Some Balanced Cabling Questions???

[jokerjkny]

hey all,

so i'm pretty familiar w/ unbalanced and balanced cabling, but i have some questions on certain scenarios:

- is a "TRS" 1/4" cable the same as "balanced" 1/4" cable?
- can i use a balanced 1/4" cable to connect two unbalanced devices? i heard i CAN NOT do this, but can do the opposite, i.e. connect two balanced devices w/ an unbalanced cable at the risk of interference using long runs.
- is all RCA "unbalanced"?

thx!

 

[TAVD]

TRS is usually balanced.

RCA is unbalanced.

You can use a TRS cable to connect 2 unbalanced devices, but you might not want to use TRS to go from balance to unbalanced, although it sometimes works. Use TS instead. The best practice is to just use the proper cable.

 

[MichaelK]

If you buy a standard TRS male to male cable at GC or online, it's a balanced cable... unless it specifically says otherwise.

A balanced 1/4'' plug is TRS, but a TRS plug can also be wired up in a send/return configuration, e.g. an insert cable. That uses a TRS plug at one end but it's an unbalanced connection. Also, if you use a standard TRS cable for, say, a stereo guitar output, it's unbalanced.

I've used TRS for unbalanced to unbalanced in a pinch and it has never NOT worked, though as D.G. says it's better practice to use the right cable.

 

[MichaelK]

As I was sitting at the synth keyboard just now I thought of another use for TRS cables (not that you asked, but what the hell)...

Some MIDI controllers, like volume/expression pedals, use TRS cables. Unbalanced cables won't work. I guess it's a MIDI in/out connection.

 

[jokerjkny]

thx guys,

but now begs the question, what is exactly a "TRS" cable for?

also, is this 1/4" cable a balanced cable? doesnt say if its unbalanced or balanced.

and is this (1/4" + RCA) cable, most likely unbalanced?

AND, i think i should explain what i'm doing with all this craziness :

trying too hook up properly my recently purchased Presonus FireBox to a house mixer. with it, i usually record most gigs i use w/ a simple stereo mic, but i found out i can also record simultaneous w/ a pair of TRS balanced line inputs into the Firebox. so i'll get a nice balanced sound of both the direct mic'd from the house mixer and the stereo ambient sound of the mics.

but i'm not really sure where or what to use on most house mixers. i guess i could use the tape out, but most i see are RCA. i guess i could use whatever 1/4" send is on the mixer, but are most 1/4" sends on a mixer balanced regardless? just wanna be sure.

and thx again guys. this lounge is sooo underrated.

 

[TAVD]

Check out the reference pages @ www.rane.com for more info than you'll ever want.

BTW, those cables are both unbalanced. You need a third conductor for balanced operation, hence the TRS plug.

 

[MichaelK]

RCA tape outs from a mixer are unbalanced. You need either RCA to 1/4", as in your second link, or RCA to RCA with two 1/4" adaptors. Your connection to the FireBox will be unbalanced, but that's the best you can do.

Most unbalanced tape outs are -10 dBV while balanced inputs are usually geared to receive +4 dBu. Your record level may seem extremely low how matter how much you crank it. The FireBox probably has instructions for how to set it to accept a -10 dBV signal. Maybe a switch or something. Just make sure you switch it back again before you connect a +4 source.

 

[TAVD]

Most live boards have balanced connections on the 2-bus outs. The main outs will be in use, feeding the PA but you might get lucky a find an aux pair of balanced outs. There are many boxes that'll get your -10 signal to +4. I don't think it'll be needed since you'll likely have a short run from the board to the firebox. As long as the firebox inputs are set accordingly, you're not going to hear a difference.

As to what connections the board has, they're all different from board to board. If you play the same place, it's not a problem once you get it set up. Otherwise, you might want to buy some adaptors and maybe some inline transformers.

You might also find that after all of this, the sound coming off the board might not be very good, with all the eq and levels to compensate for the room and stage volume, and whether there's any processing done down the line.

 

[LSchefman]

The real question is whether WE are balanced or unbalanced.

For the record, I'm unbalanced as hell.

 

[mccreadyisgod]

A balanced cable needs three wires: Hot, cold, and ground. The hot and cold carry the same signal, out-of-phase, and then the two signals are combined in-phase at the preamp or input to create a strong, interferance-free signal. XLR has three pins and three wires, hence balanced. A TRS cable has three connection points: the Tip, the Ring, and the Sleeve; and three wires as well. It is used for balanced line-level signals, whereas the XLR is used mostly for balanced mic-level signals. A TS cable (Tip-Sleeve) has two points and two wires, so it is unbalanced. Same with an RCA cable.

The way to tell the difference between a TRS and TS cable (balanced vs. unbalanced 1/4") is look for the ring. No ring = Not balanced.

The trouble comes when TRS is used for stereo or insert signals. A TRS cable can be used for stereo signal, like a headphone jack, where one wire is Left, one is Right, and one is a shared Ground. In this case, each signal only has one wire, so the signal is unbalanced. The same is true of an insert cable, where the send is on one wire, the return is the second wire, and shared ground is the third. Most insert cables have a TRS jack at one end and two separate TS jacks at the other end. Ironically enough, if you plugged the TRS end of an insert cable into a 1/4" headphone jack, one of the mono plugs on the other end will be Left and one will be Right.

Because a TRS cable can carry a stereo signal, it is occasionally referred to as "stereo 1/4". Regular TS cable is therefore referred to as "mono 1/4". TS cable for audio gear is the exact same as TS cable for guitar or keyboard... just regular instrument cable. Just be sure not to mistake it for Speaker cable, and vice versa... don't mess with shielding, impedance, and wire guages...

Comprende?

 

[fin]

nice little summary, thanks.