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Post by oldfartbassplayrwalt on Mar 14, 2021 20:47:17 GMT -5
Since you guys seem to like a good techie question to waste away your time,
please consider:
I've got a JBL Eon 10 G2 Powered Speaker with TRS input.
And a 1402 Mackie mixer with balanced/unbalanced 1/4" TRS output.
I'd like to run a balanced TRS line from mixer to the Eon 1/4" input, BUT:
according to the Eon manual:
"This 1/4” jack can accommodate one or two channels of audio.
When a two-channel source is connected by means of a TRS 1/4” plug,
both channels are summed to mono."
THERE SEEMS TO be a CONFLICT WITH my Mackie sending a balanced signal
to an input that SUMs the two signals. The manual seems to state the G2
does not specifically accept a balanced TRS input, but a stereo source.
The schematics confirm it SUMS the TRS into a mono signal.
ANY COMMENTS? Am I better off just using a TS cord? Doesn't it
seem that simply SUMMING two halves of a balanced signal would lead to
some sort of interference, since they're out of phase to each other?
Inquirying minds want to know....
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Post by oldfartbassplayrwalt on Mar 14, 2021 20:48:46 GMT -5
I have to check how using a mixer XLR out into the XLR in on the Eon works.
My friend told me he couldn't get it to work, but I SHOULD check for myself.
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Post by Peegoo 🏁 on Mar 14, 2021 23:19:52 GMT -5
I looked at the 1402 manual. The mixer has two 1/4" balanced TRS outputs (L & R) for Main Mix signal send. This applies only if you have any channels panned. If all channel strips' pan controls are centered, the signals from the L & R jacks are identical.
The JBL accepts either mono or stereo via a 1/4" TRS cable, but stereo (via TS conductors) is summed at the input. This means you can safely run a mono signal (no pan) from the mixer to the speaker using a single TRS cable from either Main Mix output jack.
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pdf64
Wholenote
Posts: 556
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Post by pdf64 on Mar 15, 2021 4:51:40 GMT -5
I wonder how the Eon decides to apply summing or differential amplification to the tip and ring signals?
The former would be necessary to create a mono mix of stereo unbalanced signals at the tip and ring.
The latter would be necessary for a mono balanced signal applied to the tip and ring.
A balanced signal applied to a summing amp would result in silence.
A stereo unbalanced signal applied to a differential amp would result in a tinny, ‘out of phase’ sound, as the anything at the centre of the mix would get cancelled out.
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Post by oldfartbassplayrwalt on Mar 15, 2021 11:38:42 GMT -5
Schematics show both signals going into an op amp labeled "SUM", which outputs a mono signal |
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pdf64
Wholenote
Posts: 556
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Post by pdf64 on Mar 15, 2021 15:11:21 GMT -5
Schematics show both signals going into an op amp labeled "SUM", which outputs a mono signal Haha, as I explained, a single ended / unbalanced summing amp will output no signal if a balanced signal is fed into its inputs, hence my confusion. I had a looky at the owner's manual jblpro.com/en/site_elements/eon10-g2-manualSee p8 'quick start', item 6 ie the 1/4" jack And on p9 ie a mono balanced signal via a TRS plug, whilst not being specifically prohibited, is not a suggested option. If you connect a balanced signal to the input 2&3 1/4" jack via the use of a TRS plug and can hear a signal, then I'm confused  Note I've have seen mixer outputs which have a 'faux' rather than a true balanced output; rather than an actual signal, resistors are used to create identical impedances on both wires of the balanced line, so that any interference will generate a common mode voltage on both wires, and hence will get canceled out. So you get noise elimination but lose 6dB signal level, because one wire has no actual signal, so the peak to peak signal level is halved. To make use of a balanced feed to its input, you'll have to use the input 1 XLR. If the mixer outputs are 1/4" TRS, then you'll need a TRS to XLR balanced cable. Have fun! |
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pdf64
Wholenote
Posts: 556
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Post by pdf64 on Mar 15, 2021 15:39:00 GMT -5
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Post by oldfartbassplayrwalt on Mar 15, 2021 15:50:01 GMT -5
AHA! thanks, guys, my eroded brain cells weren't too far off, then.
When I get the system back, I'm gonna try the XLR-XLR connection.
I don't trust my buddy's judgement on it not working. One time
when he did sound for us, he forgot to turn on the mains, and
the audience only heard our monitors for the first 10 minutes
of a coffee house gig...
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pdf64
Wholenote
Posts: 556
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Post by pdf64 on Mar 15, 2021 19:07:16 GMT -5
It’s unfortunate that this stuff can get so convoluted and complex.
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