Wire choice

[K O'Connor]

Hi Guys

When wiring a guitar amp, we have many choices about the wire, so how do we make sure we get the right stuff?

Wire has a gauge or thickness, denoted by a number: the smaller the number the fatter the wire. Gauge ONLY determines current capacity, and vice versa.

Insulation type can be cloth, PVC or Teflon, although there are some other poly names to confuse us - haha. Generally, PVC-insulated wire is the norm. Teflon is thinner and requires special wire strippers, so it can be expensive overall. Cloth is purely aesthetic and usually has a plastic inner layer to provide the actual insulation. Vintage restorationists prefer cloth-covered wire to maintain a vintage look, but the down-side is that most cloth wire is solid.

The insulation type determines the voltage capability of the wire. The cheapest wire will be rated at 300V, and 600V and 1kV ratings are available. In general, the 300V wire is good enough for most assemblies since the ratings are actually AC volts, so "300V" means 420V peak or DC. We are not concerned with the heating equivalnce between RMS-AC and DC; rather, the maximum voltage withstand capability.

Stranded-core wire is made up of many thin strands wound together forming a flexible overall wire. Solid-core wire is just that: one solid strand of wire. It is easily bent and holds its shape, which is why some amp builders prefer it. However, this same characteristic can make it more microphonic, too. We generally recommend stranded wire for all applications other than for buss wire on hand-wired cards.

TUT3 Chapter 3 discusses wire selection and wiring practice in detail.

Have fun

[nauta]

TUT3 is the amp wiring bible!!
It was a bit tricky following the wiring method in my Marshall but in the end I got it done and it is SUPER QUIET
makes you wonder why they didn't do this at the factory?
Thanks Mr O'Connor

[jmcd]

I just purchased a 100' spool of alpha RG-174 shielded wire. For regular hookup wire, I like the 20 and 22 AWG stranded wire available from TubeDepot.

[K O'Connor]

Hi Guys

RG-174 uses copper-clad steel inner conductor with tinned-copper braid shield. The shield is okay but the inner conductor adds distortion for audio signals. This may not be a concern in a guitar amp but for your hifi you will want to use all-copper.

Since this coax is designed for use at radio frequencies, the distortion is not present at RF as RF travels on the wire surface (skin effect). Low-frequency audio is a "bulk" signal travelling equally within the cross-section of the conductor.

It's hard to beat the low-capacitance.

[KenInVic]

What would you suggest as a substitute for RG-174, Kevin?

[K O'Connor]

Hi Guys

That would depend on which of the RG-174 parameters are the most important to you and what you were using it for? Obviously, we are interested in using for audio, but is for inside or outside of a chassis? You can use the same coax for both but you might have to be more careful about not stepping on foil shield more than braid, for example.

Inside the chassis you try to use thinner diameter coax and 2-conductor cable especially if there will be a lot of wiring. Remember that all the currents in a tube amp are low, especially signals in the preamp where you are likely to want coax, so the inner conductor gauge can be very small. Voltages are low, too, so the insulation layer can be thin, which should lead to lower capacitance.

Note that it is a mistake to shield all three connections to a triode as this adds significant capacitance and kills the frequency response of the circuit. Running the grid only through coax is okay.

Braid provides better magnetic shielding than foil-plus-drain-wire. Foil provides complete electrostatic shielding. So you decide which is more relevant in the chassis or for a given signal run.

Since manufacturers change their product line every now and then, and because availability of certain wire is inconsistent or changes, too, it is best to use the search functions at Mouser or Digikey to see what is available with the specific priority of parameters you might have, and then with altered priorities. That will give you actual part numbers and brands that you can use to check availability from other suppliers.

[Jollyjoe]

I'm quite fond of this stuff
Aircraft Spruce is the supplier

https://www.aircraftspruce.com/catalog/e...ldwire.php (usa)

https://www.aircraftspruce.ca/catalog/el...ldwire.php (canada)



It works wonderfully for input signals and long runs under boards to control pots.
Tinned inner and shield. Tefzel sheath and mill spec for aircraft instrumentation and signals. It is Very thin. The 20ga shielded, is slightly thinner than regular non shielded PVC jacket 600v 18ga stranded I have. Unlike most chunky coax I've seen.

Also they have wonderful 18ga, 20ga and 22ga non shielded wire in many colours. All 600v. Reasonably priced and shipping wasn't terribly expensive for the amounts I've ordered.

Cheaper than the Ebay guy that sells 10ft chunks too!


I've never needed special types of wire strippers but I've got a nice set that has many gauge options as well as an old fashioned style that you can manually adjust to any size. Although I don't normally use that pair.

[makinrose]

Thanks for links! That looks like it's perfect for amps.

[K O'Connor]

Hi Guys

Just for reference, in the Q&A section for the wire Jollyjoe bought, there is size given for #20 shielded:

"What is the diameter of 20 awg shielded wire? 
The diameter of shielded 20ga white wire M27500-20TG1T14 part # 11-14420 is 2mm."

