I bought this vintage tube amp...

[Northstar]

Here's a Maas-Rowe Carillons Model 500 50 watts church carillon tube amp.

Can anyone give me some pointers about that speaker output? What is it called and how does it work?

[Alton]

Cool! Looks like a PA amp from a church. Looks like you're missing a power tube. It has a tube rectifier. Looks to be 2 channel at about 35 to 50 watts per channel but the channels share one preamp. If you're thinking about making this a guitar amp you want to either take it to a tech or use it as a base to learn about building/repairing amps yourself. Lots of old PA amps have been successfully converted to great sounding guitar amps.

[daddymack]

this is a Carillon amp, designed to run a set of church bells. I repaired these when I was in High School....which was the last time I saw one.  These are not unlike 60's era Bogen school PA amps (which I also worked on). These amps are not easily modified for modern musical use or hi-fi, but it can be done...the output connector can be replaced with an XLR or a 1/4" jack, but check the resistance and wattage before you hook a loudspeaker to it! THE output resistance is variable depending on how it was connected. The chime out put has a fixed output resistance,...IIRC there are two other modules tha tshould go along with the Maas 50W...but I could be wrong, it has been a long time...

I don't have specific specs/diagrams available, but I converted some of these as bass amps and PA amps in the past...they generally do not work well for guitar, although they could be repurposed, I suppose. Oh, yeah...be very wary of the capacitors on  that beast!!!