What reason for curly telephone like wire in some amps ...

[Phil Harmoneeek]

Within some gut shots of certain amps there is occasionally wire that looks like the curly telephone handset wire ... what is the purpose of winding it that way, instead of just going straight to the next connection ... inquiring mind(s) want to know.

Thanks Randall

[BenH]

I guess your talking about the twisted pairs of wire that carry the A.C. current to the heaters of the tubes. This is done so that two phases of the hum emitted from the wires cancel each other out. It is also best to keep these wires away from other signal carring wires by either raising them up out of the way, or pressing them down into to corners of the chassie.
Other wires that benefit from the same treatment would be all the A.C comming from the trafo. Also the the signal from the outputtransformer to the power tubes in some cases where lead dress is an issue, as with the wires to the speaker jack.

[mbratch]

I'm thinking he means the ground wire helixed/spiraled around the outside of other signal wires in the 70s Fender amps. I believe it forms a noise shield effect.

[donnyjaguar]

Both correct. Also the filament leads are generally run as perpendicular to the audio and DC carrying wires as possible to reduce hum. Still, sometimes its not enough and the amplifier will have a hum balance control to fine-tune out the hum. This is generally the case for preamplifiers as you seldom see it in power amplifiers due to the higher signal levels. DC filaments eliminate this requirement often seen on more boutique designs.

[Phil Harmoneeek]

I'm thinking he means the ground wire helixed/spiraled around the outside of other signal wires in the 70s Fender amps. I believe it forms a noise shield effect.

Ya ... this is what I was refering to, however I didn't know that there was a wire running through it & it was for shielding (do you ground out each end of the spiraled wire or ...), why is it done on certain amps, is it just for a specific design or can other paths benefit from this ... ?

Thanks Randall

[mbratch]

Ya ... this is what I was refering to, however I didn't know that there was a wire running through it & it was for shielding (do you ground out each end of the spiraled wire or ...), why is it done on certain amps, is it just for a specific design or can other paths benefit from this ... ?I'll have to double check my 70's Fender, but I believe just one end is grounded, which makes sense if it's a shield. Fender didn't do this in their older amps. I suppose at some point their engineers decided that this was a potential source of noise and made the change.

[Tone_Terrific]

Both ends gnd on the Pro Rvb I have, here.