quasi-balanced signal

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Carlitoboy

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Hey all!

Not sure if this is the appropriate forum for this newbi question.

My guitar amp has a 'line out' to connect directly to recording equipment - In my case, my 'line in' on my PC's sound card. My owner's manual for the amp states, "Using a stereo cord in this jack will provide a quasi-balanced signal. A mono cord will provide an unbalanced signal".

Quasi-balanced sounds like a good thing! ...I think.

What's the difference between the two signals? What are the reasons why someone needs to use one or the other? What does it mean to me and my sound card?

Cheers!
 
Please tell me this isn't a Behringer amp...

This is a term that means a floating unbalanced line. Think of it as an unbalanced signal using an unnecessarily expensive cord.

RANE PRO AUDIO defines it as

"A quasi-balanced output stage consisting of an unbalanced output connected to the tip of a ¼" TRS (tip-ring-sleeve) jack through an output resistor (typically in the 50-300 ohms range). An equal valued resistor is used to tie the ring terminal to signal ground. The sleeve connection is left open or "floating." Thus, from the receiver's viewpoint, what is "seen" are two lines of equal impedance, used to transfer the signal. In this sense, the line is 'balanced," although only one line is actually being driven. Leaving the sleeve open, guarantees that only one end of the shield (the receiving end) will be grounded. A practice that unbalanced systems often require. For trouble free interconnections, balanced lines are always the preferred choice."
 
So, quasi-balanced is just another term made for unbalanced then huh.

Anyway, this article is talking about sleeve tips. Are these the rubber sleeves that cover each end of a 1/4 jack?
 
Do a google search on the term "TRS" and "audio" and you should find some good information.

The term refers to the electrical conductor on a 1/4" plug. There are two types - one with two conductors and one with three.

An unbalanced cable connector has "tip" (hot) and a "sleeve" (neutral or ground) conductors.

A balanced cable connector accommodates a third conductor - which terminates in the "ring" you see on the plug. (Similar to a headphone plug that carries two channels at once). The connector is called TRS for Tip, Ring, Sleeve. What makes a balanced line different from a headphone line is the nature of the signal it carries.

A TRS line is capable of carrying a balanced monaural signal, meaning there is a polarity inversion between two otherwise identical hot signals, that takes advantage of a trick of physics to lose accumulated line noise. Tip = hot, Ring = inverted polarity hot, and Sleeve = neutral (which is not grounded).

The same concept applies with microphone lines, usually having XLR connectors. They are also balanced lines, with only the form of connector being different. People tend to prefer XLR connectors because they are much stronger and more reliable than a 1/4 " plug.

Balanced lines are quiet. That's what it's all about.
 
Cheers Treeline! I think I got the idea now!

I never realized there's so much to consider in chords and wires!
 
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