Filament / heater wiring tech

[MakerDP]

I don't twist heater wires at all. More important than twisting is keeping any other signal wires crossing heater wires at 90 degree angles. Also keeping other wires above them.

See Soldano gut pics for great examples of what I'm talking about.

[CoffeeTones]

The Soldano uses DC referenced, elevated heaters. About 50V above ground. Do you do that along with the untwisted, equidistant heater wiring?

[MakerDP]

Yes... sorry I left that out... I always elevate my heater voltages.

There really is no reason not to whether you twist or not.

[pdf64]

I think that elevating the heaters deals with the heater 'signal' leaking through to the cathode.
Whereas heater lead dress (eg twisting) deals with reducing the radiated field from the (balanced) heater wiring.
And signal lead dress (eg cross at right angles, maintain clearance) deals with reducing the strength of the radiated field on signal wiring.

[dorrisant]

Do you supply your heaters with DC? If so, no reason to twist.

[CoffeeTones]

Not in this amp. If there is room left, I may do that. Do you have a schematic of a reliably quiet and compact DC heater setup? Here is one I have.

[CoffeeTones]

I think that elevating the heaters deals with the heater 'signal' leaking through to the cathode.
Whereas heater lead dress (eg twisting) deals with reducing the radiated field from the (balanced) heater wiring.
And signal lead dress (eg cross at right angles, maintain clearance) deals with reducing the strength of the radiated field on signal wiring.

I've not tested the theory, but have read that elevating the heaters will dull the tone a bit. I have an amp that has had elevated heaters for a long time. I plan to check that theory with that amp some day.

[dorrisant]

Not in this amp. If there is room left, I may do that. Do you have a schematic of a reliably quiet and compact DC heater setup? Here is one I have.

Looks like the schematic from an Epi SoCal 50... I used that before and it works great. The one I usually use is like the one seen in a Mesa DC3, very similar. It is pretty compact and can be done on a single strip board. I only use it for the last one or two tubes in the chain. You can see it in the middle of the second picture below.

[CoffeeTones]

LOL, it is from the SoCal 50. I still have a SoCal, but it is in pieces because I was going to build something else in the Chassis. That amp is heavy duty with lots peripheral features and a thick PCB. The signal path / circuit could be a bit better.

Thanks for the pictures.

[TUBEDUDE]

Elevating the heaters will not dull your tone.
If someone experienced that, I'd suspect a bad solder joint, or some kind of human error in the execution of the mod.

[pdf64]

Surely 6.3Vac when full wave rectified will give ~9Vdc?

[CoffeeTones]

Yes, unloaded. The load will pull that voltage down.

[dorrisant]

Surely 6.3Vac when full wave rectified will give ~9Vdc?

Some times I have put in a series resistor to get it down a bit.

LOL, it is from the SoCal 50. I still have a SoCal, but it is in pieces because I was going to build something else in the Chassis. That amp is heavy duty with lots peripheral features and a thick PCB. The signal path / circuit could be a bit better.

The piece of schematic you posted looks like a SoCal 50.... The picture I posted above is not... That is actually a Crate BV60 that I re-purposed as an ODS. The SoCal 50 I had was re-purposed as a John Mayer Signature.

https://tubeamparchive.com/viewtopic.ph ... sc&start=0

Not trying to derail... just clarifying.

[pdf64]

Yes, unloaded. The load will pull that voltage down.

If a load pulls the Vdc (average) down that much (ie to below the 6.9V or even 6.6V limiting value), then I suspect that's there's a lot of Vac ripple riding on that Vdc average, thereby making the point of dc heaters kinda tenuous.
Have you check the (loaded) Vdc heater on a scope for ripple?

[tubeswell]

I twist them and tuck them in a chassis corner before I wire everything else. I also add a humdinger and connect the pot wiper to an elevated heater ground reference. YMMV