Bad 60 hz hum with the addition of a Rane PE 15

*insertcoolname · #1 12-18-2010, 01:11 AM

Help!

I just added a Rane PE 15 parametric eq to my rack and now I'm getting really bad 60 hz hum. For reference, my rack is as follows:

4U Gator rack
Bottom two slots are a QSC PLX 3402
Next is an Aguilar DB659 preamp
Now on top I've added the Rane PE 15

I know it's the Rane because the system was very quite before adding it. I also know that it's an interaction between the DB659 and the Rane because when I turn on just the Rane and the QSC I get very minimal noise. Additionally, when the Rane and the DB659 are both on but one of them is outside of the rack, away from the other, there is very little noise. Basically I've diagnosed the problem to being an interaction between the Rane and the Aguilar.

How can I get rid of this noise? It's bad enough where I wouldn't want to play a show live with it and would definitely not want to record in the studio with it.

Help!

WingKL · #2 12-18-2010, 04:21 AM

greenboy · #3 12-18-2010, 06:59 AM

You ain't a man til yuhs chased down a ground loop and wrastled it to the, er, ground.

http://www.rane.com/note110.html

Zooberwerx · #4 12-18-2010, 07:22 AM

The PE-15's are strange agents as they use a huge-*** external power source and phone-type plug. I don't know if there is a proprietary or aftermarket replacement available. I'll assume: (1) you have the PE in your effects loop and (2) the hum remains when engaged or disengaged and (3) you're using the appropriate shielded signal cables.

Riis

billfitzmaurice · #5 12-18-2010, 07:35 AM

Quote:

Originally Posted by Zooberwerx

The PE-15's are strange agents as they use a huge-*** external power source and phone-type plug. I don't know if there is a proprietary or aftermarket replacement available. I'll assume: (1) you have the PE in your effects loop and (2) the hum remains when engaged or disengaged and (3) you're using the appropriate shielded signal cables.

The problem isn't the Rane, it's the unbalanced connections used by the Aggie. The cure is to come up with the right cable configuration per the RaneNote listed above.

*insertcoolname · #6 12-18-2010, 01:49 PM

Quote:

Originally Posted by greenboy

You ain't a man til yuhs chased down a ground loop and wrastled it to the, er, ground.

http://www.rane.com/note110.html

I've tried reading through that many times and still draw a blank on what I should do...

I've tried a bunch of different cable configurations and still nothing. Anyone want to make a suggestion on what exactly I should use as far as cabling goes between the different units?

Foz · #7 12-18-2010, 02:51 PM

use type 13 or 14 as shown on the chart linked above

Also from the fine manual...

Quote:

REGARDING PE15 NOISE
You may experience noise when using this unit with one
or more bandwidth (BW) controls set to the narrowest (.03)
possible setting. This is the noisiest possible setting. The most
usual use for this setting is deep notching. e.g. for eliminating
a specific frequency, such as problems caused by feedback or
other oscillations. Most often only one filter is required. It
should also be noted, there is a trade off between noise and
desired results, when using narrow bandwidth notching. For
example, where the system correction achieved out weighs
the noise levels generated by the required setting.

http://www.rane.com/pdf/old/pe15man.pdf

BassmanPaul · #8 12-18-2010, 03:19 PM

You could be getting a ground loop through the rails of the rack. My power amps all go directly in but anything else is isolated from the rails by little plastic tabs called Humfrees. Available from AMS among others. Another way is from the power transformer of one unit inducing hum into the circuitry of another. You can check for this by assembling and connecting the units outside of the rack Try lifting the units away from each other and seeing if the hum level falls.

*insertcoolname · #9 12-18-2010, 03:36 PM

Quote:

Originally Posted by BassmanPaul

You could be getting a ground loop through the rails of the rack. My power amps all go directly in but anything else is isolated from the rails by little plastic tabs called Humfrees. Available from AMS among others. Another way is from the power transformer of one unit inducing hum into the circuitry of another. You can check for this by assembling and connecting the units outside of the rack Try lifting the units away from each other and seeing if the hum level falls.

I think it is the power transformer. When I connect the Rane outside of the rack and turn everything on there's no noise at all, dead quiet. I've tried every combo of TS and TRS cables, along with an XLR cable and everything seems to hum badly except when the Rane is outside of the rack. The loudness of the humming is directly proportional to how close the Aguilar and the Rane are to each other.

How should I go about remedying this problem assuming that it is power transformer interaction?

billfitzmaurice · #10 12-18-2010, 04:44 PM

Quote:

Originally Posted by *insertcoolname

I've tried every combo of TS and TRS cables

Including with the shield connected at one end only? How do you have it connected? At some point you're going unbalanced to or from the Aggie, and that's probably the source of the noise.

Quote:

The loudness of the humming is directly proportional to how close the Aguilar and the Rane are to each other.

Whether the Rane is touching the metal rack rails or not?

Quote:

How should I go about remedying this problem assuming that it is power transformer interaction?

It can't be the transformer as it's remotely located.

*insertcoolname · #11 12-18-2010, 07:10 PM

Quote:

Originally Posted by billfitzmaurice

Including with the shield connected at one end only? How do you have it connected? At some point you're going unbalanced to or from the Aggie, and that's probably the source of the noise.Whether the Rane is touching the metal rack rails or not?

It can't be the transformer as it's remotely located.

Contact with the metal rails has absolutely no effect on the loudness of the noise.

It should also be noted that when I run just the Rane into the QSC, both in the rack, it's quiet. But when I turn on the Aguilar (not even connected, just in the rack) the hum starts up right away. I am almost positive that the problem is the Rane picking up something from the Aguilar. I think I'm going to return the Rane (it's definitely an older unit, fair amount of wear on it, bought it used from GC) and get something new.

billfitzmaurice · #12 12-18-2010, 08:17 PM

Quote:

Originally Posted by *insertcoolname

But when I turn on the Aguilar (not even connected, just in the rack) the hum starts up right away. .

That makes the Aggie the source of the noise. It's probably throwing off EMI. Try putting the amp in the middle, the Aggie and Rane separated by it.

dmusic148 · #13 12-18-2010, 08:25 PM

I had this exact problem with a rack preamp mounted above a rack compressor. Reversed the arrangement, problem solved.

*insertcoolname · #14 12-18-2010, 08:40 PM

Quote:

Originally Posted by dmusic148

I had this exact problem with a rack preamp mounted above a rack compressor. Reversed the arrangement, problem solved.

Tried switching them around, no help.

As far as putting the amp in the middle, this would probably work to a certain degree but I'd rather remedy the actual problem then put a band aid on it. Is there a way I can fix the actually problem other than putting the amp in the middle?

It should also be noted that when I plug the Aguilar straight into the QSC, dead quiet. When I turn on the Rane (not connected but in the rack) there's still no noise. This would mean that it's the Rane that is picking something up from the Aguilar, not the other way around.

When I tried replacing the Aguilar with an Ampeg SVPCL I still had the same issue. I honestly can't see how it would be something other than the Rane.