# 110 Ohm wire

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#### Thunau

Does paralelling of two or more 110Ohm wires preserve the characteristic impedance?

#### Jocko Homo

Nope. Divide by the number in parallel.

Jocko

#### Thunau

Thanks Jocko.
It's a bit counterintuitive since adding lenght doesn't change the characteristic impedance, but doubling up does.

But, I'm not doubting that you are correct.

Would you know of a 110-130 Ohm speaker wire?

#### Jocko Homo

That is the beauty of a transmission line..........its impedance does not change as it gets longer.

Actually, you will be hard pressed to find something that acts like a transmission line below 200 kHz or so. Long story why. But...........

The guys at Sumiko used to sell something called OCOS which was supposed to act like one at audio. It was a coax that had the dielectric doped with a conductive substance. Around 400 ohms between center and shield. Impedance was probably low, since it was a coax.

OK..........so why would you want a speaker cable in that range? Low capacitance? Any twisted pair will be close.

Jocko

#### Guido Tent

Jocko Homo said:

Actually, you will be hard pressed to find something that acts like a transmission line below 200 kHz or so. Long story why.
Jocko

short story: long wire.....

#### Jocko Homo

Yes, a long wire, but even that is pushing the lower limits. A lot of math mubo-jumbo comes into play when trying to find the lower limit for a transmission line.

So short story: forget it below 1 MHz or so. Your life will be simpler.

Jocko

#### Thunau

Jocko Homo said:
That is the beauty of a transmission line..........its impedance does not change as it gets longer.

Actually, you will be hard pressed to find something that acts like a transmission line below 200 kHz or so. Long story why. But...........

The guys at Sumiko used to sell something called OCOS which was supposed to act like one at audio. It was a coax that had the dielectric doped with a conductive substance. Around 400 ohms between center and shield. Impedance was probably low, since it was a coax.

OK..........so why would you want a speaker cable in that range? Low capacitance? Any twisted pair will be close.

Jocko

Doing a project with a Sonic Impact amp, AKG K-1000 headphones, impedance matching transformer (8 Ohm primary, 100 Ohm secondary), frequency shaping network with 4 tilt positions and an old fashion bridged "T" adjustable attenuator on the same 4 position switch. I wanted to keep the impedance as flat as possible throughout the circuit and thought that using a 120 Ohm wire would help the cause. The headphones are nominal 130 Ohm.
I guess the wire will not matter all that much, but it would be cool to see if it made a difference.

#### wa2ise

Thunau said:

I wanted to keep the impedance as flat as possible throughout the circuit and thought that using a 120 Ohm wire would help the cause. The headphones are nominal 130 Ohm.
I guess the wire will not matter all that much, but it would be cool to see if it made a difference.

Get some CAT 5 cable from the IT computer guys. If I recall correctly, each twisted pair is about 110 ohms impedance.

Or use some lamp cord, aka zip cord. Many years ago, the American Radio Relay League (ARRL, an amateur radio orginization) ran some impedance tests on zip power cord, and found that its impedance was about 100 ohms balanced. Zip cord would offer less resistance than CAT 5 anyway.

Or if you wanted 100 ohm coax cable, get some RG62. Computer IT people used to use this stuff.

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