Author Topic: Should i be using balanced input from my F1-x and SF-2 (Read 436 times)

jazzyvee · « **on:** February 21, 2015, 12:11:31 PM »

Oops i worded the title wrongly. It should be more like
Should i be plugging my F1-X output into the balanced input of my power amp.

I have a rig that is quite common for us alembic players. F1-X, SF-2 and QSCPLX power amp. The output from my pre-amp goes into the unbalanced jack input of my power amp but i'm wondering if I should really be plugging into the balanced XLR input to my power amp to get the best signal quality?
What do you think?

(Message edited by Jazzyvee on February 21, 2015)

willgunn · « **Reply #1 on:** February 21, 2015, 01:16:49 PM »

Both the XLR and 1/4 inputs on the QSC PLX Series are balanced (with the 1/4 jacks being TRS and internally paralleled with the XLR's for a given channel). However, sending an unbalanced signal to a PLX won't really degrade the sound quality or cause any problems. If you want to perform a sonic comparison of balanced VS unbalanced, try sending a signal from your F-1X via the front panel, balanced XLR DI jack to the XLR power amp input - if you can hear a difference, you have far better hearing than I do!

moongerm · « **Reply #2 on:** February 21, 2015, 01:17:54 PM »

Hey Jazzy,

If you have balanced inputs on your qsc then it couldn't hurt giving it a whirl.

Here is a thread with some great feedback on this topic from Will Gunn: http://club.alembic.com/Images/394/79311.html?1272661335

Interesting topic as I only used the f1x xlr for recording.

-Brian

moongerm · « **Reply #3 on:** February 21, 2015, 01:35:51 PM »

Hey there's Will. Hey Will!

I have been running my F1Xs into two seperate bass amps where they dont have balanced inputs. Now I am wondering if it makes more sense to consolidate with a stereo power amp like a QSC? I like the idea of your approach Will.

keith_h · « **Reply #4 on:** February 22, 2015, 05:42:57 AM »

As Will says both inputs on QSC amps are balanced. When you use the 1/4 output from an unbalanced source into the QSC 1/4 jack it becomes unbalanced. If you were to wire an adapter to use the XLR input this too would be unbalanced. Due to the short cable runs you have in a rack running balanced or unbalanced will make no difference. Where balanced or unbalanced come into play is longer connections where externally induced electrical noise can become an issue.

Keith

jazzyvee · « **Reply #5 on:** February 22, 2015, 11:14:00 AM »

Ok cool, glad I don't have to chance anything. Will I doubt if my hearing is better than yours. Maybe our response to frequencies is different. :-)

edwin · « **Reply #6 on:** February 24, 2015, 06:46:38 PM »

The balanced input only really becomes necessary if you are running long cable lengths, especially in questionable environments. You definitely want to use the balanced input from a front of house console or EQ, etc., 80 feet away, but a foot or two won't really make a difference unless the environment is extraordinarily noisy or if the preamp/amp combination has some serious interactions (not the case here).

rustyg61 · « **Reply #7 on:** April 15, 2015, 10:09:22 AM »

I have a related question, I too am running a F-2B mono output to channel A on my SF-2 set for mono & out of channel B of the SF-2 into the 1/4 input on my QSC GX7. The QSC doesn't have a switch to tie both inputs together to run the same signal to both channels, they recommend going into the XLR jack then using a TRS 1/4 cable to jumper from channel A to B. In order for me to do that I have to run the SF-2 output through my direct box to convert the 1/4' output of the SF-2 to a balanced XLR cable & when I do that it looses a lot of gain. Has anyone tried using a 1/4 Y cable to run a single signal to both sides of a power amp, or should I get a 1/4 to XLR cable & use the TRS jumper method that QSC recommends?

keith_h · « **Reply #8 on:** April 15, 2015, 03:29:18 PM »

Just use an XLR jumper. As I recall both the TRS and XLR are in parallel so you should be able to jumper either one.

Keith

edwin · « **Reply #9 on:** April 15, 2015, 03:44:40 PM »

A Y cable should be fine, too.

Definitely no sense in converting via the DI. That turns your signal into mic level, where the amp wants to see line level.

rustyg61 · « **Reply #10 on:** April 16, 2015, 03:34:35 AM »

Thanks Keith, you are correct, the 1/4 TRS & XLR are parallel inputs so I can jumper with a XLR cable too, never thought of that!

Edwin, I knew that the DI reduced the signal level, but it didn't dawn on me that it does convert the high impedance line level signal to mic level to go to the mixer. Thanks!