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Unbalanced to balanced using balanced line in VS Level Shifter Connector Box?
Old 10th November 2008
  #1
Gear Maniac
 

Unbalanced to balanced using balanced line in VS Level Shifter Connector Box?

I realise that this may fall more into the gear forum than the mastering forum, but arguably since it's about the signal chain to the monitors in my room it can fit here.

My Duet has unbalanced outs, and they go to balanced ins for my monitors (Event Project Studio 6). I've been suggested the following solutions to reduce ground hum and other noise:

1. 1/4 inch to XLR (the Events have XLR inputs in the back)
2. 1/4 inch to 1/4 inch balanced line (the one with 2 rings on the plug)
3. 1/4 inch unbalanced into box, balanced out other end

The only thing I don't like about the converter box idea is that it's more expensive, and also changes signal potentially? Supposedly the only affect that using a balanced line has on the signal is that it becomes weaker. If so, I could just crank the gain, right?

Thanks so much for anyone's responses. If this gets shoved into the gear forum, I understand, but I've had so much luck with the mastering forum before that I had to try here first.

Thanks!
Old 10th November 2008
  #2
Lives for gear
 
staudio's Avatar
 

Your speaker manufacturer will be able to tell you the exact wiring of the cables you need. Read the manual or call them. On the Duet side will be a TS jack and on the speaker side will be a XLR connector, the specific wiring is dependent on the speaker circuitry.
Old 10th November 2008
  #3
For all you would ever want to know about interconnection theory and and more look at the Rane Sound System Interconnection white paper.
All the best,
-mark
Old 11th November 2008
  #4
Gear Maniac
 

The guy on the phone at Event Electronics said that the XLR was more desirable than the 1/4 inch input. So is a balanced 1/4 inch to XLR cable plugged into the unbalanced outs of a Duet going to impact negatively the sound quality of the Duet at all? Here's the info from the manual:

input connections: Line 1 – 1/4 inch Line 2 – XLR
+ Tip Pin2
– Ring Pin3
Shield Sleeve Pin 1

LINE 1 INPUT This jack accepts a 1⁄4” TRS connector, wired either
balanced or unbalanced.
For balanced wiring, a 3-conductor 1⁄4" TRS plug is necessary. See
the INPUT CONNECTIONS wiring chart below or on the amplifier
panel.
Unbalanced wiring works with either a 2 or 3-conductor 1⁄4” TRS
connector. A 2-conductor 1⁄4" TS plug automatically grounds the
minus signal input, whereas a 3-conductor TRS plug wired
unbalanced provides the option of leaving the minus input open or
grounded. We recommend that you ground the unused input.
The LINE 1 INPUT connector is hardwired in parallel with the LINE 2
INPUT connector, so either may be used as an input or a pass-through
connection. Input specifications apply to both inputs.

LINE 2 INPUT This jack accepts XLR input connections, wired either
balanced or unbalanced. The LINE 2 INPUT connector is hardwired in
parallel with the LINE 1 INPUT connector, so either may be used as an input
or a pass-through connection. Input specifications apply to both inputs.
Old 11th November 2008
  #5
Gear Maniac
 

So looking at that chart on the Rane site, would I be best going with a 7 or a 21a?

Quote:
Originally Posted by mpdonahue View Post
For all you would ever want to know about interconnection theory and and more look at the Rane Sound System Interconnection white paper.
All the best,
-mark
Old 11th November 2008
  #6
Lives for gear
 
loujudson's Avatar
13. simple.
Old 11th November 2008
  #7
Gear Maniac
 

Thanks LouJudson. I read somewhere else that an unbalanced to balanced wouldn't be a true balanced cable. Any truth to that? Thanks!
Old 11th November 2008
  #8
Lives for gear
 
loujudson's Avatar
Yup. You need three wires to be balanced, one being the shield. You really need to go do some serious reading on basic audio practices. Not being snotty, but it is true, read, study, learn. Online forums are too filled with wiseass remarks fro reliability. My opinion!

Ts plug, tip wired to pin 2 of the XLR, 1 and 3 shorted together.
L
Old 11th November 2008
  #9
Gear Maniac
 

Now I'm slightly confused. Is what you've described here the 13?

"Ts plug, tip wired to pin 2 of the XLR, 1 and 3 shorted together."

Is the 13 truly balanced, and if not, can an unbalanced 1/4 inch to balanced XLR function as a balanced cable, or should I just get a balanced to balanced?

Thanks so much!
Old 11th November 2008
  #10
Lives for gear
 
loujudson's Avatar
Wow. Your monitor input is balanced, but your interface is not. So you need to use the 13 cble to connect the two. No, it won't be balanced, but it will work.

The only way to get a truly balanced input here is with a transformer or a line amp.

Have you tried it yet? Experimentation is so easy.

L
Old 13th November 2008
  #11
Gear Maniac
 

I tried both the unbalanced to balanced 1/4 inch to XLR male as well as balanced to balance 1/4 inch to XLR male.

The unblanaced to balanced has less of the high–pitched hum but still has the ground loop hum.

So, I've spoken with Event and have followed their directions to the T and the hum is still there.

Dump the Duet, dump the speakers or invest in hum killing/ground loop killing devices?

Cheers!
Old 13th November 2008
  #12
Lives for gear
 
loujudson's Avatar
Quote:
Originally Posted by BouncyJones View Post
I tried both the unbalanced to balanced 1/4 inch to XLR male as well as balanced to balance 1/4 inch to XLR male.

The unblanaced to balanced has less of the high–pitched hum but still has the ground loop hum.

So, I've spoken with Event and have followed their directions to the T and the hum is still there.

Dump the Duet, dump the speakers or invest in hum killing/ground loop killing devices?

Cheers!
It was not clear that you were actually having hum problems. Troubleshooting:
First, are the speakers and all the rest of your gear plugged into the same GROUNDED outlet? They should be.

If you experimentally attach a wire from the case of the duet to the case of the Events, does the hum go away?

Adding evices to stop the hum is not advised unless normal procedures fail.

Try substituting another source, say a CD player, to the monitors and see if they hum. And, do you get hum in the headphones of the Duet?

I'll stop here because I have never had hum problems in any studio I have worked in or built in 40 years, so I am not expert in solving such preoblems, especially with computer gear and powered monitors. Following accepted guidelines for power and grounding has worked for me...

PS - hum is by definition low pitched, 50 or 60 cycles with sometimes 120 or 240 harmonics. If there are higher pitch components it is buzz, or other noise.

Lou
Old 16th November 2008
  #13
Gear Maniac
 

Thanks for your detailed response Lou. Here are the solutions I found.

I had two hums. The first was speaker related, as it had the rumble even without an input from the soundcard (it alone plugged into the wall or power bar had the rumble going). I solved this by simply moving the monitors further away from my head until it was out of earshot (this is not an ideal solution, but I tried checking the ground within the speakers without any success). I'm convinced that it's a problem with the house and I'm not even sure different speakers would have a better solution. I might still try this baby to see if it does anything. I did plug the speaker in at a store and there was no hum so I think it is a wiring issue or something (I opened the speaker up and tried grounding it even more with no notiecable affect – I attached a wire from the cone to a bolt).

The second hum was a high–pitched frequency (the A above middle C) directly related to the unbalanced outputs of the Duet, in my opinion. I bought an APEX AHK1 hum killer box which has removed that pitch tone completely. All other wiring solutions did not do the trick (1/4 inch to XLR unbalanced to balanced, balanced to balanced).

Thanks for your help Lou, and thanks for listening.
Bouncy
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