quick "headphone trick" question

[surfsup]

I am about to do this to locate my OT. As my first time, I wanna be sure I'm not screwing something up and lose my PT.

The PT primaries get hooked up, the two voltage leads and the CT, and the secondaries are just taped off, right?

[overtone]

that is how I do it.
You let the PT run, unconnected as it were, after you have made all the secondaries and any other wires safe.
Your OT just has the headphones connected to the speaker connection. That is all.

If you are really unsure do a test run with some junk iron.

I found it easier to hear with everyday 'phones of around 30 Ohms rather than the old studio ones of 600 Ohms or so.

Best, tony

[Zippy]

Here're the responses from the last time you asked the same question:

https://tubeamparchive.com/viewtopic.php?t=13898

[surfsup]

Zippy, I didn't ask the question. In fact, if you re-read the post, I searched for the headphone trick, found a bunch of obscure descriptions (to a newbie like me at least) and re-wrote it for other newbies to find as a courtesy. In other words, I answered my own question. I simply wanted to confirm that I understood what to do correctly so I didn't fry a transformer.

And of course, Zippy showed up in THAT thread, as well, to point out the "trick" was already found by someone else even though I PLAINLY STATED I found it on the forum and "re-wrote" it.

[Zippy]

Zippy, I didn't ask the question. In fact, if you re-read the post, I searched for the headphone trick, found a bunch of obscure descriptions (to a newbie like me at least) and re-wrote it for other newbies to find as a courtesy. In other words, I answered my own question. I simply wanted to confirm that I understood what to do correctly so I didn't fry a transformer.

And of course, Zippy showed up in THAT thread, as well, to point out the "trick" was already found by someone else even though I PLAINLY STATED I found it on the forum and "re-wrote" it.

Got it. You wrote directions to simply for others that which you didn't understand. You were happy to provide information for others to use but you didn't sufficiently trust that information to apply it. Have I captured it?

Sorry if I rile you. I'm cabin crazy being stuck at home for two months while I recover from back surgery. It's a good thing I have a Tokai Strat that weighs in at 7 lbs as I'm not supposed to lift anything over 10 lb. If I were still playing my ES-347, I'd be hosed.

What's not working for you? Have you tried the headphone trick yet?

[surfsup]

Sorry to hear and hope everything is okay... I pulled my back out while lifting in college. Coulnt move for 5 days, could barely walk for weeks. I nearly went insane as well!

I headphoned, yes, it worked well. Wound up centerpunching the exact spot on my printout but it was interesting to listen while i turned and moved the OT around.

There's just a touch of hum in that position, but thinking about it does this particular hum even get amplified becaise it is the last component in the chain? I know RJ said it helped for him.

[Zippy]

There's just a touch of hum in that position, but thinking about it does this particular hum even get amplified becaise it is the last component in the chain?

You've nailed it. The residual noise is part of the floor - it is not amplified. You can test that in the final product by exercising the volume control and observing that the hum stays low and constant. Any other types of noise will add up on top of that noise floor.

If it were to really make an issue, you could try putting a shield of mu metal between the two transformers. Ex. I had a high temperature furnace whose power supply was inducing noise in a force cell on an adjacent load frame in a mechanical test lab. We put a shield of mu metal foil around the force cell (a much smaller component than the power supply that stands 6 feet tall) and reduced the noise to almost imperceptible.

[telentubes]

I use "the headphone trick" for all builds these days (love it), but have never grounded the CT when I've done it. Just hooked up the 120V. Is that OK? I've never fried anything so I guess it is.

[paulster]

That's fine. You don't need anything on the PT secondary or the OT primary connected anywhere whatsoever.

I always tape them off.

[surfsup]

Telen, yea that was kinda my question, too. I wound up just allligatorclipping it to the chassis. I didn't know. Now that I've done it, its easy...

[wsaraceni]

can i fully wire my PT up to everything or is it best to wait until after you find the location.

also, how does the headphone trick work for the choke?

[paulster]

Yes, you can. Just make sure you don't get shocked by anything.

You can also do the headphone trick on the choke to find a location where the noise coupled into it from the PT is minimised.

Just remember, though, that your choke will be able to couple some noise into the OT in theory so don't sit it right up against the OT.

I usually end up with an 'L' shape formation, with the PT at the corner of the L the OT to the right (or left if your PT is on the right-hand side of the amp), and the choke behind the PT.

[wsaraceni]

since the chassis already has holes for the standard express transformers, im hoping that layout will work with the choke in the rocket position.