2 conductor, shielded cable for heaters?

[hesamadman]

2 conductor, shielded cable for heaters?

anyone ever done this?

[sluckey]

I did. Once.

[hesamadman]

I did. Once.

What are your thoughts? Did it work well?

[sluckey]

Works fine. Too much trouble for no benefit. I thought it would look neat, but it really looks messier that a simple twisted filament string.

[kagliostro]

My opinion (and as said is only my opinion) is that the problem of emission of heater wires is a magnetic field due to the high current

not other kind of emission,
 
twisting wires we discourage this magnetic field going far from conductors

I don't see a good shield for magnetic field in aluminium, copper or brass

the only good shield is iron (of course Mu-metal is the top, but not easy to have)

so I don't believe that a copper mesh or aluminium foil can be a good shield for EMI

and I think that if you want to shield heater wires you must use a small pipe made by thin iron foil

no standard shielded cable is usable with high benefits to me

much better to twist and route properly heater wires

K

[EL34]

The thing that cancels the hum is the twisted pair, not shielding


You get a better twisted pair from 20 gauge solid core wire

[PRR]

> use a small pipe made by thin iron foil

Thick iron.

Or thin mu-metal.

However when directly against high-current wires, either material will *saturate*. Then it is no better than air, and a lot more work.

Conductive (copper etc) shielding "should" help some. But I don't think I have ever seen it done. Sluckey says he did, and I trust his "not worth it" opinion.

Twisted up-to-the-pins balanced AC has always been "good enough" for regular guitar amps.

Super high-gain, like mike amps, limiters, and the very-best head-banger amps, must turn to DC heat.

Also most PCB amps "should" use DC (can't twist on PCB).

[hesamadman]

> use a small pipe made by thin iron foil

Thick iron.

Or thin mu-metal.

However when directly against high-current wires, either material will *saturate*. Then it is no better than air, and a lot more work.

Conductive (copper etc) shielding "should" help some. But I don't think I have ever seen it done. Sluckey says he did, and I trust his "not worth it" opinion.

Twisted up-to-the-pins balanced AC has always been "good enough" for regular guitar amps.

Super high-gain, like mike amps, limiters, and the very-best head-banger amps, must turn to DC heat.

Also most PCB amps "should" use DC (can't twist on PCB).

What do those guys use to get their DC power for filaments?

[Merlin]

My opinion (and as said is only my opinion) is that the problem of emission of heater wires is a magnetic field due to the high current

Most common forms of heater hum are caused by the electric field rather than the magentic field. Unfortunately, most of the electric coupling takes place *inside* the valve, so shielded cable cannot help this very much. 

[jojokeo]

much better to twist and route properly heater wires

The thing that cancels the hum is the twisted pair, not shielding
You get a better twisted pair from 20 gauge solid core wire

Twisted up-to-the-pins balanced AC has always been "good enough" for regular guitar amps.

Yep, this is about as crammed as it gets with four cascaded gain stages and no hum, interference, or parasitic oscillation what so ever. (drgonzonm you link doesn't work)

[shooter]

What do those guys use to get their DC power for filaments?
[/quote]

I've done 2 dc filament builds in preamp sections, I use a 12vac 2A tranny, bridge, about 2200 to 4700uf into a heatsinked 12volt 1.5a regulator, same cap size out, plus a .01uf downstream.  both had 4 12....7s