Twists per inch on filament wiring?

[G]

Is there a recommended number of twists per inch on filament wiiring to prevent hum? Thanks.

 

[dhaen]

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).

 

[Sch3mat1c]

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...

Tim

 

[fdegrove]

Hi,

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?

Cheers,

 

[G]

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.

 

[fdegrove]

Hi,

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.

Cheers,

 

[Sch3mat1c]

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...

Tim

 

[fdegrove]

Hi,

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?

hence the sarcasticalism...

And you did consider how that neologism was going to come across....

Cheers,

 

[Guido Tent]

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

regards

 

[EC8010]

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.

 

[Guido Tent]

Re: 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.

If capacitive coupling is inducing the hum, I'd suggest a screen, much easier to apply

Mostly it is inductive coupling

Ciao

 

[EC8010]

It's both, but you don't need much of a twist to cancel the magnetic field. Screening heater wiring is possible, but tends to be fiddly. To keep this in perspective, the classic valve manufacturers managed to make RIAA pre-amplifiers with tolerable hum using AC on their heaters.

 

[Guido Tent]

It's both, but you don't need much of a twist to cancel the magnetic field. Screening heater wiring is possible, but tends to be fiddly. To keep this in perspective, the classic valve manufacturers managed to make RIAA pre-amplifiers with tolerable hum using AC on their heaters.

Hi EC8010,

The dominant coupling mechanism depends on both source and receiving impedance.

Perspective is correct, but to make it a little more quiet.....

Once had capacitive coupling from anodes of rectifier tube. Rotated that until coupling was balanced