 2- 20R bifilar wires so depending on hookup, you can get 10, 20, and 40 ohms. the wires are spirally wound to limit inductance for the 10 and 20 ohm connections and there is less than 1/10th an ohm impedance difference from 100-10Khz. Since they are not bypassed, the listening tests comparing the 20R copper winding to the 20 ohm alloy 60 winding should be interesting, and the 10, 20, and 40 ohm possibilities should be interesting also. The 20 ohm copper winding will also give 10 and 5 ohm options to add to the possibilities.

i have been promising to use some of the alloy 60 wire to do some resistors with and a recent asylum post pushed me over the edge. It seems ohmite are making audiophile resistors with a nickel copper alloy.

my gut feel is the addition of the nickel will make things sound worse, but seems to greatly increase the temperature stability (TCR) If the difference between alloy 60 and copper is small, maybe alloy 30 (3X the resistance of copper) would be a good compromise.

http://www.audioasylum.com/forums/tubed ... 79764.html

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