wiring heaters...ugh

[Phil_S]

While we're at it, Ken showed his way of doing it (I like it!). I'll show mine. I can see that my manual skills were not as good as they could be, but you get the idea. I see the up in the air and in the corner placement as the most common.

[dynaman]

I agree with playonit; always great to see lively debate on these kinds of topics, regardless of one's level of personal experience. FWIW, I had only seen the "parallel buss bar" method of running heaters on Soldanos (and dynaman's wonder toolbox amps) but had, for some reason, only associated that method where a heater supply was pure DC. I wasn't aware that this was being used with AC supplies, so, very cool.

BTW, Ken and PCCollen, I did not construe either of your comments as having an adversarial tone.

Now that you mention it, most hum issues I've experienced have been with using DC! DC just adds to the noise if not done correctly.

[Gaz]

FWIW, I've had good luck with Merlin's method. I've actually abandoned twisting wires in the hand drill, and found I it's easier to do by hand because I have more control, plus I feel like more of a badass


[IMG1536]http://img443.imageshack.us/img443/749/0922001655f.jpg[/img][/img]

[C Moore]

FWIW, I've had good luck with Merlin's method. I've actually abandoned twisting wires in the hand drill, and found I it's easier to do by hand because I have more control, plus I feel like more of a badass


[IMG1536]http://img443.imageshack.us/img443/749/0922001655f.jpg[/img][/img]

What The..!!!
I've got mushrooms coming out of my lawn.........

[PCollen]

From everything I've read, the fact that the magnetic fields (generated by the AC currents in the heater wires) are forced to occupy the same physical space tends to cancel them out, or to lower their strength enough that they don't induce voltage changes in nearby conductors. (I've read more technical/mathematical explanations, but I think that's the basic idea.)

.

The magnetic field around a current-carrying conductor has a direction of rotation (CW or CCW) depending upon the direction of current flow (re: right hand rule of thumb). The magnetic fields will re-inforce each other if the two conductors in close proximity are carrying the same current in the same direction, and will cancel (buck) each other if the currents are flowing in opposite directions. Using 12AX7 as reference with AC heaters, wiring to pin 9 is always carrying current opposite wiring to pins 4 and 5.

[PCollen]

BTW, Ken and PCCollen, I did not construe either of your comments as having an adversarial tone.

I didn't post any comment..only a picture of the wiring of an old Marshall from the late 60's with a statement that it was a pretty good wiring job given that era.

[Colossal]

BTW, Ken and PCollen, I did not construe either of your comments as having an adversarial tone.

I didn't post any comment..only a picture of the wiring of an old Marshall from the late 60's with a statement that it was a pretty good wiring job given that era.

Well no wonder I didn't take your (non) comment as adversarial Sorry, I meant Phil_S, not PCollen

[rp]

Using 12AX7 as reference with AC heaters, wiring to pin 9 is always carrying current opposite wiring to pins 4 and 5.

In other words, at least on the dual preamp tubes, zip cord would do fine? I'll do the bus bar before I do zip just 'cause i don't want anyone who hasn't read this post to go, 'jeeze, this bozo used zipcord on the heaters," but I'll keep it in mind. One day I really want to build a parts box amp with the cheapest crappiest parts in the fastest laziest way just to see what mojo comes out. This will now have zip cord heaters.

[PCollen]

Using 12AX7 as reference with AC heaters, wiring to pin 9 is always carrying current opposite wiring to pins 4 and 5.

In other words, at least on the dual preamp tubes, zip cord would do fine? I'll do the bus bar before I do zip just 'cause i don't want anyone who hasn't read this post to go, 'jeeze, this bozo used zipcord on the heaters," but I'll keep it in mind. One day I really want to build a parts box amp with the cheapest crappiest parts in the fastest laziest way just to see what mojo comes out. This will now have zip cord heaters.

"The lead dress of AC heater supplies is very important for noise reduction. The AC heater wires will have significant EM radiation and should therefore be routed well away from all signal wires, and are usually tucked into the corner of the chassis. The wires should either be made from twin cable (bell-wire) or better still, should be made by twisting the wires neatly and tightly together. In this way the wires are kept perfectly parallel and close to each other, which increases opposing field density and encourages the radiated fields to cancel out. Loosely twisted wires are no use at all.
When heaters are wired in parallel [as apposed to series], power valves should be first in the heater chain, followed by driver valves, with the input stage being last in the chain. This keeps current, and therefore radiated fields, at a minimum around the most sensitive stages of the amp. Even better is to run the pre-amp and power-amp sections from separate heater chains. If signal wires must cross the heater wires, they should do so at right angles.

The common pre-amp valves (ECC83 / 12AX7 etc.) when run from a 6.3V supply, should be wired from one side only, not by looping one heater wire all round the valve socket, which would create a hum loop and cause excessive interference noise (though many amp makers DO make this mistake and get away with it). The wire twisting must be kept very tight right up to the socket, where it matters most. Their pin arrangement is also deliberate, so that the main heater pins (4 and 5) can be orientated towards the chassis wall, allowing heater wires to be run along the wall away from any other sensitive signal wiring."

