Classic Tone Output Trans Taps?

[misterc57]

Hey Folks

Sometimes what seems simple I can turn into complexity.

I have a request to modify a Fender Super Reverb Reissue. This amp is in a head only cab.

The amp has a Classictone OT shown below. It has mutliple taps. Currently the two output jacks are connected to the 8 ohm tap. One output jack is a shorted jack, the other is a standard output jack.

The goal is to modify this so that one jack is on the 4 ohm tap and the other jack is on the 8 ohm tap.

I am thinking we do not want a shorted jack in this scenario as we do not want to have one of the taps shorted, right?

Also what about the NFB? It is the gray wire I believe in the pics. Will it only be connected to one of the jacks + side? Does it matter which OT tap has the NFB connection?

Or, would it be smarter to only have one jack and install a selector switch?

Thank you, MarkO

[Helmholtz]

I am thinking we do not want a shorted jack in this scenario as we do not want to have one of the taps shorted, right?

Right.

Also what about the NFB? It is the gray wire I believe in the pics. Will it only be connected to one of the jacks + side? Does it matter which OT tap has the NFB connection?

NFB goes to the 8 Ohm jack/tap only.

[misterc57]

I replaced the shorted jack with a regular jack.

Connected ground wire from OT across both jacks.

One jack has the green/yellow connected to the tip. 4 ohm tap
Other jack has the green wire and NFB wire connected to the tip. 8 ohm tap

[mozz]

That's fine, just make sure to tell the owner to always have a speaker plugged in. The shorting jack is just a safety thing so the trans/tubes have some sort of load when nothing is plugged into the jacks.

[Tom Phillips]

I'll add two more points.
1) Tell the customer that only one output jack can be used at a time if the correct output impedance match is to be maintained.
2) You can provide some protection for the case when no speaker load is connected by installing an internal resistor across one of the speaker jacks. I would suggest a 330 Ohm, 5W resistor across the 8 Ohm tap.

[Greg Robinson]

I'll add two more points.
1) Tell the customer that only one output jack can be used at a time if the correct output impedance match is to be maintained.

While that's also what I'd tell a customer because it avoids confusion, you can actually make good use two (or more) output taps. In this case, with 4Ω and 8Ω, you could use an 8Ω and 16Ω speaker in each jack respectively to maintain correct primary impedance. 8Ω speaker on the 4Ω tap reflects an 8k4 primary impedance, 16Ω speaker on the 8Ω tap also reflects an 8k4 primary impedance, those are in parallel, so you keep your nominal 4k2 primary impedance. One of my favourite tricks, and why I prefer heads that bring each of their output taps to seperate jacks.