Odd question about heater wires...

[AmberB]

I'm currently working on building an amp that will be much like a Princeton in configuration.  I added a midrange control to the tone section, but that's not part of my questions about the heater wiring...

First question, has anyone tried using a shielded pair of wires for the heaters?  Due to the odd layout in my long narrow chassis, I have a fairly long run from the power tube heaters to the preamp tube heaters, and I have to run the heater wires through some of the preamp circuits.  I'm going to ground the shield at one end like you would with the shielded wire  from the input to the first stage.  The wires in the shielded pair are stranded and large enough gauge to carry the heater current.

Second question, with a cathode biased push pull pair of 6V6s, is there any reason I shouldn't use the cathode connection to raise the heaters above ground like you would with a single ended amp?

Both of these are things I've not tried before.

[Ronquest]

I have to run the heater wires through some of the preamp circuits.

How are you doing this differently than any one else? 
I've thought of shielded cable for heaters, but never implemented it, then again I think about a lot of things.   I just go elevated or straight DC heaters if needed.  I doubt you need to worry about it with a modest gain amp like a Princeton.  You can float your heaters from your cathode resistor.   Sometimes I find better hum rejection by changing preamp tubes and balanced power tubes.

[pdf64]

...a shielded pair of wires for the heaters?  ...

Unless you can get shielded cable that uses ferromagnetic material for the shielding, it would be of no benefit in reducing the magnetic field.
Shielded cable works for electric fields.
Just twist the wires and leave some clearance between them and any conductor / component carrying the audio signal.


Elevating the heaters is a good idea, dunno why Fender never used it. There's no distinction in SE or PP in regard of it.

[glass54]

Another thought, DO NOT run the heater wiring in parallel with Signal cable (esp input tube).
I think you'll get away with it  Look at some very early amplifier random point to point layouts in small spaces!
We'd love to see a gutshot (please).
Not sure about your mixing earths with Cathode Bias and elevated heaters. You could try it and let us know??
Kind regards
Mirek