Unofficial Mackie User Forums > DL1608/DL806/DL32R/ProDX Mixers
Thinking about DL32R for church praise team
Kblue:
--- Quote from: WK154 on February 03, 2016, 06:20:35 PM --- What Engineering field did you practice?
--- End quote ---
Thanks for the info...
I was initially Telecom-backbone Eng... I went through so many technology changes... Spent a lot of time on early-day Internet backbone...
I was sick and tired of man-made logic... So I changed it to RF(active and passive) where more law of physics (God-made logic) plays...
Still doing some consulting work as spec writer...
Lowest Frequency I ever dealt with is around 950 MHz...generally, 14 - 30 GHz... all modulated digital signal...
This Audio world has been always amazing...100 Hz to 20,000 Hz(whatever highest)...200 times wavelength difference...
I need to read manual A&H Qu 24...
Kblue:
--- Quote from: WK154 on February 03, 2016, 06:20:35 PM ---300 ft of cable isn't helping in your case. Check the impedance of each of the twisted pairs and you'll see what I'm talking about. Bill Whitlock covers that nicely in his app notes on CMRR. What Engineering field did you practice?
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I read it very briefly by skipping some details (It has been so long I ever dealt with Op AMP...) but very interesting fact about balanced circuit.
In shielded twist pair, I seem to understand potential creation of unequal capacitance between two inner conductors in reference to the shield and this will be amplified by Diff Op-Amp... This is very good...
Maybe the problem we are having with keyboard connection is related to ground terminated both end. I will take a look at it.
I guess I need to isolate GND at DI.
Not familiar with MIC circuitry, but my gut feeling tells me shield can not be removed at receive side for passive mic and pre interface...
What about active mic like phantom? Is ground pin in XLR used for 48V return?
WK154:
I pretty much covered the gamut from X-rays to audio. Just haven't got to subsonic, it's hard to keep a whale for a pet. :) The impedance mismatch gets past the differential input circuit as noise. You definitely have two totally different ground potentials being 300 ft apart. A DI box is a essential audio tool and if it's noise from the KB the Di box will deal with it. Passive at mixer end is my preference. Yes the shield is the 48V return in the XLR.
Bill Whitlocks app notes AN003,004,006,007,009 pretty well cover all those issues.
http://www.jensen-transformers.com/application-notes/
P.S. most KB are unbalanced outputs and 300 ft. is going to be a problem.
WK154:
I don't have a good idea of the actual church layout but you said it was a 300 ft straight shot for the cables. That would be a problem for wireless as well at a 100 meters for FOH. Any chance to move closer? Also since you have 15 cables and your typical use is 10 what is the need for a 24 input mixer? Your condenser mic is what brand and model?
sam.spoons:
As WK says pin 1 (ground) is 48V -ve and pins 2 and 3 carry equal potential (48V +ve) so there is no potential between them (which would damage dynamic mics). I would have thought the DI needs to be at the keyboard so that most of that 300' run is balanced?
I guess the 300' run follows a convoluted path and the mix position is somewhat closer to the stage as the dove flies? 300' from stage to mix position might be alright at Woodstock but indoors...... (and would represent a delay of around ⅓ sec).
If you choose to go digital with faders a digital snake would remove all those issues (though 300' is towards the extreme end of what cat6s can handle in that context). Another option might be a side of stage desk position and cover the FOH mix wirelessly from the floor with an iPad (more than adequate for 10 channels). Whether you go for a desk with faders or a rack mount stagebox style like the DL32R (or Berry X32 Rack) I would still consider the small analogue desk as a backup/un-attended solution.
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