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getting a shock from my speaker cable!

Bo Faulkner

Member
Messages
3,825
What would cause my speaker cable to give me a jolt? it happened the other day.. touched the cable where it plugs into the back of my 412 cabinet and it bit me! it hasn't happened since
 

Bo Faulkner

Member
Messages
3,825
ye. s it was was plugged and on!
to the best of my knowledge grounding was ok. I would imagine there is possibility that could have been it I was thinking the amp was plugged directly into wall. pedalboard could have been plugged into something that was missing a ground plug?
 

RussB

low rent hobbyist
Messages
11,174
static or A/C shock?

Time to get a plug tester and check the outlets


 

Kyle B

Silver Supporting Member
Messages
5,035
Your amp should be OFF when connecting a speaker. You're not hot-plugging your gear are you????

If you got a shock with the amp OFF, you do indeed have a very serious problem that needs solved. Try the outlet tester. It won't find 100% of faults, but the most common scenarios are trapped by it.
 

bobshbob1

Member
Messages
3
Sounds like "+" and "-" are reversed somewhere, like if you made the speaker cable out of lamp cord and wired one end in reverse. It would still technically work but the voltage driving the speakers would show up on the plug barrel where it connects to the cab. Don't ask how I know this.
 

twangbanger

Member
Messages
1,492
ye. s it was was plugged and on!
to the best of my knowledge grounding was ok. I would imagine there is possibility that could have been it I was thinking the amp was plugged directly into wall. pedalboard could have been plugged into something that was missing a ground plug?
Not a good idea to do this while the amp is on. Still doesn't address your shocking situation but recommend that when plugging and unplugging speaker don't do it w/ the amp running. If you had someone playing through it and no load connected to the output transformer I think you might get a good shock from it or you might toast your output transformer.Did I mention this is a really bad idea?
 

dani_boy79

Member
Messages
663
Not a good idea to do this while the amp is on. Still doesn't address your shocking situation but recommend that when plugging and unplugging speaker don't do it w/ the amp running. If you had someone playing through it and no load connected to the output transformer I think you might get a good shock from it or you might toast your output transformer.Did I mention this is a really bad idea?
exactly! a no-load on the Output Transformer would cause very high Voltage to be present which could puncture the winding insulation wrecking the Transformer and possibly other components.
 

8len8

Silver Supporting Member
Messages
13,172
Sounds like "+" and "-" are reversed somewhere, like if you made the speaker cable out of lamp cord and wired one end in reverse. It would still technically work but the voltage driving the speakers would show up on the plug barrel where it connects to the cab. Don't ask how I know this.
Incorrect. The amp output is AC so polarity doesn't matter.
 

bobshbob1

Member
Messages
3
Incorrect. The amp output is AC so polarity doesn't matter.
I think the terminology I used was not the best. The reason I replied to this post is that I have experienced being shocked by a speaker cable that was wired incorrectly. The AC voltage going to the speaker is present between the tip of the plug/cable and the sleeve. The sleeve is electrically connected to the plug barrel (thing the OP touched) and also to the amp chassis, and is held at 0V. So if you touch the tip while it is connected to the amp and you are playing through the amp (applying a voltage between tip and sleeve) you will indeed get shocked, but if you touch the sleeve/plug barrel/chassis you will not (it is connected to ground). Touching the tip while it's plugged in is very hard to do, though.

Now imagine you have the two wires in the speaker cable reversed at one end. The tip at the amp end is connected to the sleeve at the cab end, and vice versa. The speakers only care about the voltage Difference between the two, so they still work normally. But now at the cab end of the cable, the tip of the plug is at ground (0V), and the sleeve/barrel is at whatever voltage is driving the speakers, so you will feel something when you touch the sleeve/barrel *at the cab end*, which is what the OP reported doing.

Sorry for such a long-winded reply, the original question just made me think of exactly that scenario. That or the speaker cable jack(s) have lost their ground connection inside the amp. I would imagine that if there was a different grounding issue, such as one originating in the wall outlet, that you would also be shocked by the guitar strings, since they should be connected to the same ground as the speaker cable. Which is not to say the electrical outlet could be a problem, I just don't think it's as likely.

OP, have you tried a different speaker cable?
 

Bo Faulkner

Member
Messages
3,825
Wasnt "hot plugging" was just checking to make sure it was properly plugged in. my jack on cab may be suspect. It is an evidence audio cable. Would a sketchy jack allow a jolt to get me?
 

J M Fahey

Member
Messages
2,149
High power speaker outs can and do tingle you, not into death or paralysis but can definitely be felt, doubly so under stage or rehearsal sweaty hands conditions.

It's the amp audio output, not DC or wall voltage passing on.

A 100W RMS into 16 ohms amp (tons of amps that type) will give you 40 volts RMS **clean** and much higher spikes, up to 70/80V peaks if overdriven into a speaker load, which is inductive.

IF the cabinet plug gets loose and you touch it, even higher voltage is possible.

Of course it translates to transformer perforating, tube and socket arcing thousands of volts at the primary.

A 300W into 4 ohms SS amp will also supply some 35V RMS (50 V peak) clean or clipping.

I have "tasted" them so many times that I took care of measuring them, go figure.

Don't even imagine what a shock big PA amp can give at its output.
 

Bruce Gerard

Member
Messages
136
If the amplifier has isolated outputs you can easily receive a shock. The "ground" of the chassis will not be the same as the "speaker ground" , so if one part of your body touches the speaker plug, while the other holds a guitar, microphone, etc.. you may just get lit up.
 

bobshbob1

Member
Messages
3
Yeah, sketchy jack or cable could do it. If you have a multimeter, different cable, and different cab it wouldn't be too hard to process of elimination-ize it.
 




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