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Title: When did pin 2 get "hot"?
Post by: Dave Potter on January 18, 2008, 03:32:17 am
XLR;
pin1 screen
pin2 hot
pin3 opposite polarity

I was recently looking at an early 80s amp which used pin3 as hot with pin 2 unconnected. As far back as I can remember (1987) pin2 was hot. A work colleague of mine mentioned that he thought that Europe had the pin2 as standard while USA was pin3 ... or it had just changed .... or something.  so;

When did we all agree that pin 2 is hot?
Title: Re: When did pin 2 get "hot"?
Post by: Art Welter on January 18, 2008, 03:43:26 am
Pin 2 to 3 hot was all over the place in the late 1970s through the mid 1980s. Towards the late 1980s it seemed to settle to pin 2  positive or "high". I never liked the change, it was simpler to wire unbalanced adapters with pin 3 hot.

Someday TRS inserts may have a universal code followed also.

Always a good idea to do polarity checks with older mics and amps.
Title: Re: When did pin 2 get "hot"?
Post by: Geoff Doane on January 18, 2008, 09:03:39 am
My memory is a bit foggy on this, but I think it was at the LA AES show in 1988, that one of the handouts at registration was a little card with a spinning arrow, that pointed to either pin 2 or 3 as "hot".  In other words, there was no AES standard yet.  I think by the next time the show was in LA (1990), pin 2 was the accepted standard.

The first piece of gear that I encountered in my pro audio career that made a difference, was a Shure M67 mixer.  It had XLR ins and outs (at mic level), but you could switch them to higher level and unbalanced, and in that configuration, the XLRs were pin 3 hot.  So for that reason, I standardized my own rig on pin 3, wherever I could.  Of course that gradually changed over the years.

GTD
Title: Re: When did pin 2 get "hot"?
Post by: trace knight on January 18, 2008, 11:42:24 am
I remembr back in those dayz...........some amps, i think I saw it on a carver, and a crest had a recessed switch pin 2-3 swap on the back panel, they couldn't make up thier minds I guess!
tk
Title: Re: When did pin 2 get "hot"?
Post by: John Roberts {JR} on January 18, 2008, 11:56:10 am
Dave Potter wrote on Fri, 18 January 2008 02:32

XLR;
pin1 screen
pin2 hot
pin3 opposite polarity

I was recently looking at an early 80s amp which used pin3 as hot with pin 2 unconnected. As far back as I can remember (1987) pin2 was hot. A work colleague of mine mentioned that he thought that Europe had the pin2 as standard while USA was pin3 ... or it had just changed .... or something.  so;

When did we all agree that pin 2 is hot?


Depends on who you consider "we" to be.

I used to write a magazine column back in the '80s and did a survey of manufacturers in the early '80s. The results were quite mixed with no real pattern other than perhaps most new companies (new in '80s) were pin 2 hot. There were established Brit and US companies in both camps. My understanding is there was an early (IEC?) pin 2 hot standard that most manufacturer's followed for microphones, but line level XLR interfaces were mixed with companies trying mainly to remain consistent with themselves. A little odd but some companies were pin 2 hot on mic XLR while pin 3 hot on line levels.

In the mid-late '80s IIRC AES published a standard defining pin 2 hot, which for many people was their first awareness of any standard. For some larger companies (like the one I worked at for a while) this was a struggle as bringing new product up to the AES standard makes you inconsistent with (in some cases) decades of existing product. But it was the right thing to do, so most companies now adhere to the AES standard.

There is some legacy gear floating around still in use that will be pin 3 hot, so this can always reach out and bite us in unbalanced or mixed wiring interfaces.  

Perhaps, significant to this time line, discussion and increased awareness for the importance of maintaining absolute polarity occurred at least in the wider recording press around this time (early '80s). PA and recording were always aware of relative polarity, but absolute polarity was dismissed by many as being inaudible, until proved at least for certain types of waveforms.

JR
Title: Re: When did pin 2 get "hot"?
Post by: John Roberts {JR} on January 18, 2008, 12:39:06 pm
trace knight wrote on Fri, 18 January 2008 10:42

I remembr back in those dayz...........some amps, i think I saw it on a carver, and a crest had a recessed switch pin 2-3 swap on the back panel, they couldn't make up thier minds I guess!
tk


The pin hot selector switch was one way to support customers with predominantly pin 3 hot systems, while also working with pin 2 hot system.

