[Berndt]

Gary, I remember way back when you stopped in to one of our Norcal get togethers and brought your altec SUT. If I remember right yours was the only step up to not hum in my system. You had mentioned connecting the ground w a resistor.
I just got a set of 4722's and an older set of western electrics that I want to implement.
I was hoping you had some advice to share?
2 questions, is there a basic schematic or wiring diagram for implementing these transformers as step ups?
And, what was your resistor arrangement to kill the hum?
Thanks in advance,Bill

[GBB]

Bill,
Your every wish is my command.  Here is the wiring diagram:




This is taken from the page over at JE Labs, where he talks about wiring up different vintage transformers as MC step ups.  Take a look here:

http://members.myactv.net/~je2a3/mic-mcstep-up.htm

The transformers that I brought to your place were S&B TX-103s, not the Altecs.  I've also used Altec 15095s with good success.  I don't think that I used any resistors to get rid of the hum.  Things were wired up just as shown here.
The only thing I did was add some sockets so that I could change loading resistors on the fly.  With my transformers, getting the right resistor load on the transformer was critical for good sound.  But this was more about getting the highs right as opposed to any hum issues.

---Gary

[Berndt]

gary, thanks! you are a saint
would there be an issue with running the case to the ground or should I just make it so I can go either way?

[GBB]

would there be an issue with running the case to the ground or should I just make it so I can go either way?

I put my transformers in plastic cases so I never dealt with that issue.  I used some cheap ABS boxes from Fry's.  If you do use a metal box, then my recommendation would be to insulate everything from the case and then hook up the case to the signal ground through a small resistor.  I'd probably use a value of 10ohms.  I'd also try it with the case not connected at all and see which one works better.
---Gary