Express Transformer Allignment

[Blackburn]

I'm positive tranny placement was based on noise reduction. I did this myself for my 'Pool with original Pacific trannies. Perfectly aligned, you get more coupling. Headphone and voltmeter methods are necessary for reducing coupling to a negligible amount. It's at its lowest when setup like the pics of the TWs we've seen. I think I recall the lowest coupling I got was between 4 - 5mv and it gets squashed from all the pre hum anyway, but it's always good practice to minimize all excess noise if possible.

[RJ Guitars]

I generally believe less hum is best and after numerous attempts to mount the transformers in some other way on a Wreck chassis, the least noise always turned out to be with them in close alignment on the center line. Whatever hum you do have from transformer coupling won't get worse as you turn the amp up because it's directly coupled into the output tranny. I have never tried moving the transformers while someone is playing through the amp to actually listen for a difference in tone so I can't say it doesn't happen... however the physics of it wouldn't inspire me to believe it. FWIW, I've never been able to get the hum due to transformer coupling to absolute zero (using the headphone trick) on a Wreck chassis, and I've tried every bodies transformers and every orientation short of opposite ends of the top plate... you can get it down to where it is "in the noise" however.

Oh one more thing - no two sets ever seemed to act exactly the same even if they were the same brand?? Some just seem to be randomly quieter than others.

[martin manning]

In my experience, the minimum coupling was found with the centerlines coincident, measuring ~1mV on the OT secondary.

[Blackburn]

In my experience, the minimum coupling was found with the centerlines coincident, measuring ~1mV on the OT secondary.

Nice results, Martin. Which trannies?

The original Wreck Pacifics I used couldn't get below around 4mv, I think. It could've been lower, but it really is minutia at this point anyway. Not an issue at all for me and won't be for anyone keeping the mv below a certain point.

Edit: I measure on the pri, from CT to each side. Could it be less measuring on the sec?

[martin manning]

Pacifics from a couple of sources. Yes, more turns in the varying magnetic field means more voltage.