Audio Snake Capacitance Issue

[abbey road d enfer]

My guess is the snake is garbage.  Any other thoughts?

You should have listened to what Granpa Abbey said...
Now you have to find why. The snake is not making noise by itself, it is subject to an interference that results in noise. Most likely there is some kind of power gear or electrical line running close to it. You may have to change the path of the snake or the location of the interference source.

 

[Siegfried Meier]

Well, you are indeed correct my friend.

There was an extension cable hidden that was powering the Mac Pro.  It was the cause all along...I removed it and plugged the Mac Pro into a different circuit and voila.  Noise is gone.  The computer's draw from that extension cord must have induced some kind of noise.  The extension cable is still there powering other things right now.

Pretty amazing that a condenser mic or the cloudlifter filtered out and removed this noise.

Thanks for all your help guys!  As much as it sucks that I tore apart the bay and need to wire things back in again, it does feel good learning stuff along the way.

EDIT - In listening and comparing so many different cables the past few days, I've decided it's best to pull the snake out and replace anyway now, since it's already disconnected from the bay.  I was pretty amazed at how good my direct mic cables sounded.  I guess everything happens for a reason eh?

 

[PRR]

> draw from that extension cord must have induced some kind of noise.

Analog telephone wires (ask your father) used to run hundreds of miles along the same roads with 240V-13,000V AC power lines.

Yeah, the phones hummed. But remarkably *little* considering the exposure.

(Tenth-Volts up to 10VAC 60Hz in suburban NJ; the high end was rare and not much audible through a Bell 500 telephone).

How did they do it with 1880 technology? Obsessive balancing. (Shielding came later.)

I'm still befuddled by your "condenser mic or the cloudlifter" observation. A dynamic mike is normally perfectly "balanced" (true floating). However depending on system layout, a hot condenser or a booster puts 10dB-20dB more level through the trashy part of the line, so it "seems" like less crap.

 

[Brian Roth]

Siegfried, I may have missed it in these pages of discussion, but what brand/model is the snake cable?

Bri

 

[hymentoptera]

Question - does the snake box itself have pin 1 connected to the chassis, which in turn then connects all the grounds together?  I've never built up a snake from scratch before, but this would negate what you've just said...I'll have to test that to see as well.

I can answer this little aside. Each individual channel has it's own shield or drain wire of course, but then THAT whole BUNDLE is wrapped in an additional shield/drain which should be tied to the box on each end and then properly grounded at the mixer end.

Maybe not all snake cable has this extra shield, but the Clark #710 I've used had this feature.

 

[Brian Roth]

While I've never used the Clark snake cable, I can say that the Gepco snakes I've used DO have the extra/overall shield.  However, that seems to be the exception.  For example, the widely used Mogami snake cable doesn't have any overall shield.  I believe some Belden (foil shield around individual pairs) that I've used also didn't have an overall shield.

Bri

 

[abbey road d enfer]

Question - does the snake box itself have pin 1 connected to the chassis, which in turn then connects all the grounds together?  I've never built up a snake from scratch before, but this would negate what you've just said...I'll have to test that to see as well.

I can answer this little aside. Each individual channel has it's own shield or drain wire of course, but then THAT whole BUNDLE is wrapped in an additional shield/drain which should be tied to the box on each end and then properly grounded at the mixer end.

Maybe not all snake cable has this extra shield, but the Clark #710 I've used had this feature.

There are are several types of multicore cables (the correct word for "snake"). Some have the dual shielding that you describe, but most don't. The most commonly used have individual shield wrapped around each pair, which allows "isolated grounds". Some of cheaper construction have only one overall shield; the main drawbacks of this type of cable are that they don't allow separating the grounds and that there is a risk of crosstalk between adjacent wires.

 

[Siegfried Meier]

OSP snake - 50'.  We bought it when we first built the studio because it was super inexpensive at a time when we were spending big bucks on the structure and a million other things.  Always wanted to swap it out when there was cash, and there were always a hundred other things that came first. 

Like I said, the second I disconnected the extension cable that was powering the Mac Pro, a power amp and our Presonus Central Station, all hum was gone.  The extension cable did come near the patchbay, so this could be where it was leaking into the audio signal.

 

[Brian Roth]

Hmmmm...not familiar with OSP at all.  Decades ago, I worked pretty much exclusively with Belden.  In more recent times, Gepco and Mogami.  Several years ago while installing a studio in Mexico City, I used quite a bit of Canare multicore, since it was about all the studio manager could find in the area.  I've never encountered noise pickup problems that I can recall with those brands.  I guess I'll make a mental note about NOT using OSP.

Bri