Are transformers rotated in steel amps?

Liz Williams · Post by **Liz Williams** » 3 Aug 2014 9:04 am

I picked up my Dynalap kit (with Wallace TruTone single coil pickup) yesterday after having Steven White, an extraordinary guitar tech, wire it up. When he turned on his guitar amp there was a noticeable hum until he picked up the lap steel and held it like you would a regular electric guitar. Steven said "Ah, the transformer in a guitar amp is rotated so the hum disappears when you're holding the guitar normally. You'll probably want to get an amp made especially for steel with the transformer aligned accordingly."

Is there such an amp?

Lane Gray · Post by **Lane Gray** » 3 Aug 2014 9:16 am

I've never heard of such a thing. And my steel is dead quiet through Fenders

Rick Barnhart · Post by **Rick Barnhart** » 3 Aug 2014 9:23 am

Don't let him change the fluid in your headlights:)

Lane Gray · Post by **Lane Gray** » 3 Aug 2014 10:05 am

Have him rotate his fluorescent lights.

Liz Williams · Post by **Liz Williams** » 3 Aug 2014 10:14 am

I appreciate your protectiveness and your experience with your quiet guitar. However, the point of my post is to learn about electronics generally rather than solve a problem.

I'm especially interested to hear what amp builders have to say about the orientation of the transformer in amplifiers generally. It would be especially cool is someone were willing to experiment and report back. I do notice that when I pick up my humming steels (I have others), the hum goes away. Maybe it's bunk, and maybe not. Anyone out there willing to wonder with me?

Lane Gray · Post by **Lane Gray** » 3 Aug 2014 10:25 am

Not meaning to be flippant, more like "it doesn't make sense."
And I've not noticed a change in transformer orientation.
Not saying that the amp ISN'T the cause, but my money is on something else in the room is the culprit.

Liz Williams · Post by **Liz Williams** » 3 Aug 2014 10:31 am

I appreciate that, Lane. Why doesn't it make sense?

Not trying to be a jerk here, I really don't understand.

Lane Gray · Post by **Lane Gray** » 3 Aug 2014 10:51 am

It doesn't make sense to me because it's usually NOT the amp that causes the hum. And steel players have been using guitar amps since the 30s. And til Jim Evans started making Sho-Bud amps, we pretty much had to.
When a Tele starts humming, a 90° rotation on nearly any plane will usually kill it. I suspect he has something ELSE in his room that hums up a guitar turned right side up (the rest of the pickers turn them wrong. After all, Martin makes flattop guitars, not flat sided...)
He might have a point, but experience and history make me raise an eyebrow

Scott Duckworth · Post by **Scott Duckworth** » 3 Aug 2014 11:18 am

Transformers transform AC current, which alternates 180 degrees every half cycle. The only way a transformer might be rotated is to put the primary on the secondary side, and vice-versa. Then it would cease to function as intended. I'm like Lane, look for something in the room causing the problem.

There is such a thing that some electricians refer to as "phase rotation" but it only applies to 3 phase circuits. An standard amp is a single phase circuit.

Lane Gray · Post by **Lane Gray** » 3 Aug 2014 11:28 am

Scott, two transformers' fields can interfere with each other, so in tube amps they mount output and power transformers at right angles (and the reverb one at a 45).
I wonder if that's where he developed his theory.

Liz Williams · Post by **Liz Williams** » 3 Aug 2014 11:58 am

Thanks for the discussion so far. I love the collective intelligence at work. I'm going to ask Steve to elaborate a bit, then post what he says.

Eric Dahlhoff · Post by **Eric Dahlhoff** » 3 Aug 2014 12:06 pm

My steel king has a massive transformer & does put out a big 60hz field. If I set the bridge end of my ZB within a foot of it, the hum is very noticeable.
Also, I found that if I set my blues jr. on top of the SK, the reverb pan in the jr picks up the 60hz.
However, aside from being really near the transformer, I have found that all other noise comes from CFLs, light dimmers, computers, etc...

Craig Baker · Post by **Craig Baker** » 3 Aug 2014 12:51 pm

Liz, et al.,
A magnetic guitar pickup is an inductive device and may be considered one winding of a transformer. It will most certainly receive signal (60 Hz hum) from nearby transformers. By varying the axis of the pickup, this hum may be fully transferred into the pickup, OR fully cancelled as the pickup goes through a null in the near-field of the power transformer. This principle is well established.

