Heater wiring in a straight line?

[nee]

I'm intrigued that in some amps the filament wiring is a bare bus wire running in a straight line from tube to tube, as in the attached image. Obviously it must work from a lack of noise perspective, but almost everyone recommends twisting and looping the filament wires. Can anyone comment on this?

Thanks!

[M Fowler]

Looks to me to be part of his grounding scheme and the wires are not going to the tube pins. You see the same thing going on with the pots. He is running shielded wire everywhere. The filament has not been wired up yet. I also think the filament wires (green) are going to a capaciter and diodes so I think he is going to wire this in DC rather than AC which will be quieter. You still twist the wires for DC heaters.

Mark

[nee]

Looks to me to be part of his grounding scheme and the wires are not going to the tube pins.

Mark

Thanks Mark, but no, it's not the grounding. I have posted a larger close-up. On the 12AX7 sockets at the front, one bare wire is going through pins 4 and 5, and the other through pin 9 of each tube. Then there is a black wire connected to the left end of each wire, which run under the board to the 2 power tubes.

[novosibir]

Soldano also doesn't twist heater wires! Look at the photo of a SLO100 below!

But to be honest, I couldn't live with the noise floor, a SLO100 is producing in the Lead sound from Gain half open onwards.

Larry

[rfgordon]

I do mine the same way. I just cover the wire with shrink between tubes. Works great, and it's way faster than twisting and soldering two sets of wires per tube.

[Bob-I]

The reason for twisting is to keep the wires equal distance from each other. Since the AC is opposite phase, the EMF will cancel as long as the wires remain equal distance.

I wire most of my amps this way too and I have almost 0 heater noise. One of my recent builds was giving me 120Hz hum and I was ready to try twisted wire, until I measured the 100/100 resistors and found one was 1K. Colorblind builders need to measure everyting . Once I fixed that this amp is whisper quiet.

[Bob-I]

But to be honest, I couldn't live with the noise floor, a SLO100 is producing in the Lead sound from Gain half open onwards.

Larry

But that's not heater noise, it's just noise period.

I built a SLO Clone a few years ago. It's a really noisy design, I believe mostly because of the low biased gain stage that compresses more than anything else. I get some cool tones but I'm with you on the noise floor, I can't gig this this amp, it's just too much noise.

[ampdoc1]

I've used this type heater wiring for 2-3 years. No noise, no hum,..and no twisting wires.

Also, I used a buss bar for my control pot grounds. The older D'Lite (top photo) connected only to the grounded tabs of the pots, while my latest grounds both the pot bodies and the individual pot tabs.

ampdoc

[drz400]

But to be honest, I couldn't live with the noise floor, a SLO100 is producing in the Lead sound from Gain half open onwards.

Larry

But that's not heater noise, it's just noise period.

I built a SLO Clone a few years ago. It's a really noisy design, I believe mostly because of the low biased gain stage that compresses more than anything else. I get some cool tones but I'm with you on the noise floor, I can't gig this this amp, it's just too much noise.

I owned 3 SLO100s
Definitely noisy both in hum/buzz and hissss.
Since the tubes are close to the pots and a lot of high impedance wires twisting does help this amp.
On the last one I attacked it, first twisted the heater wires, big help
Second I raised the heater to 70VDC, helped some more. Next I installed DC heaters to the preamp tubes, became very quiet, finally I re-did the ground path installed a correct effects loop and it became totally hum free at any volume. With a few plate caps the hiss can be calmed down without changing the freq response too much

[Merlinb]

I'm intrigued that in some amps the filament wiring is a bare bus wire running in a straight line from tube to tube, as in the attached image. Obviously it must work from a lack of noise perspective, but almost everyone recommends twisting and looping the filament wires. Can anyone comment on this?

Thanks!

I believe HiWatt used to do that too. It's a very easy way to do it, from a production-line point of view, but not recommended. The EM fields will only cancel exactly half-way between the wires- everywhere else will be noisy. It actually creates a hum-loop around each socket, so it's a no-brainer really. Ok in a lowish gain amp, but for high gain builds don't even think about it. Twisting is always the superior option.

[VacuumVoodoo]

I would not recommend this unless heaters are powered with low ripple DC.