The best angle for transformers next to each other?

[ManisMan]

Lets say you have a power and output transformer on a similar line on one side of the chassis. Is the best angle 90 degrees to avoid coupling, or 45 degrees? I saw something on this subject a while ago and I think 45 appeared to be the best prevention method.

[tubeswell]

90 degrees if the two cores are oriented in the same 2-dimensional plane.

[ManisMan]

Thanks. I imagine what occurs is an equal and opposite value of electric field from Trans A is dispersed across trans B set at 90 degree angle and therefore cancels?

[tubeswell]

There is no phase cancellation. Rather, what occurs with aligned cores is the EM flux fields link up and you get unwanted EM coupling between the PT and the OT. Orienting the cores at 90 degrees to each other minimises any possibility of this happening.

[labb]

 The headphone trick:


This is the best way to find the quietest place to put a reverb, output, driver, or any other signal transformer to get the least hum. CAUTION: THIS INVOLVES WORKING ON THE AMP WITH WALL VOLTAGE PRESENT. WALL VOLTAGE CAN BE FATAL.First set up the power transformer. If it's not installed yet, all the better, but if it is, this will still help. If the PT is not installed, wire up the primaries to a power cord, but do not wire up any secondaries-- tape the ends of the secondaries. If the PT is installed, fine, just make sure there is no circuit on any of the secondary leads (pull all tubes, and disconnect leads and tape them as necessary).
Now set up the signal transformer (output, reverb, whatever). Hook one set of OT secondaries (your choice, but I usually go from ground to the highest impedance tap, don't worry about impedance matching here!) to a set of headphones. Tape the primary leads.
Put the headphones on, plug in the power cord, and start moving the signal transformer around. Try it all over the chassis, and also rotate it. While you might expect the least hum with the transformers as far from each other as possible and at right angles (and that may be the case for you), it might come at an odd angle and/or position. Sometimes the least hum occurs when the transformers are side by side. When you find the quietest spot, use a permanent marker to mark where the mounting holes should be.
If you have more than one signal transformer, repeat this for each one. When you're finished, unplug the PT. That's it!

[jjasilli]

Tubeswell is right; that's how it's done in practice.  But you can go the extra mile to minimize tranny noise as labb states.  Also, Google: transformer headphone trick

[sluckey]

Just a thought about the transformer headphone trick... If there is enough 60Hz coupling to hear with a headphone then there is enough to see on a meter or scope. I don't trust my ears so much, especially when trying to discern differences in low level sounds. But I do trust my eyes when looking at a meter or scope. If you want to be dead nuts accurate connect some test equipment and simply orient the OT until you have minimum AC voltage reading.