That's pretty nice for inside equipment.

What is Tefzel? A brand name of Dupont, just like Teflon, for an insulation often referred to as EFTE - Teflon is often referred to as PTFE. There are many articles online that discuss the properties of these insulations, such as this one:
https://www.lectromec.com/an-overview-of...-and-etfe/

and this chart from NASA:
https://nepp.nasa.gov/npsl/Wire/insulation_guide.htm

The chart lists Teflon as being "more flexible" but this is relative to some of the other MIL-spec wire NOT to common PVC-insulated wire.

Have fun

[K O'Connor]

Hi Guys

At the other end of the spectrum you will find wire like this, from an Aliepxpress vendor:
https://www.aliexpress.com/item/28AWG-25...2e0ejmod6b

They sell 1-meter pieces but will sell continuous lengths if you request it and are buying much more.

The OD is not excessive. The insulation is just PVC so you have to be careful not to overheat it or touch it with the soldering iron. I used wire like this from suppliers close to where we used to live and it is fine when you deal with it correctly - not too bulky, low priced, convenient to handle. In short lengths inside an amp the unknown capacitance is not a problem and the spiral shield has some benefits over a foil shield with drain wire, although there is a trade-off in both directions of that comparison.

On their page, you can change the quantity and see the total price of wire + postage go up incrementally. The price goes down from 1m to 4m then jumps back up nearly to the 1m price at 5m. From 6m on it drops slowly all the way to 100m. So, you should check these things before you order a medium quantity. You do not get down to the 4m price until 16m.

Have fun

[makinrose]

For those of you in the USA McMaster-Carr is an excellent source for rolls of PVC covered wire. It's not too expensive and comes in loads of colors. They are also a good source for garolite for circuit boards.

https://www.mcmaster.com/standard-electrical-wire

[makinrose]

I'm resurrecting this thread! Does anyone know of any good overseas suppliers for Teflon covered hookup wire? I'm wanting to buy some rolls of it. I've order some off of AliExpress before but seemed less hardy than the wire I've used before so I'm suspicious that it not 600V wire. Jacket is not marked...Thanks guys!

[K O'Connor]

Hi makinrose

Teflon wire never has markings on it, so you have to go by the data on the roll itself or the description used to advertise it. With Aliepxress, you can contact the supplier prior to ordering and ask whatever questions you have. One thing I've noticed though, is that it is best to ask only one Q per message.

You can tell if it's Teflon by how it feels, how it cuts and usually the wire inside is silver-plated copper. 600V insulation is only 10mil thick; 1kV is 15mil.

[makinrose]

Hi makinrose

Teflon wire never has markings on it, so you have to go by the data on the roll itself or the description used to advertise it. With Aliepxress, you can contact the supplier prior to ordering and ask whatever questions you have. One thing I've noticed though, is that it is best to ask  only one Q per message.

You can tell if it's Teflon by how it feels, how it cuts and usually the wire inside is silver-plated copper. 600V insulation is only 10mil thick; 1kV is 15mil.

I didn't know it wasn't mark.  That's good to know.  Thanks!

[Champ81]

Thos thread is interesting regarding the wire type and insulation. On my previous build awhile back I used only Teflon wires. I like to use it simply because you don't need to worry about overheating the insulation and it folding back at times. The downside is as Kevin mentioned you need proper wire strippers specifically made for stripping Teflon and those are quite expensive. Also when I twisted the heater wires the insulation is quite slippery and it was very difficult for that part of the wiring. Other parts were fine.

[K O'Connor]

Hi Guys

TUT3 has diagrams showing the correct way to twist wires together.

In the case of heater wires, do you want the same side of each tube socket to tie to the same side of the power source? If so, then it is best to use two colours of wire.

Most people attach the two wires to the first socket where power comes in. If you orient the amp so you are facing the rear, then you will be working from left-to-right assuming the PT and AC are on the usual end of the chassis (opposite for Marshall since they did a flipped layout copying Fender).

Twist the heater wires from the PT making sure that the free ends are both corkscrewing and you are not simply winding one lead around the other. Leave a little excess so the wires can be dressed in properly and not be under tension from the PT to the first socket. Trim the wire ends and twist the strands, then insert them into the socket pins.

Trim the ends of the hookup wires to be used to link to the next socket.Twist their strands, too. You might want to twist a length of the two wires longer than what is needed for the first link. Insert the wire ends into the socket pins and then solder the socket pins. Now the hookup wire is secure at one end.

Roughly measure off the length needed to link to the 2nd socket. Decide how the wires will be dressed in: will they be up in the air? or laying flat looping beside the row of sockets on the chassis floor?

Cut the wires a bit long so there will be no tension once dressed and soldered. Trim the new ends and twist the strands, then insert into the socket.

