1940's Kalamazoo KEA

 Curious little bargain tube amp that I got to bring back from the dead..... a 1940's Kalamazoo KEA.

This is one circuit that I'll admit I have little idea of how it works. It has a single 6SJ7 driving a pair of 6V6 tubes. How this is achieved I do not know. It's not parallel single ended. Look at the schematic!

The other challenge was finding a 10" speaker that is shallow enough to fit in such a tight space. This project sat around and almost made the 'sold for parts as-is' pile. Nothing fit! But fortunately I was able to find an old CTS speaker in the bowels of Southside Guitars deep in the basement under discarded case parts...... It was dead so we had it re-coned. Speaker had the perfect holes to mount the output trasformer.

In the end it's a fantastic little amp. Not a fuzz box, very clear and defined. These are financially not worth the effort, you'll likely lose money doing what I did. But we were all so blown away by it's charming tone that an employee bought it and will be tracking with it! I have an affinity for the 6SJ7 tube. My favorite preamp of all time so it's not surprising how much I like this amp. 

Did the usual, changed the caps etc. Fortunately both transformers were good. I do not think this amp would work well without that odd asymmetrical output transformer. So make sure that part is happy before you commit to one of these. 

J

1939 Kalamazoo KEH amplifier built by Gibson

Such a cool amp. This came from a good friend of mine. He bought it at a local shop as-is and it was dead.

I love them when they are dead. It's easier to fix a dead amp than one that sort of works. Example is the Oahu amp I bought in Dallas last year at the guitar show for $100. The power switch was dis-connected. Simple fix. The rest is just change caps and resistors as needed.

This was no exception. Dis-connected wire got it going. I had to re-cap it, ground it and change a couple super microphonic 6C5 tubes but that's it.

These early Gibson amps are exceptionally well made. Easier to work on than what they produced from the 1940s on forward. Odd, cause the early ones are service friendly like a Fender. They got worse over time where Fender just kept getting better. I like how you can simply unplug the field coil speaker in these. You just pull the chassis after that and do your thing.

Plus the looks:









This is one beautiful piece of equipment!

Tubes are 3 6C5 preamp tubes, a single 6L6 and an 80 rectifier tube. They do run rather hot. This one showed evidence of the transformers getting hot. I replaced the cathode bias resistor with a bit higher value. Makes things sound a little 'looser' but you know, I'd hate to see the output transformer die in this 80 year old amp.









Tube sockets were labeled right on the socket itself. Classy!


Yup. From the glory days of American manufacturing. These were factory built. Not cheap! You need to pay a builder to get this kind of quality today. Not cheap but come on, you're worth it!

-J