Heater Wire

For those building and repairing amps on their own. Learna and share ideas.

Heater Wire

Postby skeeterbuck on Fri Sep 06, 2013 11:23 pm

Anyone here ever seen or used lamp/zip cord to the tube heaters in an amp?

The reason I ask is that I recently purchased a kit off of ebay that showed coils of multi-colored hookup wire in the listing. When the kit arrived there was a length of zip wire in the box. I contacted the seller to inquire what the zip cord was for and they informed me it was to wire the heaters. :uhh:

What do you all think about that!
skeeterbuck
Court Jester
 
Posts: 90
Joined: Mon Feb 11, 2008 1:36 pm
Location: Baltimore, MD

Re: Heater Wire

Postby Unit_1 on Sat Sep 07, 2013 1:24 am

i think it would be nearly impossible to run 14ga wire through the tiny loops in the 9 pin sockets

the wire should be fine besides that small detail

p.s. caught a cold, forgot all about the trannys till just now when i saw your handle

i have plenty of stranded teflon covered heater wire. i can send to you for the price of postage. i won a 5000 foot roll for 28 bucks + 50 shipping. lol, yes the shipping for the very heavy roll of wire was more than the auction!

ugggg.......i feel like someone filled my sinus with acid and covered it with cement. gaaaa.......
Last edited by Unit_1 on Sat Sep 07, 2013 5:13 pm, edited 1 time in total.
Image
The ability to play/make music is a gift that not everyone gets. Those of us who have it should use it.

Asimov:Individual science fiction stories may seem as trivial as ever to the blinder critics and philosophers of today — but the core of science fiction, its essence, the concept around which it revolves, has become crucial to our salvation if we are to be saved at all.
Unit_1
Prince
 
Posts: 3713
Joined: Mon Oct 03, 2011 3:29 pm
Location: Kali4ñia (a small planet orbiting the west coast of the United States)

Re: Heater Wire

Postby skeeterbuck on Sat Sep 07, 2013 3:44 am

Unit_1 wrote:i think it would be nearly impossible to run 14ga wire through the tiny loops in the 9 pin sockets

the wire should be fine besides that small detail



Thanks for the offer on the heater wire but I already have enough to do what I need. I just have a hard time thinking that in this day and age anyone would give you zip cord to wire the heaters. Even I'm not that much of a hack to use something like that! :roll:

I'll email you on the trannys.

Thanks!

Chuck
skeeterbuck
Court Jester
 
Posts: 90
Joined: Mon Feb 11, 2008 1:36 pm
Location: Baltimore, MD

Re: Heater Wire

Postby Dai on Sat Sep 07, 2013 10:48 pm

I think Marshall did in some original 18-watters. The important thing (assuming voltage and current rating are adequate) is the relative orientation to the other wires (should be at a right angle relative to plate, grid, cathode wires). Think about the heater wires (assuming AC, they are a noise source). They go inside the tube and back out, and they are very close to the grid (which is next to the cathode which surrounds the heaters). The grid must be at a right angle relative to the heaters.
Dai
Baron
 
Posts: 3377
Joined: Fri Jun 15, 2001 7:01 am
Location: lying in the harmonic marshall filth

Re: Heater Wire

Postby Vortexion on Sun Sep 08, 2013 9:44 am

Quite apart from the thickness question, it's ridiculous of them to provide you with any kind of flexible multi-strand 2-in-line wire for the purpose of carrying the heater supply. It's simply the wrong kind of wire. :roll:

As Dai says, wiring orientation/lead dress is crucial, especially if you're using AC for the heaters. Equally important is that the two conductors should be tightly and evenly twisted throughout their length in order to help cancel out the hefty AC field that emanates from them - and obviously it's virtually impossible to do this with soft, flexible wire. It should be solid core stuff. Solid core wire is easy to route exactly where you want it to go in the chassis - once positioned, it stays there! :thumbsup:

The best source I know of on this subject is Morgan Jones. I can do no better than to quote the relevant passage from pages 117-119 of his excellent, every-workshop-should-have-one book, "Building Valve Amplifiers":

"Electromagnetic fields and heater wiring:

Heater wiring is usually taken from a winding on the mains transformer to the nearest valve, and looped through, from one valve to the next, until each valve has heater power. The input valve is the most sensitive stage, so this should be the last in the heater chain, in order that the wiring leading to this valve carries the least current.

To minimise the external electromagnetic field, the heater wire should be tightly twisted. This means that although any given twist induces a current of one polarity, the twists either side of it induce opposite polarity, and so the fields tend to cancel. This twist should be maintained as close up to the pins of the valve as possible, and when one phase of the heater wire has to go to the opposite side of the base and return, as is the case when wiring past an ECC83/12AX7 to the next valve, the wire should go across the base and be twisted as it passes across. Admittedly, the return current is less than the outgoing current, but some cancellation is better than none.

The worst way to wire heaters would take the incoming pair connecting to the two heaters pins from one side, then loop around the opposite side to form a circle of heater wiring around the valve base:

Image

Heater wiring leading to valves using B9A sockets such as EL84/6BQ5, etc., is best twisted from 0.6mm (conductor diameter) insulated solid core wire, which is rated at 1.5A. Octal valves generally require more heater current, so the larger tags on their sockets can accommodate thicker wire, which could not have been connected to the pins of a B9A socket.

