Exactly how can an instrument cable used as a speaker cable..

[Occam]

...fry your OT? I saw this asked on another forum and I don't think anyone had the facts. I've heard that it's true but that's about as much info as I have. Thanks.

[mc5nrg]

Instrument cable is shielded and if I understand things correctly this changes the impedance the amplifier sees.

Also instrument cable is usually tiny gauge wire appropriate for the weak signal of guitars or line level not the much more powerful voltages put out by a poweramp thus the cable can be cooked so the amp no longer sees a load and fries.

At least that's my best guess.I'm sure the real techs will chime in.Why take a chance? Use the right type of cable for the intended use.

[brad347]

here's what I know:

Instrument cable is single conductor shielded.

Speaker cable is two conductor unshielded.

Speaker wire has a fairly hefty gauge. Instrument cable has a teeny little gauge.

So, when considering it, if you were to use an instrument cable, the shield would be trying to act as a conductor and the conductor probably wouldn't be big enough to handle the load for long.

But that's just a semi-educated guess.

[Occam]

Instrument cable is shielded and if I understand things correctly this changes the impedance the amplifier sees.

Also instrument cable is usually tiny gauge wire appropriate for the weak signal of guitars or line level not the much more powerful voltages put out by a poweramp thus the cable can be cooked so the amp no longer sees a load and fries.

At least that's my best guess.I'm sure the real techs will chime in.Why take a chance? Use the right type of cable for the intended use.

I wouldn't risk it but someone is saying that it won't blow your amp unless the cable is completely dead.

[jlummaa]

The speaker cable: You'll need thick wires to conduct the often high current so instrument cables are not strong enough. At least i wouldn't take the risk.

The worst case when using instrument cable as a speaker cable: After you short your instrument cable because the insulation of the poor cable melted (because of too high current for the cable) then you burn your OT.

[John Phillips]

Instrument cable is shielded and if I understand things correctly this changes the impedance the amplifier sees.Not significantly. This is often raised as an issue but it's almost certainly irrelevant at guitar frequencies with the capacitance of a typical cable.

Also instrument cable is usually tiny gauge wire appropriate for the weak signal of guitars or line level not the much more powerful voltages put out by a poweramp thus the cable can be cooked so the amp no longer sees a load and fries.Exactly. It's simply that if the cable fails - which it may, if you try to push many times the current it will handle down it - you end up with an open circuit.

[jay42]

The right way, the wrong way, and the Army way...if you stick to 16 or 18ga zip cord or Monster cable or whatever, you'll probably never have a problem. On the other hand, some coax is 18ga. Canare recommends GS-6 for speaker hookups.

If you're looking at a high powered bass setup with a 1,600W bridged power amp, you need to crack open the manuals and read the fine print. There's a point at which you want 14ga.

[majorledhead]

What about on a low watt amp like a Bumbox lead 1 or 5 watt Valve Jr.. I don't mean all the time but maybe in a pinch. Does the output of the amp make a difference ? Curious minds want to know.......

[GenoBluzGtr]

It's not that the cable will kill your OT, the cable will likely fail, and the open circuit (no speaker load) will THEN kill your OT.

They don't make most instrument cables a large enough gauge because then it doesn't work as well for transmitting low level signals (its intended job)

[El Caballo]

Instrument cable is a conductor and a shield. It is designed to carry a vanishingly small signal with the minimum of capacitance and electromagnetic interference -- thus the shielding. A few ohms of resistance doesn't matter with a typical 1 MOhm input stage.

Speaker cable is two conductors, usually of heavy gauge (14-18). It is designed to carry a large signal with as little resistance as possible, because even a tiny amount of resistance is significant when driving a speaker cabinet (4-16 Ohms). Electromagnetic interference generally isn't significant at these power levels.

The problem with instrument cable is that a small amount of resistance, when placed in series with a speaker cabinet, will produce a large amount of heat. The cable fails, you have an open circuit, and very soon your output transformer fails too.

Edit to add: They're easy to make, and the connectors themselves aren't any different. Just get some 14 or 16 gauge speaker wire which you probably already have lying around, a stack of good metal 1/4" plugs, and solder some up. You can even use lamp cord from the hardware store: it's the same thing, just in decor-matching colors. They're even easier to make than guitar cables because the wires are so huge.

I actually prefer the home-made ones because they don't look like instrument cables and I never mistake one for the other. With the regular black kind it can be hard to tell the difference.

[John Phillips]

What about on a low watt amp like a Bumbox lead 1 or 5 watt Valve Jr.. I don't mean all the time but maybe in a pinch. Does the output of the amp make a difference ?
Yes, it's OK to use an instrument cable at that sort of power. It's the current which is important, and you can work out what it is from the power of the amp and the impedance of the speaker. The current is equal to the square root of the power output divided by the impedance. You should allow for the maximum distorted output, so if you have a 5W amp which peaks at 8W, and an 8-ohm speaker, the maximum current is 1A.

Instrument cables aren't rated by current handling, but probably up to about 1A is OK. So if you are talking about powers of a few watts or less, it should be safe.