Old mic cables put to good use

  • Thread starter Thread starter TheChikenMaster
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TheChikenMaster

TheChikenMaster

I'm Unbalanced
This is cool. We have an aiwa nsx v70, my dad wanted the speakers on the other side of the room from the reciever. So i modified a couple of short old bad mic cables turned them into stereo cables hot left cold left. connected one cable to the receiver leaving the female connector on. and the same with the speakers accept a male connector. and there is about a 25' mic cable in between. Its so cool to take advantage of old balanced cables.
 
awesome!
except you shouldnt use shielded cable for speakers!
 
wonderfullly stupid idea... way too small guage wire...:laughings:
 
It works, and besides we are not talking about high powered amps here. If you saw the cables that came with the thing you would die of laughter. If anything this would be a step up:laughings: Cheesy consumer poop so were the cables:D
 
that it's small amps makes it all the more important that they be of a reasonable gauge... why lose what little you got by driving a bad wire??? nit picking sure... but ringing out every bit we can is what cheap recording is about...
 
Electrically speaking, this is a bad idea and risks blowing out your dad's receiver/amplifier.

In addition to the obvious risks with undersized-gauge wire, any time you have more than one wire you have capacitance between the wires. With unshielded speaker cable, you have the small capacitance between the two unshielded wires. With shielded cable, you add in the additional capacitance between each wire and the shield, leading to much greater capacitance. With a short run of 6-8 feet in a typical home stereo set-up, this may not be a big deal. But you have a 25-foot run, which increases the capacitance problem.

Capacitance on an amplifier output is a load on the signal and can cause phase shift and oscillation at high frequencies. You may not hear these high-frequency oscillations due to the limits of human hearing, but your amplifier is constantly amplifying them and overworking and overloading itself due to the oscillation. Maybe your amp burns up, maybe your speakers, maybe both.

The other problem shielded cable can cause is if you actually try to ground the shielded wire. If you have any short from the shielded wire to the speaker wires, you may blow your amp. Do a little searching on the impact of open circuits and short circuits on the outputs of solid-state and tube amplifiers if you want more specifics. A short between your shielded wire and speaker wire in this situation can happen any number of ways -- existing wear and tear on your old mic cable, plugging/unplugging the connectors, poor connector wiring, etc. If you are using a shielded speaker cable at all, the shield should be ungrounded and floating. This of course eliminates any benefit to the audio signal coming through your speakers.

Just food for thought.
 
toddyjoe said:
Electrically speaking, this is a bad idea and risks blowing out your dad's receiver/amplifier.

In addition to the obvious risks with undersized-gauge wire, any time you have more than one wire you have capacitance between the wires. With unshielded speaker cable, you have the small capacitance between the two unshielded wires. With shielded cable, you add in the additional capacitance between each wire and the shield, leading to much greater capacitance. With a short run of 6-8 feet in a typical home stereo set-up, this may not be a big deal. But you have a 25-foot run, which increases the capacitance problem.

Capacitance on an amplifier output is a load on the signal and can cause phase shift and oscillation at high frequencies. You may not hear these high-frequency oscillations due to the limits of human hearing, but your amplifier is constantly amplifying them and overworking and overloading itself due to the oscillation. Maybe your amp burns up, maybe your speakers, maybe both.

The other problem shielded cable can cause is if you actually try to ground the shielded wire. If you have any short from the shielded wire to the speaker wires, you may blow your amp. Do a little searching on the impact of open circuits and short circuits on the outputs of solid-state and tube amplifiers if you want more specifics. A short between your shielded wire and speaker wire in this situation can happen any number of ways -- existing wear and tear on your old mic cable, plugging/unplugging the connectors, poor connector wiring, etc. If you are using a shielded speaker cable at all, the shield should be ungrounded and floating. This of course eliminates any benefit to the audio signal coming through your speakers.