When wiring to valves other than rectifiers, it is useful to use a different colour for each phase, and the author has always used black and blue. When wiring to a push–pull output stage, if the same colour goes to the same pin on each valve, then the hum induced within each valve will be the same phase, and will be cancelled in the output transformer. (This argument assumes that both valves were made by the same manufacturer to the same pattern.)

Valve rectifiers such as GZ34 or GZ37 not only have a dedicated 5V heater supply, but they also have the incoming high-voltage AC, so the two should be clearly distinguished. The author uses a red twisted pair for the HT, and a blue twisted pair for the heater.

Twisting wire is easy. Cut equal lengths of wire to be twisted, pair the wires together at one end and clamp them in a vice. Gently tension both wires equally at the far end and grip them in the chuck of a drill. Hold the wires reasonably taut by pulling on the drill and start twisting. When the wire begins to accelerate you towards the vice it will have about ten twists per inch. Switch off the drill, and whilst maintaining tension by holding the wire with your fingers, undo the chuck. The wire will now try to untwist, and if allowed to do so suddenly, it will tie itself in knots. Gently release the tension in the wire and release from the vice. You now have perfectly twisted wire.

You will find that it is easier to achieve a perfect twist on longer lengths of wire than short ones, because it is easier to equalise the tension between the wires. Equal tension is important because if one wire is slack compared to the other, it tends to wrap itself around the tighter wire (which remains straight). For this reason, it is worth twisting 4m or even 6m at a time, but these longer lengths are more easily twisted with a power drill (ideally, a battery drill because they tend to run slower), whereas shorter lengths can be twisted with a hand drill.

Although solid core wire perfectly retains a tight twist, multicore wire tends to separate, reducing cancellation. The way to avoid this problem is to pre-tension each wire equally by individually twisting it in the opposite direction of the final twisted pair. Without releasing each wire’s pre-tension, grip the wires in the vice and chuck, and twist them together. The effect of this is that as the wires are twisted together, the pre-tension is relieved, so there is no latent force trying to separate the final twist. Although this method works very well, solid core wire retains the tightest twist and can be positioned more precisely, so it is superior for heater wiring.

Electromagnetic fields decay with the square of distance, so heater wiring runs should be as far away as possible from signal circuitry, and only come up to the valve at the last possible moment and in the most direct manner possible. Valve sockets should be oriented so that the pins receiving heater wiring are as close to the chassis wall as possible, and heater wire should never loop round a valve (except for rectifier valves, where hum is not an issue).

Electrostatic fields and heater wiring:

The electrostatic field is due to the voltage on the wiring. Heater wiring should be pushed firmly into the corners of the (conductive) chassis, since the electrostatic mirror at the corner tends to null some of the electrostatic field. Heater wiring must not run exposed from one valve to the next, but should return to the corner of the chassis to re-emerge at the next valve. These strictures mean that good heater wiring requires considerable time/cost, so modern commercial amplifiers sometimes skimp on the quality of their heater wiring..."


The entire book can be downloaded in PDF from here: http://www.tonicamps.com/reference/15887683-Morgan-Jones-Building-Valve-Amplifier.pdf
Vortexion
Newt
 
Posts: 1251
Joined: Thu Jan 10, 2008 4:28 pm
Location: Norwich, UK

Re: Heater Wire

Postby Dai on Tue Sep 10, 2013 10:34 pm

nice article! :)

as far as heater wiring, I would check out Soldano SLO100 (non-twisted thick strictly paralleled wires close to chassis, w/other wires short and coming over and in to pins at 90 deg angle), (one of the Hiwatt related ones--I forget the name)...same paralleled wires but run close together along/on the inside of the tube sockets, some Roccaforte (don't remember model) holes for heater wires in chassis, heater wires on OUTSIDE w/short runs up to tube pins (some don't like this for safety reasons, and this is neat but apparently not new since I've read of some old tube gear w/same physical htr configuration), recent Suhr plexi clone w/one heater wire run over the middle of socket so the strict parallel configuration is kept up to the tube pins (no center post to get in the way IIRC).
Dai
Baron
 
Posts: 3377
Joined: Fri Jun 15, 2001 7:01 am
Location: lying in the harmonic marshall filth

Re: Heater Wire

Postby skeeterbuck on Thu Sep 12, 2013 6:26 pm

Vortexion wrote:Quite apart from the thickness question, it's ridiculous of them to provide you with any kind of flexible multi-strand 2-in-line wire for the purpose of carrying the heater supply. It's simply the wrong kind of wire. :roll:


Yea, and the pic in the listing didn't show any zip cord, just some coils of hook up wire. And... this is a read panel retro fit ac30 top boost kit! :shock:
I can't think of any amp that is more sensitive to wiring/lead dress than a Vox.

Thanks too for the link to the Valve Amp building book/pages. I read them all one day at work when thing were rather slow. :wink:
Some interesting tid-bits for this amp nerd. :lol:

Chuck
skeeterbuck
Court Jester
 
Posts: 90
Joined: Mon Feb 11, 2008 1:36 pm
Location: Baltimore, MD


Return to Do It Yourself Amp Builders

Who is online

Users browsing this forum: ceeya68 and 2 guests