Wiring S.E.X. 3.0 for 16 ohm output Z?

[Sherm]

I just took advantage of the sale running on the S.E.X. + C4S and placed an order. I've wanted to build a Bottlehead kit for a long time now, so I'm excited to start soldering! I've been studying the manual the last day now and I've noticed that the only documented configuration for the output transformers is either 4 ohms or 8 ohms. If I'm reading the S.E.X. 3.0 page correctly, these output transformers are the same OT-2 irons used in the 2.1 kit. I'm interested in potentially configuring these transformers to output 16 ohms--would anyone be able to instruct me on how to do this?

Also, I plan to substitute the TRS jack for a 4-pin XLR so I can run balanced out into my headphones. Reading through previous posts about this topic for the 2.1 kit, I saw it mentioned that special considerations would need to be taken creating a pseudo-center tap for the output transformers when running 4 or 8 ohms, while 16 and 32 ohms could be grounded through a center tap. That said, if I'm looking at the schematic correctly, it doesn't seem like this is an issue with the 3.0 kit. All of the pictures I've seen of the 2.1 kit seem to deal with this grounding issue at the TRS jack (hence the need to add resistors when using an XLR jack), while the 3.0 kit deals with it at the speaker outputs. All of this considered, whether I go the default 4/8 ohm configuration or implement the 16 ohm config, I shouldn't have to worry about adding resistors to my XLR jack. Do I have this right, or is there something I am missing?

[Paul Birkeland]

I'm interested in potentially configuring these transformers to output 16 ohms [...]
Also, I plan to substitute the TRS jack for a 4-pin XLR so I can run balanced out into my headphones.

You don't want to run the amp with the 16 Ohm configuration into headphones.  We omitted it from the manual for exactly this reason.  I would suggest starting with 4 Ohms and determining if that provides adequate power for your headphones. 

For the 4 pin XLR jack, you can separate the grounds for each channel.  At the speaker jacks, put a 100-500 Ohm resistor between each binding post and the ground point (4 resistors total).  That will create a balanced output.

-PB

[Sherm]

Thank you for replying, Paul! I'll just stick to the 4 ohm configuration, then. Glad I asked about the XLR--I guess it isn't really any different than setting up the 2.1 kit for balanced.

Thanks again!