Can anyone tell me when XLR connections were first used on stereo equipment. (what years)?

This is informative:

https://en.wikipedia.org/wiki/XLR_connector

Thanks audioquest4life, that was informative. But they didn't name any stereo brands that used balanced XLR cables for their components other than speakers and microphones. I'm interested in the earliest use of XLR connectors for amps, preamps and receivers.

I first encountered XLR connectors in home audio with my Pass Labs Aleph P preamp, a product with was first offered in 1992 and revised in 1997.

The McIntosh C35 preamp sold in 1989-1992 had XLR outputs. For perspective, the preceding model C31V sold in 1987-1989 did not have XLR outputs.

XLR connectors had been in use in professional applications for many years prior, notably in microphone cables and powered speakers.

Your search for an integrated amp with XLR inputs might bear fruit focusing on those made in the mid-1990s or later.

The Luxman L570 class A integrated amp (2x50 watts) from 1989 has one pair of balanced inputs.

Thanks jwei. I'm going to surmise XLR connections were mostly limited to units that fell in the mid to upper levels of hifi. I'll look into components manufactured in the 90's and after.

'vintage' american might be reversed: from that article, verify hot and cold

"Prior to the introduction of this standard, the wiring of pins 2 and 3 varied. The pin 2 "hot" and pin 3 "cold" convention was typically used by European and Japanese equipment manufacturers, but American companies used pin 3 "hot" and pin 2 "cold". This caused problems when interconnecting equipment with unbalanced connections. The pin 3 "hot" convention is now obsolete but is still found on vintage equipment.^[21] Pin 1 has always been ground and/or shield if the cable is shielded, and many connectors connect it internally to the connector shell or case."

From what I've heard, Ralph from Atmasphere advocated for XLR connections many decades ago.

RCA or XLR?

Should be single ended (shared ground) or balanced ground.

Single ended exposes the signal to RF (etc.) contamination.

@mewsickbuff Atma-Sphere was the first home stereo manufacturer to regularly offer balanced line products. The MA-1 amplifier was first in 1987 and the MP-1 preamp followed in 1989. Both not only had balanced inputs and outputs (including LOMC phono section) but were also fully differential and balanced internally. Both also supported AES48, the balanced line standard. The MP-1 also supports +4dB operation which is common with studio equipment no intended for home use.

The MP-1 also uses a direct-coupled method of supporting the balanced standard, for which we were awarded a patent.

Thank you all for your input. XLR has quite an interesting history. Can anyone recommend other stereo brands that used XLR in and out connections? Mid-fi  and no tubes is preferred. Thanks.

BAT, Balanced Audio Technology, is a great brand that makes all balanced equipment as the name implies.  They are built like a tank and make a great integrated.

FWIW, one of the founders of BAT was a customer of ours prior to the founding of BAT.

^ Steve Bednarsky?

@coltrane1 Yes. He had an in law that lived a block from me. Steve had two sets of our MA-1s and one of the first production MP-1 preamps. He was a friend of Victor, who called me one day saying the simulation he was running of the MA-1s didn't work. I pointed out to him that the actual amp obviously did so the issue was the simulation. It requires a schematic as an input, one which Victor made on his own. This was several years before BAT was founded. We still have Steve's warranty form for his MA-1 on file. 

@atmasphere Steve is a truly nice guy! He and I had many conversations, and all the while I was thinking, don’t you have more important things to be doing than talking to me? Nope, Steve always took time to speak to people, and for many years he was the one answering the telephone at BAT. 
Victor Khomenko was nothing short of a genius. Both of them built a wonderful company that still, some near 30 years later are building great gear. And I still have a VK5i preamp that still works. 

@coltrane1 Yes- they built a nice company.

They were several years after the next company we found after us to be making balanced line equipment; Jeff Rowland. IIRC their balanced preamp showed up about 1991.

I have a Burmester 838 phono preamp and an 868 preamp/DA convertor and two 878 amps, all of which have XLR connections.  Burmester used a system to identify his components : 838 [ August of 1983 ] 868 [August of 1986 ] 878 [August of 1987]. Year followed by month.  So, I guess my earliest guess would be 1983 that Dieter started using XLR connections.  Incidentally, his were 4 pin XLRs --- the 4th pin being used to "trigger" the on/off function if desired.  His adoption of "balanced technology" is credited to 1983.  I think I've got this right.

Levinson ML-26 has balanced pre-out and optional XLR instead of phono card. 

Note that there is a difference between XLR connection and balanced operation.  Much of the benefit of XLR connectors arises from being used with a balanced circuit,.  However, as Ralph mentions above, there are plenty of ways of having balanced in/out connections without using balanced circuitry throughout the device.

If you're shopping mid-fi, there's an increased chance of running into devices using XLR into a not-truly-balanced circuit.  I'm guessing that all of the brands mentioned above are fully balanced, but defer to @atmasphere

PS I believe some Threshold preamps & amps had XLR connections in the 80s and 90s, but I don't think they ever made an integrated amp.  Much more recently, Parasound HINT & HINT 6 integrated amps include XLR ins & outs.  I don't know if any of them are truly balanced, but both companies were/are highly reputable.

Note that most consumer gear with XLRs only support 1 balanced input/output, as balanced consumer gear is rare.  Someone with a good knowledge of pro gear might be able to steer you to some other alternatives.