I encountered customers who were extremely confused and sometimes over reacted to mixed standard situations. In some cases customers introduced a polarity reversal with their modified wiring "fix"  where there wasn't a problem, thanks to the symmetrical nature of differential in and differential out interfaces.

I'm glad this is mostly behind us.

JR

Title: Re: When did pin 2 get "hot"?
Post by: John Nobile on January 18, 2008, 02:07:49 pm
I'm not sure what happened at Soundcraft. I have a 500 with pin 2+ and an 8000 which came out later, with pin 3+. Any Soundcraft I've used that was newer than the 8000 was pin 2+ .

Did pin 3+ become standard in England for a while? Or just Soundcraft?
Title: Re: When did pin 2 get "hot"?
Post by: John Roberts {JR} on January 18, 2008, 02:20:45 pm
John Nobile wrote on Fri, 18 January 2008 13:07

I'm not sure what happened at Soundcraft. I have a 500 with pin 2+ and an 8000 which came out later, with pin 3+. Any Soundcraft I've used that was newer than the 8000 was pin 2+ .

Did pin 3+ become standard in England for a while? Or just Soundcraft?


From memory pin 2 or pin 3 hot was mixed even among Brit companies. There was plenty of speculation about pin 3 being a Bit standard or US standard, but my research at the time turned up no real national patterns, just random before a certain time period, and mostly pin 2 hot after that time period.

JR


Title: Re: When did pin 2 get "hot"?
Post by: Lester Moran on January 18, 2008, 03:49:15 pm
John Roberts  {JR} wrote on Fri, 18 January 2008 17:39


I encountered customers who were extremely confused and sometimes over reacted to mixed standard situations. In some cases customers introduced a polarity reversal with their modified wiring "fix"  where there wasn't a problem, thanks to the symmetrical nature of differential in and differential out interfaces.



My KT DN 360s are "pin 3 hot".  My Ramsa WRS 840 is "pin two hot", but more importantly, the individual send and return insert points on the mixes are tip=hot, ring=cold.  If I present the inserted EQs with the Ramsa's hot signal to pin 2 of the EQs, I get 6 db loss, as compared to presenting the Ramsa's hot signal to the EQs at pin 3 (which introduces no loss).  Do you know why this would happen?...  i.e. what might be peculiar to the DN 360 balancing scheme to make it "care" whether the hot signal ran through it at pin 3 as opposed to pin 2?

Thanks,
Les
Title: Re: When did pin 2 get "hot"?
Post by: John Roberts {JR} on January 18, 2008, 04:03:27 pm
Lester Moran wrote on Fri, 18 January 2008 14:49



My KT DN 360s are "pin 3 hot".  My Ramsa WRS 840 is "pin two hot", but more importantly, the individual send and return insert points on the mixes are tip=hot, ring=cold.  If I present the inserted EQs with the Ramsa's hot signal to pin 2 of the EQs, I get 6 db loss, as compared to presenting the Ramsa's hot signal to the EQs at pin 3 (which introduces no loss).  Do you know why this would happen?...  i.e. what might be peculiar to the DN 360 balancing scheme to make it "care" whether the hot signal ran through it at pin 3 as opposed to pin 2?

Thanks,
Les



I'm pretty sure that particular product's quirks wrt to pin 2/3 hot have been well explored on this site so I suggest a search specifically for that discussion. As i recall pin 3 hot wasn't the only issue.  

The general answer is a TRS insert is converting a balanced or differential 3 circuit signal to a single ended 2 circuit signal, and then back again. Sh__ happens, between different pin 2/3 standards, and more importantly between different 3 circuit output topologies in such mixed 3 circuit to 2 circuit interfaces.

Rane also has a pretty good wiring guide on their website for working with sundry interface topologies.

JR

 
Title: Re: When did pin 2 get "hot"?
Post by: Bob Lee (QSC) on January 18, 2008, 04:59:52 pm
Yeah, that was 1990. The spinner was something that the AES LA section had made to poke fun but also plainly point out that no standard existed at the time.

