Crackling Noise

Jay Massengill · January 20th, 2011, 08:06 AM

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.

Rick Reineke · January 22nd, 2011, 10:07 AM

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

Bill Davis · January 22nd, 2011, 12:53 PM

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.)

Harry Simpson · January 26th, 2011, 08:01 PM

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?

Jay Massengill · January 27th, 2011, 09:58 AM

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.

Harry Simpson · January 27th, 2011, 12:57 PM

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?

Jay Massengill · January 27th, 2011, 01:13 PM

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.

Harry Simpson · January 28th, 2011, 08:09 AM

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.

Steve House · January 28th, 2011, 08:16 AM

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.

Harry Simpson · January 28th, 2011, 09:02 AM

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

Rick Reineke · January 28th, 2011, 10:26 AM

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.

Steve House · January 28th, 2011, 12:59 PM

Quote:

Originally Posted by Harry Simpson

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

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

January 22nd, 2011, 12:53 PM	#18
Bill Davis Trustee Join Date: Jan 2004 Location: Scottsdale, AZ 85260 Posts: 1,538	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.) __________________ Classroom editing instructor? Check out www.starteditingnow.com Turnkey editor training content including licensed training footage for classroom use.

January 26th, 2011, 08:01 PM	#19
Harry Simpson Major Player Join Date: Aug 2009 Location: Nashville, TN. Posts: 581	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? __________________ Nashville TN using Canon 5D MK3, Canon 550D, RODE SVM mic, 70-200 f2.8L II IS, 24-105 f4L IS, 50 and 85 f/1.8, Vegas Pro 11, Zoom H4n, Blackbird, Lilliput Monitor, Lightroom

January 27th, 2011, 12:57 PM	#21
Harry Simpson Major Player Join Date: Aug 2009 Location: Nashville, TN. Posts: 581	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? __________________ Nashville TN using Canon 5D MK3, Canon 550D, RODE SVM mic, 70-200 f2.8L II IS, 24-105 f4L IS, 50 and 85 f/1.8, Vegas Pro 11, Zoom H4n, Blackbird, Lilliput Monitor, Lightroom

January 28th, 2011, 08:09 AM	#23
Harry Simpson Major Player Join Date: Aug 2009 Location: Nashville, TN. Posts: 581	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. __________________ Nashville TN using Canon 5D MK3, Canon 550D, RODE SVM mic, 70-200 f2.8L II IS, 24-105 f4L IS, 50 and 85 f/1.8, Vegas Pro 11, Zoom H4n, Blackbird, Lilliput Monitor, Lightroom

January 28th, 2011, 08:16 AM	#24
Steve House Inner Circle Join Date: Mar 2005 Location: Hamilton, Ontario, Canada Posts: 5,742	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. __________________ Good news, Cousins! This week's chocolate ration is 15 grams!

January 20th, 2011, 08:06 AM	#16
Jay Massengill Trustee Join Date: Jul 2003 Location: Burlington Posts: 1,976	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.

January 22nd, 2011, 10:07 AM	#17
Rick Reineke Inner Circle Join Date: Aug 2008 Location: New York Posts: 2,039	Thanks Jay, I was not aware of the updated Rolls DI.

January 27th, 2011, 09:58 AM	#20
Jay Massengill Trustee Join Date: Jul 2003 Location: Burlington Posts: 1,976	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.

January 27th, 2011, 01:13 PM	#22
Jay Massengill Trustee Join Date: Jul 2003 Location: Burlington Posts: 1,976	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.

January 28th, 2011, 09:02 AM	#25
Harry Simpson Major Player Join Date: Aug 2009 Location: Nashville, TN. Posts: 581	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 __________________ Nashville TN using Canon 5D MK3, Canon 550D, RODE SVM mic, 70-200 f2.8L II IS, 24-105 f4L IS, 50 and 85 f/1.8, Vegas Pro 11, Zoom H4n, Blackbird, Lilliput Monitor, Lightroom

January 28th, 2011, 10:26 AM	#26
Rick Reineke Inner Circle Join Date: Aug 2008 Location: New York Posts: 2,039	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.