Hello, my son bought a Eurodesk mixer unit and we put the scope on it, to determine the various output levels, when we noticed that the "main output" was inverted compared to its inputs.
Is this the normal setting? I would have imagined that various sound effect modules, stomp boxes, equalisers, compressors etc, should not invert (or phase) the signals, else when you plug random number of units in series you'd get some random output. Similarly I had imagined that an instrument amp should not invert the signal at the speakers because if you had multiple amps plugged in you'd also get some random cancelling.
Why is the EURODESK SX3242FX inverting it then? I presume it is to eliminate microphone feedback?
Is this the normal setting? I would have imagined that various sound effect modules, stomp boxes, equalisers, compressors etc, should not invert (or phase) the signals, else when you plug random number of units in series you'd get some random output. Similarly I had imagined that an instrument amp should not invert the signal at the speakers because if you had multiple amps plugged in you'd also get some random cancelling.
Why is the EURODESK SX3242FX inverting it then? I presume it is to eliminate microphone feedback?
Interesting. I suspect you've caught out Behringer doing something sly to save a few pence that they thought you wouldn't notice!
It'd be worth checking that all the outpus (L&R and any aux, mono or groups) are in phase with each other, so that you don't get caught out if you end up driving different zones of PA, subs etc from different outs.
Assuming that's in order, just keep a set of phase reverse leads (swapping hot and cold) to hand when you use the desk in case you need them.
JMFahey: I'd assume thay either used a dual-trace 'scope to observe input and output together, or sync'd the scope timebase to the oscillator.
Diligent work anyhow chaps!
It'd be worth checking that all the outpus (L&R and any aux, mono or groups) are in phase with each other, so that you don't get caught out if you end up driving different zones of PA, subs etc from different outs.
Assuming that's in order, just keep a set of phase reverse leads (swapping hot and cold) to hand when you use the desk in case you need them.
JMFahey: I'd assume thay either used a dual-trace 'scope to observe input and output together, or sync'd the scope timebase to the oscillator.
Diligent work anyhow chaps!
I think that may be JMF's point, we cannot assume that. Too many people misinterpret what they see to make such assumptions. They may be perfectly accurate in the assessment, we just cannot assume so.
Behringer will usually put the phase relationships on the owner manual, like most OEMs.
Not everything is + to + as in to out. QSC amps being a notable example of inverted power amp outputs. JBL cabs too maybe?
Behringer will usually put the phase relationships on the owner manual, like most OEMs.
Not everything is + to + as in to out. QSC amps being a notable example of inverted power amp outputs. JBL cabs too maybe?
The mixer has a ton of "outputs" along the signal path, and we tracked it there. Basically it has an out/in post-pre-amp but pre-eq and pre-fader, then it has aux send/return and in addition it also has FX send/return. We tracked it as near the mic as is possible, at the pre-eq. This is where you are meant to add your own effects per channel, eg compression, harmoniser, delay whatever.
Fine, thanks, but it still does not answer my doubts.
1) if you scoped some point "upstream", you can't be sure about microphone phase.
2) I still don't know how you determine phase just looking at a scope image.
I mean, there's one way to do it, but I'm not so sure you used it.
So far, you seem to be saying (I may be mistaken, of course) "I hooked a scope to the output, looked at the image and knew it was out of phase".
Out of phase with what?
In fact, I do not even know *what* sound source did you use for the test
Or how did you hook your scope up.
Sorry, nothing against you, it's just that I still find a little info missing to solve the puzzle
We are looking at two traces simultaneously, they are 180 degrees off. We inject the signal in so we track it there, and once again at the main out. Being that the mixer has a ton of inputs and outputs I will do the test again just to verify. Out original test was to determine the levels at the output, not to test for phase inversion, that was an accidental observation.
akis
what pin of the XLR output are you observing pin 2 or pin 3?
being that the eurodesk should have a balanced output the inversion your observing could simply be your connection point
also if the input is single ended i.e. your signal generator which is unbalanced what pins are you connecting to pin 1 ground, pin 2 positive, pin 3 negative(180 deg )
turk
what pin of the XLR output are you observing pin 2 or pin 3?
being that the eurodesk should have a balanced output the inversion your observing could simply be your connection point
also if the input is single ended i.e. your signal generator which is unbalanced what pins are you connecting to pin 1 ground, pin 2 positive, pin 3 negative(180 deg )
turk
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All good quality mixing desks, have the option via a push button, to invert the phase on independent inputs. This is essential when sending out of phase fold-back to the monitor system on stage.
If you can imagine, miking up the bass players amplifier. If the microphone is out of phase with the front of house speakers, there will be "Holes" in the bass sound as one moves around the venue due to phasing issues. So to overcome this problem, making the front of house coincide with the bass amp will help. Also as a matter of science, only use one position for the bass speaker or weird phase shifts will occur!
Behringer do not mix different input/output phasing with the pre-amplifiers. They as everyone else, use a standard system for all inputs/outputs and they are all the same in phase unless there is a phase change switch.
I hope that clarifies the issue.
If you can imagine, miking up the bass players amplifier. If the microphone is out of phase with the front of house speakers, there will be "Holes" in the bass sound as one moves around the venue due to phasing issues. So to overcome this problem, making the front of house coincide with the bass amp will help. Also as a matter of science, only use one position for the bass speaker or weird phase shifts will occur!
Behringer do not mix different input/output phasing with the pre-amplifiers. They as everyone else, use a standard system for all inputs/outputs and they are all the same in phase unless there is a phase change switch.
I hope that clarifies the issue.
akis
xlr or mic connectors are 'bout 3/4" and are indeed mono but balanced.
the main outputs L/R are also 3/4" xlr connectors the main mix out is also available on 1/4" trs connectors in the same area as the group outs as well as your aux's and inserts patch points.
as i asked in a previous post how are you connecting your unbalanced signal genny to this input?
xlr or mic connectors are 'bout 3/4" and are indeed mono but balanced.
the main outputs L/R are also 3/4" xlr connectors the main mix out is also available on 1/4" trs connectors in the same area as the group outs as well as your aux's and inserts patch points.
as i asked in a previous post how are you connecting your unbalanced signal genny to this input?
yes indeed
i try to refer to them as TRS when they are used as mono balanced in or out jacks.
but let's not forget that a Tip/Ring/Sleeve or 1/4" stereo plug used as an insert would be Tip-send Ring-return and Sleeve-common ground as well as you mentioned good old L/R stereo!
long live the jovian cyber plug!
i try to refer to them as TRS when they are used as mono balanced in or out jacks.
but let's not forget that a Tip/Ring/Sleeve or 1/4" stereo plug used as an insert would be Tip-send Ring-return and Sleeve-common ground as well as you mentioned good old L/R stereo!
long live the jovian cyber plug!
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