Just food for thought.
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interesting thought... but i doubt that capacitence would be an issue here... as it's on an output it doesnt really feedback to the amp unles the amp is basicly un-dampted (not likely) remember passive Xovers use caps all the time...
 
dementedchord said:
interesting thought... but i doubt that capacitence would be an issue here... as it's on an output it doesnt really feedback to the amp unles the amp is basicly un-dampted (not likely) remember passive Xovers use caps all the time...
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This happens to be the case here exactly. It like in a lab dont drink anything w/o a label. Dont just plug things in.:)
Thanks for all the helpful input and info, very educating:)
 
TheChikenMaster said:
This happens to be the case here exactly. It like in a lab dont drink anything w/o a label. Dont just plug things in.:)
Thanks for all the helpful input and info, very educating:)
Click to expand...

ok... so if you Know this why ask the question??? what is your source???
 
dementedchord said:
interesting thought... but i doubt that capacitence would be an issue here... as it's on an output it doesnt really feedback to the amp unles the amp is basicly un-dampted (not likely) remember passive Xovers use caps all the time...
Click to expand...

Passive crossovers typically use caps in series with one speaker terminal (and may or may not include one or more inductors depending on the circuit). Conversely, I am referring to capacitance between the wires and in parallel to the speaker terminals, i.e., across the amplifier's output rather than in-line with one side of it. Different electrical effect. Think of the whole output circuit as one big electrical/feedback loop: positive amplifier output goes to the positive speaker terminal, through the speaker load, back out the negative speaker terminal and into the amplifier's negative output terminal. Obviously if you break this electrical loop the circuit is broke and the speaker does not produce sound. If the loop is complete but you add a capacitor midway across the loop, you change the electrical characteristics of the system as I discussed. That is analogous to the situation when you have appreciable capacitance caused by your output cabling.

Sorry for any confusion.
 
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no confusion... a passive low pass filter has a cap to grnd... no different than interelement cap of 2 wires...
 
dementedchord said:
no confusion... a passive low pass filter has a cap to grnd... no different than interelement cap of 2 wires...
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Typically, a low-pass filter on a passive crossover network is a series inductor without a capacitor, is it not? I understand that we can offer hypothetical electrical situations back and forth for hours so I do not want to detract from or sidetrack this post. I only wished to point out that generally recommending the use of old microphone cables for speaker cables on someone else's equipment (the original poster mentioned it was his father's system) should not be done without some degree of caution or at least forethought and understanding of the equipement and setup at issue. In the wrong situation you risk damage, and I think we can all agree on that.
 
toddyjoe said:
Typically, a low-pass filter on a passive crossover network is a series inductor without a capacitor, is it not?



should not be done without some degree of caution or at least forethought and understanding of the equipement and setup at issue. In the wrong situation you risk damage, and I think we can all agree on that.
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it's the cap to grnd that rolls off the highs...

agreed just wanted clarification for anyone else that reads this....
 
dementedchord said:
it's the cap to grnd that rolls off the highs...

agreed just wanted clarification for anyone else that reads this....
Click to expand...

Agreed, and I think I should also clarify my comments for technical accuracy. A capacitor-to-ground arrangement for a low-pass filter like you mention will form a feedback phase-lagging network. Indeed, all filters produce some phase shift, which is how we end up with products like phasers. My earlier comment comparing a shielded cable to a single capacitor across the output is not the best example because with a shielded cable you are actually dealing with three capacitors, not one. The three form an interconnected loop of distinct capacitors within the normal output circuit: (1) positive wire to shield capacitance; (2) negative wire to shield capacitance; and (3) positive wire to negative wire capacitance. Unlike a simple capacitor-to-ground filter, not every capacitor in this loop shares a common ground. As any Albert Collins guitar fan can tell you, the combined capacitance and filtering effect of a standard shielded cable is by no means insignificant; it is measurable and audible to the human ear with a common audio amplifier. Capacitance leads to filtering, filtering leads to phase shift, and depending on the situation and your set-up, phase shift may lead to the risks I previously mentioned.

I apologize for any incomplete explanations I gave earlier or any misleading info caused by my prior example. While I am all for re-using and recycling old equipment, I would hate for someone to read the original post and try to use an old mic cable as a makeshift speaker cable for their vintage McIntosh stereo system.
 
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