hum induction of transformer to amp

[jimtr6]

I built a little amp and used a transformer from a phone systme, it works fine but there is some hum, is there a signifcant distance the power transformer should be from the amp, mine is one inch away, also are there transformers with grounded shielding like a metal cover?

[phatt]

A link to the Schematic and better still a picture of what you have built,, otherwise it means little and we can't do much to help.  :tu:
Cheers Phil.

[J M Fahey]

What Phil said 

We don´t know what " a little amp"  is nor what  "a transformer from a phone systme" is.
Schematic? / voltage / kind of supply?

[jimtr6]

sorry, what i have is a small board with a TDA 7293, no preamp, just the amp, a transformer, and a small board with a relay to switch on the speaker with a three second delay, all mounted on a 8" x 8" piece of plywood and close to one another (inch apart), I noticed the input (shielded 5 inch lead wire with a 1/4" female) was sensitive to placement and would induce more or less hum when moved. I've since spread things out more and the hum did drop a fair amount. I guess my question would be is...is there a preferred transformer for these two rail amps that utilize these IC power amps that run on anywhere from 13 to 33 vac, possibly a shielded torroid?

[Enzo]

Your whole circuit lacks shielding, I don;t worry much about the transformer.