Respectfully,
Craig Baker 706-485-8792

cmbakerelectronics@gmail.com

C.M. Baker Electronics
P.O. Box 3965
Eatonton, GA 31024

Peter Harris · Post by **Peter Harris** » 4 Aug 2014 1:44 am

...and all this time I've been lying my Bassman on its side for no reason at all??
..Damn!!!!

Craig Baker · Post by **Craig Baker** » 4 Aug 2014 4:47 am

Peter,
You may be on to something. Things might change when you cross the Equator

Craig

Lane Gray · Post by **Lane Gray** » 4 Aug 2014 5:27 am

Peter, does changing the orientation reduce or kill the hum?
Craig, it does make the sound waves rotate the other way.

Scott Duckworth · Post by **Scott Duckworth** » 4 Aug 2014 6:55 am

Maybe to get a steel to sound like an organ, we need to explore this rotating transformer concept. Ring contacts and a stepper motor should do it. Of course when the rings contacts get dirty, it will sound like a spark gap transmitter....

And Liz, we ARE NOT picking on you... the hum could be cause any number of things.

Peter den Hartogh · Post by **Peter den Hartogh** » 4 Aug 2014 9:04 am

Steven White knows what he is talking about

John Billings · Post by **John Billings** » 4 Aug 2014 1:38 pm

"The only way a transformer might be rotated is to put the primary on the secondary side, and vice-versa. Then it would cease to function as intended. "

Scott,
One would rotate the transformer, but not change the wiring. Line still hooked to primary. Just turn the transformer, not re-wire it.

My tech and I modified my Delta Blues 15. It had tiny transformers. It couldn't handle the low-end of my Baritone. So we put in a BIG Hammond PT, and a BIG Dr Z OT. We got hum, which was cured by rotating the OT 45 degrees.

Scott Duckworth · Post by **Scott Duckworth** » 4 Aug 2014 2:46 pm

OK, maybe there is something to it...

Lane Gray · Post by **Lane Gray** » 4 Aug 2014 8:01 pm

I just had an interesting talk with C.M. Baker about this, in which he related his experience taking the hum out of a [Session 400? I forget: he called me up whilst I was doing yard work on a 95 degree day].
He decided to move the power transformer to the bottom of the cab, and the reverb tank to the top, just under the chassis.
He found that by rotating the transformer (Scott, that means the entire thing

BTW) back and forth, he could hear the hum wax and wane (not his words; that pair would have included a pun, I've no doubt), with some angles being nearly unlistenable and some being hum-free. He chose to lock down the transformer at the position that it cause the least buzz.
So Liz, I've no doubt that the phenomenon happens. But it appears to play a secondary role, and you can move the amp a bit to knock it back.
I've still never seen an amp with the transformers reoriented to accomodate a steel guitar, however.

Paul Arntson · Post by **Paul Arntson** » 4 Aug 2014 9:48 pm

I have definitely gotten hum from a flourescent light fixture mounted on the ceiling directly below where I was playing. My old practice room did this.

Peter Harris · Post by **Peter Harris** » 5 Aug 2014 2:13 am

Lane Gray wrote:Peter, does changing the orientation reduce or kill the hum?

No, but it sure makes it easier to see the controls....

Jack Stoner · Post by **Jack Stoner** » 5 Aug 2014 3:52 am

Transformers, in all amps I've seen are not "rotated". Being a former amp tech I've worked on a lot of amps and there was never indication the transformer was oriented for any particular reason.

In theory that could be the case, but that is in theory, not real world. I suppose there is some custom built/boutique or modified amp that has a transformer set a certain way, but in typical production units it is not.

Georg Sørtun · Post by **Georg Sørtun** » 5 Aug 2014 7:53 pm

Over the 40 years I have worked on electronic equipment, from stage-amps to FM-transmitters, I have learned to test if transformers and other coils are positioned and orientated for optimal co-existence and minimal noise-induction. Have fixed more "hum noise" problems than I care to remember, by making changes in position and orientation of such components, mainly to mains transformers as they usually radiate the strongest fields.

Moving instruments and equipment a little around in a room, depending on what units in the room that radiate the most electric noise, also often works wonders to lower amplified hum levels.

So, coil orientation's effect on hum levels, is a real issue.

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Are transformers rotated in steel amps?

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