Hey guys, new builder here. Thanks for all the work you guys have put into helping guys like me get started!
I too am messing with the location & orientation of the OT, and I found the “headphone trick” to test various locations before you build. I’ll paste the procedure below.
So I set this up: ran power through the PT (and fuse and on/off switch) using the primaries and attached the secondaries from the OT to a headphone jack, and listened. It seems to be a cool way to try out various OT locations.
I found though that all of the OT locations I see in photos here produce a fairly loud hum in the headphones. The location that seems most feasible and has a fairly quiet hum is in the photo. (There is also nearly no hum when the OT is placed “on its side”.) I have the Heyboer PT, if that changes things from the usual Fender in the kit?.
Maybe this technique amplifies the hum you can expect “in the wild”? Are there issues that I’m not seeing that might arise from mounting the OT like this?
Pasted from a board at ax84.com:
Author : joe b
Date : Tue, Jun 01st, 2004 @ 17:45
i’m going to include the key phrase “headphone positioning trick” in this post, so people can find it easily. I do it similar to that, but without initially dedicating the PT to a spot on the chassis…
-Use electrical tape or heat shrink on the PT secondary wires to insulate them.
-Use electrical tape or heat shrink on the OT primary wires, and all but one tap and ground on the secondary (to insulate them as well).
The important part here is that there is no chance you’re going to have the PT’s secondary wires connecting to anything, and the OT will only connect two wires to headphones (and have no other connections). There is no electrical connection between the PT and OT for this test.
-Hook the OT’s secondary tap and ground to headphones (make a wiring harness if you have to–me, I just use an old busted set of $10 walkman headphones).
-Wire the PT’s primary to a power cable.
-Put the headphones on, and plug in the power cable. Move the PT and OT around on the chassis and find a spot which gives the least amount of hum. Orienting the cores 90 degrees to one another will help a lot. But a certain amount of space is required still, or some hum may get induced from the PT to the OT.
-If your amp uses a choke, put that on the chassis for this test (isolate its wires too). Although it’s not electrically connected to the PT or OT, it can actually help induce hum from the PT to the OT if it’s placed between them. That’s why on a lot of amps, you’ll see the choke way over near the preamp section, as far from the PT as possible (within reason). Some people assume the choke will help shield the OT from induced hum, but the opposite is generally true.
This is only going to help a person determine how far apart, and what orientation the PT, OT, and choke will have with respect to one another for induced hum consideration. This has nothing to do with feedback, hiss, oscillations, heater hum, or any other noise issue. The rest of your layout, some with respect to the PT and OT positions, will tell that tale.