Re: Spacing between transformers in DIY amp


Brad McGowan wrote:
I'm in the process of building an Ampeg B15 clone out of an old Traynor
Bassmate chassis. I'm using the stock Hammond power transformer that
came with the Traynor, but I've upgraded the output transformer to a
Mercury Magnetics B15 output. I'm starting to wonder if I may have the
two transformers located too close to one another. The power
transformer is located at the end of the chassis in it's stock
location. I rotated the OT 90 degrees to that and mounted it about
1.25 inches away to take advantage of the existing wire pass through
hole. I know that original B15 amps had the two transformers at
completely opposite sides of the chassis. However I also know that the
transformers on a Marshall JCM800 are located very close to one
another...about an inch apart.

Am I putting them too close to one another? Is exessive hum the only
side effect I might experience? Does the 90 degree rotation have more
of an effect on reducing hum than placing distance between the
transformers?

Any comments or advice is greatly welcomed.

thanks,
Brad

You may get magnetic coupling between the two if they're that close.
Magnetic flux from the pwr transformer can induce a 60 hz hum into the
output xfmr. That translates to a faint hum through the speaker out
with the amp on stby. Not as much of a problem with an aluminum chassis.

.

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