PT and OT distance

[JD0x0]

Is there any negative effects of having the PT and OT right next to eachother. I see that on most amps they are on opposite ends of the chassis. But the chassis i have has them right next to eachother and i'm afraid this will have negative effects on the sound.


Any input will be great

[ChrisM]

http://ampgarage.com/forum/viewtopic.php?t=9859
That's a good example from a few days ago about PT and OT placement. In short, yes you want some distance.

[jaysg]

I see that on most amps they are on opposite ends of the chassis.

What amps are these? Soldano for sure...Ampeg V series. Most Fenders and Marshalls have the iron on one side.

There are effectively (ignoring toroids) 2 mounting strategies. Laydown or 'Z mount' and standup, or 'X mount'. If you mix Z and X, you can't go very wrong. If you have dual X mount, you need to either copy an existing amp (most often done), or test for it.

The headphone test...something I'd read about, but didn't try until recently...seriously easy thing to do. Get the PT set up with AC to it, with an on/off switch. The OT secondary should have an open jack on it. Connect headphones and make sure all the other wires are not touching anything. Move the OT around for the lowest hum. You'll find that opposite ends of a chassis are best, but they can be very close.

I'm not sure what you do with a choke or a reverb transformer....must be similar.

[JD0x0]

http://ampgarage.com/forum/viewtopic.php?t=9859
That's a good example from a few days ago about PT and OT placement. In short, yes you want some distance.

Thanks i thought of putting a peice of metal in between them but im not sure if there will be enough room. I mean the way the chassis is drilled puts them where the transformers are almost touching. Thats with a 40 watt OT and PT. I upgraded to a Marshall 100 watt PT to support KT88's and a big hammond 100 watt OT.

the entire chassis is only about 17'' wide so i dont have alot of room to work with.

[M Fowler]

Some amps have the trannies laminents running the same direction without hum or noise issues.

So why they have no problems when other transformers that are rotated 180 degrees of each other do is strange.

[JD0x0]

Some amps have the trannies laminents running the same direction without hum or noise issues.

So why they have no problems when other transformers that are rotated 180 degrees of each other do is strange.

so if i had noise problems because of the trannies i could just flip the output transformer and it'd be solved?

[M Fowler]

You can space the trannies further away and see what happens.

[talbany]

Some amps have the trannies laminents running the same direction without hum or noise issues.

So why they have no problems when other transformers that are rotated 180 degrees of each other do is strange.

so if i had noise problems because of the trannies i could just flip the output transformer and it'd be solved?

Not necessarily...Magnetic coupling varies transformer to transformer... In general.. Smaller more powerful ones seem to generate the largest field... Vibrolux...Deluxe style and some Hammonds...to name a few... Couple this with an open frame OPT and better get at least 2' between them regardless of orientation... When it comes to fields the fatter the stack smaller the field.. As a general rule..

Tony

[briane]

Yeah there are no stead fast rules....Thats said following appropriate tests I almost always with the same relationship between the 2.

the trick:

Build the power section of the amp. Wire it in a safe manner so you can do a power only power up (ie PT, power switch, and tube heaters). Use electric tape where appropriate.

Then do the headphone trick. Connect headphone to OT (with amp on), move OT around till you have minimum humm.

Works perfect every time!

[BobW]

"talbanyWhen it comes to fields the fatter the stack smaller the field...

=> greater flux density within the core and less eddy currents

Here's an understandable, non-technical reference using standard nomenclature.

http://www.jt30.com/jt30page/micKqanda/ ... orons.html

[Structo]

When you see amps that have a sheet metal shield between the power tubes and OT or between the OT and PT, doesn't that have to be a ferrous metal like steel to work?

I understand if it is for RF or other noise shielding it can be aluminum but for magnetic flux shielding it should be steel, no?

[BobW]

When you see amps that have a sheet metal shield between the power tubes and OT or between the OT and PT, doesn't that have to be a ferrous metal like steel to work?

I understand if it is for RF or other noise shielding it can be aluminum but for magnetic flux shielding it should be steel, no?

Agree, it's electrostatic vs. electromagnetic, but believe the shield serves a dual purpose, also acting as a heat sink to keep the XFMRs cooler by pulling the heat away / distributing it into the chassis.

[drz400]

Is there any negative effects of having the PT and OT right next to eachother. I see that on most amps they are on opposite ends of the chassis. But the chassis i have has them right next to eachother and i'm afraid this will have negative effects on the sound.


Any input will be great

You can easily pick up hum in output transformer from the Power transformer, especially if they are not orientated correctly.
I fixed a guys amp (Diamond) that had the transformers normal Marshall distance apart but it hummed at any volume because the laminations were orientated the same direction, turned it 90 degrees and hum went away.