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How should star quad cables be soldered to RCA connectors?

sergeauckland

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#21
Why would you use this star quad stuff for speaker cables, tho?
Normally, you wouldn't. In this case, I'm assuming it's an active sub-woofer, as otherwise it wouldn't be an RCA plug.

Star-Quad cable could be used for loudspeakers, as can Cat 5 cable, provided the run is reasonably short and the amplifier doesn't mind low inductance cable.

S.
 

Tks

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#22
Normally, you wouldn't. In this case, I'm assuming it's an active sub-woofer, as otherwise it wouldn't be an RCA plug.

Star-Quad cable could be used for loudspeakers, as can Cat 5 cable, provided the run is reasonably short and the amplifier doesn't mind low inductance cable.

S.
Is it "bad" to use it on a longer run? Leaving aside from economic downsides, I'm just wondering if using starquad is in fact causing some potential safety hazard or detriment in performance if opted for in unbalanced configurations?
 

sergeauckland

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#23
Is it "bad" to use it on a longer run? Leaving aside from economic downsides, I'm just wondering if using starquad is in fact causing some potential safety hazard or detriment in performance if opted for in unbalanced configurations?
The problem with using a microphone cable (or Cat5) for loudspeakers is the loop resistance. For short runs it doesn't matter, but for long runs it just adds a series resistance to the amplifier's output. Where the divide comes, depends on the cables and on the impedance variations in the loudspeakers, but I'd have no problem with 1-2m of any cable, go to 10m, and I'd want something thicker.

There's also the issue of capacitance and inductance. A twisted-pair microphone cable has high capacitance between cores, as they're twisted together. This is even more so for Star-Quad. Furthermore, by twisting the cores together, this reduces inductance, and there are some amplifiers out there of marginal stability that would be quite upset by the load presented by such cables. Cat 5 is less of a problem, as the 4 twisted pairs can be wired together in such a way as to avoid the increase in capacitance and decrease in inductance, so the only issue then is resistance.

As for using Star-Quad as an unbalanced interconnect, there's no benefit, and a pain to terminate. If I had to use Star-Quad cable unbalanced, I would use just one of the inner cores and the outer screen, and cut off the rest.

S.
 

H-713

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#24
Going from unbalanced RCA to balanced XLR is very easy, it's unbalancing a balanced output that's more difficult. Connecting Pins 1-3 is fine for the input, but shorting out an output is a problem. The ONLY time this can be done safely is with a fully-floating transformer-coupled output (possibly also the active equivalent, but I'm less certain about it being universal) Otherwise, the safest way is to leave XLR pin 3 floating and go between pin 1 (ground) and pin 2 (signal).

S.
Yup. The best practice is the consult the manual for the device with a differential output to see how they want it done.
 

H-713

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#25
The capacitance from star-quad microphone cable should NOT be a problem with unbalanced interconnects unless the line driver is an utterly horrible design. Seriously, what's the output impedance of a microphone? In most cases, it's much higher than for any decent balanced line driver. Do the math and figure out where your corner frequency will be with a typical line driver. It's not even close to being in the audible range.

If a power amp has such marginal stability that it can't handle the capacitance of a star-quad speaker cable, then that amplifier has no right to be on the market. The only amplifiers I've seen that are that unstable usually only last a few days before the blow up. The capacitance of a star-quad cable is high for a cable, but it's not that high. There's a good chance that if it can make it oscillate, the input capacitance from an AP box or even a scope could make it go ballistic as well.

I'm not saying that people should use starquad for interconnects and speaker cables, but I am saying that the electrical downsides are largely non-issues.
 

sergeauckland

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#26
The capacitance from star-quad microphone cable should NOT be a problem with unbalanced interconnects unless the line driver is an utterly horrible design. Seriously, what's the output impedance of a microphone? In most cases, it's much higher than for any decent balanced line driver. Do the math and figure out where your corner frequency will be with a typical line driver. It's not even close to being in the audible range.

If a power amp has such marginal stability that it can't handle the capacitance of a star-quad speaker cable, then that amplifier has no right to be on the market. The only amplifiers I've seen that are that unstable usually only last a few days before the blow up. The capacitance of a star-quad cable is high for a cable, but it's not that high. There's a good chance that if it can make it oscillate, the input capacitance from an AP box or even a scope could make it go ballistic as well.

I'm not saying that people should use starquad for interconnects and speaker cables, but I am saying that the electrical downsides are largely non-issues.
Whilst I agree that such amplifiers shouldn't be on the market, a few are. It's actually not the capacitance that's the problem, but the lack of inductance that makes them go unstable. Well designed amplifiers won't care, it's then only an issue of resistance, but not all amps are well designed.

Anyway, we're straying somewhat away from the original issue of using Star-Quad as an unbalanced interconnect for a subwoofer.

S
 
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#27
Oy, my brain...

Use the cable you have, attached the way you came up with in your revised post (Shield plus one colour connected to sleeve at both ends and the other colour as your hot / tip connection at both ends.)

