Crackling Noise
 

I finally had a chance to use my new PSC Line to Mic Pad 50dB adaptor last night at a music venue. I plugged the attenuator into the XLR input of the Zoom H4n and the @5' XLR cable into it and the other in was plugged into a XLR to 1/4" adaptor into the line out on the soundboard.

I was getting signal I heard via the headphones and it seemed good except that after a few minutes I heard a crackling and figured it was the board dude's XLR to 1/4 adaptor. During certain songs it seemed to go away and I fiddle with the adaptor but I don't know what was going on.

Bottom line I had to unplug from the board and record with the Zoom's X/Y mics for the rest of the night.

I picked up a Mogami Gold TRS to XLR which I don't even know if that's really what the problem was.
I don't know the diff between TRS, 1/4" TRS, and 1/4" TS.

Any idea where that crackle might have come from?

Crackleing is often a sign of a loose solder joint, or corrosion on two mating contacts, dirt in a volume control, or something like that that causes the signal to be made and broken very briefly. TRS means tip, ring and shield; all parts of what is often called a stereo plug. A 1/4 inch one is, yeah, a quarter-inch in diameter. The tip is usually one channel, the ring (a small area of the plug shaft between two insulators) is the other channel and the shield is usually ground (the metal part of the shaft above the tip and ring.) Mono plugs are tip and shield only, don't have the ring.

If the plug or its mating jack have bad contact or corrosion, you can get crackeling. Of course there are other kinds of crackle -- clothing noise on a lav, etc. If you were at a music venue, modern music being what it is, it's possible that you were recording over 0dbFS, which gives you distortion, which can sort of be described as crackeling, in that the sound breaks up and distorts. That's a whole nother issue....

Maybe post a sample and we can figure it out.

Thanks Battle,

I was monitoring the recording level and it was never peaking to 0 so I'm thinking the loose solder joint or something..
I was wondering if the 50 dB attunuator is a standard line to mic pad version? Could it be I'd hear this if the pad was not the correct drop down?

Also, If I'm recording the sound into the Zoom's single mono channel, should the line out from the board also be mono verses the TRS 1/4" plug which sounds like it's stereo.

1/4 TRS can carry either 2 unbalanced mono channels for stereo (tip=left, ring=right, sleeve=ground) or a single balanced mono channel (tip=hot, ring=cold, sleeve=ground). The XLR input of the Zoom expects a single balanced mono channel. You defintely should be plugging into a balanced mono out from the board. An XLR to TRS adapter can be wired differently depending on whether it's used to convert a balanced mono, to mix both stereo channels and feed them to a balanced mono, or if the plug is TS, an unbalanced 1/4 to a balanced XLR or vice versa. Do you actually know if the adapter you used was wired properly?

If the board is able to send you balanced mono on a 1/4 TRS, why go through the pad and adapter tree? Use a TRS to TRS straight through patch cable and plug one end into a send from the board, the other into the line level TRS jack in the middle of the Zoom's XLR connector. The Zoom's "line input" is not a true line level, it's actually an instrument level, so you may need to adjust the send level at the board or add a pad but it won't be the -50dB you mentioned. Would be ideal if the board had a couple of available pre-fader aux sends that you could take your feed from so you could record stereo.

<<Do you actually know if the adapter you used was wired properly?>>
No. And that's the key to the mystery unless something else pops out in my account.

New venue and soundboard and the sound man was plenty busy. All he said was it was "a 1/4" line out" and he had 1/4" to XLRm adapter and I used his adapter.....Like I said some songs or parts of songs were fine but never could tell when the crackle pop would occur.

Are most "1/4 Line out" from soundboards mono or stereo?

Not really a simple answer to "most boards." I'd say most of the output buses are mono but that might vary from manufacturer to manufacturer. And then you have have things like my Mackey that has mono outs for each stereo channel plus a mono mix output that mixes both left and right to a mono line level output.

But we're getting astray from your initial issue which was the crackles. I'd suspect a loose connection or perhaps feeding too high a level into the recorder's inputs and getting clipping as a result. If the board operator was riding gain and your output was coming from a line output post main fader, some songs or passages could clip because the gain was up and others not because the gain was down.

