DBX 160XT XLR pin 3 (+) hot -- why?
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Help Support GroupDIY Audio Forum:
If it has balanced/differential XLR inputs and outputs there is no pin hot. Pin 2 hot input will pass thru to pin 2 hot output.
There are only problems if both XLR and TRS signals are used. Because a TRS input can show up reversed on the XLR output.
JR
Here you go, John, Your article starts on page 16: https://www.worldradiohistory.com/A...-Recording-Engineer/80s/Recording-1984-04.pdf
P.S. I can't believe recording magazines used to be almost 200 pages long! There's some great stuff in that issue though.
For today's TMI/Peavey anecdote I recall at least one Peavey customer who bragged that he made a pin2/3 swap cable to use with his Peavey SKU that had balanced XLR in/out. He effectively reversed his path polarity, that wasn't broken. 
[edit- thanks for the link. I enjoy reading my 40+ years old scribbles without seeing obvious mistakes. The Letters to the Editor were always fun reading because my topics would often generate contrary responses from industry heavyweights. I enjoyed the benefit of always getting the last word. There is an old saying "don't pick arguments with people who buy ink by the truckload".
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JR
[edit- thanks for the link. I enjoy reading my 40+ years old scribbles without seeing obvious mistakes. The Letters to the Editor were always fun reading because my topics would often generate contrary responses from industry heavyweights. I enjoyed the benefit of always getting the last word. There is an old saying "don't pick arguments with people who buy ink by the truckload".
[/edit]JR
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Turns out, the input TRS tip(+) is internally wired to pin 2 of the input XLR. So internally, the unit is XLR pin 2(+) hot already -- even if the legend on the backplate says differently.
Meaning that, as is, the unit should be fully fit for use in an otherwise consistently XLR pin 2(+) hot environment -- with both balanced or unbalanced signals feedable into either the TRS or XLR inputs, and even so if TRS and XLR connections are mixed. Cos if TRS tip = XRL pin 2 at the input, any signal shows with correct polarity at TRS tip unbal out and XLR pin 2 out both bal or unbal. XLR accidentally unbal in to TRS unbal out works too.
As for an XLR pin 3(+) hot environment, the wires on pin 2 and pin 3 on the XLR input might be flipped, but I'm not sure this unit would implement that smoothly any more. Unless all peripheral cables too are consistently wired tip to XLR pin 3, I assume :/
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As for mixed environment, headache, loss of precious time.
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That manufacturer list is very interesting. Thanks for looking for and posting the article.
Good.... I recall advising the industry at the time to note on their chassis rear panel their actual wiring polarity. It's good that they made the wiring correction.
At the time or shortly after I was tasked with Peavey converting to pin 2 hot creating a conflict with decades of pin 3 hot production and inventory in the field.
JR
An internal wiring change is a relatively easy ECR (engineering change request). Changing rear panel artwork and/or owners manual literature requires dealing with factory production lead times and inventory management.
I certainly approve making the product right ASAP.
JR
I remember a lecture or two on the semantic difference between "hot" and "plus". Signal polarity wasn't a great concern in the old days. It's not uncommon to see a transformer output labelled "output" with no polarity indication on a barrier strip. "Hot" referred to the situation with the Ampex 300 where the only signal was on pin 3.
As I recall back in the 1980s within the console/recording design community the importance of absolute polarity was only then becoming apparent.
While the audibility of absolute polarity was subtle if at all (in most cases), for archival purposes it was worthwhile preserving absolute polarity for the entire audio chain, microphones to speakers and everything in between.
I am pleased that now a few decades later the entire industry is pretty much on the same page (pin 2 hot). At least for new production. There will always be older legacy products manufactured before these standards were universally embraced, so YMMV.
JR
Indeed no signal is worse than opposite polarity.
For another old Peavey anecdote back when I was working there during the transition to pin 2 hot, we encountered an older Peavey mixer that was only looking for signal on pin 3. Plugging a single ended pin 2 hot signal in resulted in no sound. The cost is typically minimal (two more resistors) to accept signal in from both pin 2 and pin 3 differentially.
JR
For another old Peavey anecdote back when I was working there during the transition to pin 2 hot, we encountered an older Peavey mixer that was only looking for signal on pin 3. Plugging a single ended pin 2 hot signal in resulted in no sound.
The cost is typically minimal (two more resistors) to accept signal in from both pin 2 and pin 3 differentially.JR
Splendid. Meanwhile, the artists went for a beer or two at a nearby joint...Plugging a single ended pin 2 hot signal in resulted in no sound.
and this was all sorted out decades ago....Splendid. Meanwhile, the artists went for a beer or two at a nearby joint...
JR
