PT-Choke-OT vs PT-OT-Choke

[Hardtailed]

It seems most amp put the OT between the PT and choke (ex: http://www.ceriatone.com/images/comp.../DSCN7616B.jpg)

Is there any reason why this would be better over a PT-Choke-OT chassis configuration? (ex: http://www.ceriatone.com/images/comp...in/front4B.jpg)

Seems to be this would help by way of getting the OT farther away from the PT.

One reason why I can see putting the choke there is because this is also where we put it in the circuit most of the time: between the OT's primary center tap and screen supply

[Old Tele man]

the PT has a large, fairly constant, 60HZ magnetic field.

the OT has a large, changing, audioHZ magnetic field about HALF the intensity of the PT.

the CHOKE has a large, basically constant 120HZ magnetic field.

...since magnetic field intensity diminishes via the 'inverse-square law' you get magnetic fields that are from BIGGEST (PT), next (PT), to LOWEST (CHOKE).

...the usual approach is to use the LEAST (and more constant) field intensive device to separate the two LARGER intensive AC fields, the PT and OT. Remember the OT carries typically less than half the power of the PT (amps seldom more than 50% efficient).

...the PT also has the filament windings--their loads are constant and HUGE, but don't carry any music content, they just heat the filaments for all the tubes, especially the rectifier!

[Hardtailed]

So if I read you correctly, the PT-Choke-OT configuration is the best (which is what intuition tells me... but intuition can be unreliable).

Then why are so many classic amps done with the OT between the PT and Choke?

[Bruce / Mission Amps]

Well, I don't really agree with that assumption but... using a choke input filter or a PI filter, which is a hi-v cap, a choke and then another hi-v cap feeding the OT center tap and the rest of the B+ rail.... choke size, choke current rating and $$ has to be taken into consideration.

IMHO, the PI filter above is superior to all the rest when money is no object and brute force filtering is required.

The way you see most filtering in guitar amps, the small choke cost less.\
For the most part, the caps cost less too.... and with enough capacitance, the filtering is still pretty good.... good enough for a guitar amp.

[Hardtailed]

Well, I don't really agree with that assumption but... using a choke input filter or a PI filter, which is a hi-v cap, a choke and then another hi-v cap feeding the OT center tap and the rest of the B+ rail.... choke size, choke current rating and $$ has to be taken into consideration.

IMHO, the PI filter above is superior to all the rest when money is no object and brute force filtering is required.

The way you see most filtering in guitar amps, the small choke cost less.\
For the most part, the caps cost less too.... and with enough capacitance, the filtering is still pretty good.... good enough for a guitar amp.

I'm talking about chassis layout of the components, sorry if that wasn't clear

[tubeswell]

So far I've put the choke between the PT and OT in 4 amps I have built that have used a CLC filter and haven't had any problems. In that position, its closest to the filter caps, so I can keep the wires short.

[Gregg]

It seems most amp put the OT between the PT and choke (ex: http://www.ceriatone.com/images/comp.../DSCN7616B.jpg)

Is there any reason why this would be better over a PT-Choke-OT chassis configuration? (ex: http://www.ceriatone.com/images/comp...in/front4B.jpg)

Seems to be this would help by way of getting the OT farther away from the PT.

One reason why I can see putting the choke there is because this is also where we put it in the circuit most of the time: between the OT's primary center tap and screen supply

The other way is to put PT and OT at the opposite sides of chassis. Choke next to PT is OK.