It's an issue mainly with equipment that goes from balanced to unbalanced or vice-versa. Anything balanced-to-balanced with XLR ins and outs is okay as long as the polarity is consistent.
Title: Re: When did pin 2 get "hot"?
Post by: Patrick Tracy on January 18, 2008, 06:25:12 pm
John Roberts  {JR} wrote on Fri, 18 January 2008 10:39

trace knight wrote on Fri, 18 January 2008 10:42

I remembr back in those dayz...........some amps, i think I saw it on a carver, and a crest had a recessed switch pin 2-3 swap on the back panel, they couldn't make up thier minds I guess!
tk


The pin hot selector switch was one way to support customers with predominantly pin 3 hot systems, while also working with pin 2 hot system.

I encountered customers who were extremely confused and sometimes over reacted to mixed standard situations. In some cases customers introduced a polarity reversal with their modified wiring "fix"  where there wasn't a problem, thanks to the symmetrical nature of differential in and differential out interfaces.

I'm glad this is mostly behind us.

JR




Do I recall you saying that Peavey had settled on pin3 hot well before there was an industry standard and retained it to maintain continuity for their customers?
Title: Re: When did pin 2 get "hot"?
Post by: Andy Peters on January 18, 2008, 06:35:21 pm
Lester Moran wrote on Fri, 18 January 2008 13:49

John Roberts  {JR} wrote on Fri, 18 January 2008 17:39


I encountered customers who were extremely confused and sometimes over reacted to mixed standard situations. In some cases customers introduced a polarity reversal with their modified wiring "fix"  where there wasn't a problem, thanks to the symmetrical nature of differential in and differential out interfaces.



My KT DN 360s are "pin 3 hot".  My Ramsa WRS 840 is "pin two hot", but more importantly, the individual send and return insert points on the mixes are tip=hot, ring=cold.  If I present the inserted EQs with the Ramsa's hot signal to pin 2 of the EQs, I get 6 db loss, as compared to presenting the Ramsa's hot signal to the EQs at pin 3 (which introduces no loss).  Do you know why this would happen?...  i.e. what might be peculiar to the DN 360 balancing scheme to make it "care" whether the hot signal ran through it at pin 3 as opposed to pin 2?


DN360s have unbalanced outputs unless fitted with the optional output transformers. In either case, Pin 3 is hot.

So if used in an unbalanced insert situation, a 6 dB loss is possible. I haven't seen the input section schematics but I assume that it's a diff amp with gain of 0.5 (6 dB loss).

-a
Title: Re: When did pin 2 get "hot"?
Post by: John Roberts {JR} on January 18, 2008, 07:09:53 pm
Patrick Tracy wrote on Fri, 18 January 2008 17:25





Do I recall you saying that Peavey had settled on pin3 hot well before there was an industry standard and retained it to maintain continuity for their customers?


No, and I still have the scars on my ass from working there during that transition. I started working there in the mid '80s as a Pin 2 guy inside a pin 3 company. They had made the pin 3 decision a few decades before I showed up. I was a pretty lonely guy, arguing for pin 2 hot, and for a while the AMR recording products (my specific responsibility) were pin 2 hot with Peavey SR gear pin 3 hot. The publicity surrounding the AES pin 2 hot endorsement a few years later was very helpful in getting the rest of the organization on board. It took years for the transition to actually take place as product lines turned over.

And like I said elsewhere many customers were very confused. Old school Peavey customers and dealers didn't appreciate the change one bit, but my philosophy regarding this was that if customers had problems interfacing mixed pin 2/3 hot gear, I wanted to be the one that was correct. Pursuing a path of staying pin 3 hot because it was easy, means being wrong in those cases.

I'm sure that was only one of many times I was a burr under the saddle there...

JR

Title: Re: When did pin 2 get "hot"?
Post by: Mark Meagher on January 18, 2008, 11:28:31 pm
My memory must have failed, but I remember the early 80's being pin 2 hot from the Brits and pin 3 elsewhere.
Maybe I'm just recalling the EQ as "British EQ". <----rhetorical, discussion not needed-> Very Happy


Title: Re: When did pin 2 get "hot"?
Post by: Moby (Mike Diack) on January 19, 2008, 05:18:37 am
"Down Under" pin 3 hot was the standard well into the 80's, and it's relatively recently that we've been dragged kicking and screaming into a pin 2 hot world. We also used XLR3Ms as standard for amp outputs and speaker inputs (hence speaker cables were XLR3F->XLR3F) mind you this was before the rise of the speakon. There were variations as to which conductors were used for what in the amp->speaker connectors, giving real meaning to the "pin X hot" conundrum, especially with primitive amps with poor protection.
M