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Old January 16th, 2011, 08:35 PM   #1
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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?
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Old January 16th, 2011, 10:38 PM   #2
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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.

Last edited by Battle Vaughan; January 16th, 2011 at 10:42 PM. Reason: addendum
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Old January 16th, 2011, 10:51 PM   #3
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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.
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Last edited by Harry Simpson; January 16th, 2011 at 10:54 PM. Reason: stereo to mono
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Old January 17th, 2011, 05:41 AM   #4
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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.
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Old January 17th, 2011, 08:15 AM   #5
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<<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?
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Old January 17th, 2011, 11:43 AM   #6
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Quote:
Originally Posted by Harry Simpson View Post
<<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.
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Old January 17th, 2011, 11:57 AM   #7
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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.
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Old January 17th, 2011, 03:13 PM   #8
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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?
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Old January 17th, 2011, 06:50 PM   #9
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"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.
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Old January 18th, 2011, 07:59 AM   #10
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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.
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Old January 18th, 2011, 04:32 PM   #11
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Thanks I just made a Guitar Center shopping list. Or maybe order from Martek....
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Old January 18th, 2011, 04:42 PM   #12
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So if I have a 1/4" three contact TRS to XLR, that is a balanced mono correct?
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Old January 19th, 2011, 08:36 AM   #13
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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.
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Old January 19th, 2011, 11:40 AM   #14
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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.
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Old January 19th, 2011, 03:22 PM   #15
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Ordered that DI box from Markertek this afternoon. Thanks for the tip.
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