Internal wiring choices (gauge)

[squiffiness]

Question to all to nail this down... since I couldn't find the thread here (but I think it is here somewhere).

Advice on internal wiring selection, for example, to make connections between the TubeLab PCB's and the "world", like the power and output transformers, input jacks, volume pot...

It struck me that Edcor chooses their tranformer insulated wire from the UL1015 standard (in Canada that's the CSA TEW class). This is thermoplastic insulated solid core and stranded wire, rated to 600VAC/VDC up to 105 degrees Celsius (about 220 deg.F) and somewhat fire resistant. It is available in sizes starting at very thin 28 gauge up to 14 gauge and beyond.

It is inexpensive, available in several common colours, including striped types and should help with internal wiring to somewhat of a standard.

The published ampacities I can find quickly (same for solid or stranded) are:

Gauge / Amps
24 / 2
22 / 3
20 / 4
18 / 6
16 / 8

There is also UL1007 and UL1061 for 300V insulation class. It is available at my local jobber (Sayal.com) for less than $1 per foot.

While I know that in most cases, "any old wire will do", I thought this might be a good topic to revisit as I noticed a few more recent "new builders" on the board, along with me. I hope to start soon.

[tomchr]

As you point out, most wire is rated for use up to 300 V DC. If the voltages in your circuit exceed 300 V DC, use 600 V rated wire. This is a matter of safety and reliability. With the thinner insulation of the 300 V wire, you risk dielectric breakdown of the insulation -- i.e. the current will shoot through the insulation. If it shoots through the insulation and hits ground, hopefully, the mains fuse will blow. But if it finds your fingers..... Or it buzzes for a while and catches fire...

600 V wire is available in many places. I found a seller on eBay who sold UL1015 wire by the foot. I got six spools of it (20 AWG, different colors, total length probably 800~900 feet (250~300 m) for a little over $100 shipped as I recall. Maybe $150.

Better safe than sorry. Unless you're into reincarnation and out-of-body experiences, of course...

~Tom

[Einric]

I use 20 or 22 gauge silver plated copper for RCA's and 16 gauge helical twist for speaker outputs.

[squiffiness]

Originally Posted by Einric

I use 20 or 22 gauge silver plated copper for RCA's and 16 gauge helical twist for speaker outputs.

Interesting and thanks for the feedback.

Question completely off topic...is that a Gainclone you've built there?

Brad

[squiffiness]

Originally Posted by tomchr

As you point out, most wire is rated for use up to 300 V DC. If the voltages in your circuit exceed 300 V DC, use 600 V rated wire. This is a matter of safety and reliability. With the thinner insulation of the 300 V wire, you risk dielectric breakdown of the insulation

~Tom

Tom,

I thought my question was [hopefully] in line with TubeLab George's message of safety on his website. Since the UL1015/1007/1061 is relatively cheap and readily available AND complies to a known US (i.e. UL) and Canadian (i.e. CSA) standard, why not use that as a construction and design choice?

It would be helpful to the thread if anyone TubeLab'bers out there have a similar standard for Europe or the Pacific Rim that is comparable, such as CE, ISA, etc.

~Brad

[rknize]

I use 20 gauge solid 600V copper wire for most things. You can get 600V insulation in both a thick and thin wall PVC-type insulation. The latter is more expensive. Most of my stuff is the thicker type...nothing fancy.

[tomchr]

Originally Posted by squiffiness

I thought my question was [hopefully] in line with TubeLab George's message of safety on his website. Since the UL1015/1007/1061 is relatively cheap and readily available AND complies to a known US (i.e. UL) and Canadian (i.e. CSA) standard, why not use that as a construction and design choice?

In that case I might have misunderstood your original question. I thought you asked if it was really necessary to use 600 V rated wire in high voltage designs or if "any ol' wire" would do.

My recommendation is pretty clear. Buy wire rated for the voltages they'll be operating at (or higher). Anything else is just a false economy. I think we agree on this.

I don't know what the EU or Pacific Rim standards would be that correspond to the UL or CSA standards. But my experience in Europe has been that the wire has been pretty clearly labeled. So it's usually not a big deal to figure out what the limits on the wire are.
The biggest issue when comparing US and EU wire sizes - in my opinion - is the conversion from the asinine (IMHO) AWG system to square mm.

~Tom

[boywonder]

As already mentioned, use wire with an insulation rating that exceeds the expected voltage for the application. I use PTFE insulated Cat5 wire for signal cabling most of the time, since it's basically free if you scrounge some dead Cat5/6 cables and I use small shielded coax from the RCA jacks to the circuit (like RG-174/U) .