can i use a trs to xlr cable for my acoustic guitar if my amp has an xlr input in both channels. i've heard you can get a cleaner quieter sound.

Probably not recommended. In most cases XLRs are used exclusively for balanced mics, not line or instrument inputs. There are plenty of exceptions of course, but that's the general rule...

The line inputs of most preamps won't be sensitive enough for a normal passive guitar output. If you use a mic input instead you risk damaging the guitar pickups if phantom power is activated accidentally, and the input impedance is only 1 or 2K instead of the 250k - 1M ohm impedance that the guitar really needs to see.

So you need to be very sure about what kind of input circuitry, sensitivity and impedance is being offered by your amp's XLR inputs.

There's also a very good chance that the socket on the guitar will be a tip-sleeve type with no ring connection. So if you plug in a TRS plug the ring connection will be left unterminated, which means that the 'cold' input (pin 3) on the XLR which feeds the differential input amplifier in your preamp will be floating (unconnected)... and that will produce more noise (and probably interference) rather than less.

So basically, the answer is NO -- unless you have an active guitar specifically designed to work this way, or there is some other good reason why it might work. It's certainly not the norm.

You could connect the guitar to a decent DI box which you then connect to the mic input of your preamp, though. I favour active DI's for the purpose...

hugh

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Technical Editor, Sound On Sound

Edited by Hugh Robjohns (21/12/11 12:33 PM)

Although Hugh is right in a general sense, there are exceptions. The Taylor Expression system is one that works best connected as you describe.

It would be helpful to know exactly what system you have in your instrument.

True... but that is a very manufacturer-specific active pickup system which is unusual and cleverly designed to work either as a standard unbalanced TS connection with a guitar-level output, or as a balanced TRS line-level connection.

Definitely NOT mic level in either case and while I presume the active cicruitry includes appropriate phantom-power protection, it would still be worthwhile taking suitable precuations!

hugh

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Technical Editor, Sound On Sound

i use a taylor 314ce with the es pickup system.

Doh! It really is important to provide ALL the relevant information when asking for help!

So, the answer you require is YES because your guitar has an active output system that is capable of sending a balanced line level signal to a balanced line input provided you use a balanced TRS-TRS or TRS-XLR cable.

Hugh

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Technical Editor, Sound On Sound

doh, sorry about that Hugh.

No problem. Glad we got to the right answer in the end.

Hugh

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Technical Editor, Sound On Sound