Most boards you encounter will likely have at least two 1/4" line level outputs (L&R) and can be used in a balanced or unbalanced configuration. Some boards, like the Mackie SR series, as I recall, have an additional summed mono output with a trim level pot. In addition, most Mackies' main XLRs are switchable between mic and line level and are transformer iso'd from the 1/4" and RCA main outs. Whenever I patch into a PA (or provide a patch) I prefer to take an auxiliary send, which allows a different mix from the 'house'. Most aux. sends are mono, so for a stereo mix one would need to use two. A pre-fader aux. send is generally preferred because it will not have the FOH mixer's fader moves. It will however be subject to the pre-amp gain settings, so if the FOH mixer is not competent, you're f---ed either way.

thanks Rick,

So above the loud music, an intellegent question to ask would be "Is this a balanced mono 1/4" line out?"
And if not best not use it to run into the mono XLR on the ZOOM correct?

"Is this a balanced mono 1/4" line out?"
Do you mean in terms of auxiliary sends? If so, yes. Generally mono @ +4dB, so care must be taken to avoid overloading a -10dB line level input. A 6 or 10dB attenuator could be used or just turning down the aux. master send works too.
On most boards there at least two mono sends.. In some instances they are referred to as "Monitor" and "Effects" (Pre & Post-fader respectably) Recording and high-end SR consoles generally have a pre/post switch on each channel send. Mid and low cost boards generally have the pre/post switch on just the Aux. master sends.
Sorry, I'm going off topic some.

There are literally thousands of possible combinations of mixers, outputs, levels, adapters and recorders.
So you need to have a variety of your own pieces that have known good wiring.
There are a number of items that can handle multiple situations and don't cost much. For example the Ebtech Hum Eliminator can convert balanced and unbalanced in either direction and provide hum isolation. It doesn't change levels though. It can be purchased in various connector types and I have 3 of them for a variety of connection tasks, often used simultaneously in different parts of my setup.
It's also handy to have several good-quality passive DI boxes with switchable attenuation and ground lift.
I have single channel units and one dual channel box.
I carry these in addition to plain XLR switchable attenuators.
TRS to XLR balanced cables in both XLR genders are a must. Remember that both genders of cable can be combined to make longer TRS to TRS cables too.
Also add good-quality shielded TS to TS cables and a few XLR gender changers in both genders.
Lastly it's important to have properly wired balanced to unbalanced cables and adapters so you will know exactly what you're connecting instead of having to depend on someone elses unknown converter.
It's rare that I don't use my own mixer for added control when receiving a feed from another board but I don't travel lightly most of the time. I know that's a big consideration for many people.

Thanks I just made a Guitar Center shopping list. Or maybe order from Martek....

So if I have a 1/4" three contact TRS to XLR, that is a balanced mono correct?

Yes if it's wired correctly that would be the normal cable to carry a balanced mono signal between devices with different connectors.
A cable with a male XLR end would go from a TRS output jack to an XLR input jack.
A cable with a female XLR end would take the signal from an XLR output jack to a TRS input jack.
I always test every new cable to make certain that it is wired correctly.
For DI boxes, you can always search the major online musical instrument sites for the best boxes they have on sale at the time. A good DI box isn't exactly cheap in cost, but a good one is such a valuable tool that they are well worth it especially if you find a good deal.

The $30USD Rolls DB25 is a good passive DI with a ground lift and two attenuation settings. (20/40db ) Though a passive DI I works fine for converting line to mic, I would not recommend that or other passive DI's for instrument level... particularly acoustic-electric guitars.
Though I have nothing against Guitar Center, I would get any cables and such from Markertek or other pro-A/V shop.

Ordered that DI box from Markertek this afternoon. Thanks for the tip.

You will probably receive the newer version of the Rolls DB25, which has a continuous attenuation adjustment rather than a two-position attenuation switch. The Markertek site does have the up to date version and description, but some sites have the old listing and picture. I have a couple of this newer version and they work well and are a little smaller for packing that some other DI boxes that I own.

Thanks Jay, I was not aware of the updated Rolls DI.

Another consideration is that intermittent popping or cracking is SOMETIMES related to sample rate issues.

I've heard audio with "snapping" sounds intermittantly and came to discover that it as a very minor difference in the sample rate of the original recording verses what was playing it back. It's as if the sample offset grows in microscopic increments, and when it gets too large, the two signals re-sync with an audible "pop."

When that happens, I look to see if one audio signal might have been locked to, for instance, a 30 frames per second video recording, and is being read by a system that expects samples at a 29.97 frames per second standard - or vice versa.

Alternately, it also could be that you were recording sounds where a VERY brief transient - like a kick drum or hot-miked tom - was spiking your level for the briefest of samples - into a zone above the A/D conversion "safe zone. When that happens, the signal goes to hell and if its sustained, it sounds like a screech - but as a momentary spike it could sound like a "crackle."

One good practice is if you hear ANY signal breakup - back off the input gain a bit and see if that resolves things.

YMMV - good luck tracking it down. These things can be hard to diagnose.

