DBX 160XT XLR pin 3 (+) hot -- why?

[Script]

The 160XT has 1/4" jack output with tip (+) hot, while the XLR has pin 3 as hot (+). It also says so on the back plate. But why ? I mean for what?

I looked into the Instruction (Owner's) Manual and it mentions it too. Usually pin two is hot (+). But the manual doesn't explain why. Were they thinking of some specific application scenario (broadcast or something maybe) or is this a shortcoming of the design ?

 

[emrr]

From the era when pin 3 was sometimes hot....was still an open question in the early '90's, and a thing to keep track of.

 

[JohnRoberts]

Back in the 80s when I was still writing my "audio mythology" magazine column I conducted a survey of manufacturers and listed who used which pins hot.

Pin 2 hot is the modern standard. I was working at Peavey during their transition from pin 3 to pin 2 hot (not fun).

JR

 

[scott2000]

the old P series Yamaha amps come with unbalanced xlrs..but can swap either 2 or 3 being grounded...neat but kinda odd...

 

[user 133392]

The story I've often heard is that pin 3 hot became a "standard" due to an Ampex manual misprint.

 

[JohnRoberts]

The story I've often heard is that pin 3 hot became a "standard" due to an Ampex manual misprint.

I've heard several different stories. I researched this for my column (40 years ago?).

As I recall (vaguely) I found back then that there was a prior existing pin 2 hot IEC standard for microphones. The later AES standard brought common Pin 2 hot usage into harmony.

JR

 

[Script]

So, it's waiting for a factory recall in vain then

 

[AudioFurga]

If I have no misunderstanding, it seems that in the USA the 3+ pin was mostly used and in Europe the 2 was used, until the arrival of the AES/EBU standards.

 

[MagnetoSound]

If I have no misunderstanding, it seems that in the USA the 3+ pin was mostly used and in Europe the 2 was used, until the arrival of the AES/EBU standards.

This was my understanding too. Altec, EV and Shure tended to pin 3, whereas Neumann, Neve and AKG were pin 2.

 

[Script]

What a nightmare... thinking of a balanced but pin2+/pin3+ mixed environment with parallel processing somewhere...

Guess I'll swap the out pins on that unit to today's standard.

If XLRs are PCB mount, could cross over signal at output resistors -- or better even, as with this unit, cross over at factory-flywired (cos only optional) output transformer. Then put sticker on backplate.

 

[abbey road d enfer]

The 160XT has 1/4" jack output with tip (+) hot, while the XLR has pin 3 as hot (+). It also says so on the back plate. But why ? I mean for what?

I looked into the Instruction (Owner's) Manual and it mentions it too. Usually pin two is hot (+). But the manual doesn't explain why. Were they thinking of some specific application scenario (broadcast or something maybe) or is this a shortcoming of the design ?

I find it slightly odd that you come to realize this issue 20+ years late. IIRC the debate was closed in the 90's.

 

[porkyc]

If I have no misunderstanding, it seems that in the USA the 3+ pin was mostly used and in Europe the 2 was used, until the arrival of the AES/EBU standards.

That would be a reasonable conclusion...................but CBS in London, being a US owned studio was pin3 hot.
Europe wired the plug physically, US wired it numerically.
Given that the German/Austrian mics were pin2 hot, you can see that the recording industry did not understand absolute phase!
Where have you been? Think of all the fun you've missed..............and when Studer A80 Mk1 machines had the (albeit pin2 hot) XLRs sexed the other way round, and we moved from Studer to MCI multitracks.

 

[abbey road d enfer]

That would be a reasonable conclusion...................but CBS in London, being a US owned studio was pin3 hot.
Europe wired the plug physically, US wired it numerically.

This is somewhat debatable, since pin 3 is betwen 1 and 2. Dyslexia?

Given that the German/Austrian mics were pin2 hot, you can see that the recording industry did not understand absolute phase!

In other words, polarity...

 

[RCAguy]

The 160XT has 1/4" jack output with tip (+) hot, while the XLR has pin 3 as hot (+). It also says so on the back plate. But why ? I mean for what?

I looked into the Instruction (Owner's) Manual and it mentions it too. Usually pin two is hot (+). But the manual doesn't explain why. Were they thinking of some specific application scenario (broadcast or something maybe) or is this a shortcoming of the design ?

Earliest convention ranked pins by voltage, and XLR pin3 was deemed higher than pin2. Shure, Ampex, and others used this pinout. Of course audio is AC and neither leg is higher voltage than the other, but somehow pin2 “won” being the positive going signal for positive-going acoustic pressure, beginning with the microphone and ending with a loudspeaker.

 

[mobyd]

Down in the lower reaches of the world (NZ. Aus etc), pin 3 hot persisted into the early 1980s. Things got stranger in the pre Neutrik Speakon era where XLR3 males were commonly used for amplifier speaker outputs AND speakerbox inputs, necessitating carrying a pile of
XLR3F-> XLR3F speaker cables.

 

[scott2000]

Lavry Da10 is default pin 3 hot. You have to open it up if you want to change it via jumper or just use the polarity switch on front..pin 3 hot brings out the details...lol

 

[JohnRoberts]

If I have no misunderstanding, it seems that in the USA the 3+ pin was mostly used and in Europe the 2 was used, until the arrival of the AES/EBU standards.

Popular wisdom like that was incorrect. That is why I had to do an actual survey of manufacturers for my magazine column because there was no reliable geographic pattern.

I am too lazy to look for a copy of my old column with the XLR list, someone more enthusiastic might find it with a web search (the column was named "audio mythology" and published in RE/P, record engineer/producer magazine back in the 1980s. )

As Abbey correctly observed this was sorted out decades ago.

JR

 

[porkyc]

This is somewhat debatable, since pin 3 is betwen 1 and 2. Dyslexia?



In other words, polarity...

No. Pin 2 being further away from pin 1

 

[abbey road d enfer]

No. Pin 2 being further away from pin 1

But, based on topology, Pin 3 should be further from pin 1, and pin 2 in-between.
3-pin DIN connectors had it right, but flubbed it for 5-pin.

 

[Gold]

Pin 3 hot originally was the USA convention because the output of the Ampex 300 was unbalanced on an xlr connector with signal on pin 3. With both legs of a balanced signal driven, or a transformer, the worst thing that happens is a polarity reversal. With an unbalanced or impedance balanced output it makes a much bigger difference.