I second Marcus on this subject. It seems to me that the less rationales beyond an idea, the less it can be fought. As already wrote, there are many counter examples and the only response I got when insisting about a silent amp I (also) made with parallel heaters is: "you've been lucky but don't chances for the future".
Equations? None...
Actually, I never read anything convincing on the subject, and IMHO research starts when doubting about anything your advisor told you, somewhat.
The only disadvantage of really tightly twisting the heater wires is that it lengthens the wiring within the same space. The heater circuit is the highest current draw in the amplifier. Twisting or parallel runs of the wire should cancel the magnetic field created by the current in each of the wires. Keeping wires as short as possible is the easiest way to minimize interaction between conductors. That being said, I’ve used all types of methods with heater wires and never seen an advantage/had noise from the wiring scheme. If the amp was on the edge of stability it could possibly be an issue. I’ve also found that drill wound wires are more difficult to deal with when attaching to the tube sockets because you have to cut them, straighten them and strip them after twisting. I’ve figured out the proper length between sockets. I cut the individual wires, hand twist them and solder.
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The purpose of twisting wires together in signal wires is to present equal exposure to outside interference, which will cancel due to phase.
The purpose of twisting heater wires is to keep the wires close to each other and parallel, so any AC hum emanating from them is cancelled out due to phase. If the heaters are perfectly parallel, and tied together, that's fine. Twisting is an easy way to ensure the wires stay parallel and tight. 3 or 4 twists is sufficient, more is fine, but this obsession with tight, tight, tight twists using power tools is just another dumb trend because they look cool when you post pictures of your build. 1. It serves no purpose; 2. It wastes wire; 3. If you use solid core, it is very easy to break a wire inside the insulation. On signal wire, it should be easy to track down. On heater wire, it is sometimes hard to find due to the low resistance in the circuit.
Plenty of unbelievably quiet vintage amps made with loose twists. I emulate them.
50Wplayer wrote: ↑Sun Jun 27, 2021 5:35 am
Working on this one now. Getting lazy with heater wiring and didn't twist. 22 GA tefzel fits between pins 4 and 5 without getting squished.
Did almost the same thing on the last build, but had a twist or two between the tubes. Worked fine.
This was easier laying in the entire black wire run in first, followed by red. Instead of red/black at the same time if that makes sense.
Jason
That looks pretty effective at keeping the heater wires close together and fairly short. What do you do at the power tube sockets?
I’m happy to twist, if nothing else, it keeps the wires tidy and together.
I also like to orient Noval sockets to take advantage of the gap between the 1 and 9 terminals for the heater wiring.
I suspect that one of the reasons in using a gap for valve location in that base design may have been to facilitate feeding heater wiring through it.
I wonder why that heater wiring arrangement isn’t more commonplace?
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