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Old 20th December 2003, 05:28 PM   #1
G is offline G  United States
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Default Twists per inch on filament wiring?

Is there a recommended number of twists per inch on filament wiiring to prevent hum? Thanks.
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Old 20th December 2003, 06:28 PM   #2
dhaen is offline dhaen  Europe
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A lot more twists are required to hold the wires together, than to hum cancel.
Have a look at the manufacturers twist in a network cable or balanced audio cable - maybe between 1 to 4 per inch! Doing more shouldn't hurt.

Don't forget that by placing the wires in thermal contact, the current rating of the wire is practically halved (for a given temperature rise).
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Old 20th December 2003, 11:39 PM   #3
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For optimum smoothness, it must be twisted exactly 162 crossings to the inch, using flat sheet type tantalum-plated silver-impregnated superconductors, wound edge-on. This assures maximum cancellation of the DC field (you're using DC heaters right? Anything else makes the sound stage ricketey as an 1860s theatre).



I could do better but I don't feel like taking the time right now...

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Old 21st December 2003, 12:23 AM   #4
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Hi,

Quote:
This assures maximum cancellation of the DC field (you're using DC heaters right? Anything else makes the sound stage ricketey as an 1860s theatre).
Weekends are just not his thing...Dunno why.

The other days of the week it's just an attitude almost as bad as mine...

DC fields...What's next?

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Old 21st December 2003, 12:27 AM   #5
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No I'm using AC heaters and I was just curious. The sarcasm is not appreciated. I don't think that it is out of the realm of possibility that more or less twists per inch would have different levels of success at cancelling 60 cycle hum.
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Old 21st December 2003, 12:34 AM   #6
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Hi,

Quote:
I don't think that it is out of the realm of possibility that more or less twists per inch would have different levels of success at cancelling 60 cycle hum.
It's not so much the number of twists that cancel the hum but I'll garantee you that it works just as it works for a twisted pair.

Just ignore the crackheads...

D'haen gave you what you need to know so go for it.

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Old 21st December 2003, 04:48 AM   #7
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Quote:
Originally posted by fdegrove
Just ignore the crackheads...
Hey, that's mine and Mark's word for you...

Ok, fine, a serious answer: yes, the field should cancel quite nicely even for plain parallel runs. But the problem would then be, for instance, capacitance coupling to nearby wires which average being closer to one wire than the other: twisting balances this statistic. So just a few twists will work. Also the wire should be near the chassis, so that the field is mostly grounded away.

Frank, you sound like DC fields don't exist... what are magnets and electromagnets? Of course, they don't make any difference to non-moving wires, hence the sarcasticalism...

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Old 21st December 2003, 05:29 AM   #8
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Hi,

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Frank, you sound like DC fields don't exist...
No, it's just that I read the threadstarter's question....

D.C. Fields? Yes, still playing with model trains are we?

Quote:
hence the sarcasticalism...
And you did consider how that neologism was going to come across....

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Old 22nd December 2003, 08:59 AM   #9
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Default Re: Twists per inch on filament wiring?

Quote:
Originally posted by G
Is there a recommended number of twists per inch on filament wiiring to prevent hum? Thanks.

Hi,

I'd suggest to twist such that the wires cross at 90 degrees

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Old 22nd December 2003, 03:16 PM   #10
EC8010 is offline EC8010  United Kingdom
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Default The more the merrier

As Sch3mat1c says, it's all about having the same capacitance from each heater wire to a given audio point. An infinite number of twists per inch would guarantee equal capacitances, and provided that the heater wiring was perfectly centre-tapped to earth, would produce zero hum. Since more twists per inch doesn't cost money, I use as many as I can. Solid core wire is much easier to twist tightly. Push it tight into the corners of the chassis, and bring it up to the valve at the last moment.
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