Topic: Other strange digital noise in recording

[nosaj56]

Hi, so I've noticed some digital noise in my recent recordings.  I've recorded about nine shows with my current setup and I've only noticed this noise on my seventh and ninth recordings.  I definitely did not hear this noise on my first through fourth recordings.  I haven't yet processed the fifth recording onward, so I've just noticed this noise through quick scrub through's.  The sound is infrequent, usually only lasting for a few seconds.  I noticed that it lasts for about 20 seconds on my most recent recording and in the sample.  It sounds like the noise I used to hear if I put my cell phone next to my computer speakers several generations ago while the cell phone was communicating with a cell tower.  I got into the habit of putting my phone into airplane mode when the show is going on.  To further isolate things, for this most recent recording (where the sample is from), I completely turned my phone off during the show and moved it to another pocket further away from my recorder.

So, I think that the noise is probably caused by the cable going from my preamp to M10.  I have used this cable since 2010 in my car to listen to music from my phone through my car stereo.  I didn't notice any problems with it on my first recordings, but now this noise has showed up.  I check the recording level frequently by removing the M10 from my pocket, so that might be part of the problem.  I definitely don't hear the noise nearly every single time I removed the M10 from my pocket and I don't think I touched the M10 during the part where the sample was recorded.  I really hope that it is the cable and not something wrong with the M10.

I haven't removed the microSD card from the M10 recently.  I have been using the supplied USB cable directly to the M10 to transfer recordings from it.  Back during my first few recordings with this setup, I would remove the microSD card and directly transfer recordings from it.  I noticed that I had to reinsert it in exactly the right way for the M10 to recognize the card again, so I stopped removing it.  Could the M10 be having some trouble writing to the microSD card and that be the problem?  I really hope the problem isn't with the preamp, mics, or the M10 itself. 

My lineage: CA-14 Cardioids > CA-9100 > 3 foot Monster stereo cable > Sony PCM-M10.

Order I would prefer to be the cause of the problem, but I hope it's just the cable:

1. 3 foot stereo cable
2. microSD card
3. preamp / mics
4. the M10 itself

Sample is here: http://www.2shared.com/file/RZKUo2lJ/digitalnoisesample.html  What do you think?

[RemotelyLocated]

Hi. Yes, that sounds just like typical GSM cell phone noise. Many preamps or amps (or recorders with those built in ...) will pick it up even if your mics and cables are perfectly isolated from RF.

I used to hear it all the time at home from my computer's small powered speakers. And so on.

So if it wasn't you, someone else nearby had their cellphone on. And yes, it could be that someone had an older phone there. You want a good 10ft. or 15ft. minimum distance away from the cellphone, methinks.

[adrianf74]

What RemotelyLocated just said...

That's definitely cellphone interference that your mics picked up.  It's one of the major nuisances with small, unbalanced, microphones.  In today's day and age, people on their cellphones (especially BlackBerry's with 2G connections) can't be avoided and this is the end result.

I can honestly say that I've never picked up cell interference with a battery box only but I'm not guaranteeing that's 100% foolproof, either.

[nosaj56]

Thanks for the quick replies, do you think that getting a different cable to go from the preamp to the M10 could improve the situation and make it less likely for interference to be picked up?  I was thinking about a GAKable:  http://taperssection.com/index.php?topic=133186.0  Changing this cable would still leave the mic cable and the rest of the setup unchanged.  I do really like this setup, but this interference is a little annoying.

[RemotelyLocated]

When I've caused this noise at home there weren't any mics around. Just a stereo system left turned on, or computer's speakers left idling. The radio (i.e. a transmitting GSM cell phone, as it searches for a tower) overpowers a nearby amplifier's ability to reject it because the FCC dropped the ball years ago by not ensuring cell manufacturers play nice with normal audio gear.

Newer phones, or perhaps simply phones operating on 3G are better designed. My iPhone4 -- an old phone today -- won't create this noise. Our original iPhone always did ... but it's 2G only. That last part may be important, because if it's caused by the older 2G cell network, even a new smartphone could cause the interference if it automatically switches over at the venue due to poor 3G reception.

Keep in mind, none of this discussion applies to CDMA phones (Verizon, Sprint networks.)

I really doubt it's normal "RF noise" that you could reject with batter cabling, because I do not suspect your mic and cables are picking it up. I think your preamp or other circuitry is, honestly, and that only greater distance away will cure it.

Try the new cable, but unless you can create the same conditions you won't know if it actually helps.