Perpendicular Transformer Placement Guarantees no Noise?

[The New Steve H]

Sorry to post twice in a row, but this is not related to the last thing I put up.

I'm about to build a new amp. Last time, I made a mistake and installed an OT so the laminates were co-planar with the laminates in the PT. It didn't make any noise, so it wasn't a problem. But I'm wondering...is it safe to assume there will be no noise issue when the laminates are NOT co-planar? If I mount an OT and PT so they're perpendicular to each other, can I be sure there won't be noise, or should I do the headphone test anyway?

[Reeltarded]

You can never be certain of most things til you prove it.

[husky]

Sorry to post twice in a row, but this is not related to the last thing I put up.

I'm about to build a new amp. Last time, I made a mistake and installed an OT so the laminates were co-planar with the laminates in the PT. It didn't make any noise, so it wasn't a problem. But I'm wondering...is it safe to assume there will be no noise issue when the laminates are NOT co-planar? If I mount an OT and PT so they're perpendicular to each other, can I be sure there won't be noise, or should I do the headphone test anyway?

When I have worked on amps that have the trannys too close and parallel it usually rears it's ugly head as hum injected in to the output transformer even with the amp in standby.... something for you to check.

[The New Steve H]

I tested everything.

Interesting thing: when I used stereo headphones, I really could not hear hum well enough to decide what to do. I reached for my MP3 earbuds, which are noise-cancelling. Made a big difference. The hum was more obvious.

The results were weird. I got hum with the transformers close together, even when the laminates were at right angles. I also got hum when I separated them--with the laminates perpendicular--until I placed the OT along the center line of the PT. Photo shows what I mean. If I were to move the OT back (away from the camera), the hum would start up. The hum band on the PT has to point at the center of the PT.

I guess this gives me a clue where the magnetic field curves run.

Now I'm wondering: will the presence of the output tubes result in feedback to the OT? They were originally going to be farther away, but the hum test made the move necessary.

[The New Steve H]

The tube boxes aren't really where I want them to be. I want the far left tube (V1) to be all by itself (to reduce noise), so there should be a big gap between it and the next tube to the right. Other than that, this is pretty much what I'm planning to do.

EDIT: I have twiddled around with the transformer angles, and I think I have a solution I like. But I have a new question. I don't recall seeing anyone talk about coupling between OTs and rectifiers, apart from diode switching noise. Do I have to be concerned if I put the rectifier between the OT and PT? I guess I can rig up capacitors and diodes to kill noise.

[Bob S]

Strange, but using the headphones on 1 amp, using the traditional TW mount positions, I found that about 5 degrees off perpendicular gave the quietest results. The amp worked out fine - negligible hum.
I usually use diodes or a bridge rectifier brick instead of a recto tube. I haven't had any sonic issues with position - apart from never being quite happy with where it is.
I suppose transparent & invisible is what I look for.
Good Luck.
Bob

[The New Steve H]

That's about where I am now. I rotated the OT 90° to make more room, and then I rotated the PT 90° and adjusted by maybe 15°. If it's okay to stick the rectifier between the transformers, I'm ready to drill!

[tubeswell]

yup hum can come from many places, but the placement of that iron looks pretty bullet-proof from this angle

[The New Steve H]

Here's the way it looks. As you can see, I lost the space behind the PT, which is where I wanted the rectifier. Now the only obvious location is between the transformers.

[LarryLarry]

I too had to mount my OT a few degrees off 90 for the least amount of hum. I used an old Foster power transformer that probably ran a gazillion tubes - it ain't pretty, but it totally rocks! The PT is mounted on plastic stand-offs that I wrapped in duct tape so they would at least look silver

Lookin' good man!

[The New Steve H]

Thanks! By the way, McMaster-Carr sells aluminum tubing that would make good standoffs.