Suppose you have simple loose wires from this point. Take the two wires in hand and roughly drape them around how you wish them to go to the next socket, running them through your fingers to make sure they are the same length. Leave some excess and cut both wires. Now twist them together so both ends corkscrew until the entire length is twisted. Loop the twisted pair how you want it be over to the 2nd socket, trim the ends, strip the ends and twist the strands, then insert into the next socket.

Repeat the steps to get to the 3rd socket, the 4th, etc. ALWAYS make sure that the free ends of the wires are corkscrewing as you twist the pair. This assures that both wires are taking part in the twisting action.

Sometimes when you have a lot of twisted wiring to install, it is easiest to twist a long length of wire first. It is easiest to do this by cutting equal lengths of the different colours to be twisted together, then line up one end of all the wires and hold this firmly. Now twirl the loose wires into a tight twist, moving your secure grip along so that you are always holding the twisted set at the twisting point. if the loose wires are very long, you will occasionally have to stop and untangle the free ends

Now, you can trim one end and attach it where it should be, then drape the twisted set to where it needs to go to, trim a little long, strip the ends, twist the strands, and so on. This makes repetitive wiring go quicker and the end result is very neat.

In my amps I only use Teflon-insulated wire and have the proper wire stripper. You can use a utility knife or possibly less expensive stripper s but you risk nicking the strands.

In many cases - if not most or all - after trimming the end and twisting the strands, you might want to tin the stripped end. Hang the wire end over a support of any kind - roll of tape, etc, or the edge of the bench - and set something on the wire to hold it, such as another tool. Then both hands are free to hold the solder and the soldering iron.

Note that it is easiest to unroll a length of solder and have this loose solder "strand" in hand rather than holding the roll (unless you have a very small roll). Thinner solder is easier to work with and melts faster.

[Champ81]

Hi Kevin

Currently I have resorted to heat shrinking the heater wires so they run parallel vs twisted. I use pvc currently.  In my last builds I twisted the Teflon wires but it was way too hard for me. Just to make it easier now I do it in parallel with pvc. It doesn't seem to introduce hum in the last two builds. The only hum was due to the current balancing of the el34s which is now solved through the BMK mod. 

The other issue I am having is for pvc wires the insulation is very fragile and I guess I'm not quick enough to let the soldering iron off at times where the insulation peels back due to the heat. 
But one thing I try to do is make sure there is not an acute bend to the wire to the socket when wiring to relieve the strain. There is also a wire called Prysmian I think from digikey. They seem to be a bit less prone to pvc peeling back. He alpha wires I used peeled back alot easier. There are also eradicated pvc which stay in place. The colours for those were are a more pastel colour.

[Champ81]

Anyone here try silicone wire? I got some from digikey rated at 600V.
Just recieved them today  and I'm thinking of using them for heater wiring. Reason being the insulation doesn't melt off the wire while soldering. It's a pain when you wire everything up and when soldering time comes the insulation peels right off for pvc.  
These are stranded wire and it seems really malleable. Meaning it feels like solid core and bends to shape easily.  The insulation itself is really soft so there's not much resistance when bending. I guess the tinned copper also contributes to the wire to take a form

Here is the part number 
3135-20-1-0500-002-1-TS

And link
https://www.digikey.ca/en/products/detai...s/15853662

[makinrose]

Anyone here try silicone wire? I got some from digikey rated at 600V.
Just recieved them today  and I'm thinking of using them for heater wiring. Reason being the insulation doesn't melt off the wire while soldering. It's a pain when you wire everything up and when soldering time comes the insulation peels right off for pvc.  
These are stranded wire and it seems really malleable. Meaning it feels like solid core and bends to shape easily.  The insulation itself is really soft so there's not much resistance when bending.  I guess the tinned copper also contributes to the wire to take a form

Here is the part number 
3135-20-1-0500-002-1-TS

And link
https://www.digikey.ca/en/products/detai...s/15853662

I've used the cloth covered wire that Weber used to have that had a silicon inner jacket. The stuff is very hard to melt which is helpful.   I use stranded wire for most everything but I use solid core for heater wiring. It's just easier to use.  I get the PVC 600V wire from MCMaster-Carr it's fairly melt resistant so long as you set the soldering iron temperature judiciously. For everything else I use Teflon coated wire.

[K O'Connor]

Hi Guys

There is no need to heat shrink heater wires if you dress them properly - which includes twisting them.

In my description above, the wiring to one socket is fully completed and soldered before tying to the next socket. If you are determined to wire everything then solder it, you are making things difficult for yourself and leaving it open to having unsoldered connections.

Tinning the stripped and twisted end before inserting it into the solder lug makes final soldering easier and allows a mechanical crimp prior to final soldering.

Silicone insulated wire is intended for high-heat situations. It is nice wire but kind of expensive, although all copper wire is pretty expensive these days.There is no need for high-voltage wire for heaters.

Since this is only #20, the wiring to the first octal socket should be the transformer fly-leads. If you have a fuse holder for the heaters, then the load side of the fuse must be fanned out separately to the octals.