I'm halfway building my first amp, and halfway, I'm suddenly wondering how thick the wires in a typical tube-amp should be. Before, I've mostly done low-voltage stuff (TTL boards and so on), so I'm used to using 0.25 mm wire.
Of course, I know that for heaters you probably should use 1.0 mm wire or so, but how thick should the wire be in other places? Is 0.25 mm enough, or should I use thicker wire in selected places?
Of course, I know that for heaters you probably should use 1.0 mm wire or so, but how thick should the wire be in other places? Is 0.25 mm enough, or should I use thicker wire in selected places?
Hey Alex,
Take a look here:
http://www.powerstream.com/Wire_Size.htm
I just completed my first amp as well:
http://www.diyaudio.com/forums/showthread.php?s=&threadid=64164
I used 20ga for signal and 18ga for ground and filament.
Best,
mr mojo
Take a look here:
http://www.powerstream.com/Wire_Size.htm
I just completed my first amp as well:
http://www.diyaudio.com/forums/showthread.php?s=&threadid=64164
I used 20ga for signal and 18ga for ground and filament.
Best,
mr mojo
Hi Glenn,
The voltage rating is the breakdown rating. Therefore, wire rated for 200V service is not safe for 400V service. There is a saftey factor but you wouldn't run a 200V cap at 400V - would you?
So ..... how do you feel about rewiring all those amps? You didn't sell them did you?
-Chris
The voltage rating is the breakdown rating. Therefore, wire rated for 200V service is not safe for 400V service. There is a saftey factor but you wouldn't run a 200V cap at 400V - would you?
So ..... how do you feel about rewiring all those amps? You didn't sell them did you?
-Chris
Hi Dave,
I use CAT-5 all the time, for networking and telephone systems. At best the insulation will be 300 VDC. I have my doubts on that rating even.
I have no idea on the rating of your 30GA. Depends on the insulation. I bet it's around 100~150VDC since the wire can not support thicker insulation. Or it's exotic wire and okay for B+.
Post #7 here
-Chris
I use CAT-5 all the time, for networking and telephone systems. At best the insulation will be 300 VDC. I have my doubts on that rating even.
I have no idea on the rating of your 30GA. Depends on the insulation. I bet it's around 100~150VDC since the wire can not support thicker insulation. Or it's exotic wire and okay for B+.
Post #7 here
-Chris
When point-to-point wiring, you tend not to let wires cross, rub and lean about, so insulation is pretty moot anyway, I could wire with 20AWG bare if I felt like it 
It's not much of a safety issue because if your hand somehow finds its way shoved below a live +400V tube chassis...shocking things are going to happen anyway.
Not recommended, but wire insulation is also overrated. Heck, I had like 5kV threatening the outside of a 24ga. 300V PVC insulated wire the other day, and it didn't say uncle!?
Oh, and also note that insulation isn't going to spontaneously break down and spark. The air around the wire, your primary defense, is much wider (between wires) and has a lower dielectric constant, so by and large, most of the electric field is across the air, not the insulation.
If you have to run hot lines along the chassis or twisted to low voltage wires, appropriate (600V+) insulation would be a good idea.
Tim
It's not much of a safety issue because if your hand somehow finds its way shoved below a live +400V tube chassis...shocking things are going to happen anyway.
Not recommended, but wire insulation is also overrated. Heck, I had like 5kV threatening the outside of a 24ga. 300V PVC insulated wire the other day, and it didn't say uncle!?
Oh, and also note that insulation isn't going to spontaneously break down and spark. The air around the wire, your primary defense, is much wider (between wires) and has a lower dielectric constant, so by and large, most of the electric field is across the air, not the insulation.
If you have to run hot lines along the chassis or twisted to low voltage wires, appropriate (600V+) insulation would be a good idea.
Tim
Hi Tim,
At least if the wire is bare, you expect to have to keep it away from other things. It's just that beginners should be aware of the dangers and why things "just blow up".
I am comfortable with bare wire also, and cracked insulation. Still, the proper wire should be used. And yes, air makes a fine dielectric, but it's a crappy barrier. You and I know when it's okay to use bare or low voltage wire. I'll bet you were taught to use the correct stuff. The same should be pointed out to people just starting out. Otherwise, why do they make that expensive 600V (or better) wire anyway?
-Chris
At least if the wire is bare, you expect to have to keep it away from other things. It's just that beginners should be aware of the dangers and why things "just blow up".
I am comfortable with bare wire also, and cracked insulation. Still, the proper wire should be used. And yes, air makes a fine dielectric, but it's a crappy barrier. You and I know when it's okay to use bare or low voltage wire. I'll bet you were taught to use the correct stuff. The same should be pointed out to people just starting out. Otherwise, why do they make that expensive 600V (or better) wire anyway?
-Chris
anatech said:Hi Glenn,
The voltage rating is the breakdown rating. Therefore, wire rated for 200V service is not safe for 400V service. There is a saftey factor but you wouldn't run a 200V cap at 400V - would you?
So ..... how do you feel about rewiring all those amps? You didn't sell them did you?
-Chris
Hey Chris-
I've never had a problem with any arcing on any of my guitar amps. I think I asked this question at the AX84 forum, and the consensus there was that 200v was acceptable because of the air gap. Most people I spoke with used 200v insulation wire.
I just wanted to hear what builders on this forum thought of this.
Glenn
Hi Glenn,
I'm not freaking, but if the wire got pushed to the chassis (by a service guy or curious customer) it may eventually break down. Possibly just discharge now and again depending on humidity. It would be difficult to troubleshoot.
I still think we should endeavor to do things properly - given a chance. In other words, I don't like to tempt fate.
-Chris
I'm not freaking, but if the wire got pushed to the chassis (by a service guy or curious customer) it may eventually break down. Possibly just discharge now and again depending on humidity. It would be difficult to troubleshoot.
I still think we should endeavor to do things properly - given a chance. In other words, I don't like to tempt fate.
-Chris
I've used CAT-5 ("plenum rated" - this version has the Teflon insulation) in an application that is at over 400V, for quite a long time, and no air between either - twisted B+/Ground pair. Although I guess the insulation could only be ~200V x 2 (once on each conductor) come to think of it . . . .
-j
-j
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