(just other things to consider.)

Got the Rolls DB25B today. Looks like the attenuator has a -20 to infinity knob to adjust. I really don't know where to set it to. The other adaptor is a strait -50 setting and it's tauted as a line to mic pad.

two 1/4" female inputs and one balanced XLR output. So I'd use this with one 1/4"M to 1/4"M cable off the sound board into the Rolls DB25B and then say plug the XLR-M output into the XLR-F of the ZOOM H4N.

How do i adjust the attenuator - by ear?

Yes, your description is correct. You will adjust by ear (distortion) and the meters (recording level) on the Zoom, taking into account the balance between all the settings in your chain so one isn't way out of line one way and having to compensate in the opposite direction with some other setting in the chain.
Having to dramatically boost or cut on the Zoom itself could cause noise from the H4n preamps or overdrive the input stage.

Also you can use the other 1/4-inch jack of the DI box to loop out to some other line-level device.
Use short unbalanced 1/4-inch cables, with longer balanced XLR cables for most of the distance.

If you are picking up hum from the connection to the house mixer, switch the ground lift on the DI back and forth to get an improvement. Some DI box ground switch labels are confusing... I listen and switch back and forth to get the best signal rather than relying on the switch label.

Thanks Jay,

That's really helpful for me!!

<<other 1/4-inch jack of the DI box to loop out to some other line-level device.>>

I was thinking that both the 1/4-inch jacks were input.......if that's so with two inputs is this contraption outputting a mix out the XLR output?

The two 1/4-inch connectors on the DI box are in parallel. So you can use them as an input and a loop-through or as two inputs. However, there is always the caution about directly summing two outputs by simply connecting them together.
Some devices don't like having two outputs tied together and depending on the two signals you're combining you could get phase cancellation or ground loop hum if using two separate devices that are connected to different AC power.

welp I took my present connectors to a venue where I will be getting sound off the board and talked with the ever new sound dude at the board.

"Have you got a mic out there on the board?"
ans: "Yes"

"Is it XLR or 1/4"?
ans: "uh, it's these..." (pointing to a column of three 1/4" connections)

"Is it mic out or line out?"
ans: "line out yes...."

Bottom line I figure they are line out if 1/4". It was right before the gig so, although tempted, I didn't pull everything out and try to hook up.

I have scheduled to be present during sound check and before for the actual gig coming up next month.
I'm seeing a venue by venue log book of what it takes to handle audio going onto my iPhone.

Thanks for all the help.

Suggest you make a note of make and model of each board you run into and download the user's manual for it online. Many vendors like Mackie and Beringer have the full manual available free as downloadable PDFs.

Like those 1/4" jacks your last guy pointed out ...you need to know if they are stereo or mono, pre- or post-master output fader, etc, etc and the user manual is the best source for all that info. Just set aside a foilder on your harddisk and start building your collecction.

Excellent suggestion Steve! Will do that. I wish I could turn back time and get that info from last night.

Aren't the three point 1/4" plugs almost always mono? This is where I need the help figuring out what I need to record into the one XLR mono input on the Zoom H4n.

My adabptor for the 1/4" to XLR has a three pt contact 1/4" plug which is mono I believe.

I know I'm rolling on training wheels right now but I'll get it!

Thanks

In my 40+ years in music & pro-audio, the only time I recall encountering a 1/4 inch Left-Right "stereo" configuration (aside from headphones) was on a Fender Passport PA head... I believe it was a stereo line-in on an input channel.

A "three point" TRS (tip, ring,sleeve) 1/4" could be either balanced mono or unbalanced stereo such as a headphone jack. True. most "sends" would be either balanced TRS or unbalanced TS (no ring on the plug) but there's no guarantee that's the case 100% of the time and for all manufacturers. There's even a third possibility that uses 1/4 TRS, an "insert" jack that combines an unbalanced output with an unbalanced input on the same plug. Used to insert external devices like hardware equalizers, processors, or reverbs into the signal path, tip is the output 'send' signal going to the external device and ring is the return signal coming back from the external device, sleeve being a common ground. An XLR to 1/4 TRS is most likely mono, balanced XLR to balanced TRS, but I have also seen them wired XLR pin 2 to both tip and ring on the TRS, XLR pin 3 or pins 1&3 to TRS sleeve to send a balanced mono signal to both left and right on a stereo input. This is usually found with a 1/8 plug or jack such as the adapters to send a mono XLR mic to a camcorder's stereo mic input but who's to say it couldn't be found on a 1/4 as well. You can't tell by looking so investing $50 or $100 in a cable tester is a good idea, certaily at least a multimeter from Radio Snack