As someone else mentioned: Unless the devices you are connecting are incompetently designed, the intrinsic capacitance, impedance and inductance of the star-quad cable *Doesn't Matter* at audio frequencies.

If you want to experiment with not connecting the shield at one end, go right ahead...

For further review, here's a handy guide from Rane Corp:

Sound System Interconnection (ranecommercial.com)
 

Chrispy

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#28
Normally, you wouldn't. In this case, I'm assuming it's an active sub-woofer, as otherwise it wouldn't be an RCA plug.

Star-Quad cable could be used for loudspeakers, as can Cat 5 cable, provided the run is reasonably short and the amplifier doesn't mind low inductance cable.

S.
Yes I can see it for active speakers/subs, but someone mentioned speaker cables earlier which made me scratch my head.
 

Robin L

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#29
Not good for speaker cable.
Ok for unbalanced terminations, though it's a waste of good microphone cable.
I'd wire the two white to hot, two blue to ground and the shield to ground.
I've read there's an theoretical advantage to soldering the shield to only one end of the interconnect, but forgot what the potential advantage is.
I've made unbalanced pairs with the stuff, get both channels on one cable, shield unwoven so it can reach the grounds on both sets of plugs on each end, get heat shrink tubing to cover the wires and make it cosmetically acceptable.
 
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#30
Oy, my brain...

Use the cable you have, attached the way you came up with in your revised post (Shield plus one colour connected to sleeve at both ends and the other colour as your hot / tip connection at both ends.)

As someone else mentioned: Unless the devices you are connecting are incompetently designed, the intrinsic capacitance, impedance and inductance of the star-quad cable *Doesn't Matter* at audio frequencies.

If you want to experiment with not connecting the shield at one end, go right ahead...

For further review, here's a handy guide from Rane Corp:

Sound System Interconnection (ranecommercial.com)
Pretty much this. Star quad isn't intended for unbalanced but don't think too hard about it, the above will work perfectly for you.
 

Chrispy

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#32
In my perusing various audio groups/fora on the interwebs seems "star quad" has some sort of "audiophile" magic going on :) Which isn't saying much considering the state of audiophilia generally.
 

tomchr

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#35
Is it "bad" to use it on a longer run?
No. It's not bad or unsafe. You just won't get any benefit from using Star Quad cable in an unbalanced interconnect.

The whole point of Star Quad is that it cancels electromagnetic fields much better than a twisted pair, so you get less hum induction on a Star Quad interconnect than you would on a regular twisted pair. Have a look here:

I've read there's an theoretical advantage to soldering the shield to only one end of the interconnect, but forgot what the potential advantage is.
I think the theoretical advantage could be that you don't have any ground current flowing in the shield. That leaves less crap to couple into the signal wire. However, the same ground current flows in the 'cold' lead and the two wires in a twisted pair are pretty tightly coupled, so you'll get some coupling of the ground crap onto the signal wire. It's possible that the capacitance from the ground wire to the signal wire is lower than that from the shield to the centre conductor in a coax, but I doubt it makes much of a difference. So in the end it's probably a wash.

This sort of stuff is why I use balanced inputs and outputs on all my gear.

Tom
 

preload

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#36
Whilst I agree that such amplifiers shouldn't be on the market, a few are. It's actually not the capacitance that's the problem, but the lack of inductance that makes them go unstable. Well designed amplifiers won't care, it's then only an issue of resistance, but not all amps are well designed.
S
That doesn't sound right. I think you have it backwards.
High capacitance can cause some amplifiers to go into oscillation, resulting in damage.
Low impedance = who cares. Even if your cable impedance is 0, your loudspeakers crossover and drivers are going to have some impedance. And even if your crossover and drivers were also 0 impedance (for the sake of argument), your amplifier would be driving a resistive load - what amplifier can't drive a resistive load?? In fact, I would go on to say that low impedance in a speaker cable is a desirable quality because it results in less frequency response variation.
 

sergeauckland

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#37
That doesn't sound right. I think you have it backwards.
High capacitance can cause some amplifiers to go into oscillation, resulting in damage.
Low impedance = who cares. Even if your cable impedance is 0, your loudspeakers crossover and drivers are going to have some impedance. And even if your crossover and drivers were also 0 impedance (for the sake of argument), your amplifier would be driving a resistive load - what amplifier can't drive a resistive load?? In fact, I would go on to say that low impedance in a speaker cable is a desirable quality because it results in less frequency response variation.
I wrote inductance, not impedance. Most amplifiers sensitive to capacitance usually have some inductance in series with the output, which counters the capacitance. However, there are some, like Naim (once, maybe still) and NVA that rely on the 'speaker cable being of high inductance for stability. Low inductance cable tends also to be high capacitance and vice-versa, but it's the lack of inductance rather than the high capacitance that causes these marginally stable amplifiers to go into oscillation.

S
 

tomchr

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#38
However, there are some, like Naim (once, maybe still) and NVA that rely on the 'speaker cable being of high inductance for stability.
That seems exceptionally sketchy. Never rely on something that's not within your control for stability.

Tom
 

H-713

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#40
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