Note that the the emphasis is to cancel out the EMF of the two wires so that it does not interfere with nearby signal wiring. Twisting the wires is to keep them tightly parallel to one another; it's more of a wiring management tool. Zip wire works just as well if it is tucked up against the "wall" of the chassis and away from signal wires.

[rp]

When heaters are wired in parallel [as apposed to series], power valves should be first in the heater chain, followed by driver valves, with the input stage being last in the chain. This keeps current, and therefore radiated fields, at a minimum around the most sensitive stages of the amp.

I like this info, I always wondered if order mattered. Kind of obvious once pointed out.

This has been an informative post. AGers are gonna have some hum free amps

[Cliff Schecht]

I use zip ties all over amps. They look nice, clean up the wire bundles well and are dirt cheap. I wouldn't shy away from them on heaters but if they are wrapped neatly, they tend to take form well anyways and don't need extra help staying put. Don't be afraid to apply them as needed though.

[Structo]

It would be interesting as an experiment to take two different twisted pairs of wires.
One as close to text book perfect as possible and the other not so good and possibly one pair not twisted at all for a control.

Apply 6.3 vac through the pairs to an appropriate load, then placing a piece of white paper over the pairs and sprinkle fine iron filings over them to show the magnetic energy present.

I'd like to see how much it actually does cancel out the magnetic fields and the associated 60 Hz noise.

Anybody up to the task?

Document it and take pictures?

[Dai H.]

"The lead dress of AC heater supplies is very important for noise reduction. The AC heater wires will have significant EM radiation and should therefore be routed well away from all signal wires, and are usually tucked into the corner of the chassis. The wires should either be made from twin cable (bell-wire) or better still, should be made by twisting the wires neatly and tightly together. In this way the wires are kept perfectly parallel and close to each other, which increases opposing field density and encourages the radiated fields to cancel out. Loosely twisted wires are no use at all.
When heaters are wired in parallel [as apposed to series], power valves should be first in the heater chain, followed by driver valves, with the input stage being last in the chain. This keeps current, and therefore radiated fields, at a minimum around the most sensitive stages of the amp. Even better is to run the pre-amp and power-amp sections from separate heater chains. If signal wires must cross the heater wires, they should do so at right angles.

The common pre-amp valves (ECC83 / 12AX7 etc.) when run from a 6.3V supply, should be wired from one side only, not by looping one heater wire all round the valve socket, which would create a hum loop and cause excessive interference noise (though many amp makers DO make this mistake and get away with it). The wire twisting must be kept very tight right up to the socket, where it matters most. Their pin arrangement is also deliberate, so that the main heater pins (4 and 5) can be orientated towards the chassis wall, allowing heater wires to be run along the wall away from any other sensitive signal wiring."

this should be attributed to the source (Valve Wizard aka Merlin Blencowe) :

http://www.freewebs.com/valvewizard/heater.html

[PCollen]

"The lead dress of AC heater supplies is very important for noise reduction. The AC heater wires will have significant EM radiation and should therefore be routed well away from all signal wires, and are usually tucked into the corner of the chassis. The wires should either be made from twin cable (bell-wire) or better still, should be made by twisting the wires neatly and tightly together. In this way the wires are kept perfectly parallel and close to each other, which increases opposing field density and encourages the radiated fields to cancel out. Loosely twisted wires are no use at all.
When heaters are wired in parallel [as apposed to series], power valves should be first in the heater chain, followed by driver valves, with the input stage being last in the chain. This keeps current, and therefore radiated fields, at a minimum around the most sensitive stages of the amp. Even better is to run the pre-amp and power-amp sections from separate heater chains. If signal wires must cross the heater wires, they should do so at right angles.

The common pre-amp valves (ECC83 / 12AX7 etc.) when run from a 6.3V supply, should be wired from one side only, not by looping one heater wire all round the valve socket, which would create a hum loop and cause excessive interference noise (though many amp makers DO make this mistake and get away with it). The wire twisting must be kept very tight right up to the socket, where it matters most. Their pin arrangement is also deliberate, so that the main heater pins (4 and 5) can be orientated towards the chassis wall, allowing heater wires to be run along the wall away from any other sensitive signal wiring."

this should be attributed to the source (Valve Wizard aka Merlin Blencowe) :

http://www.freewebs.com/valvewizard/heater.html

The quotes indicated it's a lift. Thanks for researching it, though. Where I got it from, there was no indication of the source.

[FUCHSAUDIO]

Just found this and it helped me.....

http://www.brown-note.com/heaters/



And the results....

I've done similar, and not evern did much twisting and it was plenty quiet.
The whole twisted over the top thing is overrated. It looks slick, but it doesn't seem to do dick as far as lowering noise imho.