[grc] A bit of trouble...

[Barbara K]

Hi Lanny and GRCers

It may be that the cable between the guitar and the guitar amp (or somewhere along the line between the guitar, the guitarist's effects pedal, and the amp) could be picking up the radio signal. Then, when that signal gets amplified, it's easy to hear the station.

Guitar cables are notoriously unshielded.  And due to a musician's income level, some musicians may be unable to afford high quality cable, opting for affordability and lower quality.

Stations that produce live music might consider purchasing high quality guitar cables (and a few 1/4" patch cables) to substitute in the guitarist's signal path (between guitar, pedals and amp) when interference is perceived. Just be sure to label the cables with your station's call letter as they can be easily overlooked when quickly wrapping a session.

Sometimes a long guitar cable is plugged directly into the mixing board, as often is the case with acoustic guitars.  

The longer the cable, them more opportunity for the cable to pick up interference.

Direct Input boxes, or DI boxes, reduce the length of an unshielded signal path, in that a short cable can be plugged in from guitar to DI, and a shielded mic cable comes from the output of the DI to the input of the mixing board.

Some DIs come with a ground switch which may be helpful during times of ground loops causing a buzz in the signal path.

DIs can be passive (requiring no batteries and no power) to active (requiring a power supply, often "phantom power' from a mixing board that generates phantom power and delivered through the mic cable that runs from the DI to the mixing board).

For a radio studio application, which may need to record/broadcast instruments ranging from electric/acoustic guitars to keyboards to computer generated signals, if your mixer is capable of generating phantom power, I'd suggest employing active DIs that are capable of receiving phantom power and also have a ground switch. For those without phantom power, (not being a fan of batteries for critical applications in seldom used recording equipment) I'd suggest active DIs with an external power supply and ground switch.

Barbara K


On Oct 31, 2016, at 5:41 AM, Jeff Shaw via grc <grc at maillist.peak.org> wrote:

> Hi Lanny- hopefully some actual engineers will chime in, but we would
> pick up our radio station (antenna on the roof) on our studio intercom
> system (we are also a public access tv station) until I bought a bunch
> of ferrite beads and put them on the lil' intercom cables:
> https://en.wikipedia.org/wiki/Ferrite_bead
> 
> I've also had many annoying buzzes in our poorly grounded studio when
> we've hosted bands.   Make sure the amps are plugged into the same
> circuit as the PA system (if you have a PA system).    I have to run
> long extension cords to get everything on the same circuit.    For the
> most part, this eliminated buzz. 
> 
> And yes, I've never really solved the amps picking up the radio station
> problem.  It has happened to us, though maybe it was dim enough perhaps
> we forget about it after they turn up a bit.   Plus I remember giving
> the musicians a replacement cable I believed at the time to be better
> shielded, so maybe the power of belief blinded our ears from the
> interference.    Honestly can't remember if that worked, but worth a
> shot.   Like I said, I hope some actual engineers chime in here.
> 
> Jeff
> 
> 
> On 10/30/16 8:56 PM, Frieda Werden via grc wrote:
>> A bad ground may indeed have something to do with it, but a looped wire can
>> definitely turn into an antenna.  You could have tried straightening out
>> the cords of the guitar amps so wires did not cross themselves or each
>> other, to see if that solved it.
>> 
>> On Sunday, 30 October 2016, Lanny Cotler via grc <grc at maillist.peak.org>
>> wrote:
>> 
>>> Greetings Brothers and Sisters of the Greater GRC,
>>> 
>>> As some of you know, we’re a brand new LPFM broadcasting on 97.9 out of
>>> Willits, CA (in the heart of the NorCal Redwoods. I’m hoping a couple of
>>> you might have some troubleshooting suggestions for us.
>>> 
>>> Here’s a note from our Chief Engineer, Roger Wilson,
>>> 
>>> We have a problem at the KLLG station and need experienced, professional
>>> audio engineer ideas.
>>> 
>>> Two different Bands played at the Grange main room.  Each time, when their
>>> guitar amps were plugged in on the stage; they picked up our station.
>>> 
>>> 1. I heard it.  soft voices and music (I clearly understood the voices,
>>> recognized them.) And a loud (louder than the voices) buzz. (it did not
>>> sound like just AC hum.)
>>> 2. when I placed my hand near (a couple of inches) the Amp power cord; the
>>> buzz changed.
>>> 3. The only remedy I had was to turn off our transmitter.
>>>      a. that reduced the buzz to almost not noticeable, and
>>>     b. no KLLG signal was heard at all.
>>> 4. Later, after the transmitter was off, their sound guy was cleaning up
>>> the stage (before the musicians appeared.)  When he bundled all the power
>>> cords together, the buzz disappeared.
>>> 
>>> This sounds (to me & the sound guy) like a bad ground.
>>> 
>>> help!  any suggestions would be appreciated.
>>> 
>>> Your thoughts? We’re just starting out. Better now than later.
>>> 
>>> 
>>> 
>>> 
>>> 
>>> 
>>> 
>>> 
>>> 
>>> 
>>> 
>>> 
>>> 
>>> KLLG ~ 97.9 FM
>>> Lanny Cotler, General Manager
>>> A Project of Little Lake Grange #670
>>> Willits Hometown Radio—Low Power, High Energy
>>> P.O Box 820, Willits, CA 95490
>>> 707-367-1812
>>> LANNY at KLLG.ORG <javascript:;> <mailto:LANNY at kllg.org <javascript:;>>
>>> 
>>> 
>>> 
>>> 
>>> 
>>> 
>>> _______________________________________________
>>> grc mailing list
>>> grc at maillist.peak.org <javascript:;>
>>> http://maillist.peak.org/mailman/listinfo/grc
>>> 
>> 
> 
> 
> -- 
> Production Manager, Davis Media Access
> Station Director, KDRT-LP
> 
> "There is no future that is not built in the present" - Sanchez Gordillo
> 
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