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Instrument cable?

Discussion in 'Amps and Cabs [BG]' started by ghouldani, Oct 20, 2005.

  1. ghouldani


    Sep 14, 2005
    On the back of my cab there are 2 inputs side by side. I would presume these represent the left and right channels. On the back of the head there is a mono, left, and right channel input. Can I plug an instrument cable from one of the channels on the back of the cab to the mono on the back of the head?
  2. Tryxx

    Tryxx Sputnik Forums: Bass Mod

    Jun 1, 2005
    Hurst, Texas.
    It MUST be a speaker cable. Do NOT use an instrument cable with your cab.

    I'm guessing instead of left and right, it's input and output. But I'm probably wrong with that one.
  3. ghouldani


    Sep 14, 2005
    What happens if I use an instrument cable?
  4. Tryxx

    Tryxx Sputnik Forums: Bass Mod

    Jun 1, 2005
    Hurst, Texas.
    Quoting "The Bass Player Book."

    Do not use instrument cables to hook up your speakers. This can result in intermittent power loss, cause your power amp to oscillate and damage itself and/or your speakers, and render the cable useless for any purpose.
  5. Trevorus


    Oct 18, 2002
    Urbana, IL

    Most speaker cabinets are not stereo. They usually have 2 jacks to connect to another cabinet. One goes to the amp, one to the other speaker cabinet. Do not hook this up as left and right, because you will feed your two sides of the amplifier into each other, usually resulting in mutual destruction.
  6. Brad Maestas

    Brad Maestas Gold Supporting Member

    Nov 26, 2003
    Oakland, CA
    Ah, you guys are quick! +1

    Instrument cable is shielded and speaker cable is not. You run the risk of overheating your amp and possibly destroying it if you use instrument cables between the amp and the speakers. Many people overlook this and end up with big bills.

    You said, " On the back of the head there is a mono, left, and right channel input."
    What head is it? Any Mono, Left, or Right inputs on the back of an amp are going to be for the effects loop. You want the speaker outputs.
  7. The issue with using instrument cable isn't the shielding, it's the size of the conductors in the instrument cable. Instrument cable is 22 or 24 gauge, on cheap cables maybe thinner, with itty bitty crimped or soldered connectors. This thin cable (and lousy connections) doesn't handle large amounts of current, and there's lots of resistance. On a high-powered bass amp you could be pulling several amps of current....with thin instrument cables, the cables can overheat (especially at stress points such as the connections) and even melt. A cable which has failed into a dead short can fry your amp.

    For high power bass amps, a 16 gauge speaker cable is the least I'd use, some people prefer 12 gauge (the lower the number, the heavier) or even 10 gauge. For my PA I use 12 gauge on long (50 ft) cables, but a bass speaker cable is only going to be a few feet long.

    In an instrument cable the shielding is a necessity to keep external electrical noise from entering the signal path--the signal from your bass isn't strong enough to drown out external noise. Whereas with a speaker, the signal being sent to the speaker is far stronger than any noise that the cable would normally pick up, so the shielding isn't required.

    I would doubt that a modern power amp would be so sensitive that the extra capacitance from a shielded speaker cable would cause the amp to go into oscillation. There are a few esoteric audio amps that don't handle reactive loads well, but bass amps and power amps now are generally well-behaved.
  8. The shielding does play a part in it, because it adds capacitance in some form or something yadda yadda yadda to the cable, but yeah, fire bad FIRE BAD!
  9. Also, just out of curiosity, i never knew you got 10 gauge speaker cable! surely thats a bit overkill, especially seeing standard house wiring is 12 gauge
  10. The more technical explanation: output transistors in amps are nice and stable when they have a purely resistive load. However, no circuit ever has a truly pure resistive load, there will always be some inductance and capacitance. This comprises an LCR circuit, and LCR circuits have resonant frequencies. This now is a reactive load, instead of a constant DC resistance.

    Also recall that audio signals are AC. If the reactive load is too high, the amp can become unstable--the resonant frequency is low enough for the amp to start oscillating. Bad news, output transistors fry quickly.

    But there is good news: I just saved a bunch of money on my car insurance by switching to--oh wait...

    In reality, modern amps usually don't oscillate, partly because of their design but mostly because an extremely reactive load would be required (higher than most cables--even shielded instrument cables--would be).

    Glad I stayed at a Holiday Inn express last night.
  11. Brad Maestas

    Brad Maestas Gold Supporting Member

    Nov 26, 2003
    Oakland, CA
  12. I thought most house wiring was 14 gauge? Was that older standard? That was for 15A service, 20A would require 12 GA I guess, that's not unheard of now...

    Either way, the thing they're worried about with house wiring is hot wires melting insulation causing fires, and acceptable voltage drops from the wire's resistance when you plug large loads in.

    In an audio application, you want to avoid those things also, of course, but its better to get farther away from those limits since the fidelity of the waveform that gets to the speaker is also a criterion. So you want less tolerance for voltage drops, and a nice high current low resistance path to aid in damping the speaker.

    And you know what the women think of when they see you wrapping up that big thick manly cable at the end of the night. Yeah, baby.

  13. Unchain

    Unchain I've seen footage.

    Jun 20, 2005
    Tucson, AZ
    Not really, ProCo makes stellar 8-gauge cable, which when I A/B'd it with some standard 14-gauge, it made a HUGE difference. Lots more thump.
  14. Bob Lee (QSC)

    Bob Lee (QSC) In case you missed it, I work for QSC Audio! Gold Supporting Member Commercial User

    Jul 3, 2001
    Costa Mesa, Calif.
    Technical Communications Developer, QSC Audio
    The gauge of the loudspeaker cable matters more with increased length. For a cable of only a couple feet, whether the wire is 16 gauge or 6 gauge isn't going to make any difference worth worrying about. But if it's maybe 25 feet long, yes indeed it will.
  15. iriegnome

    iriegnome Bassstar style Supporting Member

    Nov 23, 2001
    Kenosha, WI 53140
    Wire for houses is a solid core wire not intended to move or be moved. Speaker cable is stranded to better handle the wrapping and unwrapping and all of the movement. While 14g is usually better for higher power output amps, 16g works just fine. Also, the 2 inputs on the back of your cabinet are parallel inputs. Both do the exact same thing. No Difference. Also, a really affordable trick for speaker cables :confused: :confused: Regular run of the mill EXTENSION CABLES. They are really cheap - $10 - 100 feet. Cut the ends off and you have the perfect speaker cables. Add your 1/4" ends and you are done. Custom lenght cables for cheap :D . Also, you can choose your colors. We use Blue for House, Orange for Monitors and Green for Side fill :bag:
  16. It might be different over here, i just know that thats what my mate uses in houses when they are being wired ( 12 Gauge ), and he is a certified sparky, think he said its the standard over here, not 100% sure now

    When i first needed speaker cable i got told something along the same lines, just to use lawnmower cable, which i spose would be cool, bright orange, mmm :smug: