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Author Topic: Guitar Hum  (Read 1703 times)

Tony Mamoh

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Re: Guitar Hum
« Reply #10 on: July 18, 2017, 02:20:19 am »

I need some education.....

Why can't a speaker cable using  a TS jack be considered as a temporary replacement for a regular guitar cable? Both supposedly have two conductors, with TS jacks.





I am somewhat surprised that no one has bothered to mention the ground lift button on the DI.

1. Be certain you are using a proper TS guitar cable to plug the guitar into the DI. Using a 1/4" speaker cable is no good at all and TRS cables are not for this purpose.

2. If you are certain you are using the right cable, then try flipping the Ground Lift switch on the DI box. It may help reduce the noise or it may make the noise worse. You won't know until you try. I always try to start with the switches in the Grounded position and switch them to the Lift position if there is noise.

3. Also, check any pad switches on the DI box and disengage them. For a typical acoustic guitar, you should not need any engaged, unless the guitar is outfitted with an active pickup of some flavor and is providing line level output instead of instrument level. If that is the case, then you will not be able to turn the console's input sensitivity down low enough to stop from clipping the input. You will need to engage the pad on the DI box.
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Scott Holtzman

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Re: Guitar Hum
« Reply #11 on: July 18, 2017, 02:54:10 am »

I need some education.....

Why can't a speaker cable using  a TS jack be considered as a temporary replacement for a regular guitar cable? Both supposedly have two conductors, with TS jacks.

The low signal levels of an instrument are much closer to the noise floor than the high levels of a speaker.  Also the impedance of a guitar pickup is quite high, a bridge pickup is 10k.  The impedance of an instrument amplifier is also very high, possibly over 100k.  High impedance inputs require shielded cables.  Speakers require larger conductors to carry the high current.

A speaker cable will pickup noise and not conduct the low level signals of an instrument well.

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Don T. Williams

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Re: Guitar Hum
« Reply #12 on: July 19, 2017, 05:13:12 pm »

Scott is correct for the reasons he listed.  You could "possibly use" a speaker cable in an absolute emergency, but it would probably be very noisy.  Further, the reason "guitar cable" isn't advisable for speaker level signals follows the same reasoning.  It is usually small gauge (24-20 ga.) so it has a lot of resistive loss.  It is also shielded which gives it a high capacitance.  Amps don't like that.  I'll bet all of us have used a guitar cable for a speaker cable in an emergency, but there are very good reasons not too.
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Tony Mamoh

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Re: Guitar Hum
« Reply #13 on: July 19, 2017, 06:43:17 pm »

Scott is correct for the reasons he listed.  You could "possibly use" a speaker cable in an absolute emergency, but it would probably be very noisy.  Further, the reason "guitar cable" isn't advisable for speaker level signals follows the same reasoning.  It is usually small gauge (24-20 ga.) so it has a lot of resistive loss.  It is also shielded which gives it a high capacitance.  Amps don't like that.  I'll bet all of us have used a guitar cable for a speaker cable in an emergency, but there are very good reasons not too.

I know for sure a guitar cable is of very high gauge and therefore will not conduct some of the high currents that pass through a power amp to a speaker. I wouldn't use a guitar cable even in an emergency for a speaker!! That could result in a fire!!. I'd rather use 2 conductors from a power cable.

Okay folks. I hear you. The biggest reason why a speaker cable cant be used in an emergency for a guitar cable is the SHIELD. I understand all that. I also understand high Z devices. Case closed. Many thanks for your clarification.

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Andy Thisse

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Re: Guitar Hum
« Reply #14 on: July 26, 2017, 12:55:00 pm »

You might also check to see if the phantom power (+48V) is turned on in your guitar channel.  Sometimes you can have problems with active devices while sending phantom power.  You could also try turning the "battery" switch on & off to see if there is any change (maybe change the battery as well).  Just something else to try once the other suggestions have been tried.  Looks like that DI accepts balanced or unbalanced inputs, but I have never worked with that model personally.
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Andy Thisse

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Re: Guitar Hum
« Reply #15 on: July 26, 2017, 01:01:50 pm »

Just looked at a picture of the device and it says "Phantom or 9V battery powered", so just to clarify on my previous post, maybe it's getting double powered (both 9V and console power) and creating noise. Since it was previously clean, not sure that this is the issue, but worth a try.
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William Schnake

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Re: Guitar Hum
« Reply #16 on: July 26, 2017, 09:36:25 pm »


Would there be any other ways of eliminating this hum?
Thanks

Joel, does you D/I have a ground lift?  If so try that and see if it helps or not.

Bill
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